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Linux/include/linux/skbuff.h

  1 /*
  2  *      Definitions for the 'struct sk_buff' memory handlers.
  3  *
  4  *      Authors:
  5  *              Alan Cox, <gw4pts@gw4pts.ampr.org>
  6  *              Florian La Roche, <rzsfl@rz.uni-sb.de>
  7  *
  8  *      This program is free software; you can redistribute it and/or
  9  *      modify it under the terms of the GNU General Public License
 10  *      as published by the Free Software Foundation; either version
 11  *      2 of the License, or (at your option) any later version.
 12  */
 13 
 14 #ifndef _LINUX_SKBUFF_H
 15 #define _LINUX_SKBUFF_H
 16 
 17 #include <linux/kernel.h>
 18 #include <linux/kmemcheck.h>
 19 #include <linux/compiler.h>
 20 #include <linux/time.h>
 21 #include <linux/bug.h>
 22 #include <linux/cache.h>
 23 #include <linux/rbtree.h>
 24 #include <linux/socket.h>
 25 
 26 #include <linux/atomic.h>
 27 #include <asm/types.h>
 28 #include <linux/spinlock.h>
 29 #include <linux/net.h>
 30 #include <linux/textsearch.h>
 31 #include <net/checksum.h>
 32 #include <linux/rcupdate.h>
 33 #include <linux/hrtimer.h>
 34 #include <linux/dma-mapping.h>
 35 #include <linux/netdev_features.h>
 36 #include <linux/sched.h>
 37 #include <net/flow_dissector.h>
 38 #include <linux/splice.h>
 39 #include <linux/in6.h>
 40 #include <net/flow.h>
 41 
 42 /* The interface for checksum offload between the stack and networking drivers
 43  * is as follows...
 44  *
 45  * A. IP checksum related features
 46  *
 47  * Drivers advertise checksum offload capabilities in the features of a device.
 48  * From the stack's point of view these are capabilities offered by the driver,
 49  * a driver typically only advertises features that it is capable of offloading
 50  * to its device.
 51  *
 52  * The checksum related features are:
 53  *
 54  *      NETIF_F_HW_CSUM - The driver (or its device) is able to compute one
 55  *                        IP (one's complement) checksum for any combination
 56  *                        of protocols or protocol layering. The checksum is
 57  *                        computed and set in a packet per the CHECKSUM_PARTIAL
 58  *                        interface (see below).
 59  *
 60  *      NETIF_F_IP_CSUM - Driver (device) is only able to checksum plain
 61  *                        TCP or UDP packets over IPv4. These are specifically
 62  *                        unencapsulated packets of the form IPv4|TCP or
 63  *                        IPv4|UDP where the Protocol field in the IPv4 header
 64  *                        is TCP or UDP. The IPv4 header may contain IP options
 65  *                        This feature cannot be set in features for a device
 66  *                        with NETIF_F_HW_CSUM also set. This feature is being
 67  *                        DEPRECATED (see below).
 68  *
 69  *      NETIF_F_IPV6_CSUM - Driver (device) is only able to checksum plain
 70  *                        TCP or UDP packets over IPv6. These are specifically
 71  *                        unencapsulated packets of the form IPv6|TCP or
 72  *                        IPv4|UDP where the Next Header field in the IPv6
 73  *                        header is either TCP or UDP. IPv6 extension headers
 74  *                        are not supported with this feature. This feature
 75  *                        cannot be set in features for a device with
 76  *                        NETIF_F_HW_CSUM also set. This feature is being
 77  *                        DEPRECATED (see below).
 78  *
 79  *      NETIF_F_RXCSUM - Driver (device) performs receive checksum offload.
 80  *                       This flag is used only used to disable the RX checksum
 81  *                       feature for a device. The stack will accept receive
 82  *                       checksum indication in packets received on a device
 83  *                       regardless of whether NETIF_F_RXCSUM is set.
 84  *
 85  * B. Checksumming of received packets by device. Indication of checksum
 86  *    verification is in set skb->ip_summed. Possible values are:
 87  *
 88  * CHECKSUM_NONE:
 89  *
 90  *   Device did not checksum this packet e.g. due to lack of capabilities.
 91  *   The packet contains full (though not verified) checksum in packet but
 92  *   not in skb->csum. Thus, skb->csum is undefined in this case.
 93  *
 94  * CHECKSUM_UNNECESSARY:
 95  *
 96  *   The hardware you're dealing with doesn't calculate the full checksum
 97  *   (as in CHECKSUM_COMPLETE), but it does parse headers and verify checksums
 98  *   for specific protocols. For such packets it will set CHECKSUM_UNNECESSARY
 99  *   if their checksums are okay. skb->csum is still undefined in this case
100  *   though. A driver or device must never modify the checksum field in the
101  *   packet even if checksum is verified.
102  *
103  *   CHECKSUM_UNNECESSARY is applicable to following protocols:
104  *     TCP: IPv6 and IPv4.
105  *     UDP: IPv4 and IPv6. A device may apply CHECKSUM_UNNECESSARY to a
106  *       zero UDP checksum for either IPv4 or IPv6, the networking stack
107  *       may perform further validation in this case.
108  *     GRE: only if the checksum is present in the header.
109  *     SCTP: indicates the CRC in SCTP header has been validated.
110  *
111  *   skb->csum_level indicates the number of consecutive checksums found in
112  *   the packet minus one that have been verified as CHECKSUM_UNNECESSARY.
113  *   For instance if a device receives an IPv6->UDP->GRE->IPv4->TCP packet
114  *   and a device is able to verify the checksums for UDP (possibly zero),
115  *   GRE (checksum flag is set), and TCP-- skb->csum_level would be set to
116  *   two. If the device were only able to verify the UDP checksum and not
117  *   GRE, either because it doesn't support GRE checksum of because GRE
118  *   checksum is bad, skb->csum_level would be set to zero (TCP checksum is
119  *   not considered in this case).
120  *
121  * CHECKSUM_COMPLETE:
122  *
123  *   This is the most generic way. The device supplied checksum of the _whole_
124  *   packet as seen by netif_rx() and fills out in skb->csum. Meaning, the
125  *   hardware doesn't need to parse L3/L4 headers to implement this.
126  *
127  *   Note: Even if device supports only some protocols, but is able to produce
128  *   skb->csum, it MUST use CHECKSUM_COMPLETE, not CHECKSUM_UNNECESSARY.
129  *
130  * CHECKSUM_PARTIAL:
131  *
132  *   A checksum is set up to be offloaded to a device as described in the
133  *   output description for CHECKSUM_PARTIAL. This may occur on a packet
134  *   received directly from another Linux OS, e.g., a virtualized Linux kernel
135  *   on the same host, or it may be set in the input path in GRO or remote
136  *   checksum offload. For the purposes of checksum verification, the checksum
137  *   referred to by skb->csum_start + skb->csum_offset and any preceding
138  *   checksums in the packet are considered verified. Any checksums in the
139  *   packet that are after the checksum being offloaded are not considered to
140  *   be verified.
141  *
142  * C. Checksumming on transmit for non-GSO. The stack requests checksum offload
143  *    in the skb->ip_summed for a packet. Values are:
144  *
145  * CHECKSUM_PARTIAL:
146  *
147  *   The driver is required to checksum the packet as seen by hard_start_xmit()
148  *   from skb->csum_start up to the end, and to record/write the checksum at
149  *   offset skb->csum_start + skb->csum_offset. A driver may verify that the
150  *   csum_start and csum_offset values are valid values given the length and
151  *   offset of the packet, however they should not attempt to validate that the
152  *   checksum refers to a legitimate transport layer checksum-- it is the
153  *   purview of the stack to validate that csum_start and csum_offset are set
154  *   correctly.
155  *
156  *   When the stack requests checksum offload for a packet, the driver MUST
157  *   ensure that the checksum is set correctly. A driver can either offload the
158  *   checksum calculation to the device, or call skb_checksum_help (in the case
159  *   that the device does not support offload for a particular checksum).
160  *
161  *   NETIF_F_IP_CSUM and NETIF_F_IPV6_CSUM are being deprecated in favor of
162  *   NETIF_F_HW_CSUM. New devices should use NETIF_F_HW_CSUM to indicate
163  *   checksum offload capability. If a  device has limited checksum capabilities
164  *   (for instance can only perform NETIF_F_IP_CSUM or NETIF_F_IPV6_CSUM as
165  *   described above) a helper function can be called to resolve
166  *   CHECKSUM_PARTIAL. The helper functions are skb_csum_off_chk*. The helper
167  *   function takes a spec argument that describes the protocol layer that is
168  *   supported for checksum offload and can be called for each packet. If a
169  *   packet does not match the specification for offload, skb_checksum_help
170  *   is called to resolve the checksum.
171  *
172  * CHECKSUM_NONE:
173  *
174  *   The skb was already checksummed by the protocol, or a checksum is not
175  *   required.
176  *
177  * CHECKSUM_UNNECESSARY:
178  *
179  *   This has the same meaning on as CHECKSUM_NONE for checksum offload on
180  *   output.
181  *
182  * CHECKSUM_COMPLETE:
183  *   Not used in checksum output. If a driver observes a packet with this value
184  *   set in skbuff, if should treat as CHECKSUM_NONE being set.
185  *
186  * D. Non-IP checksum (CRC) offloads
187  *
188  *   NETIF_F_SCTP_CRC - This feature indicates that a device is capable of
189  *     offloading the SCTP CRC in a packet. To perform this offload the stack
190  *     will set ip_summed to CHECKSUM_PARTIAL and set csum_start and csum_offset
191  *     accordingly. Note the there is no indication in the skbuff that the
192  *     CHECKSUM_PARTIAL refers to an SCTP checksum, a driver that supports
193  *     both IP checksum offload and SCTP CRC offload must verify which offload
194  *     is configured for a packet presumably by inspecting packet headers.
195  *
196  *   NETIF_F_FCOE_CRC - This feature indicates that a device is capable of
197  *     offloading the FCOE CRC in a packet. To perform this offload the stack
198  *     will set ip_summed to CHECKSUM_PARTIAL and set csum_start and csum_offset
199  *     accordingly. Note the there is no indication in the skbuff that the
200  *     CHECKSUM_PARTIAL refers to an FCOE checksum, a driver that supports
201  *     both IP checksum offload and FCOE CRC offload must verify which offload
202  *     is configured for a packet presumably by inspecting packet headers.
203  *
204  * E. Checksumming on output with GSO.
205  *
206  * In the case of a GSO packet (skb_is_gso(skb) is true), checksum offload
207  * is implied by the SKB_GSO_* flags in gso_type. Most obviously, if the
208  * gso_type is SKB_GSO_TCPV4 or SKB_GSO_TCPV6, TCP checksum offload as
209  * part of the GSO operation is implied. If a checksum is being offloaded
210  * with GSO then ip_summed is CHECKSUM_PARTIAL, csum_start and csum_offset
211  * are set to refer to the outermost checksum being offload (two offloaded
212  * checksums are possible with UDP encapsulation).
213  */
214 
215 /* Don't change this without changing skb_csum_unnecessary! */
216 #define CHECKSUM_NONE           0
217 #define CHECKSUM_UNNECESSARY    1
218 #define CHECKSUM_COMPLETE       2
219 #define CHECKSUM_PARTIAL        3
220 
221 /* Maximum value in skb->csum_level */
222 #define SKB_MAX_CSUM_LEVEL      3
223 
224 #define SKB_DATA_ALIGN(X)       ALIGN(X, SMP_CACHE_BYTES)
225 #define SKB_WITH_OVERHEAD(X)    \
226         ((X) - SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
227 #define SKB_MAX_ORDER(X, ORDER) \
228         SKB_WITH_OVERHEAD((PAGE_SIZE << (ORDER)) - (X))
229 #define SKB_MAX_HEAD(X)         (SKB_MAX_ORDER((X), 0))
230 #define SKB_MAX_ALLOC           (SKB_MAX_ORDER(0, 2))
231 
232 /* return minimum truesize of one skb containing X bytes of data */
233 #define SKB_TRUESIZE(X) ((X) +                                          \
234                          SKB_DATA_ALIGN(sizeof(struct sk_buff)) +       \
235                          SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
236 
237 struct net_device;
238 struct scatterlist;
239 struct pipe_inode_info;
240 struct iov_iter;
241 struct napi_struct;
242 
243 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
244 struct nf_conntrack {
245         atomic_t use;
246 };
247 #endif
248 
249 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
250 struct nf_bridge_info {
251         atomic_t                use;
252         enum {
253                 BRNF_PROTO_UNCHANGED,
254                 BRNF_PROTO_8021Q,
255                 BRNF_PROTO_PPPOE
256         } orig_proto:8;
257         u8                      pkt_otherhost:1;
258         u8                      in_prerouting:1;
259         u8                      bridged_dnat:1;
260         __u16                   frag_max_size;
261         struct net_device       *physindev;
262 
263         /* always valid & non-NULL from FORWARD on, for physdev match */
264         struct net_device       *physoutdev;
265         union {
266                 /* prerouting: detect dnat in orig/reply direction */
267                 __be32          ipv4_daddr;
268                 struct in6_addr ipv6_daddr;
269 
270                 /* after prerouting + nat detected: store original source
271                  * mac since neigh resolution overwrites it, only used while
272                  * skb is out in neigh layer.
273                  */
274                 char neigh_header[8];
275         };
276 };
277 #endif
278 
279 struct sk_buff_head {
280         /* These two members must be first. */
281         struct sk_buff  *next;
282         struct sk_buff  *prev;
283 
284         __u32           qlen;
285         spinlock_t      lock;
286 };
287 
288 struct sk_buff;
289 
290 /* To allow 64K frame to be packed as single skb without frag_list we
291  * require 64K/PAGE_SIZE pages plus 1 additional page to allow for
292  * buffers which do not start on a page boundary.
293  *
294  * Since GRO uses frags we allocate at least 16 regardless of page
295  * size.
296  */
297 #if (65536/PAGE_SIZE + 1) < 16
298 #define MAX_SKB_FRAGS 16UL
299 #else
300 #define MAX_SKB_FRAGS (65536/PAGE_SIZE + 1)
301 #endif
302 extern int sysctl_max_skb_frags;
303 
304 typedef struct skb_frag_struct skb_frag_t;
305 
306 struct skb_frag_struct {
307         struct {
308                 struct page *p;
309         } page;
310 #if (BITS_PER_LONG > 32) || (PAGE_SIZE >= 65536)
311         __u32 page_offset;
312         __u32 size;
313 #else
314         __u16 page_offset;
315         __u16 size;
316 #endif
317 };
318 
319 static inline unsigned int skb_frag_size(const skb_frag_t *frag)
320 {
321         return frag->size;
322 }
323 
324 static inline void skb_frag_size_set(skb_frag_t *frag, unsigned int size)
325 {
326         frag->size = size;
327 }
328 
329 static inline void skb_frag_size_add(skb_frag_t *frag, int delta)
330 {
331         frag->size += delta;
332 }
333 
334 static inline void skb_frag_size_sub(skb_frag_t *frag, int delta)
335 {
336         frag->size -= delta;
337 }
338 
339 #define HAVE_HW_TIME_STAMP
340 
341 /**
342  * struct skb_shared_hwtstamps - hardware time stamps
343  * @hwtstamp:   hardware time stamp transformed into duration
344  *              since arbitrary point in time
345  *
346  * Software time stamps generated by ktime_get_real() are stored in
347  * skb->tstamp.
348  *
349  * hwtstamps can only be compared against other hwtstamps from
350  * the same device.
351  *
352  * This structure is attached to packets as part of the
353  * &skb_shared_info. Use skb_hwtstamps() to get a pointer.
354  */
355 struct skb_shared_hwtstamps {
356         ktime_t hwtstamp;
357 };
358 
359 /* Definitions for tx_flags in struct skb_shared_info */
360 enum {
361         /* generate hardware time stamp */
362         SKBTX_HW_TSTAMP = 1 << 0,
363 
364         /* generate software time stamp when queueing packet to NIC */
365         SKBTX_SW_TSTAMP = 1 << 1,
366 
367         /* device driver is going to provide hardware time stamp */
368         SKBTX_IN_PROGRESS = 1 << 2,
369 
370         /* device driver supports TX zero-copy buffers */
371         SKBTX_DEV_ZEROCOPY = 1 << 3,
372 
373         /* generate wifi status information (where possible) */
374         SKBTX_WIFI_STATUS = 1 << 4,
375 
376         /* This indicates at least one fragment might be overwritten
377          * (as in vmsplice(), sendfile() ...)
378          * If we need to compute a TX checksum, we'll need to copy
379          * all frags to avoid possible bad checksum
380          */
381         SKBTX_SHARED_FRAG = 1 << 5,
382 
383         /* generate software time stamp when entering packet scheduling */
384         SKBTX_SCHED_TSTAMP = 1 << 6,
385 };
386 
387 #define SKBTX_ANY_SW_TSTAMP     (SKBTX_SW_TSTAMP    | \
388                                  SKBTX_SCHED_TSTAMP)
389 #define SKBTX_ANY_TSTAMP        (SKBTX_HW_TSTAMP | SKBTX_ANY_SW_TSTAMP)
390 
391 /*
392  * The callback notifies userspace to release buffers when skb DMA is done in
393  * lower device, the skb last reference should be 0 when calling this.
394  * The zerocopy_success argument is true if zero copy transmit occurred,
395  * false on data copy or out of memory error caused by data copy attempt.
396  * The ctx field is used to track device context.
397  * The desc field is used to track userspace buffer index.
398  */
399 struct ubuf_info {
400         void (*callback)(struct ubuf_info *, bool zerocopy_success);
401         void *ctx;
402         unsigned long desc;
403 };
404 
405 /* This data is invariant across clones and lives at
406  * the end of the header data, ie. at skb->end.
407  */
408 struct skb_shared_info {
409         unsigned char   nr_frags;
410         __u8            tx_flags;
411         unsigned short  gso_size;
412         /* Warning: this field is not always filled in (UFO)! */
413         unsigned short  gso_segs;
414         unsigned short  gso_type;
415         struct sk_buff  *frag_list;
416         struct skb_shared_hwtstamps hwtstamps;
417         u32             tskey;
418         __be32          ip6_frag_id;
419 
420         /*
421          * Warning : all fields before dataref are cleared in __alloc_skb()
422          */
423         atomic_t        dataref;
424 
425         /* Intermediate layers must ensure that destructor_arg
426          * remains valid until skb destructor */
427         void *          destructor_arg;
428 
429         /* must be last field, see pskb_expand_head() */
430         skb_frag_t      frags[MAX_SKB_FRAGS];
431 };
432 
433 /* We divide dataref into two halves.  The higher 16 bits hold references
434  * to the payload part of skb->data.  The lower 16 bits hold references to
435  * the entire skb->data.  A clone of a headerless skb holds the length of
436  * the header in skb->hdr_len.
437  *
438  * All users must obey the rule that the skb->data reference count must be
439  * greater than or equal to the payload reference count.
440  *
441  * Holding a reference to the payload part means that the user does not
442  * care about modifications to the header part of skb->data.
443  */
444 #define SKB_DATAREF_SHIFT 16
445 #define SKB_DATAREF_MASK ((1 << SKB_DATAREF_SHIFT) - 1)
446 
447 
448 enum {
449         SKB_FCLONE_UNAVAILABLE, /* skb has no fclone (from head_cache) */
450         SKB_FCLONE_ORIG,        /* orig skb (from fclone_cache) */
451         SKB_FCLONE_CLONE,       /* companion fclone skb (from fclone_cache) */
452 };
453 
454 enum {
455         SKB_GSO_TCPV4 = 1 << 0,
456         SKB_GSO_UDP = 1 << 1,
457 
458         /* This indicates the skb is from an untrusted source. */
459         SKB_GSO_DODGY = 1 << 2,
460 
461         /* This indicates the tcp segment has CWR set. */
462         SKB_GSO_TCP_ECN = 1 << 3,
463 
464         SKB_GSO_TCP_FIXEDID = 1 << 4,
465 
466         SKB_GSO_TCPV6 = 1 << 5,
467 
468         SKB_GSO_FCOE = 1 << 6,
469 
470         SKB_GSO_GRE = 1 << 7,
471 
472         SKB_GSO_GRE_CSUM = 1 << 8,
473 
474         SKB_GSO_IPXIP4 = 1 << 9,
475 
476         SKB_GSO_IPXIP6 = 1 << 10,
477 
478         SKB_GSO_UDP_TUNNEL = 1 << 11,
479 
480         SKB_GSO_UDP_TUNNEL_CSUM = 1 << 12,
481 
482         SKB_GSO_PARTIAL = 1 << 13,
483 
484         SKB_GSO_TUNNEL_REMCSUM = 1 << 14,
485 };
486 
487 #if BITS_PER_LONG > 32
488 #define NET_SKBUFF_DATA_USES_OFFSET 1
489 #endif
490 
491 #ifdef NET_SKBUFF_DATA_USES_OFFSET
492 typedef unsigned int sk_buff_data_t;
493 #else
494 typedef unsigned char *sk_buff_data_t;
495 #endif
496 
497 /**
498  * struct skb_mstamp - multi resolution time stamps
499  * @stamp_us: timestamp in us resolution
500  * @stamp_jiffies: timestamp in jiffies
501  */
502 struct skb_mstamp {
503         union {
504                 u64             v64;
505                 struct {
506                         u32     stamp_us;
507                         u32     stamp_jiffies;
508                 };
509         };
510 };
511 
512 /**
513  * skb_mstamp_get - get current timestamp
514  * @cl: place to store timestamps
515  */
516 static inline void skb_mstamp_get(struct skb_mstamp *cl)
517 {
518         u64 val = local_clock();
519 
520         do_div(val, NSEC_PER_USEC);
521         cl->stamp_us = (u32)val;
522         cl->stamp_jiffies = (u32)jiffies;
523 }
524 
525 /**
526  * skb_mstamp_delta - compute the difference in usec between two skb_mstamp
527  * @t1: pointer to newest sample
528  * @t0: pointer to oldest sample
529  */
530 static inline u32 skb_mstamp_us_delta(const struct skb_mstamp *t1,
531                                       const struct skb_mstamp *t0)
532 {
533         s32 delta_us = t1->stamp_us - t0->stamp_us;
534         u32 delta_jiffies = t1->stamp_jiffies - t0->stamp_jiffies;
535 
536         /* If delta_us is negative, this might be because interval is too big,
537          * or local_clock() drift is too big : fallback using jiffies.
538          */
539         if (delta_us <= 0 ||
540             delta_jiffies >= (INT_MAX / (USEC_PER_SEC / HZ)))
541 
542                 delta_us = jiffies_to_usecs(delta_jiffies);
543 
544         return delta_us;
545 }
546 
547 static inline bool skb_mstamp_after(const struct skb_mstamp *t1,
548                                     const struct skb_mstamp *t0)
549 {
550         s32 diff = t1->stamp_jiffies - t0->stamp_jiffies;
551 
552         if (!diff)
553                 diff = t1->stamp_us - t0->stamp_us;
554         return diff > 0;
555 }
556 
557 /** 
558  *      struct sk_buff - socket buffer
559  *      @next: Next buffer in list
560  *      @prev: Previous buffer in list
561  *      @tstamp: Time we arrived/left
562  *      @rbnode: RB tree node, alternative to next/prev for netem/tcp
563  *      @sk: Socket we are owned by
564  *      @dev: Device we arrived on/are leaving by
565  *      @cb: Control buffer. Free for use by every layer. Put private vars here
566  *      @_skb_refdst: destination entry (with norefcount bit)
567  *      @sp: the security path, used for xfrm
568  *      @len: Length of actual data
569  *      @data_len: Data length
570  *      @mac_len: Length of link layer header
571  *      @hdr_len: writable header length of cloned skb
572  *      @csum: Checksum (must include start/offset pair)
573  *      @csum_start: Offset from skb->head where checksumming should start
574  *      @csum_offset: Offset from csum_start where checksum should be stored
575  *      @priority: Packet queueing priority
576  *      @ignore_df: allow local fragmentation
577  *      @cloned: Head may be cloned (check refcnt to be sure)
578  *      @ip_summed: Driver fed us an IP checksum
579  *      @nohdr: Payload reference only, must not modify header
580  *      @nfctinfo: Relationship of this skb to the connection
581  *      @pkt_type: Packet class
582  *      @fclone: skbuff clone status
583  *      @ipvs_property: skbuff is owned by ipvs
584  *      @peeked: this packet has been seen already, so stats have been
585  *              done for it, don't do them again
586  *      @nf_trace: netfilter packet trace flag
587  *      @protocol: Packet protocol from driver
588  *      @destructor: Destruct function
589  *      @nfct: Associated connection, if any
590  *      @nf_bridge: Saved data about a bridged frame - see br_netfilter.c
591  *      @skb_iif: ifindex of device we arrived on
592  *      @tc_index: Traffic control index
593  *      @tc_verd: traffic control verdict
594  *      @hash: the packet hash
595  *      @queue_mapping: Queue mapping for multiqueue devices
596  *      @xmit_more: More SKBs are pending for this queue
597  *      @ndisc_nodetype: router type (from link layer)
598  *      @ooo_okay: allow the mapping of a socket to a queue to be changed
599  *      @l4_hash: indicate hash is a canonical 4-tuple hash over transport
600  *              ports.
601  *      @sw_hash: indicates hash was computed in software stack
602  *      @wifi_acked_valid: wifi_acked was set
603  *      @wifi_acked: whether frame was acked on wifi or not
604  *      @no_fcs:  Request NIC to treat last 4 bytes as Ethernet FCS
605   *     @napi_id: id of the NAPI struct this skb came from
606  *      @secmark: security marking
607  *      @offload_fwd_mark: fwding offload mark
608  *      @mark: Generic packet mark
609  *      @vlan_proto: vlan encapsulation protocol
610  *      @vlan_tci: vlan tag control information
611  *      @inner_protocol: Protocol (encapsulation)
612  *      @inner_transport_header: Inner transport layer header (encapsulation)
613  *      @inner_network_header: Network layer header (encapsulation)
614  *      @inner_mac_header: Link layer header (encapsulation)
615  *      @transport_header: Transport layer header
616  *      @network_header: Network layer header
617  *      @mac_header: Link layer header
618  *      @tail: Tail pointer
619  *      @end: End pointer
620  *      @head: Head of buffer
621  *      @data: Data head pointer
622  *      @truesize: Buffer size
623  *      @users: User count - see {datagram,tcp}.c
624  */
625 
626 struct sk_buff {
627         union {
628                 struct {
629                         /* These two members must be first. */
630                         struct sk_buff          *next;
631                         struct sk_buff          *prev;
632 
633                         union {
634                                 ktime_t         tstamp;
635                                 struct skb_mstamp skb_mstamp;
636                         };
637                 };
638                 struct rb_node  rbnode; /* used in netem & tcp stack */
639         };
640         struct sock             *sk;
641         struct net_device       *dev;
642 
643         /*
644          * This is the control buffer. It is free to use for every
645          * layer. Please put your private variables there. If you
646          * want to keep them across layers you have to do a skb_clone()
647          * first. This is owned by whoever has the skb queued ATM.
648          */
649         char                    cb[48] __aligned(8);
650 
651         unsigned long           _skb_refdst;
652         void                    (*destructor)(struct sk_buff *skb);
653 #ifdef CONFIG_XFRM
654         struct  sec_path        *sp;
655 #endif
656 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
657         struct nf_conntrack     *nfct;
658 #endif
659 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
660         struct nf_bridge_info   *nf_bridge;
661 #endif
662         unsigned int            len,
663                                 data_len;
664         __u16                   mac_len,
665                                 hdr_len;
666 
667         /* Following fields are _not_ copied in __copy_skb_header()
668          * Note that queue_mapping is here mostly to fill a hole.
669          */
670         kmemcheck_bitfield_begin(flags1);
671         __u16                   queue_mapping;
672         __u8                    cloned:1,
673                                 nohdr:1,
674                                 fclone:2,
675                                 peeked:1,
676                                 head_frag:1,
677                                 xmit_more:1;
678         /* one bit hole */
679         kmemcheck_bitfield_end(flags1);
680 
681         /* fields enclosed in headers_start/headers_end are copied
682          * using a single memcpy() in __copy_skb_header()
683          */
684         /* private: */
685         __u32                   headers_start[0];
686         /* public: */
687 
688 /* if you move pkt_type around you also must adapt those constants */
689 #ifdef __BIG_ENDIAN_BITFIELD
690 #define PKT_TYPE_MAX    (7 << 5)
691 #else
692 #define PKT_TYPE_MAX    7
693 #endif
694 #define PKT_TYPE_OFFSET()       offsetof(struct sk_buff, __pkt_type_offset)
695 
696         __u8                    __pkt_type_offset[0];
697         __u8                    pkt_type:3;
698         __u8                    pfmemalloc:1;
699         __u8                    ignore_df:1;
700         __u8                    nfctinfo:3;
701 
702         __u8                    nf_trace:1;
703         __u8                    ip_summed:2;
704         __u8                    ooo_okay:1;
705         __u8                    l4_hash:1;
706         __u8                    sw_hash:1;
707         __u8                    wifi_acked_valid:1;
708         __u8                    wifi_acked:1;
709 
710         __u8                    no_fcs:1;
711         /* Indicates the inner headers are valid in the skbuff. */
712         __u8                    encapsulation:1;
713         __u8                    encap_hdr_csum:1;
714         __u8                    csum_valid:1;
715         __u8                    csum_complete_sw:1;
716         __u8                    csum_level:2;
717         __u8                    csum_bad:1;
718 
719 #ifdef CONFIG_IPV6_NDISC_NODETYPE
720         __u8                    ndisc_nodetype:2;
721 #endif
722         __u8                    ipvs_property:1;
723         __u8                    inner_protocol_type:1;
724         __u8                    remcsum_offload:1;
725         /* 3 or 5 bit hole */
726 
727 #ifdef CONFIG_NET_SCHED
728         __u16                   tc_index;       /* traffic control index */
729 #ifdef CONFIG_NET_CLS_ACT
730         __u16                   tc_verd;        /* traffic control verdict */
731 #endif
732 #endif
733 
734         union {
735                 __wsum          csum;
736                 struct {
737                         __u16   csum_start;
738                         __u16   csum_offset;
739                 };
740         };
741         __u32                   priority;
742         int                     skb_iif;
743         __u32                   hash;
744         __be16                  vlan_proto;
745         __u16                   vlan_tci;
746 #if defined(CONFIG_NET_RX_BUSY_POLL) || defined(CONFIG_XPS)
747         union {
748                 unsigned int    napi_id;
749                 unsigned int    sender_cpu;
750         };
751 #endif
752         union {
753 #ifdef CONFIG_NETWORK_SECMARK
754                 __u32           secmark;
755 #endif
756 #ifdef CONFIG_NET_SWITCHDEV
757                 __u32           offload_fwd_mark;
758 #endif
759         };
760 
761         union {
762                 __u32           mark;
763                 __u32           reserved_tailroom;
764         };
765 
766         union {
767                 __be16          inner_protocol;
768                 __u8            inner_ipproto;
769         };
770 
771         __u16                   inner_transport_header;
772         __u16                   inner_network_header;
773         __u16                   inner_mac_header;
774 
775         __be16                  protocol;
776         __u16                   transport_header;
777         __u16                   network_header;
778         __u16                   mac_header;
779 
780         /* private: */
781         __u32                   headers_end[0];
782         /* public: */
783 
784         /* These elements must be at the end, see alloc_skb() for details.  */
785         sk_buff_data_t          tail;
786         sk_buff_data_t          end;
787         unsigned char           *head,
788                                 *data;
789         unsigned int            truesize;
790         atomic_t                users;
791 };
792 
793 #ifdef __KERNEL__
794 /*
795  *      Handling routines are only of interest to the kernel
796  */
797 #include <linux/slab.h>
798 
799 
800 #define SKB_ALLOC_FCLONE        0x01
801 #define SKB_ALLOC_RX            0x02
802 #define SKB_ALLOC_NAPI          0x04
803 
804 /* Returns true if the skb was allocated from PFMEMALLOC reserves */
805 static inline bool skb_pfmemalloc(const struct sk_buff *skb)
806 {
807         return unlikely(skb->pfmemalloc);
808 }
809 
810 /*
811  * skb might have a dst pointer attached, refcounted or not.
812  * _skb_refdst low order bit is set if refcount was _not_ taken
813  */
814 #define SKB_DST_NOREF   1UL
815 #define SKB_DST_PTRMASK ~(SKB_DST_NOREF)
816 
817 /**
818  * skb_dst - returns skb dst_entry
819  * @skb: buffer
820  *
821  * Returns skb dst_entry, regardless of reference taken or not.
822  */
823 static inline struct dst_entry *skb_dst(const struct sk_buff *skb)
824 {
825         /* If refdst was not refcounted, check we still are in a 
826          * rcu_read_lock section
827          */
828         WARN_ON((skb->_skb_refdst & SKB_DST_NOREF) &&
829                 !rcu_read_lock_held() &&
830                 !rcu_read_lock_bh_held());
831         return (struct dst_entry *)(skb->_skb_refdst & SKB_DST_PTRMASK);
832 }
833 
834 /**
835  * skb_dst_set - sets skb dst
836  * @skb: buffer
837  * @dst: dst entry
838  *
839  * Sets skb dst, assuming a reference was taken on dst and should
840  * be released by skb_dst_drop()
841  */
842 static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst)
843 {
844         skb->_skb_refdst = (unsigned long)dst;
845 }
846 
847 /**
848  * skb_dst_set_noref - sets skb dst, hopefully, without taking reference
849  * @skb: buffer
850  * @dst: dst entry
851  *
852  * Sets skb dst, assuming a reference was not taken on dst.
853  * If dst entry is cached, we do not take reference and dst_release
854  * will be avoided by refdst_drop. If dst entry is not cached, we take
855  * reference, so that last dst_release can destroy the dst immediately.
856  */
857 static inline void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst)
858 {
859         WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
860         skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF;
861 }
862 
863 /**
864  * skb_dst_is_noref - Test if skb dst isn't refcounted
865  * @skb: buffer
866  */
867 static inline bool skb_dst_is_noref(const struct sk_buff *skb)
868 {
869         return (skb->_skb_refdst & SKB_DST_NOREF) && skb_dst(skb);
870 }
871 
872 static inline struct rtable *skb_rtable(const struct sk_buff *skb)
873 {
874         return (struct rtable *)skb_dst(skb);
875 }
876 
877 void kfree_skb(struct sk_buff *skb);
878 void kfree_skb_list(struct sk_buff *segs);
879 void skb_tx_error(struct sk_buff *skb);
880 void consume_skb(struct sk_buff *skb);
881 void  __kfree_skb(struct sk_buff *skb);
882 extern struct kmem_cache *skbuff_head_cache;
883 
884 void kfree_skb_partial(struct sk_buff *skb, bool head_stolen);
885 bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
886                       bool *fragstolen, int *delta_truesize);
887 
888 struct sk_buff *__alloc_skb(unsigned int size, gfp_t priority, int flags,
889                             int node);
890 struct sk_buff *__build_skb(void *data, unsigned int frag_size);
891 struct sk_buff *build_skb(void *data, unsigned int frag_size);
892 static inline struct sk_buff *alloc_skb(unsigned int size,
893                                         gfp_t priority)
894 {
895         return __alloc_skb(size, priority, 0, NUMA_NO_NODE);
896 }
897 
898 struct sk_buff *alloc_skb_with_frags(unsigned long header_len,
899                                      unsigned long data_len,
900                                      int max_page_order,
901                                      int *errcode,
902                                      gfp_t gfp_mask);
903 
904 /* Layout of fast clones : [skb1][skb2][fclone_ref] */
905 struct sk_buff_fclones {
906         struct sk_buff  skb1;
907 
908         struct sk_buff  skb2;
909 
910         atomic_t        fclone_ref;
911 };
912 
913 /**
914  *      skb_fclone_busy - check if fclone is busy
915  *      @skb: buffer
916  *
917  * Returns true if skb is a fast clone, and its clone is not freed.
918  * Some drivers call skb_orphan() in their ndo_start_xmit(),
919  * so we also check that this didnt happen.
920  */
921 static inline bool skb_fclone_busy(const struct sock *sk,
922                                    const struct sk_buff *skb)
923 {
924         const struct sk_buff_fclones *fclones;
925 
926         fclones = container_of(skb, struct sk_buff_fclones, skb1);
927 
928         return skb->fclone == SKB_FCLONE_ORIG &&
929                atomic_read(&fclones->fclone_ref) > 1 &&
930                fclones->skb2.sk == sk;
931 }
932 
933 static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
934                                                gfp_t priority)
935 {
936         return __alloc_skb(size, priority, SKB_ALLOC_FCLONE, NUMA_NO_NODE);
937 }
938 
939 struct sk_buff *__alloc_skb_head(gfp_t priority, int node);
940 static inline struct sk_buff *alloc_skb_head(gfp_t priority)
941 {
942         return __alloc_skb_head(priority, -1);
943 }
944 
945 struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);
946 int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask);
947 struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t priority);
948 struct sk_buff *skb_copy(const struct sk_buff *skb, gfp_t priority);
949 struct sk_buff *__pskb_copy_fclone(struct sk_buff *skb, int headroom,
950                                    gfp_t gfp_mask, bool fclone);
951 static inline struct sk_buff *__pskb_copy(struct sk_buff *skb, int headroom,
952                                           gfp_t gfp_mask)
953 {
954         return __pskb_copy_fclone(skb, headroom, gfp_mask, false);
955 }
956 
957 int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, gfp_t gfp_mask);
958 struct sk_buff *skb_realloc_headroom(struct sk_buff *skb,
959                                      unsigned int headroom);
960 struct sk_buff *skb_copy_expand(const struct sk_buff *skb, int newheadroom,
961                                 int newtailroom, gfp_t priority);
962 int skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg,
963                         int offset, int len);
964 int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset,
965                  int len);
966 int skb_cow_data(struct sk_buff *skb, int tailbits, struct sk_buff **trailer);
967 int skb_pad(struct sk_buff *skb, int pad);
968 #define dev_kfree_skb(a)        consume_skb(a)
969 
970 int skb_append_datato_frags(struct sock *sk, struct sk_buff *skb,
971                             int getfrag(void *from, char *to, int offset,
972                                         int len, int odd, struct sk_buff *skb),
973                             void *from, int length);
974 
975 int skb_append_pagefrags(struct sk_buff *skb, struct page *page,
976                          int offset, size_t size);
977 
978 struct skb_seq_state {
979         __u32           lower_offset;
980         __u32           upper_offset;
981         __u32           frag_idx;
982         __u32           stepped_offset;
983         struct sk_buff  *root_skb;
984         struct sk_buff  *cur_skb;
985         __u8            *frag_data;
986 };
987 
988 void skb_prepare_seq_read(struct sk_buff *skb, unsigned int from,
989                           unsigned int to, struct skb_seq_state *st);
990 unsigned int skb_seq_read(unsigned int consumed, const u8 **data,
991                           struct skb_seq_state *st);
992 void skb_abort_seq_read(struct skb_seq_state *st);
993 
994 unsigned int skb_find_text(struct sk_buff *skb, unsigned int from,
995                            unsigned int to, struct ts_config *config);
996 
997 /*
998  * Packet hash types specify the type of hash in skb_set_hash.
999  *
1000  * Hash types refer to the protocol layer addresses which are used to
1001  * construct a packet's hash. The hashes are used to differentiate or identify
1002  * flows of the protocol layer for the hash type. Hash types are either
1003  * layer-2 (L2), layer-3 (L3), or layer-4 (L4).
1004  *
1005  * Properties of hashes:
1006  *
1007  * 1) Two packets in different flows have different hash values
1008  * 2) Two packets in the same flow should have the same hash value
1009  *
1010  * A hash at a higher layer is considered to be more specific. A driver should
1011  * set the most specific hash possible.
1012  *
1013  * A driver cannot indicate a more specific hash than the layer at which a hash
1014  * was computed. For instance an L3 hash cannot be set as an L4 hash.
1015  *
1016  * A driver may indicate a hash level which is less specific than the
1017  * actual layer the hash was computed on. For instance, a hash computed
1018  * at L4 may be considered an L3 hash. This should only be done if the
1019  * driver can't unambiguously determine that the HW computed the hash at
1020  * the higher layer. Note that the "should" in the second property above
1021  * permits this.
1022  */
1023 enum pkt_hash_types {
1024         PKT_HASH_TYPE_NONE,     /* Undefined type */
1025         PKT_HASH_TYPE_L2,       /* Input: src_MAC, dest_MAC */
1026         PKT_HASH_TYPE_L3,       /* Input: src_IP, dst_IP */
1027         PKT_HASH_TYPE_L4,       /* Input: src_IP, dst_IP, src_port, dst_port */
1028 };
1029 
1030 static inline void skb_clear_hash(struct sk_buff *skb)
1031 {
1032         skb->hash = 0;
1033         skb->sw_hash = 0;
1034         skb->l4_hash = 0;
1035 }
1036 
1037 static inline void skb_clear_hash_if_not_l4(struct sk_buff *skb)
1038 {
1039         if (!skb->l4_hash)
1040                 skb_clear_hash(skb);
1041 }
1042 
1043 static inline void
1044 __skb_set_hash(struct sk_buff *skb, __u32 hash, bool is_sw, bool is_l4)
1045 {
1046         skb->l4_hash = is_l4;
1047         skb->sw_hash = is_sw;
1048         skb->hash = hash;
1049 }
1050 
1051 static inline void
1052 skb_set_hash(struct sk_buff *skb, __u32 hash, enum pkt_hash_types type)
1053 {
1054         /* Used by drivers to set hash from HW */
1055         __skb_set_hash(skb, hash, false, type == PKT_HASH_TYPE_L4);
1056 }
1057 
1058 static inline void
1059 __skb_set_sw_hash(struct sk_buff *skb, __u32 hash, bool is_l4)
1060 {
1061         __skb_set_hash(skb, hash, true, is_l4);
1062 }
1063 
1064 void __skb_get_hash(struct sk_buff *skb);
1065 u32 __skb_get_hash_symmetric(struct sk_buff *skb);
1066 u32 skb_get_poff(const struct sk_buff *skb);
1067 u32 __skb_get_poff(const struct sk_buff *skb, void *data,
1068                    const struct flow_keys *keys, int hlen);
1069 __be32 __skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto,
1070                             void *data, int hlen_proto);
1071 
1072 static inline __be32 skb_flow_get_ports(const struct sk_buff *skb,
1073                                         int thoff, u8 ip_proto)
1074 {
1075         return __skb_flow_get_ports(skb, thoff, ip_proto, NULL, 0);
1076 }
1077 
1078 void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
1079                              const struct flow_dissector_key *key,
1080                              unsigned int key_count);
1081 
1082 bool __skb_flow_dissect(const struct sk_buff *skb,
1083                         struct flow_dissector *flow_dissector,
1084                         void *target_container,
1085                         void *data, __be16 proto, int nhoff, int hlen,
1086                         unsigned int flags);
1087 
1088 static inline bool skb_flow_dissect(const struct sk_buff *skb,
1089                                     struct flow_dissector *flow_dissector,
1090                                     void *target_container, unsigned int flags)
1091 {
1092         return __skb_flow_dissect(skb, flow_dissector, target_container,
1093                                   NULL, 0, 0, 0, flags);
1094 }
1095 
1096 static inline bool skb_flow_dissect_flow_keys(const struct sk_buff *skb,
1097                                               struct flow_keys *flow,
1098                                               unsigned int flags)
1099 {
1100         memset(flow, 0, sizeof(*flow));
1101         return __skb_flow_dissect(skb, &flow_keys_dissector, flow,
1102                                   NULL, 0, 0, 0, flags);
1103 }
1104 
1105 static inline bool skb_flow_dissect_flow_keys_buf(struct flow_keys *flow,
1106                                                   void *data, __be16 proto,
1107                                                   int nhoff, int hlen,
1108                                                   unsigned int flags)
1109 {
1110         memset(flow, 0, sizeof(*flow));
1111         return __skb_flow_dissect(NULL, &flow_keys_buf_dissector, flow,
1112                                   data, proto, nhoff, hlen, flags);
1113 }
1114 
1115 static inline __u32 skb_get_hash(struct sk_buff *skb)
1116 {
1117         if (!skb->l4_hash && !skb->sw_hash)
1118                 __skb_get_hash(skb);
1119 
1120         return skb->hash;
1121 }
1122 
1123 __u32 __skb_get_hash_flowi6(struct sk_buff *skb, const struct flowi6 *fl6);
1124 
1125 static inline __u32 skb_get_hash_flowi6(struct sk_buff *skb, const struct flowi6 *fl6)
1126 {
1127         if (!skb->l4_hash && !skb->sw_hash) {
1128                 struct flow_keys keys;
1129                 __u32 hash = __get_hash_from_flowi6(fl6, &keys);
1130 
1131                 __skb_set_sw_hash(skb, hash, flow_keys_have_l4(&keys));
1132         }
1133 
1134         return skb->hash;
1135 }
1136 
1137 __u32 __skb_get_hash_flowi4(struct sk_buff *skb, const struct flowi4 *fl);
1138 
1139 static inline __u32 skb_get_hash_flowi4(struct sk_buff *skb, const struct flowi4 *fl4)
1140 {
1141         if (!skb->l4_hash && !skb->sw_hash) {
1142                 struct flow_keys keys;
1143                 __u32 hash = __get_hash_from_flowi4(fl4, &keys);
1144 
1145                 __skb_set_sw_hash(skb, hash, flow_keys_have_l4(&keys));
1146         }
1147 
1148         return skb->hash;
1149 }
1150 
1151 __u32 skb_get_hash_perturb(const struct sk_buff *skb, u32 perturb);
1152 
1153 static inline __u32 skb_get_hash_raw(const struct sk_buff *skb)
1154 {
1155         return skb->hash;
1156 }
1157 
1158 static inline void skb_copy_hash(struct sk_buff *to, const struct sk_buff *from)
1159 {
1160         to->hash = from->hash;
1161         to->sw_hash = from->sw_hash;
1162         to->l4_hash = from->l4_hash;
1163 };
1164 
1165 #ifdef NET_SKBUFF_DATA_USES_OFFSET
1166 static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
1167 {
1168         return skb->head + skb->end;
1169 }
1170 
1171 static inline unsigned int skb_end_offset(const struct sk_buff *skb)
1172 {
1173         return skb->end;
1174 }
1175 #else
1176 static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
1177 {
1178         return skb->end;
1179 }
1180 
1181 static inline unsigned int skb_end_offset(const struct sk_buff *skb)
1182 {
1183         return skb->end - skb->head;
1184 }
1185 #endif
1186 
1187 /* Internal */
1188 #define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB)))
1189 
1190 static inline struct skb_shared_hwtstamps *skb_hwtstamps(struct sk_buff *skb)
1191 {
1192         return &skb_shinfo(skb)->hwtstamps;
1193 }
1194 
1195 /**
1196  *      skb_queue_empty - check if a queue is empty
1197  *      @list: queue head
1198  *
1199  *      Returns true if the queue is empty, false otherwise.
1200  */
1201 static inline int skb_queue_empty(const struct sk_buff_head *list)
1202 {
1203         return list->next == (const struct sk_buff *) list;
1204 }
1205 
1206 /**
1207  *      skb_queue_is_last - check if skb is the last entry in the queue
1208  *      @list: queue head
1209  *      @skb: buffer
1210  *
1211  *      Returns true if @skb is the last buffer on the list.
1212  */
1213 static inline bool skb_queue_is_last(const struct sk_buff_head *list,
1214                                      const struct sk_buff *skb)
1215 {
1216         return skb->next == (const struct sk_buff *) list;
1217 }
1218 
1219 /**
1220  *      skb_queue_is_first - check if skb is the first entry in the queue
1221  *      @list: queue head
1222  *      @skb: buffer
1223  *
1224  *      Returns true if @skb is the first buffer on the list.
1225  */
1226 static inline bool skb_queue_is_first(const struct sk_buff_head *list,
1227                                       const struct sk_buff *skb)
1228 {
1229         return skb->prev == (const struct sk_buff *) list;
1230 }
1231 
1232 /**
1233  *      skb_queue_next - return the next packet in the queue
1234  *      @list: queue head
1235  *      @skb: current buffer
1236  *
1237  *      Return the next packet in @list after @skb.  It is only valid to
1238  *      call this if skb_queue_is_last() evaluates to false.
1239  */
1240 static inline struct sk_buff *skb_queue_next(const struct sk_buff_head *list,
1241                                              const struct sk_buff *skb)
1242 {
1243         /* This BUG_ON may seem severe, but if we just return then we
1244          * are going to dereference garbage.
1245          */
1246         BUG_ON(skb_queue_is_last(list, skb));
1247         return skb->next;
1248 }
1249 
1250 /**
1251  *      skb_queue_prev - return the prev packet in the queue
1252  *      @list: queue head
1253  *      @skb: current buffer
1254  *
1255  *      Return the prev packet in @list before @skb.  It is only valid to
1256  *      call this if skb_queue_is_first() evaluates to false.
1257  */
1258 static inline struct sk_buff *skb_queue_prev(const struct sk_buff_head *list,
1259                                              const struct sk_buff *skb)
1260 {
1261         /* This BUG_ON may seem severe, but if we just return then we
1262          * are going to dereference garbage.
1263          */
1264         BUG_ON(skb_queue_is_first(list, skb));
1265         return skb->prev;
1266 }
1267 
1268 /**
1269  *      skb_get - reference buffer
1270  *      @skb: buffer to reference
1271  *
1272  *      Makes another reference to a socket buffer and returns a pointer
1273  *      to the buffer.
1274  */
1275 static inline struct sk_buff *skb_get(struct sk_buff *skb)
1276 {
1277         atomic_inc(&skb->users);
1278         return skb;
1279 }
1280 
1281 /*
1282  * If users == 1, we are the only owner and are can avoid redundant
1283  * atomic change.
1284  */
1285 
1286 /**
1287  *      skb_cloned - is the buffer a clone
1288  *      @skb: buffer to check
1289  *
1290  *      Returns true if the buffer was generated with skb_clone() and is
1291  *      one of multiple shared copies of the buffer. Cloned buffers are
1292  *      shared data so must not be written to under normal circumstances.
1293  */
1294 static inline int skb_cloned(const struct sk_buff *skb)
1295 {
1296         return skb->cloned &&
1297                (atomic_read(&skb_shinfo(skb)->dataref) & SKB_DATAREF_MASK) != 1;
1298 }
1299 
1300 static inline int skb_unclone(struct sk_buff *skb, gfp_t pri)
1301 {
1302         might_sleep_if(gfpflags_allow_blocking(pri));
1303 
1304         if (skb_cloned(skb))
1305                 return pskb_expand_head(skb, 0, 0, pri);
1306 
1307         return 0;
1308 }
1309 
1310 /**
1311  *      skb_header_cloned - is the header a clone
1312  *      @skb: buffer to check
1313  *
1314  *      Returns true if modifying the header part of the buffer requires
1315  *      the data to be copied.
1316  */
1317 static inline int skb_header_cloned(const struct sk_buff *skb)
1318 {
1319         int dataref;
1320 
1321         if (!skb->cloned)
1322                 return 0;
1323 
1324         dataref = atomic_read(&skb_shinfo(skb)->dataref);
1325         dataref = (dataref & SKB_DATAREF_MASK) - (dataref >> SKB_DATAREF_SHIFT);
1326         return dataref != 1;
1327 }
1328 
1329 static inline int skb_header_unclone(struct sk_buff *skb, gfp_t pri)
1330 {
1331         might_sleep_if(gfpflags_allow_blocking(pri));
1332 
1333         if (skb_header_cloned(skb))
1334                 return pskb_expand_head(skb, 0, 0, pri);
1335 
1336         return 0;
1337 }
1338 
1339 /**
1340  *      skb_header_release - release reference to header
1341  *      @skb: buffer to operate on
1342  *
1343  *      Drop a reference to the header part of the buffer.  This is done
1344  *      by acquiring a payload reference.  You must not read from the header
1345  *      part of skb->data after this.
1346  *      Note : Check if you can use __skb_header_release() instead.
1347  */
1348 static inline void skb_header_release(struct sk_buff *skb)
1349 {
1350         BUG_ON(skb->nohdr);
1351         skb->nohdr = 1;
1352         atomic_add(1 << SKB_DATAREF_SHIFT, &skb_shinfo(skb)->dataref);
1353 }
1354 
1355 /**
1356  *      __skb_header_release - release reference to header
1357  *      @skb: buffer to operate on
1358  *
1359  *      Variant of skb_header_release() assuming skb is private to caller.
1360  *      We can avoid one atomic operation.
1361  */
1362 static inline void __skb_header_release(struct sk_buff *skb)
1363 {
1364         skb->nohdr = 1;
1365         atomic_set(&skb_shinfo(skb)->dataref, 1 + (1 << SKB_DATAREF_SHIFT));
1366 }
1367 
1368 
1369 /**
1370  *      skb_shared - is the buffer shared
1371  *      @skb: buffer to check
1372  *
1373  *      Returns true if more than one person has a reference to this
1374  *      buffer.
1375  */
1376 static inline int skb_shared(const struct sk_buff *skb)
1377 {
1378         return atomic_read(&skb->users) != 1;
1379 }
1380 
1381 /**
1382  *      skb_share_check - check if buffer is shared and if so clone it
1383  *      @skb: buffer to check
1384  *      @pri: priority for memory allocation
1385  *
1386  *      If the buffer is shared the buffer is cloned and the old copy
1387  *      drops a reference. A new clone with a single reference is returned.
1388  *      If the buffer is not shared the original buffer is returned. When
1389  *      being called from interrupt status or with spinlocks held pri must
1390  *      be GFP_ATOMIC.
1391  *
1392  *      NULL is returned on a memory allocation failure.
1393  */
1394 static inline struct sk_buff *skb_share_check(struct sk_buff *skb, gfp_t pri)
1395 {
1396         might_sleep_if(gfpflags_allow_blocking(pri));
1397         if (skb_shared(skb)) {
1398                 struct sk_buff *nskb = skb_clone(skb, pri);
1399 
1400                 if (likely(nskb))
1401                         consume_skb(skb);
1402                 else
1403                         kfree_skb(skb);
1404                 skb = nskb;
1405         }
1406         return skb;
1407 }
1408 
1409 /*
1410  *      Copy shared buffers into a new sk_buff. We effectively do COW on
1411  *      packets to handle cases where we have a local reader and forward
1412  *      and a couple of other messy ones. The normal one is tcpdumping
1413  *      a packet thats being forwarded.
1414  */
1415 
1416 /**
1417  *      skb_unshare - make a copy of a shared buffer
1418  *      @skb: buffer to check
1419  *      @pri: priority for memory allocation
1420  *
1421  *      If the socket buffer is a clone then this function creates a new
1422  *      copy of the data, drops a reference count on the old copy and returns
1423  *      the new copy with the reference count at 1. If the buffer is not a clone
1424  *      the original buffer is returned. When called with a spinlock held or
1425  *      from interrupt state @pri must be %GFP_ATOMIC
1426  *
1427  *      %NULL is returned on a memory allocation failure.
1428  */
1429 static inline struct sk_buff *skb_unshare(struct sk_buff *skb,
1430                                           gfp_t pri)
1431 {
1432         might_sleep_if(gfpflags_allow_blocking(pri));
1433         if (skb_cloned(skb)) {
1434                 struct sk_buff *nskb = skb_copy(skb, pri);
1435 
1436                 /* Free our shared copy */
1437                 if (likely(nskb))
1438                         consume_skb(skb);
1439                 else
1440                         kfree_skb(skb);
1441                 skb = nskb;
1442         }
1443         return skb;
1444 }
1445 
1446 /**
1447  *      skb_peek - peek at the head of an &sk_buff_head
1448  *      @list_: list to peek at
1449  *
1450  *      Peek an &sk_buff. Unlike most other operations you _MUST_
1451  *      be careful with this one. A peek leaves the buffer on the
1452  *      list and someone else may run off with it. You must hold
1453  *      the appropriate locks or have a private queue to do this.
1454  *
1455  *      Returns %NULL for an empty list or a pointer to the head element.
1456  *      The reference count is not incremented and the reference is therefore
1457  *      volatile. Use with caution.
1458  */
1459 static inline struct sk_buff *skb_peek(const struct sk_buff_head *list_)
1460 {
1461         struct sk_buff *skb = list_->next;
1462 
1463         if (skb == (struct sk_buff *)list_)
1464                 skb = NULL;
1465         return skb;
1466 }
1467 
1468 /**
1469  *      skb_peek_next - peek skb following the given one from a queue
1470  *      @skb: skb to start from
1471  *      @list_: list to peek at
1472  *
1473  *      Returns %NULL when the end of the list is met or a pointer to the
1474  *      next element. The reference count is not incremented and the
1475  *      reference is therefore volatile. Use with caution.
1476  */
1477 static inline struct sk_buff *skb_peek_next(struct sk_buff *skb,
1478                 const struct sk_buff_head *list_)
1479 {
1480         struct sk_buff *next = skb->next;
1481 
1482         if (next == (struct sk_buff *)list_)
1483                 next = NULL;
1484         return next;
1485 }
1486 
1487 /**
1488  *      skb_peek_tail - peek at the tail of an &sk_buff_head
1489  *      @list_: list to peek at
1490  *
1491  *      Peek an &sk_buff. Unlike most other operations you _MUST_
1492  *      be careful with this one. A peek leaves the buffer on the
1493  *      list and someone else may run off with it. You must hold
1494  *      the appropriate locks or have a private queue to do this.
1495  *
1496  *      Returns %NULL for an empty list or a pointer to the tail element.
1497  *      The reference count is not incremented and the reference is therefore
1498  *      volatile. Use with caution.
1499  */
1500 static inline struct sk_buff *skb_peek_tail(const struct sk_buff_head *list_)
1501 {
1502         struct sk_buff *skb = list_->prev;
1503 
1504         if (skb == (struct sk_buff *)list_)
1505                 skb = NULL;
1506         return skb;
1507 
1508 }
1509 
1510 /**
1511  *      skb_queue_len   - get queue length
1512  *      @list_: list to measure
1513  *
1514  *      Return the length of an &sk_buff queue.
1515  */
1516 static inline __u32 skb_queue_len(const struct sk_buff_head *list_)
1517 {
1518         return list_->qlen;
1519 }
1520 
1521 /**
1522  *      __skb_queue_head_init - initialize non-spinlock portions of sk_buff_head
1523  *      @list: queue to initialize
1524  *
1525  *      This initializes only the list and queue length aspects of
1526  *      an sk_buff_head object.  This allows to initialize the list
1527  *      aspects of an sk_buff_head without reinitializing things like
1528  *      the spinlock.  It can also be used for on-stack sk_buff_head
1529  *      objects where the spinlock is known to not be used.
1530  */
1531 static inline void __skb_queue_head_init(struct sk_buff_head *list)
1532 {
1533         list->prev = list->next = (struct sk_buff *)list;
1534         list->qlen = 0;
1535 }
1536 
1537 /*
1538  * This function creates a split out lock class for each invocation;
1539  * this is needed for now since a whole lot of users of the skb-queue
1540  * infrastructure in drivers have different locking usage (in hardirq)
1541  * than the networking core (in softirq only). In the long run either the
1542  * network layer or drivers should need annotation to consolidate the
1543  * main types of usage into 3 classes.
1544  */
1545 static inline void skb_queue_head_init(struct sk_buff_head *list)
1546 {
1547         spin_lock_init(&list->lock);
1548         __skb_queue_head_init(list);
1549 }
1550 
1551 static inline void skb_queue_head_init_class(struct sk_buff_head *list,
1552                 struct lock_class_key *class)
1553 {
1554         skb_queue_head_init(list);
1555         lockdep_set_class(&list->lock, class);
1556 }
1557 
1558 /*
1559  *      Insert an sk_buff on a list.
1560  *
1561  *      The "__skb_xxxx()" functions are the non-atomic ones that
1562  *      can only be called with interrupts disabled.
1563  */
1564 void skb_insert(struct sk_buff *old, struct sk_buff *newsk,
1565                 struct sk_buff_head *list);
1566 static inline void __skb_insert(struct sk_buff *newsk,
1567                                 struct sk_buff *prev, struct sk_buff *next,
1568                                 struct sk_buff_head *list)
1569 {
1570         newsk->next = next;
1571         newsk->prev = prev;
1572         next->prev  = prev->next = newsk;
1573         list->qlen++;
1574 }
1575 
1576 static inline void __skb_queue_splice(const struct sk_buff_head *list,
1577                                       struct sk_buff *prev,
1578                                       struct sk_buff *next)
1579 {
1580         struct sk_buff *first = list->next;
1581         struct sk_buff *last = list->prev;
1582 
1583         first->prev = prev;
1584         prev->next = first;
1585 
1586         last->next = next;
1587         next->prev = last;
1588 }
1589 
1590 /**
1591  *      skb_queue_splice - join two skb lists, this is designed for stacks
1592  *      @list: the new list to add
1593  *      @head: the place to add it in the first list
1594  */
1595 static inline void skb_queue_splice(const struct sk_buff_head *list,
1596                                     struct sk_buff_head *head)
1597 {
1598         if (!skb_queue_empty(list)) {
1599                 __skb_queue_splice(list, (struct sk_buff *) head, head->next);
1600                 head->qlen += list->qlen;
1601         }
1602 }
1603 
1604 /**
1605  *      skb_queue_splice_init - join two skb lists and reinitialise the emptied list
1606  *      @list: the new list to add
1607  *      @head: the place to add it in the first list
1608  *
1609  *      The list at @list is reinitialised
1610  */
1611 static inline void skb_queue_splice_init(struct sk_buff_head *list,
1612                                          struct sk_buff_head *head)
1613 {
1614         if (!skb_queue_empty(list)) {
1615                 __skb_queue_splice(list, (struct sk_buff *) head, head->next);
1616                 head->qlen += list->qlen;
1617                 __skb_queue_head_init(list);
1618         }
1619 }
1620 
1621 /**
1622  *      skb_queue_splice_tail - join two skb lists, each list being a queue
1623  *      @list: the new list to add
1624  *      @head: the place to add it in the first list
1625  */
1626 static inline void skb_queue_splice_tail(const struct sk_buff_head *list,
1627                                          struct sk_buff_head *head)
1628 {
1629         if (!skb_queue_empty(list)) {
1630                 __skb_queue_splice(list, head->prev, (struct sk_buff *) head);
1631                 head->qlen += list->qlen;
1632         }
1633 }
1634 
1635 /**
1636  *      skb_queue_splice_tail_init - join two skb lists and reinitialise the emptied list
1637  *      @list: the new list to add
1638  *      @head: the place to add it in the first list
1639  *
1640  *      Each of the lists is a queue.
1641  *      The list at @list is reinitialised
1642  */
1643 static inline void skb_queue_splice_tail_init(struct sk_buff_head *list,
1644                                               struct sk_buff_head *head)
1645 {
1646         if (!skb_queue_empty(list)) {
1647                 __skb_queue_splice(list, head->prev, (struct sk_buff *) head);
1648                 head->qlen += list->qlen;
1649                 __skb_queue_head_init(list);
1650         }
1651 }
1652 
1653 /**
1654  *      __skb_queue_after - queue a buffer at the list head
1655  *      @list: list to use
1656  *      @prev: place after this buffer
1657  *      @newsk: buffer to queue
1658  *
1659  *      Queue a buffer int the middle of a list. This function takes no locks
1660  *      and you must therefore hold required locks before calling it.
1661  *
1662  *      A buffer cannot be placed on two lists at the same time.
1663  */
1664 static inline void __skb_queue_after(struct sk_buff_head *list,
1665                                      struct sk_buff *prev,
1666                                      struct sk_buff *newsk)
1667 {
1668         __skb_insert(newsk, prev, prev->next, list);
1669 }
1670 
1671 void skb_append(struct sk_buff *old, struct sk_buff *newsk,
1672                 struct sk_buff_head *list);
1673 
1674 static inline void __skb_queue_before(struct sk_buff_head *list,
1675                                       struct sk_buff *next,
1676                                       struct sk_buff *newsk)
1677 {
1678         __skb_insert(newsk, next->prev, next, list);
1679 }
1680 
1681 /**
1682  *      __skb_queue_head - queue a buffer at the list head
1683  *      @list: list to use
1684  *      @newsk: buffer to queue
1685  *
1686  *      Queue a buffer at the start of a list. This function takes no locks
1687  *      and you must therefore hold required locks before calling it.
1688  *
1689  *      A buffer cannot be placed on two lists at the same time.
1690  */
1691 void skb_queue_head(struct sk_buff_head *list, struct sk_buff *newsk);
1692 static inline void __skb_queue_head(struct sk_buff_head *list,
1693                                     struct sk_buff *newsk)
1694 {
1695         __skb_queue_after(list, (struct sk_buff *)list, newsk);
1696 }
1697 
1698 /**
1699  *      __skb_queue_tail - queue a buffer at the list tail
1700  *      @list: list to use
1701  *      @newsk: buffer to queue
1702  *
1703  *      Queue a buffer at the end of a list. This function takes no locks
1704  *      and you must therefore hold required locks before calling it.
1705  *
1706  *      A buffer cannot be placed on two lists at the same time.
1707  */
1708 void skb_queue_tail(struct sk_buff_head *list, struct sk_buff *newsk);
1709 static inline void __skb_queue_tail(struct sk_buff_head *list,
1710                                    struct sk_buff *newsk)
1711 {
1712         __skb_queue_before(list, (struct sk_buff *)list, newsk);
1713 }
1714 
1715 /*
1716  * remove sk_buff from list. _Must_ be called atomically, and with
1717  * the list known..
1718  */
1719 void skb_unlink(struct sk_buff *skb, struct sk_buff_head *list);
1720 static inline void __skb_unlink(struct sk_buff *skb, struct sk_buff_head *list)
1721 {
1722         struct sk_buff *next, *prev;
1723 
1724         list->qlen--;
1725         next       = skb->next;
1726         prev       = skb->prev;
1727         skb->next  = skb->prev = NULL;
1728         next->prev = prev;
1729         prev->next = next;
1730 }
1731 
1732 /**
1733  *      __skb_dequeue - remove from the head of the queue
1734  *      @list: list to dequeue from
1735  *
1736  *      Remove the head of the list. This function does not take any locks
1737  *      so must be used with appropriate locks held only. The head item is
1738  *      returned or %NULL if the list is empty.
1739  */
1740 struct sk_buff *skb_dequeue(struct sk_buff_head *list);
1741 static inline struct sk_buff *__skb_dequeue(struct sk_buff_head *list)
1742 {
1743         struct sk_buff *skb = skb_peek(list);
1744         if (skb)
1745                 __skb_unlink(skb, list);
1746         return skb;
1747 }
1748 
1749 /**
1750  *      __skb_dequeue_tail - remove from the tail of the queue
1751  *      @list: list to dequeue from
1752  *
1753  *      Remove the tail of the list. This function does not take any locks
1754  *      so must be used with appropriate locks held only. The tail item is
1755  *      returned or %NULL if the list is empty.
1756  */
1757 struct sk_buff *skb_dequeue_tail(struct sk_buff_head *list);
1758 static inline struct sk_buff *__skb_dequeue_tail(struct sk_buff_head *list)
1759 {
1760         struct sk_buff *skb = skb_peek_tail(list);
1761         if (skb)
1762                 __skb_unlink(skb, list);
1763         return skb;
1764 }
1765 
1766 
1767 static inline bool skb_is_nonlinear(const struct sk_buff *skb)
1768 {
1769         return skb->data_len;
1770 }
1771 
1772 static inline unsigned int skb_headlen(const struct sk_buff *skb)
1773 {
1774         return skb->len - skb->data_len;
1775 }
1776 
1777 static inline int skb_pagelen(const struct sk_buff *skb)
1778 {
1779         int i, len = 0;
1780 
1781         for (i = (int)skb_shinfo(skb)->nr_frags - 1; i >= 0; i--)
1782                 len += skb_frag_size(&skb_shinfo(skb)->frags[i]);
1783         return len + skb_headlen(skb);
1784 }
1785 
1786 /**
1787  * __skb_fill_page_desc - initialise a paged fragment in an skb
1788  * @skb: buffer containing fragment to be initialised
1789  * @i: paged fragment index to initialise
1790  * @page: the page to use for this fragment
1791  * @off: the offset to the data with @page
1792  * @size: the length of the data
1793  *
1794  * Initialises the @i'th fragment of @skb to point to &size bytes at
1795  * offset @off within @page.
1796  *
1797  * Does not take any additional reference on the fragment.
1798  */
1799 static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
1800                                         struct page *page, int off, int size)
1801 {
1802         skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
1803 
1804         /*
1805          * Propagate page pfmemalloc to the skb if we can. The problem is
1806          * that not all callers have unique ownership of the page but rely
1807          * on page_is_pfmemalloc doing the right thing(tm).
1808          */
1809         frag->page.p              = page;
1810         frag->page_offset         = off;
1811         skb_frag_size_set(frag, size);
1812 
1813         page = compound_head(page);
1814         if (page_is_pfmemalloc(page))
1815                 skb->pfmemalloc = true;
1816 }
1817 
1818 /**
1819  * skb_fill_page_desc - initialise a paged fragment in an skb
1820  * @skb: buffer containing fragment to be initialised
1821  * @i: paged fragment index to initialise
1822  * @page: the page to use for this fragment
1823  * @off: the offset to the data with @page
1824  * @size: the length of the data
1825  *
1826  * As per __skb_fill_page_desc() -- initialises the @i'th fragment of
1827  * @skb to point to @size bytes at offset @off within @page. In
1828  * addition updates @skb such that @i is the last fragment.
1829  *
1830  * Does not take any additional reference on the fragment.
1831  */
1832 static inline void skb_fill_page_desc(struct sk_buff *skb, int i,
1833                                       struct page *page, int off, int size)
1834 {
1835         __skb_fill_page_desc(skb, i, page, off, size);
1836         skb_shinfo(skb)->nr_frags = i + 1;
1837 }
1838 
1839 void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
1840                      int size, unsigned int truesize);
1841 
1842 void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int size,
1843                           unsigned int truesize);
1844 
1845 #define SKB_PAGE_ASSERT(skb)    BUG_ON(skb_shinfo(skb)->nr_frags)
1846 #define SKB_FRAG_ASSERT(skb)    BUG_ON(skb_has_frag_list(skb))
1847 #define SKB_LINEAR_ASSERT(skb)  BUG_ON(skb_is_nonlinear(skb))
1848 
1849 #ifdef NET_SKBUFF_DATA_USES_OFFSET
1850 static inline unsigned char *skb_tail_pointer(const struct sk_buff *skb)
1851 {
1852         return skb->head + skb->tail;
1853 }
1854 
1855 static inline void skb_reset_tail_pointer(struct sk_buff *skb)
1856 {
1857         skb->tail = skb->data - skb->head;
1858 }
1859 
1860 static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)
1861 {
1862         skb_reset_tail_pointer(skb);
1863         skb->tail += offset;
1864 }
1865 
1866 #else /* NET_SKBUFF_DATA_USES_OFFSET */
1867 static inline unsigned char *skb_tail_pointer(const struct sk_buff *skb)
1868 {
1869         return skb->tail;
1870 }
1871 
1872 static inline void skb_reset_tail_pointer(struct sk_buff *skb)
1873 {
1874         skb->tail = skb->data;
1875 }
1876 
1877 static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)
1878 {
1879         skb->tail = skb->data + offset;
1880 }
1881 
1882 #endif /* NET_SKBUFF_DATA_USES_OFFSET */
1883 
1884 /*
1885  *      Add data to an sk_buff
1886  */
1887 unsigned char *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len);
1888 unsigned char *skb_put(struct sk_buff *skb, unsigned int len);
1889 static inline unsigned char *__skb_put(struct sk_buff *skb, unsigned int len)
1890 {
1891         unsigned char *tmp = skb_tail_pointer(skb);
1892         SKB_LINEAR_ASSERT(skb);
1893         skb->tail += len;
1894         skb->len  += len;
1895         return tmp;
1896 }
1897 
1898 unsigned char *skb_push(struct sk_buff *skb, unsigned int len);
1899 static inline unsigned char *__skb_push(struct sk_buff *skb, unsigned int len)
1900 {
1901         skb->data -= len;
1902         skb->len  += len;
1903         return skb->data;
1904 }
1905 
1906 unsigned char *skb_pull(struct sk_buff *skb, unsigned int len);
1907 static inline unsigned char *__skb_pull(struct sk_buff *skb, unsigned int len)
1908 {
1909         skb->len -= len;
1910         BUG_ON(skb->len < skb->data_len);
1911         return skb->data += len;
1912 }
1913 
1914 static inline unsigned char *skb_pull_inline(struct sk_buff *skb, unsigned int len)
1915 {
1916         return unlikely(len > skb->len) ? NULL : __skb_pull(skb, len);
1917 }
1918 
1919 unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta);
1920 
1921 static inline unsigned char *__pskb_pull(struct sk_buff *skb, unsigned int len)
1922 {
1923         if (len > skb_headlen(skb) &&
1924             !__pskb_pull_tail(skb, len - skb_headlen(skb)))
1925                 return NULL;
1926         skb->len -= len;
1927         return skb->data += len;
1928 }
1929 
1930 static inline unsigned char *pskb_pull(struct sk_buff *skb, unsigned int len)
1931 {
1932         return unlikely(len > skb->len) ? NULL : __pskb_pull(skb, len);
1933 }
1934 
1935 static inline int pskb_may_pull(struct sk_buff *skb, unsigned int len)
1936 {
1937         if (likely(len <= skb_headlen(skb)))
1938                 return 1;
1939         if (unlikely(len > skb->len))
1940                 return 0;
1941         return __pskb_pull_tail(skb, len - skb_headlen(skb)) != NULL;
1942 }
1943 
1944 /**
1945  *      skb_headroom - bytes at buffer head
1946  *      @skb: buffer to check
1947  *
1948  *      Return the number of bytes of free space at the head of an &sk_buff.
1949  */
1950 static inline unsigned int skb_headroom(const struct sk_buff *skb)
1951 {
1952         return skb->data - skb->head;
1953 }
1954 
1955 /**
1956  *      skb_tailroom - bytes at buffer end
1957  *      @skb: buffer to check
1958  *
1959  *      Return the number of bytes of free space at the tail of an sk_buff
1960  */
1961 static inline int skb_tailroom(const struct sk_buff *skb)
1962 {
1963         return skb_is_nonlinear(skb) ? 0 : skb->end - skb->tail;
1964 }
1965 
1966 /**
1967  *      skb_availroom - bytes at buffer end
1968  *      @skb: buffer to check
1969  *
1970  *      Return the number of bytes of free space at the tail of an sk_buff
1971  *      allocated by sk_stream_alloc()
1972  */
1973 static inline int skb_availroom(const struct sk_buff *skb)
1974 {
1975         if (skb_is_nonlinear(skb))
1976                 return 0;
1977 
1978         return skb->end - skb->tail - skb->reserved_tailroom;
1979 }
1980 
1981 /**
1982  *      skb_reserve - adjust headroom
1983  *      @skb: buffer to alter
1984  *      @len: bytes to move
1985  *
1986  *      Increase the headroom of an empty &sk_buff by reducing the tail
1987  *      room. This is only allowed for an empty buffer.
1988  */
1989 static inline void skb_reserve(struct sk_buff *skb, int len)
1990 {
1991         skb->data += len;
1992         skb->tail += len;
1993 }
1994 
1995 /**
1996  *      skb_tailroom_reserve - adjust reserved_tailroom
1997  *      @skb: buffer to alter
1998  *      @mtu: maximum amount of headlen permitted
1999  *      @needed_tailroom: minimum amount of reserved_tailroom
2000  *
2001  *      Set reserved_tailroom so that headlen can be as large as possible but
2002  *      not larger than mtu and tailroom cannot be smaller than
2003  *      needed_tailroom.
2004  *      The required headroom should already have been reserved before using
2005  *      this function.
2006  */
2007 static inline void skb_tailroom_reserve(struct sk_buff *skb, unsigned int mtu,
2008                                         unsigned int needed_tailroom)
2009 {
2010         SKB_LINEAR_ASSERT(skb);
2011         if (mtu < skb_tailroom(skb) - needed_tailroom)
2012                 /* use at most mtu */
2013                 skb->reserved_tailroom = skb_tailroom(skb) - mtu;
2014         else
2015                 /* use up to all available space */
2016                 skb->reserved_tailroom = needed_tailroom;
2017 }
2018 
2019 #define ENCAP_TYPE_ETHER        0
2020 #define ENCAP_TYPE_IPPROTO      1
2021 
2022 static inline void skb_set_inner_protocol(struct sk_buff *skb,
2023                                           __be16 protocol)
2024 {
2025         skb->inner_protocol = protocol;
2026         skb->inner_protocol_type = ENCAP_TYPE_ETHER;
2027 }
2028 
2029 static inline void skb_set_inner_ipproto(struct sk_buff *skb,
2030                                          __u8 ipproto)
2031 {
2032         skb->inner_ipproto = ipproto;
2033         skb->inner_protocol_type = ENCAP_TYPE_IPPROTO;
2034 }
2035 
2036 static inline void skb_reset_inner_headers(struct sk_buff *skb)
2037 {
2038         skb->inner_mac_header = skb->mac_header;
2039         skb->inner_network_header = skb->network_header;
2040         skb->inner_transport_header = skb->transport_header;
2041 }
2042 
2043 static inline void skb_reset_mac_len(struct sk_buff *skb)
2044 {
2045         skb->mac_len = skb->network_header - skb->mac_header;
2046 }
2047 
2048 static inline unsigned char *skb_inner_transport_header(const struct sk_buff
2049                                                         *skb)
2050 {
2051         return skb->head + skb->inner_transport_header;
2052 }
2053 
2054 static inline int skb_inner_transport_offset(const struct sk_buff *skb)
2055 {
2056         return skb_inner_transport_header(skb) - skb->data;
2057 }
2058 
2059 static inline void skb_reset_inner_transport_header(struct sk_buff *skb)
2060 {
2061         skb->inner_transport_header = skb->data - skb->head;
2062 }
2063 
2064 static inline void skb_set_inner_transport_header(struct sk_buff *skb,
2065                                                    const int offset)
2066 {
2067         skb_reset_inner_transport_header(skb);
2068         skb->inner_transport_header += offset;
2069 }
2070 
2071 static inline unsigned char *skb_inner_network_header(const struct sk_buff *skb)
2072 {
2073         return skb->head + skb->inner_network_header;
2074 }
2075 
2076 static inline void skb_reset_inner_network_header(struct sk_buff *skb)
2077 {
2078         skb->inner_network_header = skb->data - skb->head;
2079 }
2080 
2081 static inline void skb_set_inner_network_header(struct sk_buff *skb,
2082                                                 const int offset)
2083 {
2084         skb_reset_inner_network_header(skb);
2085         skb->inner_network_header += offset;
2086 }
2087 
2088 static inline unsigned char *skb_inner_mac_header(const struct sk_buff *skb)
2089 {
2090         return skb->head + skb->inner_mac_header;
2091 }
2092 
2093 static inline void skb_reset_inner_mac_header(struct sk_buff *skb)
2094 {
2095         skb->inner_mac_header = skb->data - skb->head;
2096 }
2097 
2098 static inline void skb_set_inner_mac_header(struct sk_buff *skb,
2099                                             const int offset)
2100 {
2101         skb_reset_inner_mac_header(skb);
2102         skb->inner_mac_header += offset;
2103 }
2104 static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
2105 {
2106         return skb->transport_header != (typeof(skb->transport_header))~0U;
2107 }
2108 
2109 static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
2110 {
2111         return skb->head + skb->transport_header;
2112 }
2113 
2114 static inline void skb_reset_transport_header(struct sk_buff *skb)
2115 {
2116         skb->transport_header = skb->data - skb->head;
2117 }
2118 
2119 static inline void skb_set_transport_header(struct sk_buff *skb,
2120                                             const int offset)
2121 {
2122         skb_reset_transport_header(skb);
2123         skb->transport_header += offset;
2124 }
2125 
2126 static inline unsigned char *skb_network_header(const struct sk_buff *skb)
2127 {
2128         return skb->head + skb->network_header;
2129 }
2130 
2131 static inline void skb_reset_network_header(struct sk_buff *skb)
2132 {
2133         skb->network_header = skb->data - skb->head;
2134 }
2135 
2136 static inline void skb_set_network_header(struct sk_buff *skb, const int offset)
2137 {
2138         skb_reset_network_header(skb);
2139         skb->network_header += offset;
2140 }
2141 
2142 static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
2143 {
2144         return skb->head + skb->mac_header;
2145 }
2146 
2147 static inline int skb_mac_header_was_set(const struct sk_buff *skb)
2148 {
2149         return skb->mac_header != (typeof(skb->mac_header))~0U;
2150 }
2151 
2152 static inline void skb_reset_mac_header(struct sk_buff *skb)
2153 {
2154         skb->mac_header = skb->data - skb->head;
2155 }
2156 
2157 static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)
2158 {
2159         skb_reset_mac_header(skb);
2160         skb->mac_header += offset;
2161 }
2162 
2163 static inline void skb_pop_mac_header(struct sk_buff *skb)
2164 {
2165         skb->mac_header = skb->network_header;
2166 }
2167 
2168 static inline void skb_probe_transport_header(struct sk_buff *skb,
2169                                               const int offset_hint)
2170 {
2171         struct flow_keys keys;
2172 
2173         if (skb_transport_header_was_set(skb))
2174                 return;
2175         else if (skb_flow_dissect_flow_keys(skb, &keys, 0))
2176                 skb_set_transport_header(skb, keys.control.thoff);
2177         else
2178                 skb_set_transport_header(skb, offset_hint);
2179 }
2180 
2181 static inline void skb_mac_header_rebuild(struct sk_buff *skb)
2182 {
2183         if (skb_mac_header_was_set(skb)) {
2184                 const unsigned char *old_mac = skb_mac_header(skb);
2185 
2186                 skb_set_mac_header(skb, -skb->mac_len);
2187                 memmove(skb_mac_header(skb), old_mac, skb->mac_len);
2188         }
2189 }
2190 
2191 static inline int skb_checksum_start_offset(const struct sk_buff *skb)
2192 {
2193         return skb->csum_start - skb_headroom(skb);
2194 }
2195 
2196 static inline unsigned char *skb_checksum_start(const struct sk_buff *skb)
2197 {
2198         return skb->head + skb->csum_start;
2199 }
2200 
2201 static inline int skb_transport_offset(const struct sk_buff *skb)
2202 {
2203         return skb_transport_header(skb) - skb->data;
2204 }
2205 
2206 static inline u32 skb_network_header_len(const struct sk_buff *skb)
2207 {
2208         return skb->transport_header - skb->network_header;
2209 }
2210 
2211 static inline u32 skb_inner_network_header_len(const struct sk_buff *skb)
2212 {
2213         return skb->inner_transport_header - skb->inner_network_header;
2214 }
2215 
2216 static inline int skb_network_offset(const struct sk_buff *skb)
2217 {
2218         return skb_network_header(skb) - skb->data;
2219 }
2220 
2221 static inline int skb_inner_network_offset(const struct sk_buff *skb)
2222 {
2223         return skb_inner_network_header(skb) - skb->data;
2224 }
2225 
2226 static inline int pskb_network_may_pull(struct sk_buff *skb, unsigned int len)
2227 {
2228         return pskb_may_pull(skb, skb_network_offset(skb) + len);
2229 }
2230 
2231 /*
2232  * CPUs often take a performance hit when accessing unaligned memory
2233  * locations. The actual performance hit varies, it can be small if the
2234  * hardware handles it or large if we have to take an exception and fix it
2235  * in software.
2236  *
2237  * Since an ethernet header is 14 bytes network drivers often end up with
2238  * the IP header at an unaligned offset. The IP header can be aligned by
2239  * shifting the start of the packet by 2 bytes. Drivers should do this
2240  * with:
2241  *
2242  * skb_reserve(skb, NET_IP_ALIGN);
2243  *
2244  * The downside to this alignment of the IP header is that the DMA is now
2245  * unaligned. On some architectures the cost of an unaligned DMA is high
2246  * and this cost outweighs the gains made by aligning the IP header.
2247  *
2248  * Since this trade off varies between architectures, we allow NET_IP_ALIGN
2249  * to be overridden.
2250  */
2251 #ifndef NET_IP_ALIGN
2252 #define NET_IP_ALIGN    2
2253 #endif
2254 
2255 /*
2256  * The networking layer reserves some headroom in skb data (via
2257  * dev_alloc_skb). This is used to avoid having to reallocate skb data when
2258  * the header has to grow. In the default case, if the header has to grow
2259  * 32 bytes or less we avoid the reallocation.
2260  *
2261  * Unfortunately this headroom changes the DMA alignment of the resulting
2262  * network packet. As for NET_IP_ALIGN, this unaligned DMA is expensive
2263  * on some architectures. An architecture can override this value,
2264  * perhaps setting it to a cacheline in size (since that will maintain
2265  * cacheline alignment of the DMA). It must be a power of 2.
2266  *
2267  * Various parts of the networking layer expect at least 32 bytes of
2268  * headroom, you should not reduce this.
2269  *
2270  * Using max(32, L1_CACHE_BYTES) makes sense (especially with RPS)
2271  * to reduce average number of cache lines per packet.
2272  * get_rps_cpus() for example only access one 64 bytes aligned block :
2273  * NET_IP_ALIGN(2) + ethernet_header(14) + IP_header(20/40) + ports(8)
2274  */
2275 #ifndef NET_SKB_PAD
2276 #define NET_SKB_PAD     max(32, L1_CACHE_BYTES)
2277 #endif
2278 
2279 int ___pskb_trim(struct sk_buff *skb, unsigned int len);
2280 
2281 static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
2282 {
2283         if (unlikely(skb_is_nonlinear(skb))) {
2284                 WARN_ON(1);
2285                 return;
2286         }
2287         skb->len = len;
2288         skb_set_tail_pointer(skb, len);
2289 }
2290 
2291 void skb_trim(struct sk_buff *skb, unsigned int len);
2292 
2293 static inline int __pskb_trim(struct sk_buff *skb, unsigned int len)
2294 {
2295         if (skb->data_len)
2296                 return ___pskb_trim(skb, len);
2297         __skb_trim(skb, len);
2298         return 0;
2299 }
2300 
2301 static inline int pskb_trim(struct sk_buff *skb, unsigned int len)
2302 {
2303         return (len < skb->len) ? __pskb_trim(skb, len) : 0;
2304 }
2305 
2306 /**
2307  *      pskb_trim_unique - remove end from a paged unique (not cloned) buffer
2308  *      @skb: buffer to alter
2309  *      @len: new length
2310  *
2311  *      This is identical to pskb_trim except that the caller knows that
2312  *      the skb is not cloned so we should never get an error due to out-
2313  *      of-memory.
2314  */
2315 static inline void pskb_trim_unique(struct sk_buff *skb, unsigned int len)
2316 {
2317         int err = pskb_trim(skb, len);
2318         BUG_ON(err);
2319 }
2320 
2321 /**
2322  *      skb_orphan - orphan a buffer
2323  *      @skb: buffer to orphan
2324  *
2325  *      If a buffer currently has an owner then we call the owner's
2326  *      destructor function and make the @skb unowned. The buffer continues
2327  *      to exist but is no longer charged to its former owner.
2328  */
2329 static inline void skb_orphan(struct sk_buff *skb)
2330 {
2331         if (skb->destructor) {
2332                 skb->destructor(skb);
2333                 skb->destructor = NULL;
2334                 skb->sk         = NULL;
2335         } else {
2336                 BUG_ON(skb->sk);
2337         }
2338 }
2339 
2340 /**
2341  *      skb_orphan_frags - orphan the frags contained in a buffer
2342  *      @skb: buffer to orphan frags from
2343  *      @gfp_mask: allocation mask for replacement pages
2344  *
2345  *      For each frag in the SKB which needs a destructor (i.e. has an
2346  *      owner) create a copy of that frag and release the original
2347  *      page by calling the destructor.
2348  */
2349 static inline int skb_orphan_frags(struct sk_buff *skb, gfp_t gfp_mask)
2350 {
2351         if (likely(!(skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY)))
2352                 return 0;
2353         return skb_copy_ubufs(skb, gfp_mask);
2354 }
2355 
2356 /**
2357  *      __skb_queue_purge - empty a list
2358  *      @list: list to empty
2359  *
2360  *      Delete all buffers on an &sk_buff list. Each buffer is removed from
2361  *      the list and one reference dropped. This function does not take the
2362  *      list lock and the caller must hold the relevant locks to use it.
2363  */
2364 void skb_queue_purge(struct sk_buff_head *list);
2365 static inline void __skb_queue_purge(struct sk_buff_head *list)
2366 {
2367         struct sk_buff *skb;
2368         while ((skb = __skb_dequeue(list)) != NULL)
2369                 kfree_skb(skb);
2370 }
2371 
2372 void *netdev_alloc_frag(unsigned int fragsz);
2373 
2374 struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int length,
2375                                    gfp_t gfp_mask);
2376 
2377 /**
2378  *      netdev_alloc_skb - allocate an skbuff for rx on a specific device
2379  *      @dev: network device to receive on
2380  *      @length: length to allocate
2381  *
2382  *      Allocate a new &sk_buff and assign it a usage count of one. The
2383  *      buffer has unspecified headroom built in. Users should allocate
2384  *      the headroom they think they need without accounting for the
2385  *      built in space. The built in space is used for optimisations.
2386  *
2387  *      %NULL is returned if there is no free memory. Although this function
2388  *      allocates memory it can be called from an interrupt.
2389  */
2390 static inline struct sk_buff *netdev_alloc_skb(struct net_device *dev,
2391                                                unsigned int length)
2392 {
2393         return __netdev_alloc_skb(dev, length, GFP_ATOMIC);
2394 }
2395 
2396 /* legacy helper around __netdev_alloc_skb() */
2397 static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
2398                                               gfp_t gfp_mask)
2399 {
2400         return __netdev_alloc_skb(NULL, length, gfp_mask);
2401 }
2402 
2403 /* legacy helper around netdev_alloc_skb() */
2404 static inline struct sk_buff *dev_alloc_skb(unsigned int length)
2405 {
2406         return netdev_alloc_skb(NULL, length);
2407 }
2408 
2409 
2410 static inline struct sk_buff *__netdev_alloc_skb_ip_align(struct net_device *dev,
2411                 unsigned int length, gfp_t gfp)
2412 {
2413         struct sk_buff *skb = __netdev_alloc_skb(dev, length + NET_IP_ALIGN, gfp);
2414 
2415         if (NET_IP_ALIGN && skb)
2416                 skb_reserve(skb, NET_IP_ALIGN);
2417         return skb;
2418 }
2419 
2420 static inline struct sk_buff *netdev_alloc_skb_ip_align(struct net_device *dev,
2421                 unsigned int length)
2422 {
2423         return __netdev_alloc_skb_ip_align(dev, length, GFP_ATOMIC);
2424 }
2425 
2426 static inline void skb_free_frag(void *addr)
2427 {
2428         __free_page_frag(addr);
2429 }
2430 
2431 void *napi_alloc_frag(unsigned int fragsz);
2432 struct sk_buff *__napi_alloc_skb(struct napi_struct *napi,
2433                                  unsigned int length, gfp_t gfp_mask);
2434 static inline struct sk_buff *napi_alloc_skb(struct napi_struct *napi,
2435                                              unsigned int length)
2436 {
2437         return __napi_alloc_skb(napi, length, GFP_ATOMIC);
2438 }
2439 void napi_consume_skb(struct sk_buff *skb, int budget);
2440 
2441 void __kfree_skb_flush(void);
2442 void __kfree_skb_defer(struct sk_buff *skb);
2443 
2444 /**
2445  * __dev_alloc_pages - allocate page for network Rx
2446  * @gfp_mask: allocation priority. Set __GFP_NOMEMALLOC if not for network Rx
2447  * @order: size of the allocation
2448  *
2449  * Allocate a new page.
2450  *
2451  * %NULL is returned if there is no free memory.
2452 */
2453 static inline struct page *__dev_alloc_pages(gfp_t gfp_mask,
2454                                              unsigned int order)
2455 {
2456         /* This piece of code contains several assumptions.
2457          * 1.  This is for device Rx, therefor a cold page is preferred.
2458          * 2.  The expectation is the user wants a compound page.
2459          * 3.  If requesting a order 0 page it will not be compound
2460          *     due to the check to see if order has a value in prep_new_page
2461          * 4.  __GFP_MEMALLOC is ignored if __GFP_NOMEMALLOC is set due to
2462          *     code in gfp_to_alloc_flags that should be enforcing this.
2463          */
2464         gfp_mask |= __GFP_COLD | __GFP_COMP | __GFP_MEMALLOC;
2465 
2466         return alloc_pages_node(NUMA_NO_NODE, gfp_mask, order);
2467 }
2468 
2469 static inline struct page *dev_alloc_pages(unsigned int order)
2470 {
2471         return __dev_alloc_pages(GFP_ATOMIC | __GFP_NOWARN, order);
2472 }
2473 
2474 /**
2475  * __dev_alloc_page - allocate a page for network Rx
2476  * @gfp_mask: allocation priority. Set __GFP_NOMEMALLOC if not for network Rx
2477  *
2478  * Allocate a new page.
2479  *
2480  * %NULL is returned if there is no free memory.
2481  */
2482 static inline struct page *__dev_alloc_page(gfp_t gfp_mask)
2483 {
2484         return __dev_alloc_pages(gfp_mask, 0);
2485 }
2486 
2487 static inline struct page *dev_alloc_page(void)
2488 {
2489         return dev_alloc_pages(0);
2490 }
2491 
2492 /**
2493  *      skb_propagate_pfmemalloc - Propagate pfmemalloc if skb is allocated after RX page
2494  *      @page: The page that was allocated from skb_alloc_page
2495  *      @skb: The skb that may need pfmemalloc set
2496  */
2497 static inline void skb_propagate_pfmemalloc(struct page *page,
2498                                              struct sk_buff *skb)
2499 {
2500         if (page_is_pfmemalloc(page))
2501                 skb->pfmemalloc = true;
2502 }
2503 
2504 /**
2505  * skb_frag_page - retrieve the page referred to by a paged fragment
2506  * @frag: the paged fragment
2507  *
2508  * Returns the &struct page associated with @frag.
2509  */
2510 static inline struct page *skb_frag_page(const skb_frag_t *frag)
2511 {
2512         return frag->page.p;
2513 }
2514 
2515 /**
2516  * __skb_frag_ref - take an addition reference on a paged fragment.
2517  * @frag: the paged fragment
2518  *
2519  * Takes an additional reference on the paged fragment @frag.
2520  */
2521 static inline void __skb_frag_ref(skb_frag_t *frag)
2522 {
2523         get_page(skb_frag_page(frag));
2524 }
2525 
2526 /**
2527  * skb_frag_ref - take an addition reference on a paged fragment of an skb.
2528  * @skb: the buffer
2529  * @f: the fragment offset.
2530  *
2531  * Takes an additional reference on the @f'th paged fragment of @skb.
2532  */
2533 static inline void skb_frag_ref(struct sk_buff *skb, int f)
2534 {
2535         __skb_frag_ref(&skb_shinfo(skb)->frags[f]);
2536 }
2537 
2538 /**
2539  * __skb_frag_unref - release a reference on a paged fragment.
2540  * @frag: the paged fragment
2541  *
2542  * Releases a reference on the paged fragment @frag.
2543  */
2544 static inline void __skb_frag_unref(skb_frag_t *frag)
2545 {
2546         put_page(skb_frag_page(frag));
2547 }
2548 
2549 /**
2550  * skb_frag_unref - release a reference on a paged fragment of an skb.
2551  * @skb: the buffer
2552  * @f: the fragment offset
2553  *
2554  * Releases a reference on the @f'th paged fragment of @skb.
2555  */
2556 static inline void skb_frag_unref(struct sk_buff *skb, int f)
2557 {
2558         __skb_frag_unref(&skb_shinfo(skb)->frags[f]);
2559 }
2560 
2561 /**
2562  * skb_frag_address - gets the address of the data contained in a paged fragment
2563  * @frag: the paged fragment buffer
2564  *
2565  * Returns the address of the data within @frag. The page must already
2566  * be mapped.
2567  */
2568 static inline void *skb_frag_address(const skb_frag_t *frag)
2569 {
2570         return page_address(skb_frag_page(frag)) + frag->page_offset;
2571 }
2572 
2573 /**
2574  * skb_frag_address_safe - gets the address of the data contained in a paged fragment
2575  * @frag: the paged fragment buffer
2576  *
2577  * Returns the address of the data within @frag. Checks that the page
2578  * is mapped and returns %NULL otherwise.
2579  */
2580 static inline void *skb_frag_address_safe(const skb_frag_t *frag)
2581 {
2582         void *ptr = page_address(skb_frag_page(frag));
2583         if (unlikely(!ptr))
2584                 return NULL;
2585 
2586         return ptr + frag->page_offset;
2587 }
2588 
2589 /**
2590  * __skb_frag_set_page - sets the page contained in a paged fragment
2591  * @frag: the paged fragment
2592  * @page: the page to set
2593  *
2594  * Sets the fragment @frag to contain @page.
2595  */
2596 static inline void __skb_frag_set_page(skb_frag_t *frag, struct page *page)
2597 {
2598         frag->page.p = page;
2599 }
2600 
2601 /**
2602  * skb_frag_set_page - sets the page contained in a paged fragment of an skb
2603  * @skb: the buffer
2604  * @f: the fragment offset
2605  * @page: the page to set
2606  *
2607  * Sets the @f'th fragment of @skb to contain @page.
2608  */
2609 static inline void skb_frag_set_page(struct sk_buff *skb, int f,
2610                                      struct page *page)
2611 {
2612         __skb_frag_set_page(&skb_shinfo(skb)->frags[f], page);
2613 }
2614 
2615 bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t prio);
2616 
2617 /**
2618  * skb_frag_dma_map - maps a paged fragment via the DMA API
2619  * @dev: the device to map the fragment to
2620  * @frag: the paged fragment to map
2621  * @offset: the offset within the fragment (starting at the
2622  *          fragment's own offset)
2623  * @size: the number of bytes to map
2624  * @dir: the direction of the mapping (%PCI_DMA_*)
2625  *
2626  * Maps the page associated with @frag to @device.
2627  */
2628 static inline dma_addr_t skb_frag_dma_map(struct device *dev,
2629                                           const skb_frag_t *frag,
2630                                           size_t offset, size_t size,
2631                                           enum dma_data_direction dir)
2632 {
2633         return dma_map_page(dev, skb_frag_page(frag),
2634                             frag->page_offset + offset, size, dir);
2635 }
2636 
2637 static inline struct sk_buff *pskb_copy(struct sk_buff *skb,
2638                                         gfp_t gfp_mask)
2639 {
2640         return __pskb_copy(skb, skb_headroom(skb), gfp_mask);
2641 }
2642 
2643 
2644 static inline struct sk_buff *pskb_copy_for_clone(struct sk_buff *skb,
2645                                                   gfp_t gfp_mask)
2646 {
2647         return __pskb_copy_fclone(skb, skb_headroom(skb), gfp_mask, true);
2648 }
2649 
2650 
2651 /**
2652  *      skb_clone_writable - is the header of a clone writable
2653  *      @skb: buffer to check
2654  *      @len: length up to which to write
2655  *
2656  *      Returns true if modifying the header part of the cloned buffer
2657  *      does not requires the data to be copied.
2658  */
2659 static inline int skb_clone_writable(const struct sk_buff *skb, unsigned int len)
2660 {
2661         return !skb_header_cloned(skb) &&
2662                skb_headroom(skb) + len <= skb->hdr_len;
2663 }
2664 
2665 static inline int skb_try_make_writable(struct sk_buff *skb,
2666                                         unsigned int write_len)
2667 {
2668         return skb_cloned(skb) && !skb_clone_writable(skb, write_len) &&
2669                pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
2670 }
2671 
2672 static inline int __skb_cow(struct sk_buff *skb, unsigned int headroom,
2673                             int cloned)
2674 {
2675         int delta = 0;
2676 
2677         if (headroom > skb_headroom(skb))
2678                 delta = headroom - skb_headroom(skb);
2679 
2680         if (delta || cloned)
2681                 return pskb_expand_head(skb, ALIGN(delta, NET_SKB_PAD), 0,
2682                                         GFP_ATOMIC);
2683         return 0;
2684 }
2685 
2686 /**
2687  *      skb_cow - copy header of skb when it is required
2688  *      @skb: buffer to cow
2689  *      @headroom: needed headroom
2690  *
2691  *      If the skb passed lacks sufficient headroom or its data part
2692  *      is shared, data is reallocated. If reallocation fails, an error
2693  *      is returned and original skb is not changed.
2694  *
2695  *      The result is skb with writable area skb->head...skb->tail
2696  *      and at least @headroom of space at head.
2697  */
2698 static inline int skb_cow(struct sk_buff *skb, unsigned int headroom)
2699 {
2700         return __skb_cow(skb, headroom, skb_cloned(skb));
2701 }
2702 
2703 /**
2704  *      skb_cow_head - skb_cow but only making the head writable
2705  *      @skb: buffer to cow
2706  *      @headroom: needed headroom
2707  *
2708  *      This function is identical to skb_cow except that we replace the
2709  *      skb_cloned check by skb_header_cloned.  It should be used when
2710  *      you only need to push on some header and do not need to modify
2711  *      the data.
2712  */
2713 static inline int skb_cow_head(struct sk_buff *skb, unsigned int headroom)
2714 {
2715         return __skb_cow(skb, headroom, skb_header_cloned(skb));
2716 }
2717 
2718 /**
2719  *      skb_padto       - pad an skbuff up to a minimal size
2720  *      @skb: buffer to pad
2721  *      @len: minimal length
2722  *
2723  *      Pads up a buffer to ensure the trailing bytes exist and are
2724  *      blanked. If the buffer already contains sufficient data it
2725  *      is untouched. Otherwise it is extended. Returns zero on
2726  *      success. The skb is freed on error.
2727  */
2728 static inline int skb_padto(struct sk_buff *skb, unsigned int len)
2729 {
2730         unsigned int size = skb->len;
2731         if (likely(size >= len))
2732                 return 0;
2733         return skb_pad(skb, len - size);
2734 }
2735 
2736 /**
2737  *      skb_put_padto - increase size and pad an skbuff up to a minimal size
2738  *      @skb: buffer to pad
2739  *      @len: minimal length
2740  *
2741  *      Pads up a buffer to ensure the trailing bytes exist and are
2742  *      blanked. If the buffer already contains sufficient data it
2743  *      is untouched. Otherwise it is extended. Returns zero on
2744  *      success. The skb is freed on error.
2745  */
2746 static inline int skb_put_padto(struct sk_buff *skb, unsigned int len)
2747 {
2748         unsigned int size = skb->len;
2749 
2750         if (unlikely(size < len)) {
2751                 len -= size;
2752                 if (skb_pad(skb, len))
2753                         return -ENOMEM;
2754                 __skb_put(skb, len);
2755         }
2756         return 0;
2757 }
2758 
2759 static inline int skb_add_data(struct sk_buff *skb,
2760                                struct iov_iter *from, int copy)
2761 {
2762         const int off = skb->len;
2763 
2764         if (skb->ip_summed == CHECKSUM_NONE) {
2765                 __wsum csum = 0;
2766                 if (csum_and_copy_from_iter(skb_put(skb, copy), copy,
2767                                             &csum, from) == copy) {
2768                         skb->csum = csum_block_add(skb->csum, csum, off);
2769                         return 0;
2770                 }
2771         } else if (copy_from_iter(skb_put(skb, copy), copy, from) == copy)
2772                 return 0;
2773 
2774         __skb_trim(skb, off);
2775         return -EFAULT;
2776 }
2777 
2778 static inline bool skb_can_coalesce(struct sk_buff *skb, int i,
2779                                     const struct page *page, int off)
2780 {
2781         if (i) {
2782                 const struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[i - 1];
2783 
2784                 return page == skb_frag_page(frag) &&
2785                        off == frag->page_offset + skb_frag_size(frag);
2786         }
2787         return false;
2788 }
2789 
2790 static inline int __skb_linearize(struct sk_buff *skb)
2791 {
2792         return __pskb_pull_tail(skb, skb->data_len) ? 0 : -ENOMEM;
2793 }
2794 
2795 /**
2796  *      skb_linearize - convert paged skb to linear one
2797  *      @skb: buffer to linarize
2798  *
2799  *      If there is no free memory -ENOMEM is returned, otherwise zero
2800  *      is returned and the old skb data released.
2801  */
2802 static inline int skb_linearize(struct sk_buff *skb)
2803 {
2804         return skb_is_nonlinear(skb) ? __skb_linearize(skb) : 0;
2805 }
2806 
2807 /**
2808  * skb_has_shared_frag - can any frag be overwritten
2809  * @skb: buffer to test
2810  *
2811  * Return true if the skb has at least one frag that might be modified
2812  * by an external entity (as in vmsplice()/sendfile())
2813  */
2814 static inline bool skb_has_shared_frag(const struct sk_buff *skb)
2815 {
2816         return skb_is_nonlinear(skb) &&
2817                skb_shinfo(skb)->tx_flags & SKBTX_SHARED_FRAG;
2818 }
2819 
2820 /**
2821  *      skb_linearize_cow - make sure skb is linear and writable
2822  *      @skb: buffer to process
2823  *
2824  *      If there is no free memory -ENOMEM is returned, otherwise zero
2825  *      is returned and the old skb data released.
2826  */
2827 static inline int skb_linearize_cow(struct sk_buff *skb)
2828 {
2829         return skb_is_nonlinear(skb) || skb_cloned(skb) ?
2830                __skb_linearize(skb) : 0;
2831 }
2832 
2833 /**
2834  *      skb_postpull_rcsum - update checksum for received skb after pull
2835  *      @skb: buffer to update
2836  *      @start: start of data before pull
2837  *      @len: length of data pulled
2838  *
2839  *      After doing a pull on a received packet, you need to call this to
2840  *      update the CHECKSUM_COMPLETE checksum, or set ip_summed to
2841  *      CHECKSUM_NONE so that it can be recomputed from scratch.
2842  */
2843 
2844 static inline void skb_postpull_rcsum(struct sk_buff *skb,
2845                                       const void *start, unsigned int len)
2846 {
2847         if (skb->ip_summed == CHECKSUM_COMPLETE)
2848                 skb->csum = csum_sub(skb->csum, csum_partial(start, len, 0));
2849         else if (skb->ip_summed == CHECKSUM_PARTIAL &&
2850                  skb_checksum_start_offset(skb) < 0)
2851                 skb->ip_summed = CHECKSUM_NONE;
2852 }
2853 
2854 unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);
2855 
2856 static inline void skb_postpush_rcsum(struct sk_buff *skb,
2857                                       const void *start, unsigned int len)
2858 {
2859         /* For performing the reverse operation to skb_postpull_rcsum(),
2860          * we can instead of ...
2861          *
2862          *   skb->csum = csum_add(skb->csum, csum_partial(start, len, 0));
2863          *
2864          * ... just use this equivalent version here to save a few
2865          * instructions. Feeding csum of 0 in csum_partial() and later
2866          * on adding skb->csum is equivalent to feed skb->csum in the
2867          * first place.
2868          */
2869         if (skb->ip_summed == CHECKSUM_COMPLETE)
2870                 skb->csum = csum_partial(start, len, skb->csum);
2871 }
2872 
2873 /**
2874  *      skb_push_rcsum - push skb and update receive checksum
2875  *      @skb: buffer to update
2876  *      @len: length of data pulled
2877  *
2878  *      This function performs an skb_push on the packet and updates
2879  *      the CHECKSUM_COMPLETE checksum.  It should be used on
2880  *      receive path processing instead of skb_push unless you know
2881  *      that the checksum difference is zero (e.g., a valid IP header)
2882  *      or you are setting ip_summed to CHECKSUM_NONE.
2883  */
2884 static inline unsigned char *skb_push_rcsum(struct sk_buff *skb,
2885                                             unsigned int len)
2886 {
2887         skb_push(skb, len);
2888         skb_postpush_rcsum(skb, skb->data, len);
2889         return skb->data;
2890 }
2891 
2892 /**
2893  *      pskb_trim_rcsum - trim received skb and update checksum
2894  *      @skb: buffer to trim
2895  *      @len: new length
2896  *
2897  *      This is exactly the same as pskb_trim except that it ensures the
2898  *      checksum of received packets are still valid after the operation.
2899  */
2900 
2901 static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)
2902 {
2903         if (likely(len >= skb->len))
2904                 return 0;
2905         if (skb->ip_summed == CHECKSUM_COMPLETE)
2906                 skb->ip_summed = CHECKSUM_NONE;
2907         return __pskb_trim(skb, len);
2908 }
2909 
2910 #define skb_queue_walk(queue, skb) \
2911                 for (skb = (queue)->next;                                       \
2912                      skb != (struct sk_buff *)(queue);                          \
2913                      skb = skb->next)
2914 
2915 #define skb_queue_walk_safe(queue, skb, tmp)                                    \
2916                 for (skb = (queue)->next, tmp = skb->next;                      \
2917                      skb != (struct sk_buff *)(queue);                          \
2918                      skb = tmp, tmp = skb->next)
2919 
2920 #define skb_queue_walk_from(queue, skb)                                         \
2921                 for (; skb != (struct sk_buff *)(queue);                        \
2922                      skb = skb->next)
2923 
2924 #define skb_queue_walk_from_safe(queue, skb, tmp)                               \
2925                 for (tmp = skb->next;                                           \
2926                      skb != (struct sk_buff *)(queue);                          \
2927                      skb = tmp, tmp = skb->next)
2928 
2929 #define skb_queue_reverse_walk(queue, skb) \
2930                 for (skb = (queue)->prev;                                       \
2931                      skb != (struct sk_buff *)(queue);                          \
2932                      skb = skb->prev)
2933 
2934 #define skb_queue_reverse_walk_safe(queue, skb, tmp)                            \
2935                 for (skb = (queue)->prev, tmp = skb->prev;                      \
2936                      skb != (struct sk_buff *)(queue);                          \
2937                      skb = tmp, tmp = skb->prev)
2938 
2939 #define skb_queue_reverse_walk_from_safe(queue, skb, tmp)                       \
2940                 for (tmp = skb->prev;                                           \
2941                      skb != (struct sk_buff *)(queue);                          \
2942                      skb = tmp, tmp = skb->prev)
2943 
2944 static inline bool skb_has_frag_list(const struct sk_buff *skb)
2945 {
2946         return skb_shinfo(skb)->frag_list != NULL;
2947 }
2948 
2949 static inline void skb_frag_list_init(struct sk_buff *skb)
2950 {
2951         skb_shinfo(skb)->frag_list = NULL;
2952 }
2953 
2954 #define skb_walk_frags(skb, iter)       \
2955         for (iter = skb_shinfo(skb)->frag_list; iter; iter = iter->next)
2956 
2957 
2958 int __skb_wait_for_more_packets(struct sock *sk, int *err, long *timeo_p,
2959                                 const struct sk_buff *skb);
2960 struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned flags,
2961                                         int *peeked, int *off, int *err,
2962                                         struct sk_buff **last);
2963 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
2964                                     int *peeked, int *off, int *err);
2965 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags, int noblock,
2966                                   int *err);
2967 unsigned int datagram_poll(struct file *file, struct socket *sock,
2968                            struct poll_table_struct *wait);
2969 int skb_copy_datagram_iter(const struct sk_buff *from, int offset,
2970                            struct iov_iter *to, int size);
2971 static inline int skb_copy_datagram_msg(const struct sk_buff *from, int offset,
2972                                         struct msghdr *msg, int size)
2973 {
2974         return skb_copy_datagram_iter(from, offset, &msg->msg_iter, size);
2975 }
2976 int skb_copy_and_csum_datagram_msg(struct sk_buff *skb, int hlen,
2977                                    struct msghdr *msg);
2978 int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
2979                                  struct iov_iter *from, int len);
2980 int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *frm);
2981 void skb_free_datagram(struct sock *sk, struct sk_buff *skb);
2982 void __skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb, int len);
2983 static inline void skb_free_datagram_locked(struct sock *sk,
2984                                             struct sk_buff *skb)
2985 {
2986         __skb_free_datagram_locked(sk, skb, 0);
2987 }
2988 int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags);
2989 int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len);
2990 int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len);
2991 __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, u8 *to,
2992                               int len, __wsum csum);
2993 ssize_t skb_socket_splice(struct sock *sk,
2994                           struct pipe_inode_info *pipe,
2995                           struct splice_pipe_desc *spd);
2996 int skb_splice_bits(struct sk_buff *skb, struct sock *sk, unsigned int offset,
2997                     struct pipe_inode_info *pipe, unsigned int len,
2998                     unsigned int flags,
2999                     ssize_t (*splice_cb)(struct sock *,
3000                                          struct pipe_inode_info *,
3001                                          struct splice_pipe_desc *));
3002 void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
3003 unsigned int skb_zerocopy_headlen(const struct sk_buff *from);
3004 int skb_zerocopy(struct sk_buff *to, struct sk_buff *from,
3005                  int len, int hlen);
3006 void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len);
3007 int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen);
3008 void skb_scrub_packet(struct sk_buff *skb, bool xnet);
3009 unsigned int skb_gso_transport_seglen(const struct sk_buff *skb);
3010 struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);
3011 struct sk_buff *skb_vlan_untag(struct sk_buff *skb);
3012 int skb_ensure_writable(struct sk_buff *skb, int write_len);
3013 int skb_vlan_pop(struct sk_buff *skb);
3014 int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);
3015 struct sk_buff *pskb_extract(struct sk_buff *skb, int off, int to_copy,
3016                              gfp_t gfp);
3017 
3018 static inline int memcpy_from_msg(void *data, struct msghdr *msg, int len)
3019 {
3020         return copy_from_iter(data, len, &msg->msg_iter) == len ? 0 : -EFAULT;
3021 }
3022 
3023 static inline int memcpy_to_msg(struct msghdr *msg, void *data, int len)
3024 {
3025         return copy_to_iter(data, len, &msg->msg_iter) == len ? 0 : -EFAULT;
3026 }
3027 
3028 struct skb_checksum_ops {
3029         __wsum (*update)(const void *mem, int len, __wsum wsum);
3030         __wsum (*combine)(__wsum csum, __wsum csum2, int offset, int len);
3031 };
3032 
3033 __wsum __skb_checksum(const struct sk_buff *skb, int offset, int len,
3034                       __wsum csum, const struct skb_checksum_ops *ops);
3035 __wsum skb_checksum(const struct sk_buff *skb, int offset, int len,
3036                     __wsum csum);
3037 
3038 static inline void * __must_check
3039 __skb_header_pointer(const struct sk_buff *skb, int offset,
3040                      int len, void *data, int hlen, void *buffer)
3041 {
3042         if (hlen - offset >= len)
3043                 return data + offset;
3044 
3045         if (!skb ||
3046             skb_copy_bits(skb, offset, buffer, len) < 0)
3047                 return NULL;
3048 
3049         return buffer;
3050 }
3051 
3052 static inline void * __must_check
3053 skb_header_pointer(const struct sk_buff *skb, int offset, int len, void *buffer)
3054 {
3055         return __skb_header_pointer(skb, offset, len, skb->data,
3056                                     skb_headlen(skb), buffer);
3057 }
3058 
3059 /**
3060  *      skb_needs_linearize - check if we need to linearize a given skb
3061  *                            depending on the given device features.
3062  *      @skb: socket buffer to check
3063  *      @features: net device features
3064  *
3065  *      Returns true if either:
3066  *      1. skb has frag_list and the device doesn't support FRAGLIST, or
3067  *      2. skb is fragmented and the device does not support SG.
3068  */
3069 static inline bool skb_needs_linearize(struct sk_buff *skb,
3070                                        netdev_features_t features)
3071 {
3072         return skb_is_nonlinear(skb) &&
3073                ((skb_has_frag_list(skb) && !(features & NETIF_F_FRAGLIST)) ||
3074                 (skb_shinfo(skb)->nr_frags && !(features & NETIF_F_SG)));
3075 }
3076 
3077 static inline void skb_copy_from_linear_data(const struct sk_buff *skb,
3078                                              void *to,
3079                                              const unsigned int len)
3080 {
3081         memcpy(to, skb->data, len);
3082 }
3083 
3084 static inline void skb_copy_from_linear_data_offset(const struct sk_buff *skb,
3085                                                     const int offset, void *to,
3086                                                     const unsigned int len)
3087 {
3088         memcpy(to, skb->data + offset, len);
3089 }
3090 
3091 static inline void skb_copy_to_linear_data(struct sk_buff *skb,
3092                                            const void *from,
3093                                            const unsigned int len)
3094 {
3095         memcpy(skb->data, from, len);
3096 }
3097 
3098 static inline void skb_copy_to_linear_data_offset(struct sk_buff *skb,
3099                                                   const int offset,
3100                                                   const void *from,
3101                                                   const unsigned int len)
3102 {
3103         memcpy(skb->data + offset, from, len);
3104 }
3105 
3106 void skb_init(void);
3107 
3108 static inline ktime_t skb_get_ktime(const struct sk_buff *skb)
3109 {
3110         return skb->tstamp;
3111 }
3112 
3113 /**
3114  *      skb_get_timestamp - get timestamp from a skb
3115  *      @skb: skb to get stamp from
3116  *      @stamp: pointer to struct timeval to store stamp in
3117  *
3118  *      Timestamps are stored in the skb as offsets to a base timestamp.
3119  *      This function converts the offset back to a struct timeval and stores
3120  *      it in stamp.
3121  */
3122 static inline void skb_get_timestamp(const struct sk_buff *skb,
3123                                      struct timeval *stamp)
3124 {
3125         *stamp = ktime_to_timeval(skb->tstamp);
3126 }
3127 
3128 static inline void skb_get_timestampns(const struct sk_buff *skb,
3129                                        struct timespec *stamp)
3130 {
3131         *stamp = ktime_to_timespec(skb->tstamp);
3132 }
3133 
3134 static inline void __net_timestamp(struct sk_buff *skb)
3135 {
3136         skb->tstamp = ktime_get_real();
3137 }
3138 
3139 static inline ktime_t net_timedelta(ktime_t t)
3140 {
3141         return ktime_sub(ktime_get_real(), t);
3142 }
3143 
3144 static inline ktime_t net_invalid_timestamp(void)
3145 {
3146         return ktime_set(0, 0);
3147 }
3148 
3149 struct sk_buff *skb_clone_sk(struct sk_buff *skb);
3150 
3151 #ifdef CONFIG_NETWORK_PHY_TIMESTAMPING
3152 
3153 void skb_clone_tx_timestamp(struct sk_buff *skb);
3154 bool skb_defer_rx_timestamp(struct sk_buff *skb);
3155 
3156 #else /* CONFIG_NETWORK_PHY_TIMESTAMPING */
3157 
3158 static inline void skb_clone_tx_timestamp(struct sk_buff *skb)
3159 {
3160 }
3161 
3162 static inline bool skb_defer_rx_timestamp(struct sk_buff *skb)
3163 {
3164         return false;
3165 }
3166 
3167 #endif /* !CONFIG_NETWORK_PHY_TIMESTAMPING */
3168 
3169 /**
3170  * skb_complete_tx_timestamp() - deliver cloned skb with tx timestamps
3171  *
3172  * PHY drivers may accept clones of transmitted packets for
3173  * timestamping via their phy_driver.txtstamp method. These drivers
3174  * must call this function to return the skb back to the stack with a
3175  * timestamp.
3176  *
3177  * @skb: clone of the the original outgoing packet
3178  * @hwtstamps: hardware time stamps
3179  *
3180  */
3181 void skb_complete_tx_timestamp(struct sk_buff *skb,
3182                                struct skb_shared_hwtstamps *hwtstamps);
3183 
3184 void __skb_tstamp_tx(struct sk_buff *orig_skb,
3185                      struct skb_shared_hwtstamps *hwtstamps,
3186                      struct sock *sk, int tstype);
3187 
3188 /**
3189  * skb_tstamp_tx - queue clone of skb with send time stamps
3190  * @orig_skb:   the original outgoing packet
3191  * @hwtstamps:  hardware time stamps, may be NULL if not available
3192  *
3193  * If the skb has a socket associated, then this function clones the
3194  * skb (thus sharing the actual data and optional structures), stores
3195  * the optional hardware time stamping information (if non NULL) or
3196  * generates a software time stamp (otherwise), then queues the clone
3197  * to the error queue of the socket.  Errors are silently ignored.
3198  */
3199 void skb_tstamp_tx(struct sk_buff *orig_skb,
3200                    struct skb_shared_hwtstamps *hwtstamps);
3201 
3202 static inline void sw_tx_timestamp(struct sk_buff *skb)
3203 {
3204         if (skb_shinfo(skb)->tx_flags & SKBTX_SW_TSTAMP &&
3205             !(skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS))
3206                 skb_tstamp_tx(skb, NULL);
3207 }
3208 
3209 /**
3210  * skb_tx_timestamp() - Driver hook for transmit timestamping
3211  *
3212  * Ethernet MAC Drivers should call this function in their hard_xmit()
3213  * function immediately before giving the sk_buff to the MAC hardware.
3214  *
3215  * Specifically, one should make absolutely sure that this function is
3216  * called before TX completion of this packet can trigger.  Otherwise
3217  * the packet could potentially already be freed.
3218  *
3219  * @skb: A socket buffer.
3220  */
3221 static inline void skb_tx_timestamp(struct sk_buff *skb)
3222 {
3223         skb_clone_tx_timestamp(skb);
3224         sw_tx_timestamp(skb);
3225 }
3226 
3227 /**
3228  * skb_complete_wifi_ack - deliver skb with wifi status
3229  *
3230  * @skb: the original outgoing packet
3231  * @acked: ack status
3232  *
3233  */
3234 void skb_complete_wifi_ack(struct sk_buff *skb, bool acked);
3235 
3236 __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len);
3237 __sum16 __skb_checksum_complete(struct sk_buff *skb);
3238 
3239 static inline int skb_csum_unnecessary(const struct sk_buff *skb)
3240 {
3241         return ((skb->ip_summed == CHECKSUM_UNNECESSARY) ||
3242                 skb->csum_valid ||
3243                 (skb->ip_summed == CHECKSUM_PARTIAL &&
3244                  skb_checksum_start_offset(skb) >= 0));
3245 }
3246 
3247 /**
3248  *      skb_checksum_complete - Calculate checksum of an entire packet
3249  *      @skb: packet to process
3250  *
3251  *      This function calculates the checksum over the entire packet plus
3252  *      the value of skb->csum.  The latter can be used to supply the
3253  *      checksum of a pseudo header as used by TCP/UDP.  It returns the
3254  *      checksum.
3255  *
3256  *      For protocols that contain complete checksums such as ICMP/TCP/UDP,
3257  *      this function can be used to verify that checksum on received
3258  *      packets.  In that case the function should return zero if the
3259  *      checksum is correct.  In particular, this function will return zero
3260  *      if skb->ip_summed is CHECKSUM_UNNECESSARY which indicates that the
3261  *      hardware has already verified the correctness of the checksum.
3262  */
3263 static inline __sum16 skb_checksum_complete(struct sk_buff *skb)
3264 {
3265         return skb_csum_unnecessary(skb) ?
3266                0 : __skb_checksum_complete(skb);
3267 }
3268 
3269 static inline void __skb_decr_checksum_unnecessary(struct sk_buff *skb)
3270 {
3271         if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
3272                 if (skb->csum_level == 0)
3273                         skb->ip_summed = CHECKSUM_NONE;
3274                 else
3275                         skb->csum_level--;
3276         }
3277 }
3278 
3279 static inline void __skb_incr_checksum_unnecessary(struct sk_buff *skb)
3280 {
3281         if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
3282                 if (skb->csum_level < SKB_MAX_CSUM_LEVEL)
3283                         skb->csum_level++;
3284         } else if (skb->ip_summed == CHECKSUM_NONE) {
3285                 skb->ip_summed = CHECKSUM_UNNECESSARY;
3286                 skb->csum_level = 0;
3287         }
3288 }
3289 
3290 static inline void __skb_mark_checksum_bad(struct sk_buff *skb)
3291 {
3292         /* Mark current checksum as bad (typically called from GRO
3293          * path). In the case that ip_summed is CHECKSUM_NONE
3294          * this must be the first checksum encountered in the packet.
3295          * When ip_summed is CHECKSUM_UNNECESSARY, this is the first
3296          * checksum after the last one validated. For UDP, a zero
3297          * checksum can not be marked as bad.
3298          */
3299 
3300         if (skb->ip_summed == CHECKSUM_NONE ||
3301             skb->ip_summed == CHECKSUM_UNNECESSARY)
3302                 skb->csum_bad = 1;
3303 }
3304 
3305 /* Check if we need to perform checksum complete validation.
3306  *
3307  * Returns true if checksum complete is needed, false otherwise
3308  * (either checksum is unnecessary or zero checksum is allowed).
3309  */
3310 static inline bool __skb_checksum_validate_needed(struct sk_buff *skb,
3311                                                   bool zero_okay,
3312                                                   __sum16 check)
3313 {
3314         if (skb_csum_unnecessary(skb) || (zero_okay && !check)) {
3315                 skb->csum_valid = 1;
3316                 __skb_decr_checksum_unnecessary(skb);
3317                 return false;
3318         }
3319 
3320         return true;
3321 }
3322 
3323 /* For small packets <= CHECKSUM_BREAK peform checksum complete directly
3324  * in checksum_init.
3325  */
3326 #define CHECKSUM_BREAK 76
3327 
3328 /* Unset checksum-complete
3329  *
3330  * Unset checksum complete can be done when packet is being modified
3331  * (uncompressed for instance) and checksum-complete value is
3332  * invalidated.
3333  */
3334 static inline void skb_checksum_complete_unset(struct sk_buff *skb)
3335 {
3336         if (skb->ip_summed == CHECKSUM_COMPLETE)
3337                 skb->ip_summed = CHECKSUM_NONE;
3338 }
3339 
3340 /* Validate (init) checksum based on checksum complete.
3341  *
3342  * Return values:
3343  *   0: checksum is validated or try to in skb_checksum_complete. In the latter
3344  *      case the ip_summed will not be CHECKSUM_UNNECESSARY and the pseudo
3345  *      checksum is stored in skb->csum for use in __skb_checksum_complete
3346  *   non-zero: value of invalid checksum
3347  *
3348  */
3349 static inline __sum16 __skb_checksum_validate_complete(struct sk_buff *skb,
3350                                                        bool complete,
3351                                                        __wsum psum)
3352 {
3353         if (skb->ip_summed == CHECKSUM_COMPLETE) {
3354                 if (!csum_fold(csum_add(psum, skb->csum))) {
3355                         skb->csum_valid = 1;
3356                         return 0;
3357                 }
3358         } else if (skb->csum_bad) {
3359                 /* ip_summed == CHECKSUM_NONE in this case */
3360                 return (__force __sum16)1;
3361         }
3362 
3363         skb->csum = psum;
3364 
3365         if (complete || skb->len <= CHECKSUM_BREAK) {
3366                 __sum16 csum;
3367 
3368                 csum = __skb_checksum_complete(skb);
3369                 skb->csum_valid = !csum;
3370                 return csum;
3371         }
3372 
3373         return 0;
3374 }
3375 
3376 static inline __wsum null_compute_pseudo(struct sk_buff *skb, int proto)
3377 {
3378         return 0;
3379 }
3380 
3381 /* Perform checksum validate (init). Note that this is a macro since we only
3382  * want to calculate the pseudo header which is an input function if necessary.
3383  * First we try to validate without any computation (checksum unnecessary) and
3384  * then calculate based on checksum complete calling the function to compute
3385  * pseudo header.
3386  *
3387  * Return values:
3388  *   0: checksum is validated or try to in skb_checksum_complete
3389  *   non-zero: value of invalid checksum
3390  */
3391 #define __skb_checksum_validate(skb, proto, complete,                   \
3392                                 zero_okay, check, compute_pseudo)       \
3393 ({                                                                      \
3394         __sum16 __ret = 0;                                              \
3395         skb->csum_valid = 0;                                            \
3396         if (__skb_checksum_validate_needed(skb, zero_okay, check))      \
3397                 __ret = __skb_checksum_validate_complete(skb,           \
3398                                 complete, compute_pseudo(skb, proto));  \
3399         __ret;                                                          \
3400 })
3401 
3402 #define skb_checksum_init(skb, proto, compute_pseudo)                   \
3403         __skb_checksum_validate(skb, proto, false, false, 0, compute_pseudo)
3404 
3405 #define skb_checksum_init_zero_check(skb, proto, check, compute_pseudo) \
3406         __skb_checksum_validate(skb, proto, false, true, check, compute_pseudo)
3407 
3408 #define skb_checksum_validate(skb, proto, compute_pseudo)               \
3409         __skb_checksum_validate(skb, proto, true, false, 0, compute_pseudo)
3410 
3411 #define skb_checksum_validate_zero_check(skb, proto, check,             \
3412                                          compute_pseudo)                \
3413         __skb_checksum_validate(skb, proto, true, true, check, compute_pseudo)
3414 
3415 #define skb_checksum_simple_validate(skb)                               \
3416         __skb_checksum_validate(skb, 0, true, false, 0, null_compute_pseudo)
3417 
3418 static inline bool __skb_checksum_convert_check(struct sk_buff *skb)
3419 {
3420         return (skb->ip_summed == CHECKSUM_NONE &&
3421                 skb->csum_valid && !skb->csum_bad);
3422 }
3423 
3424 static inline void __skb_checksum_convert(struct sk_buff *skb,
3425                                           __sum16 check, __wsum pseudo)
3426 {
3427         skb->csum = ~pseudo;
3428         skb->ip_summed = CHECKSUM_COMPLETE;
3429 }
3430 
3431 #define skb_checksum_try_convert(skb, proto, check, compute_pseudo)     \
3432 do {                                                                    \
3433         if (__skb_checksum_convert_check(skb))                          \
3434                 __skb_checksum_convert(skb, check,                      \
3435                                        compute_pseudo(skb, proto));     \
3436 } while (0)
3437 
3438 static inline void skb_remcsum_adjust_partial(struct sk_buff *skb, void *ptr,
3439                                               u16 start, u16 offset)
3440 {
3441         skb->ip_summed = CHECKSUM_PARTIAL;
3442         skb->csum_start = ((unsigned char *)ptr + start) - skb->head;
3443         skb->csum_offset = offset - start;
3444 }
3445 
3446 /* Update skbuf and packet to reflect the remote checksum offload operation.
3447  * When called, ptr indicates the starting point for skb->csum when
3448  * ip_summed is CHECKSUM_COMPLETE. If we need create checksum complete
3449  * here, skb_postpull_rcsum is done so skb->csum start is ptr.
3450  */
3451 static inline void skb_remcsum_process(struct sk_buff *skb, void *ptr,
3452                                        int start, int offset, bool nopartial)
3453 {
3454         __wsum delta;
3455 
3456         if (!nopartial) {
3457                 skb_remcsum_adjust_partial(skb, ptr, start, offset);
3458                 return;
3459         }
3460 
3461          if (unlikely(skb->ip_summed != CHECKSUM_COMPLETE)) {
3462                 __skb_checksum_complete(skb);
3463                 skb_postpull_rcsum(skb, skb->data, ptr - (void *)skb->data);
3464         }
3465 
3466         delta = remcsum_adjust(ptr, skb->csum, start, offset);
3467 
3468         /* Adjust skb->csum since we changed the packet */
3469         skb->csum = csum_add(skb->csum, delta);
3470 }
3471 
3472 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
3473 void nf_conntrack_destroy(struct nf_conntrack *nfct);
3474 static inline void nf_conntrack_put(struct nf_conntrack *nfct)
3475 {
3476         if (nfct && atomic_dec_and_test(&nfct->use))
3477                 nf_conntrack_destroy(nfct);
3478 }
3479 static inline void nf_conntrack_get(struct nf_conntrack *nfct)
3480 {
3481         if (nfct)
3482                 atomic_inc(&nfct->use);
3483 }
3484 #endif
3485 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
3486 static inline void nf_bridge_put(struct nf_bridge_info *nf_bridge)
3487 {
3488         if (nf_bridge && atomic_dec_and_test(&nf_bridge->use))
3489                 kfree(nf_bridge);
3490 }
3491 static inline void nf_bridge_get(struct nf_bridge_info *nf_bridge)
3492 {
3493         if (nf_bridge)
3494                 atomic_inc(&nf_bridge->use);
3495 }
3496 #endif /* CONFIG_BRIDGE_NETFILTER */
3497 static inline void nf_reset(struct sk_buff *skb)
3498 {
3499 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
3500         nf_conntrack_put(skb->nfct);
3501         skb->nfct = NULL;
3502 #endif
3503 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
3504         nf_bridge_put(skb->nf_bridge);
3505         skb->nf_bridge = NULL;
3506 #endif
3507 }
3508 
3509 static inline void nf_reset_trace(struct sk_buff *skb)
3510 {
3511 #if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE) || defined(CONFIG_NF_TABLES)
3512         skb->nf_trace = 0;
3513 #endif
3514 }
3515 
3516 /* Note: This doesn't put any conntrack and bridge info in dst. */
3517 static inline void __nf_copy(struct sk_buff *dst, const struct sk_buff *src,
3518                              bool copy)
3519 {
3520 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
3521         dst->nfct = src->nfct;
3522         nf_conntrack_get(src->nfct);
3523         if (copy)
3524                 dst->nfctinfo = src->nfctinfo;
3525 #endif
3526 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
3527         dst->nf_bridge  = src->nf_bridge;
3528         nf_bridge_get(src->nf_bridge);
3529 #endif
3530 #if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE) || defined(CONFIG_NF_TABLES)
3531         if (copy)
3532                 dst->nf_trace = src->nf_trace;
3533 #endif
3534 }
3535 
3536 static inline void nf_copy(struct sk_buff *dst, const struct sk_buff *src)
3537 {
3538 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
3539         nf_conntrack_put(dst->nfct);
3540 #endif
3541 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
3542         nf_bridge_put(dst->nf_bridge);
3543 #endif
3544         __nf_copy(dst, src, true);
3545 }
3546 
3547 #ifdef CONFIG_NETWORK_SECMARK
3548 static inline void skb_copy_secmark(struct sk_buff *to, const struct sk_buff *from)
3549 {
3550         to->secmark = from->secmark;
3551 }
3552 
3553 static inline void skb_init_secmark(struct sk_buff *skb)
3554 {
3555         skb->secmark = 0;
3556 }
3557 #else
3558 static inline void skb_copy_secmark(struct sk_buff *to, const struct sk_buff *from)
3559 { }
3560 
3561 static inline void skb_init_secmark(struct sk_buff *skb)
3562 { }
3563 #endif
3564 
3565 static inline bool skb_irq_freeable(const struct sk_buff *skb)
3566 {
3567         return !skb->destructor &&
3568 #if IS_ENABLED(CONFIG_XFRM)
3569                 !skb->sp &&
3570 #endif
3571 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
3572                 !skb->nfct &&
3573 #endif
3574                 !skb->_skb_refdst &&
3575                 !skb_has_frag_list(skb);
3576 }
3577 
3578 static inline void skb_set_queue_mapping(struct sk_buff *skb, u16 queue_mapping)
3579 {
3580         skb->queue_mapping = queue_mapping;
3581 }
3582 
3583 static inline u16 skb_get_queue_mapping(const struct sk_buff *skb)
3584 {
3585         return skb->queue_mapping;
3586 }
3587 
3588 static inline void skb_copy_queue_mapping(struct sk_buff *to, const struct sk_buff *from)
3589 {
3590         to->queue_mapping = from->queue_mapping;
3591 }
3592 
3593 static inline void skb_record_rx_queue(struct sk_buff *skb, u16 rx_queue)
3594 {
3595         skb->queue_mapping = rx_queue + 1;
3596 }
3597 
3598 static inline u16 skb_get_rx_queue(const struct sk_buff *skb)
3599 {
3600         return skb->queue_mapping - 1;
3601 }
3602 
3603 static inline bool skb_rx_queue_recorded(const struct sk_buff *skb)
3604 {
3605         return skb->queue_mapping != 0;
3606 }
3607 
3608 static inline struct sec_path *skb_sec_path(struct sk_buff *skb)
3609 {
3610 #ifdef CONFIG_XFRM
3611         return skb->sp;
3612 #else
3613         return NULL;
3614 #endif
3615 }
3616 
3617 /* Keeps track of mac header offset relative to skb->head.
3618  * It is useful for TSO of Tunneling protocol. e.g. GRE.
3619  * For non-tunnel skb it points to skb_mac_header() and for
3620  * tunnel skb it points to outer mac header.
3621  * Keeps track of level of encapsulation of network headers.
3622  */
3623 struct skb_gso_cb {
3624         union {
3625                 int     mac_offset;
3626                 int     data_offset;
3627         };
3628         int     encap_level;
3629         __wsum  csum;
3630         __u16   csum_start;
3631 };
3632 #define SKB_SGO_CB_OFFSET       32
3633 #define SKB_GSO_CB(skb) ((struct skb_gso_cb *)((skb)->cb + SKB_SGO_CB_OFFSET))
3634 
3635 static inline int skb_tnl_header_len(const struct sk_buff *inner_skb)
3636 {
3637         return (skb_mac_header(inner_skb) - inner_skb->head) -
3638                 SKB_GSO_CB(inner_skb)->mac_offset;
3639 }
3640 
3641 static inline int gso_pskb_expand_head(struct sk_buff *skb, int extra)
3642 {
3643         int new_headroom, headroom;
3644         int ret;
3645 
3646         headroom = skb_headroom(skb);
3647         ret = pskb_expand_head(skb, extra, 0, GFP_ATOMIC);
3648         if (ret)
3649                 return ret;
3650 
3651         new_headroom = skb_headroom(skb);
3652         SKB_GSO_CB(skb)->mac_offset += (new_headroom - headroom);
3653         return 0;
3654 }
3655 
3656 static inline void gso_reset_checksum(struct sk_buff *skb, __wsum res)
3657 {
3658         /* Do not update partial checksums if remote checksum is enabled. */
3659         if (skb->remcsum_offload)
3660                 return;
3661 
3662         SKB_GSO_CB(skb)->csum = res;
3663         SKB_GSO_CB(skb)->csum_start = skb_checksum_start(skb) - skb->head;
3664 }
3665 
3666 /* Compute the checksum for a gso segment. First compute the checksum value
3667  * from the start of transport header to SKB_GSO_CB(skb)->csum_start, and
3668  * then add in skb->csum (checksum from csum_start to end of packet).
3669  * skb->csum and csum_start are then updated to reflect the checksum of the
3670  * resultant packet starting from the transport header-- the resultant checksum
3671  * is in the res argument (i.e. normally zero or ~ of checksum of a pseudo
3672  * header.
3673  */
3674 static inline __sum16 gso_make_checksum(struct sk_buff *skb, __wsum res)
3675 {
3676         unsigned char *csum_start = skb_transport_header(skb);
3677         int plen = (skb->head + SKB_GSO_CB(skb)->csum_start) - csum_start;
3678         __wsum partial = SKB_GSO_CB(skb)->csum;
3679 
3680         SKB_GSO_CB(skb)->csum = res;
3681         SKB_GSO_CB(skb)->csum_start = csum_start - skb->head;
3682 
3683         return csum_fold(csum_partial(csum_start, plen, partial));
3684 }
3685 
3686 static inline bool skb_is_gso(const struct sk_buff *skb)
3687 {
3688         return skb_shinfo(skb)->gso_size;
3689 }
3690 
3691 /* Note: Should be called only if skb_is_gso(skb) is true */
3692 static inline bool skb_is_gso_v6(const struct sk_buff *skb)
3693 {
3694         return skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6;
3695 }
3696 
3697 void __skb_warn_lro_forwarding(const struct sk_buff *skb);
3698 
3699 static inline bool skb_warn_if_lro(const struct sk_buff *skb)
3700 {
3701         /* LRO sets gso_size but not gso_type, whereas if GSO is really
3702          * wanted then gso_type will be set. */
3703         const struct skb_shared_info *shinfo = skb_shinfo(skb);
3704 
3705         if (skb_is_nonlinear(skb) && shinfo->gso_size != 0 &&
3706             unlikely(shinfo->gso_type == 0)) {
3707                 __skb_warn_lro_forwarding(skb);
3708                 return true;
3709         }
3710         return false;
3711 }
3712 
3713 static inline void skb_forward_csum(struct sk_buff *skb)
3714 {
3715         /* Unfortunately we don't support this one.  Any brave souls? */
3716         if (skb->ip_summed == CHECKSUM_COMPLETE)
3717                 skb->ip_summed = CHECKSUM_NONE;
3718 }
3719 
3720 /**
3721  * skb_checksum_none_assert - make sure skb ip_summed is CHECKSUM_NONE
3722  * @skb: skb to check
3723  *
3724  * fresh skbs have their ip_summed set to CHECKSUM_NONE.
3725  * Instead of forcing ip_summed to CHECKSUM_NONE, we can
3726  * use this helper, to document places where we make this assertion.
3727  */
3728 static inline void skb_checksum_none_assert(const struct sk_buff *skb)
3729 {
3730 #ifdef DEBUG
3731         BUG_ON(skb->ip_summed != CHECKSUM_NONE);
3732 #endif
3733 }
3734 
3735 bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off);
3736 
3737 int skb_checksum_setup(struct sk_buff *skb, bool recalculate);
3738 struct sk_buff *skb_checksum_trimmed(struct sk_buff *skb,
3739                                      unsigned int transport_len,
3740                                      __sum16(*skb_chkf)(struct sk_buff *skb));
3741 
3742 /**
3743  * skb_head_is_locked - Determine if the skb->head is locked down
3744  * @skb: skb to check
3745  *
3746  * The head on skbs build around a head frag can be removed if they are
3747  * not cloned.  This function returns true if the skb head is locked down
3748  * due to either being allocated via kmalloc, or by being a clone with
3749  * multiple references to the head.
3750  */
3751 static inline bool skb_head_is_locked(const struct sk_buff *skb)
3752 {
3753         return !skb->head_frag || skb_cloned(skb);
3754 }
3755 
3756 /**
3757  * skb_gso_network_seglen - Return length of individual segments of a gso packet
3758  *
3759  * @skb: GSO skb
3760  *
3761  * skb_gso_network_seglen is used to determine the real size of the
3762  * individual segments, including Layer3 (IP, IPv6) and L4 headers (TCP/UDP).
3763  *
3764  * The MAC/L2 header is not accounted for.
3765  */
3766 static inline unsigned int skb_gso_network_seglen(const struct sk_buff *skb)
3767 {
3768         unsigned int hdr_len = skb_transport_header(skb) -
3769                                skb_network_header(skb);
3770         return hdr_len + skb_gso_transport_seglen(skb);
3771 }
3772 
3773 /* Local Checksum Offload.
3774  * Compute outer checksum based on the assumption that the
3775  * inner checksum will be offloaded later.
3776  * See Documentation/networking/checksum-offloads.txt for
3777  * explanation of how this works.
3778  * Fill in outer checksum adjustment (e.g. with sum of outer
3779  * pseudo-header) before calling.
3780  * Also ensure that inner checksum is in linear data area.
3781  */
3782 static inline __wsum lco_csum(struct sk_buff *skb)
3783 {
3784         unsigned char *csum_start = skb_checksum_start(skb);
3785         unsigned char *l4_hdr = skb_transport_header(skb);
3786         __wsum partial;
3787 
3788         /* Start with complement of inner checksum adjustment */
3789         partial = ~csum_unfold(*(__force __sum16 *)(csum_start +
3790                                                     skb->csum_offset));
3791 
3792         /* Add in checksum of our headers (incl. outer checksum
3793          * adjustment filled in by caller) and return result.
3794          */
3795         return csum_partial(l4_hdr, csum_start - l4_hdr, partial);
3796 }
3797 
3798 #endif  /* __KERNEL__ */
3799 #endif  /* _LINUX_SKBUFF_H */
3800 

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