Version:  2.0.40 2.2.26 2.4.37 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5

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         /* generate software timestamp on peer data acknowledgment */
387         SKBTX_ACK_TSTAMP = 1 << 7,
388 };
389 
390 #define SKBTX_ANY_SW_TSTAMP     (SKBTX_SW_TSTAMP    | \
391                                  SKBTX_SCHED_TSTAMP | \
392                                  SKBTX_ACK_TSTAMP)
393 #define SKBTX_ANY_TSTAMP        (SKBTX_HW_TSTAMP | SKBTX_ANY_SW_TSTAMP)
394 
395 /*
396  * The callback notifies userspace to release buffers when skb DMA is done in
397  * lower device, the skb last reference should be 0 when calling this.
398  * The zerocopy_success argument is true if zero copy transmit occurred,
399  * false on data copy or out of memory error caused by data copy attempt.
400  * The ctx field is used to track device context.
401  * The desc field is used to track userspace buffer index.
402  */
403 struct ubuf_info {
404         void (*callback)(struct ubuf_info *, bool zerocopy_success);
405         void *ctx;
406         unsigned long desc;
407 };
408 
409 /* This data is invariant across clones and lives at
410  * the end of the header data, ie. at skb->end.
411  */
412 struct skb_shared_info {
413         unsigned char   nr_frags;
414         __u8            tx_flags;
415         unsigned short  gso_size;
416         /* Warning: this field is not always filled in (UFO)! */
417         unsigned short  gso_segs;
418         unsigned short  gso_type;
419         struct sk_buff  *frag_list;
420         struct skb_shared_hwtstamps hwtstamps;
421         u32             tskey;
422         __be32          ip6_frag_id;
423 
424         /*
425          * Warning : all fields before dataref are cleared in __alloc_skb()
426          */
427         atomic_t        dataref;
428 
429         /* Intermediate layers must ensure that destructor_arg
430          * remains valid until skb destructor */
431         void *          destructor_arg;
432 
433         /* must be last field, see pskb_expand_head() */
434         skb_frag_t      frags[MAX_SKB_FRAGS];
435 };
436 
437 /* We divide dataref into two halves.  The higher 16 bits hold references
438  * to the payload part of skb->data.  The lower 16 bits hold references to
439  * the entire skb->data.  A clone of a headerless skb holds the length of
440  * the header in skb->hdr_len.
441  *
442  * All users must obey the rule that the skb->data reference count must be
443  * greater than or equal to the payload reference count.
444  *
445  * Holding a reference to the payload part means that the user does not
446  * care about modifications to the header part of skb->data.
447  */
448 #define SKB_DATAREF_SHIFT 16
449 #define SKB_DATAREF_MASK ((1 << SKB_DATAREF_SHIFT) - 1)
450 
451 
452 enum {
453         SKB_FCLONE_UNAVAILABLE, /* skb has no fclone (from head_cache) */
454         SKB_FCLONE_ORIG,        /* orig skb (from fclone_cache) */
455         SKB_FCLONE_CLONE,       /* companion fclone skb (from fclone_cache) */
456 };
457 
458 enum {
459         SKB_GSO_TCPV4 = 1 << 0,
460         SKB_GSO_UDP = 1 << 1,
461 
462         /* This indicates the skb is from an untrusted source. */
463         SKB_GSO_DODGY = 1 << 2,
464 
465         /* This indicates the tcp segment has CWR set. */
466         SKB_GSO_TCP_ECN = 1 << 3,
467 
468         SKB_GSO_TCPV6 = 1 << 4,
469 
470         SKB_GSO_FCOE = 1 << 5,
471 
472         SKB_GSO_GRE = 1 << 6,
473 
474         SKB_GSO_GRE_CSUM = 1 << 7,
475 
476         SKB_GSO_IPIP = 1 << 8,
477 
478         SKB_GSO_SIT = 1 << 9,
479 
480         SKB_GSO_UDP_TUNNEL = 1 << 10,
481 
482         SKB_GSO_UDP_TUNNEL_CSUM = 1 << 11,
483 
484         SKB_GSO_TUNNEL_REMCSUM = 1 << 12,
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_poff(const struct sk_buff *skb);
1066 u32 __skb_get_poff(const struct sk_buff *skb, void *data,
1067                    const struct flow_keys *keys, int hlen);
1068 __be32 __skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto,
1069                             void *data, int hlen_proto);
1070 
1071 static inline __be32 skb_flow_get_ports(const struct sk_buff *skb,
1072                                         int thoff, u8 ip_proto)
1073 {
1074         return __skb_flow_get_ports(skb, thoff, ip_proto, NULL, 0);
1075 }
1076 
1077 void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
1078                              const struct flow_dissector_key *key,
1079                              unsigned int key_count);
1080 
1081 bool __skb_flow_dissect(const struct sk_buff *skb,
1082                         struct flow_dissector *flow_dissector,
1083                         void *target_container,
1084                         void *data, __be16 proto, int nhoff, int hlen,
1085                         unsigned int flags);
1086 
1087 static inline bool skb_flow_dissect(const struct sk_buff *skb,
1088                                     struct flow_dissector *flow_dissector,
1089                                     void *target_container, unsigned int flags)
1090 {
1091         return __skb_flow_dissect(skb, flow_dissector, target_container,
1092                                   NULL, 0, 0, 0, flags);
1093 }
1094 
1095 static inline bool skb_flow_dissect_flow_keys(const struct sk_buff *skb,
1096                                               struct flow_keys *flow,
1097                                               unsigned int flags)
1098 {
1099         memset(flow, 0, sizeof(*flow));
1100         return __skb_flow_dissect(skb, &flow_keys_dissector, flow,
1101                                   NULL, 0, 0, 0, flags);
1102 }
1103 
1104 static inline bool skb_flow_dissect_flow_keys_buf(struct flow_keys *flow,
1105                                                   void *data, __be16 proto,
1106                                                   int nhoff, int hlen,
1107                                                   unsigned int flags)
1108 {
1109         memset(flow, 0, sizeof(*flow));
1110         return __skb_flow_dissect(NULL, &flow_keys_buf_dissector, flow,
1111                                   data, proto, nhoff, hlen, flags);
1112 }
1113 
1114 static inline __u32 skb_get_hash(struct sk_buff *skb)
1115 {
1116         if (!skb->l4_hash && !skb->sw_hash)
1117                 __skb_get_hash(skb);
1118 
1119         return skb->hash;
1120 }
1121 
1122 __u32 __skb_get_hash_flowi6(struct sk_buff *skb, const struct flowi6 *fl6);
1123 
1124 static inline __u32 skb_get_hash_flowi6(struct sk_buff *skb, const struct flowi6 *fl6)
1125 {
1126         if (!skb->l4_hash && !skb->sw_hash) {
1127                 struct flow_keys keys;
1128                 __u32 hash = __get_hash_from_flowi6(fl6, &keys);
1129 
1130                 __skb_set_sw_hash(skb, hash, flow_keys_have_l4(&keys));
1131         }
1132 
1133         return skb->hash;
1134 }
1135 
1136 __u32 __skb_get_hash_flowi4(struct sk_buff *skb, const struct flowi4 *fl);
1137 
1138 static inline __u32 skb_get_hash_flowi4(struct sk_buff *skb, const struct flowi4 *fl4)
1139 {
1140         if (!skb->l4_hash && !skb->sw_hash) {
1141                 struct flow_keys keys;
1142                 __u32 hash = __get_hash_from_flowi4(fl4, &keys);
1143 
1144                 __skb_set_sw_hash(skb, hash, flow_keys_have_l4(&keys));
1145         }
1146 
1147         return skb->hash;
1148 }
1149 
1150 __u32 skb_get_hash_perturb(const struct sk_buff *skb, u32 perturb);
1151 
1152 static inline __u32 skb_get_hash_raw(const struct sk_buff *skb)
1153 {
1154         return skb->hash;
1155 }
1156 
1157 static inline void skb_copy_hash(struct sk_buff *to, const struct sk_buff *from)
1158 {
1159         to->hash = from->hash;
1160         to->sw_hash = from->sw_hash;
1161         to->l4_hash = from->l4_hash;
1162 };
1163 
1164 static inline void skb_sender_cpu_clear(struct sk_buff *skb)
1165 {
1166 }
1167 
1168 #ifdef NET_SKBUFF_DATA_USES_OFFSET
1169 static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
1170 {
1171         return skb->head + skb->end;
1172 }
1173 
1174 static inline unsigned int skb_end_offset(const struct sk_buff *skb)
1175 {
1176         return skb->end;
1177 }
1178 #else
1179 static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
1180 {
1181         return skb->end;
1182 }
1183 
1184 static inline unsigned int skb_end_offset(const struct sk_buff *skb)
1185 {
1186         return skb->end - skb->head;
1187 }
1188 #endif
1189 
1190 /* Internal */
1191 #define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB)))
1192 
1193 static inline struct skb_shared_hwtstamps *skb_hwtstamps(struct sk_buff *skb)
1194 {
1195         return &skb_shinfo(skb)->hwtstamps;
1196 }
1197 
1198 /**
1199  *      skb_queue_empty - check if a queue is empty
1200  *      @list: queue head
1201  *
1202  *      Returns true if the queue is empty, false otherwise.
1203  */
1204 static inline int skb_queue_empty(const struct sk_buff_head *list)
1205 {
1206         return list->next == (const struct sk_buff *) list;
1207 }
1208 
1209 /**
1210  *      skb_queue_is_last - check if skb is the last entry in the queue
1211  *      @list: queue head
1212  *      @skb: buffer
1213  *
1214  *      Returns true if @skb is the last buffer on the list.
1215  */
1216 static inline bool skb_queue_is_last(const struct sk_buff_head *list,
1217                                      const struct sk_buff *skb)
1218 {
1219         return skb->next == (const struct sk_buff *) list;
1220 }
1221 
1222 /**
1223  *      skb_queue_is_first - check if skb is the first entry in the queue
1224  *      @list: queue head
1225  *      @skb: buffer
1226  *
1227  *      Returns true if @skb is the first buffer on the list.
1228  */
1229 static inline bool skb_queue_is_first(const struct sk_buff_head *list,
1230                                       const struct sk_buff *skb)
1231 {
1232         return skb->prev == (const struct sk_buff *) list;
1233 }
1234 
1235 /**
1236  *      skb_queue_next - return the next packet in the queue
1237  *      @list: queue head
1238  *      @skb: current buffer
1239  *
1240  *      Return the next packet in @list after @skb.  It is only valid to
1241  *      call this if skb_queue_is_last() evaluates to false.
1242  */
1243 static inline struct sk_buff *skb_queue_next(const struct sk_buff_head *list,
1244                                              const struct sk_buff *skb)
1245 {
1246         /* This BUG_ON may seem severe, but if we just return then we
1247          * are going to dereference garbage.
1248          */
1249         BUG_ON(skb_queue_is_last(list, skb));
1250         return skb->next;
1251 }
1252 
1253 /**
1254  *      skb_queue_prev - return the prev packet in the queue
1255  *      @list: queue head
1256  *      @skb: current buffer
1257  *
1258  *      Return the prev packet in @list before @skb.  It is only valid to
1259  *      call this if skb_queue_is_first() evaluates to false.
1260  */
1261 static inline struct sk_buff *skb_queue_prev(const struct sk_buff_head *list,
1262                                              const struct sk_buff *skb)
1263 {
1264         /* This BUG_ON may seem severe, but if we just return then we
1265          * are going to dereference garbage.
1266          */
1267         BUG_ON(skb_queue_is_first(list, skb));
1268         return skb->prev;
1269 }
1270 
1271 /**
1272  *      skb_get - reference buffer
1273  *      @skb: buffer to reference
1274  *
1275  *      Makes another reference to a socket buffer and returns a pointer
1276  *      to the buffer.
1277  */
1278 static inline struct sk_buff *skb_get(struct sk_buff *skb)
1279 {
1280         atomic_inc(&skb->users);
1281         return skb;
1282 }
1283 
1284 /*
1285  * If users == 1, we are the only owner and are can avoid redundant
1286  * atomic change.
1287  */
1288 
1289 /**
1290  *      skb_cloned - is the buffer a clone
1291  *      @skb: buffer to check
1292  *
1293  *      Returns true if the buffer was generated with skb_clone() and is
1294  *      one of multiple shared copies of the buffer. Cloned buffers are
1295  *      shared data so must not be written to under normal circumstances.
1296  */
1297 static inline int skb_cloned(const struct sk_buff *skb)
1298 {
1299         return skb->cloned &&
1300                (atomic_read(&skb_shinfo(skb)->dataref) & SKB_DATAREF_MASK) != 1;
1301 }
1302 
1303 static inline int skb_unclone(struct sk_buff *skb, gfp_t pri)
1304 {
1305         might_sleep_if(gfpflags_allow_blocking(pri));
1306 
1307         if (skb_cloned(skb))
1308                 return pskb_expand_head(skb, 0, 0, pri);
1309 
1310         return 0;
1311 }
1312 
1313 /**
1314  *      skb_header_cloned - is the header a clone
1315  *      @skb: buffer to check
1316  *
1317  *      Returns true if modifying the header part of the buffer requires
1318  *      the data to be copied.
1319  */
1320 static inline int skb_header_cloned(const struct sk_buff *skb)
1321 {
1322         int dataref;
1323 
1324         if (!skb->cloned)
1325                 return 0;
1326 
1327         dataref = atomic_read(&skb_shinfo(skb)->dataref);
1328         dataref = (dataref & SKB_DATAREF_MASK) - (dataref >> SKB_DATAREF_SHIFT);
1329         return dataref != 1;
1330 }
1331 
1332 /**
1333  *      skb_header_release - release reference to header
1334  *      @skb: buffer to operate on
1335  *
1336  *      Drop a reference to the header part of the buffer.  This is done
1337  *      by acquiring a payload reference.  You must not read from the header
1338  *      part of skb->data after this.
1339  *      Note : Check if you can use __skb_header_release() instead.
1340  */
1341 static inline void skb_header_release(struct sk_buff *skb)
1342 {
1343         BUG_ON(skb->nohdr);
1344         skb->nohdr = 1;
1345         atomic_add(1 << SKB_DATAREF_SHIFT, &skb_shinfo(skb)->dataref);
1346 }
1347 
1348 /**
1349  *      __skb_header_release - release reference to header
1350  *      @skb: buffer to operate on
1351  *
1352  *      Variant of skb_header_release() assuming skb is private to caller.
1353  *      We can avoid one atomic operation.
1354  */
1355 static inline void __skb_header_release(struct sk_buff *skb)
1356 {
1357         skb->nohdr = 1;
1358         atomic_set(&skb_shinfo(skb)->dataref, 1 + (1 << SKB_DATAREF_SHIFT));
1359 }
1360 
1361 
1362 /**
1363  *      skb_shared - is the buffer shared
1364  *      @skb: buffer to check
1365  *
1366  *      Returns true if more than one person has a reference to this
1367  *      buffer.
1368  */
1369 static inline int skb_shared(const struct sk_buff *skb)
1370 {
1371         return atomic_read(&skb->users) != 1;
1372 }
1373 
1374 /**
1375  *      skb_share_check - check if buffer is shared and if so clone it
1376  *      @skb: buffer to check
1377  *      @pri: priority for memory allocation
1378  *
1379  *      If the buffer is shared the buffer is cloned and the old copy
1380  *      drops a reference. A new clone with a single reference is returned.
1381  *      If the buffer is not shared the original buffer is returned. When
1382  *      being called from interrupt status or with spinlocks held pri must
1383  *      be GFP_ATOMIC.
1384  *
1385  *      NULL is returned on a memory allocation failure.
1386  */
1387 static inline struct sk_buff *skb_share_check(struct sk_buff *skb, gfp_t pri)
1388 {
1389         might_sleep_if(gfpflags_allow_blocking(pri));
1390         if (skb_shared(skb)) {
1391                 struct sk_buff *nskb = skb_clone(skb, pri);
1392 
1393                 if (likely(nskb))
1394                         consume_skb(skb);
1395                 else
1396                         kfree_skb(skb);
1397                 skb = nskb;
1398         }
1399         return skb;
1400 }
1401 
1402 /*
1403  *      Copy shared buffers into a new sk_buff. We effectively do COW on
1404  *      packets to handle cases where we have a local reader and forward
1405  *      and a couple of other messy ones. The normal one is tcpdumping
1406  *      a packet thats being forwarded.
1407  */
1408 
1409 /**
1410  *      skb_unshare - make a copy of a shared buffer
1411  *      @skb: buffer to check
1412  *      @pri: priority for memory allocation
1413  *
1414  *      If the socket buffer is a clone then this function creates a new
1415  *      copy of the data, drops a reference count on the old copy and returns
1416  *      the new copy with the reference count at 1. If the buffer is not a clone
1417  *      the original buffer is returned. When called with a spinlock held or
1418  *      from interrupt state @pri must be %GFP_ATOMIC
1419  *
1420  *      %NULL is returned on a memory allocation failure.
1421  */
1422 static inline struct sk_buff *skb_unshare(struct sk_buff *skb,
1423                                           gfp_t pri)
1424 {
1425         might_sleep_if(gfpflags_allow_blocking(pri));
1426         if (skb_cloned(skb)) {
1427                 struct sk_buff *nskb = skb_copy(skb, pri);
1428 
1429                 /* Free our shared copy */
1430                 if (likely(nskb))
1431                         consume_skb(skb);
1432                 else
1433                         kfree_skb(skb);
1434                 skb = nskb;
1435         }
1436         return skb;
1437 }
1438 
1439 /**
1440  *      skb_peek - peek at the head of an &sk_buff_head
1441  *      @list_: list to peek at
1442  *
1443  *      Peek an &sk_buff. Unlike most other operations you _MUST_
1444  *      be careful with this one. A peek leaves the buffer on the
1445  *      list and someone else may run off with it. You must hold
1446  *      the appropriate locks or have a private queue to do this.
1447  *
1448  *      Returns %NULL for an empty list or a pointer to the head element.
1449  *      The reference count is not incremented and the reference is therefore
1450  *      volatile. Use with caution.
1451  */
1452 static inline struct sk_buff *skb_peek(const struct sk_buff_head *list_)
1453 {
1454         struct sk_buff *skb = list_->next;
1455 
1456         if (skb == (struct sk_buff *)list_)
1457                 skb = NULL;
1458         return skb;
1459 }
1460 
1461 /**
1462  *      skb_peek_next - peek skb following the given one from a queue
1463  *      @skb: skb to start from
1464  *      @list_: list to peek at
1465  *
1466  *      Returns %NULL when the end of the list is met or a pointer to the
1467  *      next element. The reference count is not incremented and the
1468  *      reference is therefore volatile. Use with caution.
1469  */
1470 static inline struct sk_buff *skb_peek_next(struct sk_buff *skb,
1471                 const struct sk_buff_head *list_)
1472 {
1473         struct sk_buff *next = skb->next;
1474 
1475         if (next == (struct sk_buff *)list_)
1476                 next = NULL;
1477         return next;
1478 }
1479 
1480 /**
1481  *      skb_peek_tail - peek at the tail of an &sk_buff_head
1482  *      @list_: list to peek at
1483  *
1484  *      Peek an &sk_buff. Unlike most other operations you _MUST_
1485  *      be careful with this one. A peek leaves the buffer on the
1486  *      list and someone else may run off with it. You must hold
1487  *      the appropriate locks or have a private queue to do this.
1488  *
1489  *      Returns %NULL for an empty list or a pointer to the tail element.
1490  *      The reference count is not incremented and the reference is therefore
1491  *      volatile. Use with caution.
1492  */
1493 static inline struct sk_buff *skb_peek_tail(const struct sk_buff_head *list_)
1494 {
1495         struct sk_buff *skb = list_->prev;
1496 
1497         if (skb == (struct sk_buff *)list_)
1498                 skb = NULL;
1499         return skb;
1500 
1501 }
1502 
1503 /**
1504  *      skb_queue_len   - get queue length
1505  *      @list_: list to measure
1506  *
1507  *      Return the length of an &sk_buff queue.
1508  */
1509 static inline __u32 skb_queue_len(const struct sk_buff_head *list_)
1510 {
1511         return list_->qlen;
1512 }
1513 
1514 /**
1515  *      __skb_queue_head_init - initialize non-spinlock portions of sk_buff_head
1516  *      @list: queue to initialize
1517  *
1518  *      This initializes only the list and queue length aspects of
1519  *      an sk_buff_head object.  This allows to initialize the list
1520  *      aspects of an sk_buff_head without reinitializing things like
1521  *      the spinlock.  It can also be used for on-stack sk_buff_head
1522  *      objects where the spinlock is known to not be used.
1523  */
1524 static inline void __skb_queue_head_init(struct sk_buff_head *list)
1525 {
1526         list->prev = list->next = (struct sk_buff *)list;
1527         list->qlen = 0;
1528 }
1529 
1530 /*
1531  * This function creates a split out lock class for each invocation;
1532  * this is needed for now since a whole lot of users of the skb-queue
1533  * infrastructure in drivers have different locking usage (in hardirq)
1534  * than the networking core (in softirq only). In the long run either the
1535  * network layer or drivers should need annotation to consolidate the
1536  * main types of usage into 3 classes.
1537  */
1538 static inline void skb_queue_head_init(struct sk_buff_head *list)
1539 {
1540         spin_lock_init(&list->lock);
1541         __skb_queue_head_init(list);
1542 }
1543 
1544 static inline void skb_queue_head_init_class(struct sk_buff_head *list,
1545                 struct lock_class_key *class)
1546 {
1547         skb_queue_head_init(list);
1548         lockdep_set_class(&list->lock, class);
1549 }
1550 
1551 /*
1552  *      Insert an sk_buff on a list.
1553  *
1554  *      The "__skb_xxxx()" functions are the non-atomic ones that
1555  *      can only be called with interrupts disabled.
1556  */
1557 void skb_insert(struct sk_buff *old, struct sk_buff *newsk,
1558                 struct sk_buff_head *list);
1559 static inline void __skb_insert(struct sk_buff *newsk,
1560                                 struct sk_buff *prev, struct sk_buff *next,
1561                                 struct sk_buff_head *list)
1562 {
1563         newsk->next = next;
1564         newsk->prev = prev;
1565         next->prev  = prev->next = newsk;
1566         list->qlen++;
1567 }
1568 
1569 static inline void __skb_queue_splice(const struct sk_buff_head *list,
1570                                       struct sk_buff *prev,
1571                                       struct sk_buff *next)
1572 {
1573         struct sk_buff *first = list->next;
1574         struct sk_buff *last = list->prev;
1575 
1576         first->prev = prev;
1577         prev->next = first;
1578 
1579         last->next = next;
1580         next->prev = last;
1581 }
1582 
1583 /**
1584  *      skb_queue_splice - join two skb lists, this is designed for stacks
1585  *      @list: the new list to add
1586  *      @head: the place to add it in the first list
1587  */
1588 static inline void skb_queue_splice(const struct sk_buff_head *list,
1589                                     struct sk_buff_head *head)
1590 {
1591         if (!skb_queue_empty(list)) {
1592                 __skb_queue_splice(list, (struct sk_buff *) head, head->next);
1593                 head->qlen += list->qlen;
1594         }
1595 }
1596 
1597 /**
1598  *      skb_queue_splice_init - join two skb lists and reinitialise the emptied list
1599  *      @list: the new list to add
1600  *      @head: the place to add it in the first list
1601  *
1602  *      The list at @list is reinitialised
1603  */
1604 static inline void skb_queue_splice_init(struct sk_buff_head *list,
1605                                          struct sk_buff_head *head)
1606 {
1607         if (!skb_queue_empty(list)) {
1608                 __skb_queue_splice(list, (struct sk_buff *) head, head->next);
1609                 head->qlen += list->qlen;
1610                 __skb_queue_head_init(list);
1611         }
1612 }
1613 
1614 /**
1615  *      skb_queue_splice_tail - join two skb lists, each list being a queue
1616  *      @list: the new list to add
1617  *      @head: the place to add it in the first list
1618  */
1619 static inline void skb_queue_splice_tail(const struct sk_buff_head *list,
1620                                          struct sk_buff_head *head)
1621 {
1622         if (!skb_queue_empty(list)) {
1623                 __skb_queue_splice(list, head->prev, (struct sk_buff *) head);
1624                 head->qlen += list->qlen;
1625         }
1626 }
1627 
1628 /**
1629  *      skb_queue_splice_tail_init - join two skb lists and reinitialise the emptied list
1630  *      @list: the new list to add
1631  *      @head: the place to add it in the first list
1632  *
1633  *      Each of the lists is a queue.
1634  *      The list at @list is reinitialised
1635  */
1636 static inline void skb_queue_splice_tail_init(struct sk_buff_head *list,
1637                                               struct sk_buff_head *head)
1638 {
1639         if (!skb_queue_empty(list)) {
1640                 __skb_queue_splice(list, head->prev, (struct sk_buff *) head);
1641                 head->qlen += list->qlen;
1642                 __skb_queue_head_init(list);
1643         }
1644 }
1645 
1646 /**
1647  *      __skb_queue_after - queue a buffer at the list head
1648  *      @list: list to use
1649  *      @prev: place after this buffer
1650  *      @newsk: buffer to queue
1651  *
1652  *      Queue a buffer int the middle of a list. This function takes no locks
1653  *      and you must therefore hold required locks before calling it.
1654  *
1655  *      A buffer cannot be placed on two lists at the same time.
1656  */
1657 static inline void __skb_queue_after(struct sk_buff_head *list,
1658                                      struct sk_buff *prev,
1659                                      struct sk_buff *newsk)
1660 {
1661         __skb_insert(newsk, prev, prev->next, list);
1662 }
1663 
1664 void skb_append(struct sk_buff *old, struct sk_buff *newsk,
1665                 struct sk_buff_head *list);
1666 
1667 static inline void __skb_queue_before(struct sk_buff_head *list,
1668                                       struct sk_buff *next,
1669                                       struct sk_buff *newsk)
1670 {
1671         __skb_insert(newsk, next->prev, next, list);
1672 }
1673 
1674 /**
1675  *      __skb_queue_head - queue a buffer at the list head
1676  *      @list: list to use
1677  *      @newsk: buffer to queue
1678  *
1679  *      Queue a buffer at the start of a list. This function takes no locks
1680  *      and you must therefore hold required locks before calling it.
1681  *
1682  *      A buffer cannot be placed on two lists at the same time.
1683  */
1684 void skb_queue_head(struct sk_buff_head *list, struct sk_buff *newsk);
1685 static inline void __skb_queue_head(struct sk_buff_head *list,
1686                                     struct sk_buff *newsk)
1687 {
1688         __skb_queue_after(list, (struct sk_buff *)list, newsk);
1689 }
1690 
1691 /**
1692  *      __skb_queue_tail - queue a buffer at the list tail
1693  *      @list: list to use
1694  *      @newsk: buffer to queue
1695  *
1696  *      Queue a buffer at the end of a list. This function takes no locks
1697  *      and you must therefore hold required locks before calling it.
1698  *
1699  *      A buffer cannot be placed on two lists at the same time.
1700  */
1701 void skb_queue_tail(struct sk_buff_head *list, struct sk_buff *newsk);
1702 static inline void __skb_queue_tail(struct sk_buff_head *list,
1703                                    struct sk_buff *newsk)
1704 {
1705         __skb_queue_before(list, (struct sk_buff *)list, newsk);
1706 }
1707 
1708 /*
1709  * remove sk_buff from list. _Must_ be called atomically, and with
1710  * the list known..
1711  */
1712 void skb_unlink(struct sk_buff *skb, struct sk_buff_head *list);
1713 static inline void __skb_unlink(struct sk_buff *skb, struct sk_buff_head *list)
1714 {
1715         struct sk_buff *next, *prev;
1716 
1717         list->qlen--;
1718         next       = skb->next;
1719         prev       = skb->prev;
1720         skb->next  = skb->prev = NULL;
1721         next->prev = prev;
1722         prev->next = next;
1723 }
1724 
1725 /**
1726  *      __skb_dequeue - remove from the head of the queue
1727  *      @list: list to dequeue from
1728  *
1729  *      Remove the head of the list. This function does not take any locks
1730  *      so must be used with appropriate locks held only. The head item is
1731  *      returned or %NULL if the list is empty.
1732  */
1733 struct sk_buff *skb_dequeue(struct sk_buff_head *list);
1734 static inline struct sk_buff *__skb_dequeue(struct sk_buff_head *list)
1735 {
1736         struct sk_buff *skb = skb_peek(list);
1737         if (skb)
1738                 __skb_unlink(skb, list);
1739         return skb;
1740 }
1741 
1742 /**
1743  *      __skb_dequeue_tail - remove from the tail of the queue
1744  *      @list: list to dequeue from
1745  *
1746  *      Remove the tail of the list. This function does not take any locks
1747  *      so must be used with appropriate locks held only. The tail item is
1748  *      returned or %NULL if the list is empty.
1749  */
1750 struct sk_buff *skb_dequeue_tail(struct sk_buff_head *list);
1751 static inline struct sk_buff *__skb_dequeue_tail(struct sk_buff_head *list)
1752 {
1753         struct sk_buff *skb = skb_peek_tail(list);
1754         if (skb)
1755                 __skb_unlink(skb, list);
1756         return skb;
1757 }
1758 
1759 
1760 static inline bool skb_is_nonlinear(const struct sk_buff *skb)
1761 {
1762         return skb->data_len;
1763 }
1764 
1765 static inline unsigned int skb_headlen(const struct sk_buff *skb)
1766 {
1767         return skb->len - skb->data_len;
1768 }
1769 
1770 static inline int skb_pagelen(const struct sk_buff *skb)
1771 {
1772         int i, len = 0;
1773 
1774         for (i = (int)skb_shinfo(skb)->nr_frags - 1; i >= 0; i--)
1775                 len += skb_frag_size(&skb_shinfo(skb)->frags[i]);
1776         return len + skb_headlen(skb);
1777 }
1778 
1779 /**
1780  * __skb_fill_page_desc - initialise a paged fragment in an skb
1781  * @skb: buffer containing fragment to be initialised
1782  * @i: paged fragment index to initialise
1783  * @page: the page to use for this fragment
1784  * @off: the offset to the data with @page
1785  * @size: the length of the data
1786  *
1787  * Initialises the @i'th fragment of @skb to point to &size bytes at
1788  * offset @off within @page.
1789  *
1790  * Does not take any additional reference on the fragment.
1791  */
1792 static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
1793                                         struct page *page, int off, int size)
1794 {
1795         skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
1796 
1797         /*
1798          * Propagate page pfmemalloc to the skb if we can. The problem is
1799          * that not all callers have unique ownership of the page but rely
1800          * on page_is_pfmemalloc doing the right thing(tm).
1801          */
1802         frag->page.p              = page;
1803         frag->page_offset         = off;
1804         skb_frag_size_set(frag, size);
1805 
1806         page = compound_head(page);
1807         if (page_is_pfmemalloc(page))
1808                 skb->pfmemalloc = true;
1809 }
1810 
1811 /**
1812  * skb_fill_page_desc - initialise a paged fragment in an skb
1813  * @skb: buffer containing fragment to be initialised
1814  * @i: paged fragment index to initialise
1815  * @page: the page to use for this fragment
1816  * @off: the offset to the data with @page
1817  * @size: the length of the data
1818  *
1819  * As per __skb_fill_page_desc() -- initialises the @i'th fragment of
1820  * @skb to point to @size bytes at offset @off within @page. In
1821  * addition updates @skb such that @i is the last fragment.
1822  *
1823  * Does not take any additional reference on the fragment.
1824  */
1825 static inline void skb_fill_page_desc(struct sk_buff *skb, int i,
1826                                       struct page *page, int off, int size)
1827 {
1828         __skb_fill_page_desc(skb, i, page, off, size);
1829         skb_shinfo(skb)->nr_frags = i + 1;
1830 }
1831 
1832 void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
1833                      int size, unsigned int truesize);
1834 
1835 void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int size,
1836                           unsigned int truesize);
1837 
1838 #define SKB_PAGE_ASSERT(skb)    BUG_ON(skb_shinfo(skb)->nr_frags)
1839 #define SKB_FRAG_ASSERT(skb)    BUG_ON(skb_has_frag_list(skb))
1840 #define SKB_LINEAR_ASSERT(skb)  BUG_ON(skb_is_nonlinear(skb))
1841 
1842 #ifdef NET_SKBUFF_DATA_USES_OFFSET
1843 static inline unsigned char *skb_tail_pointer(const struct sk_buff *skb)
1844 {
1845         return skb->head + skb->tail;
1846 }
1847 
1848 static inline void skb_reset_tail_pointer(struct sk_buff *skb)
1849 {
1850         skb->tail = skb->data - skb->head;
1851 }
1852 
1853 static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)
1854 {
1855         skb_reset_tail_pointer(skb);
1856         skb->tail += offset;
1857 }
1858 
1859 #else /* NET_SKBUFF_DATA_USES_OFFSET */
1860 static inline unsigned char *skb_tail_pointer(const struct sk_buff *skb)
1861 {
1862         return skb->tail;
1863 }
1864 
1865 static inline void skb_reset_tail_pointer(struct sk_buff *skb)
1866 {
1867         skb->tail = skb->data;
1868 }
1869 
1870 static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)
1871 {
1872         skb->tail = skb->data + offset;
1873 }
1874 
1875 #endif /* NET_SKBUFF_DATA_USES_OFFSET */
1876 
1877 /*
1878  *      Add data to an sk_buff
1879  */
1880 unsigned char *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len);
1881 unsigned char *skb_put(struct sk_buff *skb, unsigned int len);
1882 static inline unsigned char *__skb_put(struct sk_buff *skb, unsigned int len)
1883 {
1884         unsigned char *tmp = skb_tail_pointer(skb);
1885         SKB_LINEAR_ASSERT(skb);
1886         skb->tail += len;
1887         skb->len  += len;
1888         return tmp;
1889 }
1890 
1891 unsigned char *skb_push(struct sk_buff *skb, unsigned int len);
1892 static inline unsigned char *__skb_push(struct sk_buff *skb, unsigned int len)
1893 {
1894         skb->data -= len;
1895         skb->len  += len;
1896         return skb->data;
1897 }
1898 
1899 unsigned char *skb_pull(struct sk_buff *skb, unsigned int len);
1900 static inline unsigned char *__skb_pull(struct sk_buff *skb, unsigned int len)
1901 {
1902         skb->len -= len;
1903         BUG_ON(skb->len < skb->data_len);
1904         return skb->data += len;
1905 }
1906 
1907 static inline unsigned char *skb_pull_inline(struct sk_buff *skb, unsigned int len)
1908 {
1909         return unlikely(len > skb->len) ? NULL : __skb_pull(skb, len);
1910 }
1911 
1912 unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta);
1913 
1914 static inline unsigned char *__pskb_pull(struct sk_buff *skb, unsigned int len)
1915 {
1916         if (len > skb_headlen(skb) &&
1917             !__pskb_pull_tail(skb, len - skb_headlen(skb)))
1918                 return NULL;
1919         skb->len -= len;
1920         return skb->data += len;
1921 }
1922 
1923 static inline unsigned char *pskb_pull(struct sk_buff *skb, unsigned int len)
1924 {
1925         return unlikely(len > skb->len) ? NULL : __pskb_pull(skb, len);
1926 }
1927 
1928 static inline int pskb_may_pull(struct sk_buff *skb, unsigned int len)
1929 {
1930         if (likely(len <= skb_headlen(skb)))
1931                 return 1;
1932         if (unlikely(len > skb->len))
1933                 return 0;
1934         return __pskb_pull_tail(skb, len - skb_headlen(skb)) != NULL;
1935 }
1936 
1937 /**
1938  *      skb_headroom - bytes at buffer head
1939  *      @skb: buffer to check
1940  *
1941  *      Return the number of bytes of free space at the head of an &sk_buff.
1942  */
1943 static inline unsigned int skb_headroom(const struct sk_buff *skb)
1944 {
1945         return skb->data - skb->head;
1946 }
1947 
1948 /**
1949  *      skb_tailroom - bytes at buffer end
1950  *      @skb: buffer to check
1951  *
1952  *      Return the number of bytes of free space at the tail of an sk_buff
1953  */
1954 static inline int skb_tailroom(const struct sk_buff *skb)
1955 {
1956         return skb_is_nonlinear(skb) ? 0 : skb->end - skb->tail;
1957 }
1958 
1959 /**
1960  *      skb_availroom - bytes at buffer end
1961  *      @skb: buffer to check
1962  *
1963  *      Return the number of bytes of free space at the tail of an sk_buff
1964  *      allocated by sk_stream_alloc()
1965  */
1966 static inline int skb_availroom(const struct sk_buff *skb)
1967 {
1968         if (skb_is_nonlinear(skb))
1969                 return 0;
1970 
1971         return skb->end - skb->tail - skb->reserved_tailroom;
1972 }
1973 
1974 /**
1975  *      skb_reserve - adjust headroom
1976  *      @skb: buffer to alter
1977  *      @len: bytes to move
1978  *
1979  *      Increase the headroom of an empty &sk_buff by reducing the tail
1980  *      room. This is only allowed for an empty buffer.
1981  */
1982 static inline void skb_reserve(struct sk_buff *skb, int len)
1983 {
1984         skb->data += len;
1985         skb->tail += len;
1986 }
1987 
1988 /**
1989  *      skb_tailroom_reserve - adjust reserved_tailroom
1990  *      @skb: buffer to alter
1991  *      @mtu: maximum amount of headlen permitted
1992  *      @needed_tailroom: minimum amount of reserved_tailroom
1993  *
1994  *      Set reserved_tailroom so that headlen can be as large as possible but
1995  *      not larger than mtu and tailroom cannot be smaller than
1996  *      needed_tailroom.
1997  *      The required headroom should already have been reserved before using
1998  *      this function.
1999  */
2000 static inline void skb_tailroom_reserve(struct sk_buff *skb, unsigned int mtu,
2001                                         unsigned int needed_tailroom)
2002 {
2003         SKB_LINEAR_ASSERT(skb);
2004         if (mtu < skb_tailroom(skb) - needed_tailroom)
2005                 /* use at most mtu */
2006                 skb->reserved_tailroom = skb_tailroom(skb) - mtu;
2007         else
2008                 /* use up to all available space */
2009                 skb->reserved_tailroom = needed_tailroom;
2010 }
2011 
2012 #define ENCAP_TYPE_ETHER        0
2013 #define ENCAP_TYPE_IPPROTO      1
2014 
2015 static inline void skb_set_inner_protocol(struct sk_buff *skb,
2016                                           __be16 protocol)
2017 {
2018         skb->inner_protocol = protocol;
2019         skb->inner_protocol_type = ENCAP_TYPE_ETHER;
2020 }
2021 
2022 static inline void skb_set_inner_ipproto(struct sk_buff *skb,
2023                                          __u8 ipproto)
2024 {
2025         skb->inner_ipproto = ipproto;
2026         skb->inner_protocol_type = ENCAP_TYPE_IPPROTO;
2027 }
2028 
2029 static inline void skb_reset_inner_headers(struct sk_buff *skb)
2030 {
2031         skb->inner_mac_header = skb->mac_header;
2032         skb->inner_network_header = skb->network_header;
2033         skb->inner_transport_header = skb->transport_header;
2034 }
2035 
2036 static inline void skb_reset_mac_len(struct sk_buff *skb)
2037 {
2038         skb->mac_len = skb->network_header - skb->mac_header;
2039 }
2040 
2041 static inline unsigned char *skb_inner_transport_header(const struct sk_buff
2042                                                         *skb)
2043 {
2044         return skb->head + skb->inner_transport_header;
2045 }
2046 
2047 static inline int skb_inner_transport_offset(const struct sk_buff *skb)
2048 {
2049         return skb_inner_transport_header(skb) - skb->data;
2050 }
2051 
2052 static inline void skb_reset_inner_transport_header(struct sk_buff *skb)
2053 {
2054         skb->inner_transport_header = skb->data - skb->head;
2055 }
2056 
2057 static inline void skb_set_inner_transport_header(struct sk_buff *skb,
2058                                                    const int offset)
2059 {
2060         skb_reset_inner_transport_header(skb);
2061         skb->inner_transport_header += offset;
2062 }
2063 
2064 static inline unsigned char *skb_inner_network_header(const struct sk_buff *skb)
2065 {
2066         return skb->head + skb->inner_network_header;
2067 }
2068 
2069 static inline void skb_reset_inner_network_header(struct sk_buff *skb)
2070 {
2071         skb->inner_network_header = skb->data - skb->head;
2072 }
2073 
2074 static inline void skb_set_inner_network_header(struct sk_buff *skb,
2075                                                 const int offset)
2076 {
2077         skb_reset_inner_network_header(skb);
2078         skb->inner_network_header += offset;
2079 }
2080 
2081 static inline unsigned char *skb_inner_mac_header(const struct sk_buff *skb)
2082 {
2083         return skb->head + skb->inner_mac_header;
2084 }
2085 
2086 static inline void skb_reset_inner_mac_header(struct sk_buff *skb)
2087 {
2088         skb->inner_mac_header = skb->data - skb->head;
2089 }
2090 
2091 static inline void skb_set_inner_mac_header(struct sk_buff *skb,
2092                                             const int offset)
2093 {
2094         skb_reset_inner_mac_header(skb);
2095         skb->inner_mac_header += offset;
2096 }
2097 static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
2098 {
2099         return skb->transport_header != (typeof(skb->transport_header))~0U;
2100 }
2101 
2102 static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
2103 {
2104         return skb->head + skb->transport_header;
2105 }
2106 
2107 static inline void skb_reset_transport_header(struct sk_buff *skb)
2108 {
2109         skb->transport_header = skb->data - skb->head;
2110 }
2111 
2112 static inline void skb_set_transport_header(struct sk_buff *skb,
2113                                             const int offset)
2114 {
2115         skb_reset_transport_header(skb);
2116         skb->transport_header += offset;
2117 }
2118 
2119 static inline unsigned char *skb_network_header(const struct sk_buff *skb)
2120 {
2121         return skb->head + skb->network_header;
2122 }
2123 
2124 static inline void skb_reset_network_header(struct sk_buff *skb)
2125 {
2126         skb->network_header = skb->data - skb->head;
2127 }
2128 
2129 static inline void skb_set_network_header(struct sk_buff *skb, const int offset)
2130 {
2131         skb_reset_network_header(skb);
2132         skb->network_header += offset;
2133 }
2134 
2135 static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
2136 {
2137         return skb->head + skb->mac_header;
2138 }
2139 
2140 static inline int skb_mac_header_was_set(const struct sk_buff *skb)
2141 {
2142         return skb->mac_header != (typeof(skb->mac_header))~0U;
2143 }
2144 
2145 static inline void skb_reset_mac_header(struct sk_buff *skb)
2146 {
2147         skb->mac_header = skb->data - skb->head;
2148 }
2149 
2150 static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)
2151 {
2152         skb_reset_mac_header(skb);
2153         skb->mac_header += offset;
2154 }
2155 
2156 static inline void skb_pop_mac_header(struct sk_buff *skb)
2157 {
2158         skb->mac_header = skb->network_header;
2159 }
2160 
2161 static inline void skb_probe_transport_header(struct sk_buff *skb,
2162                                               const int offset_hint)
2163 {
2164         struct flow_keys keys;
2165 
2166         if (skb_transport_header_was_set(skb))
2167                 return;
2168         else if (skb_flow_dissect_flow_keys(skb, &keys, 0))
2169                 skb_set_transport_header(skb, keys.control.thoff);
2170         else
2171                 skb_set_transport_header(skb, offset_hint);
2172 }
2173 
2174 static inline void skb_mac_header_rebuild(struct sk_buff *skb)
2175 {
2176         if (skb_mac_header_was_set(skb)) {
2177                 const unsigned char *old_mac = skb_mac_header(skb);
2178 
2179                 skb_set_mac_header(skb, -skb->mac_len);
2180                 memmove(skb_mac_header(skb), old_mac, skb->mac_len);
2181         }
2182 }
2183 
2184 static inline int skb_checksum_start_offset(const struct sk_buff *skb)
2185 {
2186         return skb->csum_start - skb_headroom(skb);
2187 }
2188 
2189 static inline int skb_transport_offset(const struct sk_buff *skb)
2190 {
2191         return skb_transport_header(skb) - skb->data;
2192 }
2193 
2194 static inline u32 skb_network_header_len(const struct sk_buff *skb)
2195 {
2196         return skb->transport_header - skb->network_header;
2197 }
2198 
2199 static inline u32 skb_inner_network_header_len(const struct sk_buff *skb)
2200 {
2201         return skb->inner_transport_header - skb->inner_network_header;
2202 }
2203 
2204 static inline int skb_network_offset(const struct sk_buff *skb)
2205 {
2206         return skb_network_header(skb) - skb->data;
2207 }
2208 
2209 static inline int skb_inner_network_offset(const struct sk_buff *skb)
2210 {
2211         return skb_inner_network_header(skb) - skb->data;
2212 }
2213 
2214 static inline int pskb_network_may_pull(struct sk_buff *skb, unsigned int len)
2215 {
2216         return pskb_may_pull(skb, skb_network_offset(skb) + len);
2217 }
2218 
2219 /*
2220  * CPUs often take a performance hit when accessing unaligned memory
2221  * locations. The actual performance hit varies, it can be small if the
2222  * hardware handles it or large if we have to take an exception and fix it
2223  * in software.
2224  *
2225  * Since an ethernet header is 14 bytes network drivers often end up with
2226  * the IP header at an unaligned offset. The IP header can be aligned by
2227  * shifting the start of the packet by 2 bytes. Drivers should do this
2228  * with:
2229  *
2230  * skb_reserve(skb, NET_IP_ALIGN);
2231  *
2232  * The downside to this alignment of the IP header is that the DMA is now
2233  * unaligned. On some architectures the cost of an unaligned DMA is high
2234  * and this cost outweighs the gains made by aligning the IP header.
2235  *
2236  * Since this trade off varies between architectures, we allow NET_IP_ALIGN
2237  * to be overridden.
2238  */
2239 #ifndef NET_IP_ALIGN
2240 #define NET_IP_ALIGN    2
2241 #endif
2242 
2243 /*
2244  * The networking layer reserves some headroom in skb data (via
2245  * dev_alloc_skb). This is used to avoid having to reallocate skb data when
2246  * the header has to grow. In the default case, if the header has to grow
2247  * 32 bytes or less we avoid the reallocation.
2248  *
2249  * Unfortunately this headroom changes the DMA alignment of the resulting
2250  * network packet. As for NET_IP_ALIGN, this unaligned DMA is expensive
2251  * on some architectures. An architecture can override this value,
2252  * perhaps setting it to a cacheline in size (since that will maintain
2253  * cacheline alignment of the DMA). It must be a power of 2.
2254  *
2255  * Various parts of the networking layer expect at least 32 bytes of
2256  * headroom, you should not reduce this.
2257  *
2258  * Using max(32, L1_CACHE_BYTES) makes sense (especially with RPS)
2259  * to reduce average number of cache lines per packet.
2260  * get_rps_cpus() for example only access one 64 bytes aligned block :
2261  * NET_IP_ALIGN(2) + ethernet_header(14) + IP_header(20/40) + ports(8)
2262  */
2263 #ifndef NET_SKB_PAD
2264 #define NET_SKB_PAD     max(32, L1_CACHE_BYTES)
2265 #endif
2266 
2267 int ___pskb_trim(struct sk_buff *skb, unsigned int len);
2268 
2269 static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
2270 {
2271         if (unlikely(skb_is_nonlinear(skb))) {
2272                 WARN_ON(1);
2273                 return;
2274         }
2275         skb->len = len;
2276         skb_set_tail_pointer(skb, len);
2277 }
2278 
2279 void skb_trim(struct sk_buff *skb, unsigned int len);
2280 
2281 static inline int __pskb_trim(struct sk_buff *skb, unsigned int len)
2282 {
2283         if (skb->data_len)
2284                 return ___pskb_trim(skb, len);
2285         __skb_trim(skb, len);
2286         return 0;
2287 }
2288 
2289 static inline int pskb_trim(struct sk_buff *skb, unsigned int len)
2290 {
2291         return (len < skb->len) ? __pskb_trim(skb, len) : 0;
2292 }
2293 
2294 /**
2295  *      pskb_trim_unique - remove end from a paged unique (not cloned) buffer
2296  *      @skb: buffer to alter
2297  *      @len: new length
2298  *
2299  *      This is identical to pskb_trim except that the caller knows that
2300  *      the skb is not cloned so we should never get an error due to out-
2301  *      of-memory.
2302  */
2303 static inline void pskb_trim_unique(struct sk_buff *skb, unsigned int len)
2304 {
2305         int err = pskb_trim(skb, len);
2306         BUG_ON(err);
2307 }
2308 
2309 /**
2310  *      skb_orphan - orphan a buffer
2311  *      @skb: buffer to orphan
2312  *
2313  *      If a buffer currently has an owner then we call the owner's
2314  *      destructor function and make the @skb unowned. The buffer continues
2315  *      to exist but is no longer charged to its former owner.
2316  */
2317 static inline void skb_orphan(struct sk_buff *skb)
2318 {
2319         if (skb->destructor) {
2320                 skb->destructor(skb);
2321                 skb->destructor = NULL;
2322                 skb->sk         = NULL;
2323         } else {
2324                 BUG_ON(skb->sk);
2325         }
2326 }
2327 
2328 /**
2329  *      skb_orphan_frags - orphan the frags contained in a buffer
2330  *      @skb: buffer to orphan frags from
2331  *      @gfp_mask: allocation mask for replacement pages
2332  *
2333  *      For each frag in the SKB which needs a destructor (i.e. has an
2334  *      owner) create a copy of that frag and release the original
2335  *      page by calling the destructor.
2336  */
2337 static inline int skb_orphan_frags(struct sk_buff *skb, gfp_t gfp_mask)
2338 {
2339         if (likely(!(skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY)))
2340                 return 0;
2341         return skb_copy_ubufs(skb, gfp_mask);
2342 }
2343 
2344 /**
2345  *      __skb_queue_purge - empty a list
2346  *      @list: list to empty
2347  *
2348  *      Delete all buffers on an &sk_buff list. Each buffer is removed from
2349  *      the list and one reference dropped. This function does not take the
2350  *      list lock and the caller must hold the relevant locks to use it.
2351  */
2352 void skb_queue_purge(struct sk_buff_head *list);
2353 static inline void __skb_queue_purge(struct sk_buff_head *list)
2354 {
2355         struct sk_buff *skb;
2356         while ((skb = __skb_dequeue(list)) != NULL)
2357                 kfree_skb(skb);
2358 }
2359 
2360 void *netdev_alloc_frag(unsigned int fragsz);
2361 
2362 struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int length,
2363                                    gfp_t gfp_mask);
2364 
2365 /**
2366  *      netdev_alloc_skb - allocate an skbuff for rx on a specific device
2367  *      @dev: network device to receive on
2368  *      @length: length to allocate
2369  *
2370  *      Allocate a new &sk_buff and assign it a usage count of one. The
2371  *      buffer has unspecified headroom built in. Users should allocate
2372  *      the headroom they think they need without accounting for the
2373  *      built in space. The built in space is used for optimisations.
2374  *
2375  *      %NULL is returned if there is no free memory. Although this function
2376  *      allocates memory it can be called from an interrupt.
2377  */
2378 static inline struct sk_buff *netdev_alloc_skb(struct net_device *dev,
2379                                                unsigned int length)
2380 {
2381         return __netdev_alloc_skb(dev, length, GFP_ATOMIC);
2382 }
2383 
2384 /* legacy helper around __netdev_alloc_skb() */
2385 static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
2386                                               gfp_t gfp_mask)
2387 {
2388         return __netdev_alloc_skb(NULL, length, gfp_mask);
2389 }
2390 
2391 /* legacy helper around netdev_alloc_skb() */
2392 static inline struct sk_buff *dev_alloc_skb(unsigned int length)
2393 {
2394         return netdev_alloc_skb(NULL, length);
2395 }
2396 
2397 
2398 static inline struct sk_buff *__netdev_alloc_skb_ip_align(struct net_device *dev,
2399                 unsigned int length, gfp_t gfp)
2400 {
2401         struct sk_buff *skb = __netdev_alloc_skb(dev, length + NET_IP_ALIGN, gfp);
2402 
2403         if (NET_IP_ALIGN && skb)
2404                 skb_reserve(skb, NET_IP_ALIGN);
2405         return skb;
2406 }
2407 
2408 static inline struct sk_buff *netdev_alloc_skb_ip_align(struct net_device *dev,
2409                 unsigned int length)
2410 {
2411         return __netdev_alloc_skb_ip_align(dev, length, GFP_ATOMIC);
2412 }
2413 
2414 static inline void skb_free_frag(void *addr)
2415 {
2416         __free_page_frag(addr);
2417 }
2418 
2419 void *napi_alloc_frag(unsigned int fragsz);
2420 struct sk_buff *__napi_alloc_skb(struct napi_struct *napi,
2421                                  unsigned int length, gfp_t gfp_mask);
2422 static inline struct sk_buff *napi_alloc_skb(struct napi_struct *napi,
2423                                              unsigned int length)
2424 {
2425         return __napi_alloc_skb(napi, length, GFP_ATOMIC);
2426 }
2427 
2428 /**
2429  * __dev_alloc_pages - allocate page for network Rx
2430  * @gfp_mask: allocation priority. Set __GFP_NOMEMALLOC if not for network Rx
2431  * @order: size of the allocation
2432  *
2433  * Allocate a new page.
2434  *
2435  * %NULL is returned if there is no free memory.
2436 */
2437 static inline struct page *__dev_alloc_pages(gfp_t gfp_mask,
2438                                              unsigned int order)
2439 {
2440         /* This piece of code contains several assumptions.
2441          * 1.  This is for device Rx, therefor a cold page is preferred.
2442          * 2.  The expectation is the user wants a compound page.
2443          * 3.  If requesting a order 0 page it will not be compound
2444          *     due to the check to see if order has a value in prep_new_page
2445          * 4.  __GFP_MEMALLOC is ignored if __GFP_NOMEMALLOC is set due to
2446          *     code in gfp_to_alloc_flags that should be enforcing this.
2447          */
2448         gfp_mask |= __GFP_COLD | __GFP_COMP | __GFP_MEMALLOC;
2449 
2450         return alloc_pages_node(NUMA_NO_NODE, gfp_mask, order);
2451 }
2452 
2453 static inline struct page *dev_alloc_pages(unsigned int order)
2454 {
2455         return __dev_alloc_pages(GFP_ATOMIC, order);
2456 }
2457 
2458 /**
2459  * __dev_alloc_page - allocate a page for network Rx
2460  * @gfp_mask: allocation priority. Set __GFP_NOMEMALLOC if not for network Rx
2461  *
2462  * Allocate a new page.
2463  *
2464  * %NULL is returned if there is no free memory.
2465  */
2466 static inline struct page *__dev_alloc_page(gfp_t gfp_mask)
2467 {
2468         return __dev_alloc_pages(gfp_mask, 0);
2469 }
2470 
2471 static inline struct page *dev_alloc_page(void)
2472 {
2473         return __dev_alloc_page(GFP_ATOMIC);
2474 }
2475 
2476 /**
2477  *      skb_propagate_pfmemalloc - Propagate pfmemalloc if skb is allocated after RX page
2478  *      @page: The page that was allocated from skb_alloc_page
2479  *      @skb: The skb that may need pfmemalloc set
2480  */
2481 static inline void skb_propagate_pfmemalloc(struct page *page,
2482                                              struct sk_buff *skb)
2483 {
2484         if (page_is_pfmemalloc(page))
2485                 skb->pfmemalloc = true;
2486 }
2487 
2488 /**
2489  * skb_frag_page - retrieve the page referred to by a paged fragment
2490  * @frag: the paged fragment
2491  *
2492  * Returns the &struct page associated with @frag.
2493  */
2494 static inline struct page *skb_frag_page(const skb_frag_t *frag)
2495 {
2496         return frag->page.p;
2497 }
2498 
2499 /**
2500  * __skb_frag_ref - take an addition reference on a paged fragment.
2501  * @frag: the paged fragment
2502  *
2503  * Takes an additional reference on the paged fragment @frag.
2504  */
2505 static inline void __skb_frag_ref(skb_frag_t *frag)
2506 {
2507         get_page(skb_frag_page(frag));
2508 }
2509 
2510 /**
2511  * skb_frag_ref - take an addition reference on a paged fragment of an skb.
2512  * @skb: the buffer
2513  * @f: the fragment offset.
2514  *
2515  * Takes an additional reference on the @f'th paged fragment of @skb.
2516  */
2517 static inline void skb_frag_ref(struct sk_buff *skb, int f)
2518 {
2519         __skb_frag_ref(&skb_shinfo(skb)->frags[f]);
2520 }
2521 
2522 /**
2523  * __skb_frag_unref - release a reference on a paged fragment.
2524  * @frag: the paged fragment
2525  *
2526  * Releases a reference on the paged fragment @frag.
2527  */
2528 static inline void __skb_frag_unref(skb_frag_t *frag)
2529 {
2530         put_page(skb_frag_page(frag));
2531 }
2532 
2533 /**
2534  * skb_frag_unref - release a reference on a paged fragment of an skb.
2535  * @skb: the buffer
2536  * @f: the fragment offset
2537  *
2538  * Releases a reference on the @f'th paged fragment of @skb.
2539  */
2540 static inline void skb_frag_unref(struct sk_buff *skb, int f)
2541 {
2542         __skb_frag_unref(&skb_shinfo(skb)->frags[f]);
2543 }
2544 
2545 /**
2546  * skb_frag_address - gets the address of the data contained in a paged fragment
2547  * @frag: the paged fragment buffer
2548  *
2549  * Returns the address of the data within @frag. The page must already
2550  * be mapped.
2551  */
2552 static inline void *skb_frag_address(const skb_frag_t *frag)
2553 {
2554         return page_address(skb_frag_page(frag)) + frag->page_offset;
2555 }
2556 
2557 /**
2558  * skb_frag_address_safe - gets the address of the data contained in a paged fragment
2559  * @frag: the paged fragment buffer
2560  *
2561  * Returns the address of the data within @frag. Checks that the page
2562  * is mapped and returns %NULL otherwise.
2563  */
2564 static inline void *skb_frag_address_safe(const skb_frag_t *frag)
2565 {
2566         void *ptr = page_address(skb_frag_page(frag));
2567         if (unlikely(!ptr))
2568                 return NULL;
2569 
2570         return ptr + frag->page_offset;
2571 }
2572 
2573 /**
2574  * __skb_frag_set_page - sets the page contained in a paged fragment
2575  * @frag: the paged fragment
2576  * @page: the page to set
2577  *
2578  * Sets the fragment @frag to contain @page.
2579  */
2580 static inline void __skb_frag_set_page(skb_frag_t *frag, struct page *page)
2581 {
2582         frag->page.p = page;
2583 }
2584 
2585 /**
2586  * skb_frag_set_page - sets the page contained in a paged fragment of an skb
2587  * @skb: the buffer
2588  * @f: the fragment offset
2589  * @page: the page to set
2590  *
2591  * Sets the @f'th fragment of @skb to contain @page.
2592  */
2593 static inline void skb_frag_set_page(struct sk_buff *skb, int f,
2594                                      struct page *page)
2595 {
2596         __skb_frag_set_page(&skb_shinfo(skb)->frags[f], page);
2597 }
2598 
2599 bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t prio);
2600 
2601 /**
2602  * skb_frag_dma_map - maps a paged fragment via the DMA API
2603  * @dev: the device to map the fragment to
2604  * @frag: the paged fragment to map
2605  * @offset: the offset within the fragment (starting at the
2606  *          fragment's own offset)
2607  * @size: the number of bytes to map
2608  * @dir: the direction of the mapping (%PCI_DMA_*)
2609  *
2610  * Maps the page associated with @frag to @device.
2611  */
2612 static inline dma_addr_t skb_frag_dma_map(struct device *dev,
2613                                           const skb_frag_t *frag,
2614                                           size_t offset, size_t size,
2615                                           enum dma_data_direction dir)
2616 {
2617         return dma_map_page(dev, skb_frag_page(frag),
2618                             frag->page_offset + offset, size, dir);
2619 }
2620 
2621 static inline struct sk_buff *pskb_copy(struct sk_buff *skb,
2622                                         gfp_t gfp_mask)
2623 {
2624         return __pskb_copy(skb, skb_headroom(skb), gfp_mask);
2625 }
2626 
2627 
2628 static inline struct sk_buff *pskb_copy_for_clone(struct sk_buff *skb,
2629                                                   gfp_t gfp_mask)
2630 {
2631         return __pskb_copy_fclone(skb, skb_headroom(skb), gfp_mask, true);
2632 }
2633 
2634 
2635 /**
2636  *      skb_clone_writable - is the header of a clone writable
2637  *      @skb: buffer to check
2638  *      @len: length up to which to write
2639  *
2640  *      Returns true if modifying the header part of the cloned buffer
2641  *      does not requires the data to be copied.
2642  */
2643 static inline int skb_clone_writable(const struct sk_buff *skb, unsigned int len)
2644 {
2645         return !skb_header_cloned(skb) &&
2646                skb_headroom(skb) + len <= skb->hdr_len;
2647 }
2648 
2649 static inline int __skb_cow(struct sk_buff *skb, unsigned int headroom,
2650                             int cloned)
2651 {
2652         int delta = 0;
2653 
2654         if (headroom > skb_headroom(skb))
2655                 delta = headroom - skb_headroom(skb);
2656 
2657         if (delta || cloned)
2658                 return pskb_expand_head(skb, ALIGN(delta, NET_SKB_PAD), 0,
2659                                         GFP_ATOMIC);
2660         return 0;
2661 }
2662 
2663 /**
2664  *      skb_cow - copy header of skb when it is required
2665  *      @skb: buffer to cow
2666  *      @headroom: needed headroom
2667  *
2668  *      If the skb passed lacks sufficient headroom or its data part
2669  *      is shared, data is reallocated. If reallocation fails, an error
2670  *      is returned and original skb is not changed.
2671  *
2672  *      The result is skb with writable area skb->head...skb->tail
2673  *      and at least @headroom of space at head.
2674  */
2675 static inline int skb_cow(struct sk_buff *skb, unsigned int headroom)
2676 {
2677         return __skb_cow(skb, headroom, skb_cloned(skb));
2678 }
2679 
2680 /**
2681  *      skb_cow_head - skb_cow but only making the head writable
2682  *      @skb: buffer to cow
2683  *      @headroom: needed headroom
2684  *
2685  *      This function is identical to skb_cow except that we replace the
2686  *      skb_cloned check by skb_header_cloned.  It should be used when
2687  *      you only need to push on some header and do not need to modify
2688  *      the data.
2689  */
2690 static inline int skb_cow_head(struct sk_buff *skb, unsigned int headroom)
2691 {
2692         return __skb_cow(skb, headroom, skb_header_cloned(skb));
2693 }
2694 
2695 /**
2696  *      skb_padto       - pad an skbuff up to a minimal size
2697  *      @skb: buffer to pad
2698  *      @len: minimal length
2699  *
2700  *      Pads up a buffer to ensure the trailing bytes exist and are
2701  *      blanked. If the buffer already contains sufficient data it
2702  *      is untouched. Otherwise it is extended. Returns zero on
2703  *      success. The skb is freed on error.
2704  */
2705 static inline int skb_padto(struct sk_buff *skb, unsigned int len)
2706 {
2707         unsigned int size = skb->len;
2708         if (likely(size >= len))
2709                 return 0;
2710         return skb_pad(skb, len - size);
2711 }
2712 
2713 /**
2714  *      skb_put_padto - increase size and pad an skbuff up to a minimal size
2715  *      @skb: buffer to pad
2716  *      @len: minimal length
2717  *
2718  *      Pads up a buffer to ensure the trailing bytes exist and are
2719  *      blanked. If the buffer already contains sufficient data it
2720  *      is untouched. Otherwise it is extended. Returns zero on
2721  *      success. The skb is freed on error.
2722  */
2723 static inline int skb_put_padto(struct sk_buff *skb, unsigned int len)
2724 {
2725         unsigned int size = skb->len;
2726 
2727         if (unlikely(size < len)) {
2728                 len -= size;
2729                 if (skb_pad(skb, len))
2730                         return -ENOMEM;
2731                 __skb_put(skb, len);
2732         }
2733         return 0;
2734 }
2735 
2736 static inline int skb_add_data(struct sk_buff *skb,
2737                                struct iov_iter *from, int copy)
2738 {
2739         const int off = skb->len;
2740 
2741         if (skb->ip_summed == CHECKSUM_NONE) {
2742                 __wsum csum = 0;
2743                 if (csum_and_copy_from_iter(skb_put(skb, copy), copy,
2744                                             &csum, from) == copy) {
2745                         skb->csum = csum_block_add(skb->csum, csum, off);
2746                         return 0;
2747                 }
2748         } else if (copy_from_iter(skb_put(skb, copy), copy, from) == copy)
2749                 return 0;
2750 
2751         __skb_trim(skb, off);
2752         return -EFAULT;
2753 }
2754 
2755 static inline bool skb_can_coalesce(struct sk_buff *skb, int i,
2756                                     const struct page *page, int off)
2757 {
2758         if (i) {
2759                 const struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[i - 1];
2760 
2761                 return page == skb_frag_page(frag) &&
2762                        off == frag->page_offset + skb_frag_size(frag);
2763         }
2764         return false;
2765 }
2766 
2767 static inline int __skb_linearize(struct sk_buff *skb)
2768 {
2769         return __pskb_pull_tail(skb, skb->data_len) ? 0 : -ENOMEM;
2770 }
2771 
2772 /**
2773  *      skb_linearize - convert paged skb to linear one
2774  *      @skb: buffer to linarize
2775  *
2776  *      If there is no free memory -ENOMEM is returned, otherwise zero
2777  *      is returned and the old skb data released.
2778  */
2779 static inline int skb_linearize(struct sk_buff *skb)
2780 {
2781         return skb_is_nonlinear(skb) ? __skb_linearize(skb) : 0;
2782 }
2783 
2784 /**
2785  * skb_has_shared_frag - can any frag be overwritten
2786  * @skb: buffer to test
2787  *
2788  * Return true if the skb has at least one frag that might be modified
2789  * by an external entity (as in vmsplice()/sendfile())
2790  */
2791 static inline bool skb_has_shared_frag(const struct sk_buff *skb)
2792 {
2793         return skb_is_nonlinear(skb) &&
2794                skb_shinfo(skb)->tx_flags & SKBTX_SHARED_FRAG;
2795 }
2796 
2797 /**
2798  *      skb_linearize_cow - make sure skb is linear and writable
2799  *      @skb: buffer to process
2800  *
2801  *      If there is no free memory -ENOMEM is returned, otherwise zero
2802  *      is returned and the old skb data released.
2803  */
2804 static inline int skb_linearize_cow(struct sk_buff *skb)
2805 {
2806         return skb_is_nonlinear(skb) || skb_cloned(skb) ?
2807                __skb_linearize(skb) : 0;
2808 }
2809 
2810 /**
2811  *      skb_postpull_rcsum - update checksum for received skb after pull
2812  *      @skb: buffer to update
2813  *      @start: start of data before pull
2814  *      @len: length of data pulled
2815  *
2816  *      After doing a pull on a received packet, you need to call this to
2817  *      update the CHECKSUM_COMPLETE checksum, or set ip_summed to
2818  *      CHECKSUM_NONE so that it can be recomputed from scratch.
2819  */
2820 
2821 static inline void skb_postpull_rcsum(struct sk_buff *skb,
2822                                       const void *start, unsigned int len)
2823 {
2824         if (skb->ip_summed == CHECKSUM_COMPLETE)
2825                 skb->csum = csum_sub(skb->csum, csum_partial(start, len, 0));
2826         else if (skb->ip_summed == CHECKSUM_PARTIAL &&
2827                  skb_checksum_start_offset(skb) < 0)
2828                 skb->ip_summed = CHECKSUM_NONE;
2829 }
2830 
2831 unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);
2832 
2833 static inline void skb_postpush_rcsum(struct sk_buff *skb,
2834                                       const void *start, unsigned int len)
2835 {
2836         /* For performing the reverse operation to skb_postpull_rcsum(),
2837          * we can instead of ...
2838          *
2839          *   skb->csum = csum_add(skb->csum, csum_partial(start, len, 0));
2840          *
2841          * ... just use this equivalent version here to save a few
2842          * instructions. Feeding csum of 0 in csum_partial() and later
2843          * on adding skb->csum is equivalent to feed skb->csum in the
2844          * first place.
2845          */
2846         if (skb->ip_summed == CHECKSUM_COMPLETE)
2847                 skb->csum = csum_partial(start, len, skb->csum);
2848 }
2849 
2850 /**
2851  *      pskb_trim_rcsum - trim received skb and update checksum
2852  *      @skb: buffer to trim
2853  *      @len: new length
2854  *
2855  *      This is exactly the same as pskb_trim except that it ensures the
2856  *      checksum of received packets are still valid after the operation.
2857  */
2858 
2859 static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)
2860 {
2861         if (likely(len >= skb->len))
2862                 return 0;
2863         if (skb->ip_summed == CHECKSUM_COMPLETE)
2864                 skb->ip_summed = CHECKSUM_NONE;
2865         return __pskb_trim(skb, len);
2866 }
2867 
2868 #define skb_queue_walk(queue, skb) \
2869                 for (skb = (queue)->next;                                       \
2870                      skb != (struct sk_buff *)(queue);                          \
2871                      skb = skb->next)
2872 
2873 #define skb_queue_walk_safe(queue, skb, tmp)                                    \
2874                 for (skb = (queue)->next, tmp = skb->next;                      \
2875                      skb != (struct sk_buff *)(queue);                          \
2876                      skb = tmp, tmp = skb->next)
2877 
2878 #define skb_queue_walk_from(queue, skb)                                         \
2879                 for (; skb != (struct sk_buff *)(queue);                        \
2880                      skb = skb->next)
2881 
2882 #define skb_queue_walk_from_safe(queue, skb, tmp)                               \
2883                 for (tmp = skb->next;                                           \
2884                      skb != (struct sk_buff *)(queue);                          \
2885                      skb = tmp, tmp = skb->next)
2886 
2887 #define skb_queue_reverse_walk(queue, skb) \
2888                 for (skb = (queue)->prev;                                       \
2889                      skb != (struct sk_buff *)(queue);                          \
2890                      skb = skb->prev)
2891 
2892 #define skb_queue_reverse_walk_safe(queue, skb, tmp)                            \
2893                 for (skb = (queue)->prev, tmp = skb->prev;                      \
2894                      skb != (struct sk_buff *)(queue);                          \
2895                      skb = tmp, tmp = skb->prev)
2896 
2897 #define skb_queue_reverse_walk_from_safe(queue, skb, tmp)                       \
2898                 for (tmp = skb->prev;                                           \
2899                      skb != (struct sk_buff *)(queue);                          \
2900                      skb = tmp, tmp = skb->prev)
2901 
2902 static inline bool skb_has_frag_list(const struct sk_buff *skb)
2903 {
2904         return skb_shinfo(skb)->frag_list != NULL;
2905 }
2906 
2907 static inline void skb_frag_list_init(struct sk_buff *skb)
2908 {
2909         skb_shinfo(skb)->frag_list = NULL;
2910 }
2911 
2912 #define skb_walk_frags(skb, iter)       \
2913         for (iter = skb_shinfo(skb)->frag_list; iter; iter = iter->next)
2914 
2915 
2916 int __skb_wait_for_more_packets(struct sock *sk, int *err, long *timeo_p,
2917                                 const struct sk_buff *skb);
2918 struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned flags,
2919                                         int *peeked, int *off, int *err,
2920                                         struct sk_buff **last);
2921 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
2922                                     int *peeked, int *off, int *err);
2923 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags, int noblock,
2924                                   int *err);
2925 unsigned int datagram_poll(struct file *file, struct socket *sock,
2926                            struct poll_table_struct *wait);
2927 int skb_copy_datagram_iter(const struct sk_buff *from, int offset,
2928                            struct iov_iter *to, int size);
2929 static inline int skb_copy_datagram_msg(const struct sk_buff *from, int offset,
2930                                         struct msghdr *msg, int size)
2931 {
2932         return skb_copy_datagram_iter(from, offset, &msg->msg_iter, size);
2933 }
2934 int skb_copy_and_csum_datagram_msg(struct sk_buff *skb, int hlen,
2935                                    struct msghdr *msg);
2936 int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
2937                                  struct iov_iter *from, int len);
2938 int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *frm);
2939 void skb_free_datagram(struct sock *sk, struct sk_buff *skb);
2940 void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb);
2941 int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags);
2942 int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len);
2943 int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len);
2944 __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, u8 *to,
2945                               int len, __wsum csum);
2946 ssize_t skb_socket_splice(struct sock *sk,
2947                           struct pipe_inode_info *pipe,
2948                           struct splice_pipe_desc *spd);
2949 int skb_splice_bits(struct sk_buff *skb, struct sock *sk, unsigned int offset,
2950                     struct pipe_inode_info *pipe, unsigned int len,
2951                     unsigned int flags,
2952                     ssize_t (*splice_cb)(struct sock *,
2953                                          struct pipe_inode_info *,
2954                                          struct splice_pipe_desc *));
2955 void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
2956 unsigned int skb_zerocopy_headlen(const struct sk_buff *from);
2957 int skb_zerocopy(struct sk_buff *to, struct sk_buff *from,
2958                  int len, int hlen);
2959 void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len);
2960 int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen);
2961 void skb_scrub_packet(struct sk_buff *skb, bool xnet);
2962 unsigned int skb_gso_transport_seglen(const struct sk_buff *skb);
2963 struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);
2964 struct sk_buff *skb_vlan_untag(struct sk_buff *skb);
2965 int skb_ensure_writable(struct sk_buff *skb, int write_len);
2966 int skb_vlan_pop(struct sk_buff *skb);
2967 int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);
2968 
2969 static inline int memcpy_from_msg(void *data, struct msghdr *msg, int len)
2970 {
2971         return copy_from_iter(data, len, &msg->msg_iter) == len ? 0 : -EFAULT;
2972 }
2973 
2974 static inline int memcpy_to_msg(struct msghdr *msg, void *data, int len)
2975 {
2976         return copy_to_iter(data, len, &msg->msg_iter) == len ? 0 : -EFAULT;
2977 }
2978 
2979 struct skb_checksum_ops {
2980         __wsum (*update)(const void *mem, int len, __wsum wsum);
2981         __wsum (*combine)(__wsum csum, __wsum csum2, int offset, int len);
2982 };
2983 
2984 __wsum __skb_checksum(const struct sk_buff *skb, int offset, int len,
2985                       __wsum csum, const struct skb_checksum_ops *ops);
2986 __wsum skb_checksum(const struct sk_buff *skb, int offset, int len,
2987                     __wsum csum);
2988 
2989 static inline void * __must_check
2990 __skb_header_pointer(const struct sk_buff *skb, int offset,
2991                      int len, void *data, int hlen, void *buffer)
2992 {
2993         if (hlen - offset >= len)
2994                 return data + offset;
2995 
2996         if (!skb ||
2997             skb_copy_bits(skb, offset, buffer, len) < 0)
2998                 return NULL;
2999 
3000         return buffer;
3001 }
3002 
3003 static inline void * __must_check
3004 skb_header_pointer(const struct sk_buff *skb, int offset, int len, void *buffer)
3005 {
3006         return __skb_header_pointer(skb, offset, len, skb->data,
3007                                     skb_headlen(skb), buffer);
3008 }
3009 
3010 /**
3011  *      skb_needs_linearize - check if we need to linearize a given skb
3012  *                            depending on the given device features.
3013  *      @skb: socket buffer to check
3014  *      @features: net device features
3015  *
3016  *      Returns true if either:
3017  *      1. skb has frag_list and the device doesn't support FRAGLIST, or
3018  *      2. skb is fragmented and the device does not support SG.
3019  */
3020 static inline bool skb_needs_linearize(struct sk_buff *skb,
3021                                        netdev_features_t features)
3022 {
3023         return skb_is_nonlinear(skb) &&
3024                ((skb_has_frag_list(skb) && !(features & NETIF_F_FRAGLIST)) ||
3025                 (skb_shinfo(skb)->nr_frags && !(features & NETIF_F_SG)));
3026 }
3027 
3028 static inline void skb_copy_from_linear_data(const struct sk_buff *skb,
3029                                              void *to,
3030                                              const unsigned int len)
3031 {
3032         memcpy(to, skb->data, len);
3033 }
3034 
3035 static inline void skb_copy_from_linear_data_offset(const struct sk_buff *skb,
3036                                                     const int offset, void *to,
3037                                                     const unsigned int len)
3038 {
3039         memcpy(to, skb->data + offset, len);
3040 }
3041 
3042 static inline void skb_copy_to_linear_data(struct sk_buff *skb,
3043                                            const void *from,
3044                                            const unsigned int len)
3045 {
3046         memcpy(skb->data, from, len);
3047 }
3048 
3049 static inline void skb_copy_to_linear_data_offset(struct sk_buff *skb,
3050                                                   const int offset,
3051                                                   const void *from,
3052                                                   const unsigned int len)
3053 {
3054         memcpy(skb->data + offset, from, len);
3055 }
3056 
3057 void skb_init(void);
3058 
3059 static inline ktime_t skb_get_ktime(const struct sk_buff *skb)
3060 {
3061         return skb->tstamp;
3062 }
3063 
3064 /**
3065  *      skb_get_timestamp - get timestamp from a skb
3066  *      @skb: skb to get stamp from
3067  *      @stamp: pointer to struct timeval to store stamp in
3068  *
3069  *      Timestamps are stored in the skb as offsets to a base timestamp.
3070  *      This function converts the offset back to a struct timeval and stores
3071  *      it in stamp.
3072  */
3073 static inline void skb_get_timestamp(const struct sk_buff *skb,
3074                                      struct timeval *stamp)
3075 {
3076         *stamp = ktime_to_timeval(skb->tstamp);
3077 }
3078 
3079 static inline void skb_get_timestampns(const struct sk_buff *skb,
3080                                        struct timespec *stamp)
3081 {
3082         *stamp = ktime_to_timespec(skb->tstamp);
3083 }
3084 
3085 static inline void __net_timestamp(struct sk_buff *skb)
3086 {
3087         skb->tstamp = ktime_get_real();
3088 }
3089 
3090 static inline ktime_t net_timedelta(ktime_t t)
3091 {
3092         return ktime_sub(ktime_get_real(), t);
3093 }
3094 
3095 static inline ktime_t net_invalid_timestamp(void)
3096 {
3097         return ktime_set(0, 0);
3098 }
3099 
3100 struct sk_buff *skb_clone_sk(struct sk_buff *skb);
3101 
3102 #ifdef CONFIG_NETWORK_PHY_TIMESTAMPING
3103 
3104 void skb_clone_tx_timestamp(struct sk_buff *skb);
3105 bool skb_defer_rx_timestamp(struct sk_buff *skb);
3106 
3107 #else /* CONFIG_NETWORK_PHY_TIMESTAMPING */
3108 
3109 static inline void skb_clone_tx_timestamp(struct sk_buff *skb)
3110 {
3111 }
3112 
3113 static inline bool skb_defer_rx_timestamp(struct sk_buff *skb)
3114 {
3115         return false;
3116 }
3117 
3118 #endif /* !CONFIG_NETWORK_PHY_TIMESTAMPING */
3119 
3120 /**
3121  * skb_complete_tx_timestamp() - deliver cloned skb with tx timestamps
3122  *
3123  * PHY drivers may accept clones of transmitted packets for
3124  * timestamping via their phy_driver.txtstamp method. These drivers
3125  * must call this function to return the skb back to the stack with a
3126  * timestamp.
3127  *
3128  * @skb: clone of the the original outgoing packet
3129  * @hwtstamps: hardware time stamps
3130  *
3131  */
3132 void skb_complete_tx_timestamp(struct sk_buff *skb,
3133                                struct skb_shared_hwtstamps *hwtstamps);
3134 
3135 void __skb_tstamp_tx(struct sk_buff *orig_skb,
3136                      struct skb_shared_hwtstamps *hwtstamps,
3137                      struct sock *sk, int tstype);
3138 
3139 /**
3140  * skb_tstamp_tx - queue clone of skb with send time stamps
3141  * @orig_skb:   the original outgoing packet
3142  * @hwtstamps:  hardware time stamps, may be NULL if not available
3143  *
3144  * If the skb has a socket associated, then this function clones the
3145  * skb (thus sharing the actual data and optional structures), stores
3146  * the optional hardware time stamping information (if non NULL) or
3147  * generates a software time stamp (otherwise), then queues the clone
3148  * to the error queue of the socket.  Errors are silently ignored.
3149  */
3150 void skb_tstamp_tx(struct sk_buff *orig_skb,
3151                    struct skb_shared_hwtstamps *hwtstamps);
3152 
3153 static inline void sw_tx_timestamp(struct sk_buff *skb)
3154 {
3155         if (skb_shinfo(skb)->tx_flags & SKBTX_SW_TSTAMP &&
3156             !(skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS))
3157                 skb_tstamp_tx(skb, NULL);
3158 }
3159 
3160 /**
3161  * skb_tx_timestamp() - Driver hook for transmit timestamping
3162  *
3163  * Ethernet MAC Drivers should call this function in their hard_xmit()
3164  * function immediately before giving the sk_buff to the MAC hardware.
3165  *
3166  * Specifically, one should make absolutely sure that this function is
3167  * called before TX completion of this packet can trigger.  Otherwise
3168  * the packet could potentially already be freed.
3169  *
3170  * @skb: A socket buffer.
3171  */
3172 static inline void skb_tx_timestamp(struct sk_buff *skb)
3173 {
3174         skb_clone_tx_timestamp(skb);
3175         sw_tx_timestamp(skb);
3176 }
3177 
3178 /**
3179  * skb_complete_wifi_ack - deliver skb with wifi status
3180  *
3181  * @skb: the original outgoing packet
3182  * @acked: ack status
3183  *
3184  */
3185 void skb_complete_wifi_ack(struct sk_buff *skb, bool acked);
3186 
3187 __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len);
3188 __sum16 __skb_checksum_complete(struct sk_buff *skb);
3189 
3190 static inline int skb_csum_unnecessary(const struct sk_buff *skb)
3191 {
3192         return ((skb->ip_summed == CHECKSUM_UNNECESSARY) ||
3193                 skb->csum_valid ||
3194                 (skb->ip_summed == CHECKSUM_PARTIAL &&
3195                  skb_checksum_start_offset(skb) >= 0));
3196 }
3197 
3198 /**
3199  *      skb_checksum_complete - Calculate checksum of an entire packet
3200  *      @skb: packet to process
3201  *
3202  *      This function calculates the checksum over the entire packet plus
3203  *      the value of skb->csum.  The latter can be used to supply the
3204  *      checksum of a pseudo header as used by TCP/UDP.  It returns the
3205  *      checksum.
3206  *
3207  *      For protocols that contain complete checksums such as ICMP/TCP/UDP,
3208  *      this function can be used to verify that checksum on received
3209  *      packets.  In that case the function should return zero if the
3210  *      checksum is correct.  In particular, this function will return zero
3211  *      if skb->ip_summed is CHECKSUM_UNNECESSARY which indicates that the
3212  *      hardware has already verified the correctness of the checksum.
3213  */
3214 static inline __sum16 skb_checksum_complete(struct sk_buff *skb)
3215 {
3216         return skb_csum_unnecessary(skb) ?
3217                0 : __skb_checksum_complete(skb);
3218 }
3219 
3220 static inline void __skb_decr_checksum_unnecessary(struct sk_buff *skb)
3221 {
3222         if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
3223                 if (skb->csum_level == 0)
3224                         skb->ip_summed = CHECKSUM_NONE;
3225                 else
3226                         skb->csum_level--;
3227         }
3228 }
3229 
3230 static inline void __skb_incr_checksum_unnecessary(struct sk_buff *skb)
3231 {
3232         if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
3233                 if (skb->csum_level < SKB_MAX_CSUM_LEVEL)
3234                         skb->csum_level++;
3235         } else if (skb->ip_summed == CHECKSUM_NONE) {
3236                 skb->ip_summed = CHECKSUM_UNNECESSARY;
3237                 skb->csum_level = 0;
3238         }
3239 }
3240 
3241 static inline void __skb_mark_checksum_bad(struct sk_buff *skb)
3242 {
3243         /* Mark current checksum as bad (typically called from GRO
3244          * path). In the case that ip_summed is CHECKSUM_NONE
3245          * this must be the first checksum encountered in the packet.
3246          * When ip_summed is CHECKSUM_UNNECESSARY, this is the first
3247          * checksum after the last one validated. For UDP, a zero
3248          * checksum can not be marked as bad.
3249          */
3250 
3251         if (skb->ip_summed == CHECKSUM_NONE ||
3252             skb->ip_summed == CHECKSUM_UNNECESSARY)
3253                 skb->csum_bad = 1;
3254 }
3255 
3256 /* Check if we need to perform checksum complete validation.
3257  *
3258  * Returns true if checksum complete is needed, false otherwise
3259  * (either checksum is unnecessary or zero checksum is allowed).
3260  */
3261 static inline bool __skb_checksum_validate_needed(struct sk_buff *skb,
3262                                                   bool zero_okay,
3263                                                   __sum16 check)
3264 {
3265         if (skb_csum_unnecessary(skb) || (zero_okay && !check)) {
3266                 skb->csum_valid = 1;
3267                 __skb_decr_checksum_unnecessary(skb);
3268                 return false;
3269         }
3270 
3271         return true;
3272 }
3273 
3274 /* For small packets <= CHECKSUM_BREAK peform checksum complete directly
3275  * in checksum_init.
3276  */
3277 #define CHECKSUM_BREAK 76
3278 
3279 /* Unset checksum-complete
3280  *
3281  * Unset checksum complete can be done when packet is being modified
3282  * (uncompressed for instance) and checksum-complete value is
3283  * invalidated.
3284  */
3285 static inline void skb_checksum_complete_unset(struct sk_buff *skb)
3286 {
3287         if (skb->ip_summed == CHECKSUM_COMPLETE)
3288                 skb->ip_summed = CHECKSUM_NONE;
3289 }
3290 
3291 /* Validate (init) checksum based on checksum complete.
3292  *
3293  * Return values:
3294  *   0: checksum is validated or try to in skb_checksum_complete. In the latter
3295  *      case the ip_summed will not be CHECKSUM_UNNECESSARY and the pseudo
3296  *      checksum is stored in skb->csum for use in __skb_checksum_complete
3297  *   non-zero: value of invalid checksum
3298  *
3299  */
3300 static inline __sum16 __skb_checksum_validate_complete(struct sk_buff *skb,
3301                                                        bool complete,
3302                                                        __wsum psum)
3303 {
3304         if (skb->ip_summed == CHECKSUM_COMPLETE) {
3305                 if (!csum_fold(csum_add(psum, skb->csum))) {
3306                         skb->csum_valid = 1;
3307                         return 0;
3308                 }
3309         } else if (skb->csum_bad) {
3310                 /* ip_summed == CHECKSUM_NONE in this case */
3311                 return (__force __sum16)1;
3312         }
3313 
3314         skb->csum = psum;
3315 
3316         if (complete || skb->len <= CHECKSUM_BREAK) {
3317                 __sum16 csum;
3318 
3319                 csum = __skb_checksum_complete(skb);
3320                 skb->csum_valid = !csum;
3321                 return csum;
3322         }
3323 
3324         return 0;
3325 }
3326 
3327 static inline __wsum null_compute_pseudo(struct sk_buff *skb, int proto)
3328 {
3329         return 0;
3330 }
3331 
3332 /* Perform checksum validate (init). Note that this is a macro since we only
3333  * want to calculate the pseudo header which is an input function if necessary.
3334  * First we try to validate without any computation (checksum unnecessary) and
3335  * then calculate based on checksum complete calling the function to compute
3336  * pseudo header.
3337  *
3338  * Return values:
3339  *   0: checksum is validated or try to in skb_checksum_complete
3340  *   non-zero: value of invalid checksum
3341  */
3342 #define __skb_checksum_validate(skb, proto, complete,                   \
3343                                 zero_okay, check, compute_pseudo)       \
3344 ({                                                                      \
3345         __sum16 __ret = 0;                                              \
3346         skb->csum_valid = 0;                                            \
3347         if (__skb_checksum_validate_needed(skb, zero_okay, check))      \
3348                 __ret = __skb_checksum_validate_complete(skb,           \
3349                                 complete, compute_pseudo(skb, proto));  \
3350         __ret;                                                          \
3351 })
3352 
3353 #define skb_checksum_init(skb, proto, compute_pseudo)                   \
3354         __skb_checksum_validate(skb, proto, false, false, 0, compute_pseudo)
3355 
3356 #define skb_checksum_init_zero_check(skb, proto, check, compute_pseudo) \
3357         __skb_checksum_validate(skb, proto, false, true, check, compute_pseudo)
3358 
3359 #define skb_checksum_validate(skb, proto, compute_pseudo)               \
3360         __skb_checksum_validate(skb, proto, true, false, 0, compute_pseudo)
3361 
3362 #define skb_checksum_validate_zero_check(skb, proto, check,             \
3363                                          compute_pseudo)                \
3364         __skb_checksum_validate(skb, proto, true, true, check, compute_pseudo)
3365 
3366 #define skb_checksum_simple_validate(skb)                               \
3367         __skb_checksum_validate(skb, 0, true, false, 0, null_compute_pseudo)
3368 
3369 static inline bool __skb_checksum_convert_check(struct sk_buff *skb)
3370 {
3371         return (skb->ip_summed == CHECKSUM_NONE &&
3372                 skb->csum_valid && !skb->csum_bad);
3373 }
3374 
3375 static inline void __skb_checksum_convert(struct sk_buff *skb,
3376                                           __sum16 check, __wsum pseudo)
3377 {
3378         skb->csum = ~pseudo;
3379         skb->ip_summed = CHECKSUM_COMPLETE;
3380 }
3381 
3382 #define skb_checksum_try_convert(skb, proto, check, compute_pseudo)     \
3383 do {                                                                    \
3384         if (__skb_checksum_convert_check(skb))                          \
3385                 __skb_checksum_convert(skb, check,                      \
3386                                        compute_pseudo(skb, proto));     \
3387 } while (0)
3388 
3389 static inline void skb_remcsum_adjust_partial(struct sk_buff *skb, void *ptr,
3390                                               u16 start, u16 offset)
3391 {
3392         skb->ip_summed = CHECKSUM_PARTIAL;
3393         skb->csum_start = ((unsigned char *)ptr + start) - skb->head;
3394         skb->csum_offset = offset - start;
3395 }
3396 
3397 /* Update skbuf and packet to reflect the remote checksum offload operation.
3398  * When called, ptr indicates the starting point for skb->csum when
3399  * ip_summed is CHECKSUM_COMPLETE. If we need create checksum complete
3400  * here, skb_postpull_rcsum is done so skb->csum start is ptr.
3401  */
3402 static inline void skb_remcsum_process(struct sk_buff *skb, void *ptr,
3403                                        int start, int offset, bool nopartial)
3404 {
3405         __wsum delta;
3406 
3407         if (!nopartial) {
3408                 skb_remcsum_adjust_partial(skb, ptr, start, offset);
3409                 return;
3410         }
3411 
3412          if (unlikely(skb->ip_summed != CHECKSUM_COMPLETE)) {
3413                 __skb_checksum_complete(skb);
3414                 skb_postpull_rcsum(skb, skb->data, ptr - (void *)skb->data);
3415         }
3416 
3417         delta = remcsum_adjust(ptr, skb->csum, start, offset);
3418 
3419         /* Adjust skb->csum since we changed the packet */
3420         skb->csum = csum_add(skb->csum, delta);
3421 }
3422 
3423 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
3424 void nf_conntrack_destroy(struct nf_conntrack *nfct);
3425 static inline void nf_conntrack_put(struct nf_conntrack *nfct)
3426 {
3427         if (nfct && atomic_dec_and_test(&nfct->use))
3428                 nf_conntrack_destroy(nfct);
3429 }
3430 static inline void nf_conntrack_get(struct nf_conntrack *nfct)
3431 {
3432         if (nfct)
3433                 atomic_inc(&nfct->use);
3434 }
3435 #endif
3436 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
3437 static inline void nf_bridge_put(struct nf_bridge_info *nf_bridge)
3438 {
3439         if (nf_bridge && atomic_dec_and_test(&nf_bridge->use))
3440                 kfree(nf_bridge);
3441 }
3442 static inline void nf_bridge_get(struct nf_bridge_info *nf_bridge)
3443 {
3444         if (nf_bridge)
3445                 atomic_inc(&nf_bridge->use);
3446 }
3447 #endif /* CONFIG_BRIDGE_NETFILTER */
3448 static inline void nf_reset(struct sk_buff *skb)
3449 {
3450 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
3451         nf_conntrack_put(skb->nfct);
3452         skb->nfct = NULL;
3453 #endif
3454 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
3455         nf_bridge_put(skb->nf_bridge);
3456         skb->nf_bridge = NULL;
3457 #endif
3458 }
3459 
3460 static inline void nf_reset_trace(struct sk_buff *skb)
3461 {
3462 #if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE) || defined(CONFIG_NF_TABLES)
3463         skb->nf_trace = 0;
3464 #endif
3465 }
3466 
3467 /* Note: This doesn't put any conntrack and bridge info in dst. */
3468 static inline void __nf_copy(struct sk_buff *dst, const struct sk_buff *src,
3469                              bool copy)
3470 {
3471 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
3472         dst->nfct = src->nfct;
3473         nf_conntrack_get(src->nfct);
3474         if (copy)
3475                 dst->nfctinfo = src->nfctinfo;
3476 #endif
3477 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
3478         dst->nf_bridge  = src->nf_bridge;
3479         nf_bridge_get(src->nf_bridge);
3480 #endif
3481 #if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE) || defined(CONFIG_NF_TABLES)
3482         if (copy)
3483                 dst->nf_trace = src->nf_trace;
3484 #endif
3485 }
3486 
3487 static inline void nf_copy(struct sk_buff *dst, const struct sk_buff *src)
3488 {
3489 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
3490         nf_conntrack_put(dst->nfct);
3491 #endif
3492 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
3493         nf_bridge_put(dst->nf_bridge);
3494 #endif
3495         __nf_copy(dst, src, true);
3496 }
3497 
3498 #ifdef CONFIG_NETWORK_SECMARK
3499 static inline void skb_copy_secmark(struct sk_buff *to, const struct sk_buff *from)
3500 {
3501         to->secmark = from->secmark;
3502 }
3503 
3504 static inline void skb_init_secmark(struct sk_buff *skb)
3505 {
3506         skb->secmark = 0;
3507 }
3508 #else
3509 static inline void skb_copy_secmark(struct sk_buff *to, const struct sk_buff *from)
3510 { }
3511 
3512 static inline void skb_init_secmark(struct sk_buff *skb)
3513 { }
3514 #endif
3515 
3516 static inline bool skb_irq_freeable(const struct sk_buff *skb)
3517 {
3518         return !skb->destructor &&
3519 #if IS_ENABLED(CONFIG_XFRM)
3520                 !skb->sp &&
3521 #endif
3522 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
3523                 !skb->nfct &&
3524 #endif
3525                 !skb->_skb_refdst &&
3526                 !skb_has_frag_list(skb);
3527 }
3528 
3529 static inline void skb_set_queue_mapping(struct sk_buff *skb, u16 queue_mapping)
3530 {
3531         skb->queue_mapping = queue_mapping;
3532 }
3533 
3534 static inline u16 skb_get_queue_mapping(const struct sk_buff *skb)
3535 {
3536         return skb->queue_mapping;
3537 }
3538 
3539 static inline void skb_copy_queue_mapping(struct sk_buff *to, const struct sk_buff *from)
3540 {
3541         to->queue_mapping = from->queue_mapping;
3542 }
3543 
3544 static inline void skb_record_rx_queue(struct sk_buff *skb, u16 rx_queue)
3545 {
3546         skb->queue_mapping = rx_queue + 1;
3547 }
3548 
3549 static inline u16 skb_get_rx_queue(const struct sk_buff *skb)
3550 {
3551         return skb->queue_mapping - 1;
3552 }
3553 
3554 static inline bool skb_rx_queue_recorded(const struct sk_buff *skb)
3555 {
3556         return skb->queue_mapping != 0;
3557 }
3558 
3559 static inline struct sec_path *skb_sec_path(struct sk_buff *skb)
3560 {
3561 #ifdef CONFIG_XFRM
3562         return skb->sp;
3563 #else
3564         return NULL;
3565 #endif
3566 }
3567 
3568 /* Keeps track of mac header offset relative to skb->head.
3569  * It is useful for TSO of Tunneling protocol. e.g. GRE.
3570  * For non-tunnel skb it points to skb_mac_header() and for
3571  * tunnel skb it points to outer mac header.
3572  * Keeps track of level of encapsulation of network headers.
3573  */
3574 struct skb_gso_cb {
3575         int     mac_offset;
3576         int     encap_level;
3577         __u16   csum_start;
3578 };
3579 #define SKB_SGO_CB_OFFSET       32
3580 #define SKB_GSO_CB(skb) ((struct skb_gso_cb *)((skb)->cb + SKB_SGO_CB_OFFSET))
3581 
3582 static inline int skb_tnl_header_len(const struct sk_buff *inner_skb)
3583 {
3584         return (skb_mac_header(inner_skb) - inner_skb->head) -
3585                 SKB_GSO_CB(inner_skb)->mac_offset;
3586 }
3587 
3588 static inline int gso_pskb_expand_head(struct sk_buff *skb, int extra)
3589 {
3590         int new_headroom, headroom;
3591         int ret;
3592 
3593         headroom = skb_headroom(skb);
3594         ret = pskb_expand_head(skb, extra, 0, GFP_ATOMIC);
3595         if (ret)
3596                 return ret;
3597 
3598         new_headroom = skb_headroom(skb);
3599         SKB_GSO_CB(skb)->mac_offset += (new_headroom - headroom);
3600         return 0;
3601 }
3602 
3603 /* Compute the checksum for a gso segment. First compute the checksum value
3604  * from the start of transport header to SKB_GSO_CB(skb)->csum_start, and
3605  * then add in skb->csum (checksum from csum_start to end of packet).
3606  * skb->csum and csum_start are then updated to reflect the checksum of the
3607  * resultant packet starting from the transport header-- the resultant checksum
3608  * is in the res argument (i.e. normally zero or ~ of checksum of a pseudo
3609  * header.
3610  */
3611 static inline __sum16 gso_make_checksum(struct sk_buff *skb, __wsum res)
3612 {
3613         int plen = SKB_GSO_CB(skb)->csum_start - skb_headroom(skb) -
3614                    skb_transport_offset(skb);
3615         __wsum partial;
3616 
3617         partial = csum_partial(skb_transport_header(skb), plen, skb->csum);
3618         skb->csum = res;
3619         SKB_GSO_CB(skb)->csum_start -= plen;
3620 
3621         return csum_fold(partial);
3622 }
3623 
3624 static inline bool skb_is_gso(const struct sk_buff *skb)
3625 {
3626         return skb_shinfo(skb)->gso_size;
3627 }
3628 
3629 /* Note: Should be called only if skb_is_gso(skb) is true */
3630 static inline bool skb_is_gso_v6(const struct sk_buff *skb)
3631 {
3632         return skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6;
3633 }
3634 
3635 void __skb_warn_lro_forwarding(const struct sk_buff *skb);
3636 
3637 static inline bool skb_warn_if_lro(const struct sk_buff *skb)
3638 {
3639         /* LRO sets gso_size but not gso_type, whereas if GSO is really
3640          * wanted then gso_type will be set. */
3641         const struct skb_shared_info *shinfo = skb_shinfo(skb);
3642 
3643         if (skb_is_nonlinear(skb) && shinfo->gso_size != 0 &&
3644             unlikely(shinfo->gso_type == 0)) {
3645                 __skb_warn_lro_forwarding(skb);
3646                 return true;
3647         }
3648         return false;
3649 }
3650 
3651 static inline void skb_forward_csum(struct sk_buff *skb)
3652 {
3653         /* Unfortunately we don't support this one.  Any brave souls? */
3654         if (skb->ip_summed == CHECKSUM_COMPLETE)
3655                 skb->ip_summed = CHECKSUM_NONE;
3656 }
3657 
3658 /**
3659  * skb_checksum_none_assert - make sure skb ip_summed is CHECKSUM_NONE
3660  * @skb: skb to check
3661  *
3662  * fresh skbs have their ip_summed set to CHECKSUM_NONE.
3663  * Instead of forcing ip_summed to CHECKSUM_NONE, we can
3664  * use this helper, to document places where we make this assertion.
3665  */
3666 static inline void skb_checksum_none_assert(const struct sk_buff *skb)
3667 {
3668 #ifdef DEBUG
3669         BUG_ON(skb->ip_summed != CHECKSUM_NONE);
3670 #endif
3671 }
3672 
3673 bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off);
3674 
3675 int skb_checksum_setup(struct sk_buff *skb, bool recalculate);
3676 struct sk_buff *skb_checksum_trimmed(struct sk_buff *skb,
3677                                      unsigned int transport_len,
3678                                      __sum16(*skb_chkf)(struct sk_buff *skb));
3679 
3680 /**
3681  * skb_head_is_locked - Determine if the skb->head is locked down
3682  * @skb: skb to check
3683  *
3684  * The head on skbs build around a head frag can be removed if they are
3685  * not cloned.  This function returns true if the skb head is locked down
3686  * due to either being allocated via kmalloc, or by being a clone with
3687  * multiple references to the head.
3688  */
3689 static inline bool skb_head_is_locked(const struct sk_buff *skb)
3690 {
3691         return !skb->head_frag || skb_cloned(skb);
3692 }
3693 
3694 /**
3695  * skb_gso_network_seglen - Return length of individual segments of a gso packet
3696  *
3697  * @skb: GSO skb
3698  *
3699  * skb_gso_network_seglen is used to determine the real size of the
3700  * individual segments, including Layer3 (IP, IPv6) and L4 headers (TCP/UDP).
3701  *
3702  * The MAC/L2 header is not accounted for.
3703  */
3704 static inline unsigned int skb_gso_network_seglen(const struct sk_buff *skb)
3705 {
3706         unsigned int hdr_len = skb_transport_header(skb) -
3707                                skb_network_header(skb);
3708         return hdr_len + skb_gso_transport_seglen(skb);
3709 }
3710 
3711 #endif  /* __KERNEL__ */
3712 #endif  /* _LINUX_SKBUFF_H */
3713 

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