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Linux/include/net/dst.h

  1 /*
  2  * net/dst.h    Protocol independent destination cache definitions.
  3  *
  4  * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
  5  *
  6  */
  7 
  8 #ifndef _NET_DST_H
  9 #define _NET_DST_H
 10 
 11 #include <net/dst_ops.h>
 12 #include <linux/netdevice.h>
 13 #include <linux/rtnetlink.h>
 14 #include <linux/rcupdate.h>
 15 #include <linux/bug.h>
 16 #include <linux/jiffies.h>
 17 #include <net/neighbour.h>
 18 #include <asm/processor.h>
 19 
 20 #define DST_GC_MIN      (HZ/10)
 21 #define DST_GC_INC      (HZ/2)
 22 #define DST_GC_MAX      (120*HZ)
 23 
 24 /* Each dst_entry has reference count and sits in some parent list(s).
 25  * When it is removed from parent list, it is "freed" (dst_free).
 26  * After this it enters dead state (dst->obsolete > 0) and if its refcnt
 27  * is zero, it can be destroyed immediately, otherwise it is added
 28  * to gc list and garbage collector periodically checks the refcnt.
 29  */
 30 
 31 struct sk_buff;
 32 
 33 struct dst_entry {
 34         struct rcu_head         rcu_head;
 35         struct dst_entry        *child;
 36         struct net_device       *dev;
 37         struct  dst_ops         *ops;
 38         unsigned long           _metrics;
 39         unsigned long           expires;
 40         struct dst_entry        *path;
 41         struct dst_entry        *from;
 42 #ifdef CONFIG_XFRM
 43         struct xfrm_state       *xfrm;
 44 #else
 45         void                    *__pad1;
 46 #endif
 47         int                     (*input)(struct sk_buff *);
 48         int                     (*output)(struct net *net, struct sock *sk, struct sk_buff *skb);
 49 
 50         unsigned short          flags;
 51 #define DST_HOST                0x0001
 52 #define DST_NOXFRM              0x0002
 53 #define DST_NOPOLICY            0x0004
 54 #define DST_NOHASH              0x0008
 55 #define DST_NOCACHE             0x0010
 56 #define DST_NOCOUNT             0x0020
 57 #define DST_FAKE_RTABLE         0x0040
 58 #define DST_XFRM_TUNNEL         0x0080
 59 #define DST_XFRM_QUEUE          0x0100
 60 #define DST_METADATA            0x0200
 61 
 62         unsigned short          pending_confirm;
 63 
 64         short                   error;
 65 
 66         /* A non-zero value of dst->obsolete forces by-hand validation
 67          * of the route entry.  Positive values are set by the generic
 68          * dst layer to indicate that the entry has been forcefully
 69          * destroyed.
 70          *
 71          * Negative values are used by the implementation layer code to
 72          * force invocation of the dst_ops->check() method.
 73          */
 74         short                   obsolete;
 75 #define DST_OBSOLETE_NONE       0
 76 #define DST_OBSOLETE_DEAD       2
 77 #define DST_OBSOLETE_FORCE_CHK  -1
 78 #define DST_OBSOLETE_KILL       -2
 79         unsigned short          header_len;     /* more space at head required */
 80         unsigned short          trailer_len;    /* space to reserve at tail */
 81 #ifdef CONFIG_IP_ROUTE_CLASSID
 82         __u32                   tclassid;
 83 #else
 84         __u32                   __pad2;
 85 #endif
 86 
 87 #ifdef CONFIG_64BIT
 88         struct lwtunnel_state   *lwtstate;
 89         /*
 90          * Align __refcnt to a 64 bytes alignment
 91          * (L1_CACHE_SIZE would be too much)
 92          */
 93         long                    __pad_to_align_refcnt[1];
 94 #endif
 95         /*
 96          * __refcnt wants to be on a different cache line from
 97          * input/output/ops or performance tanks badly
 98          */
 99         atomic_t                __refcnt;       /* client references    */
100         int                     __use;
101         unsigned long           lastuse;
102 #ifndef CONFIG_64BIT
103         struct lwtunnel_state   *lwtstate;
104 #endif
105         union {
106                 struct dst_entry        *next;
107                 struct rtable __rcu     *rt_next;
108                 struct rt6_info         *rt6_next;
109                 struct dn_route __rcu   *dn_next;
110         };
111 };
112 
113 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old);
114 extern const u32 dst_default_metrics[];
115 
116 #define DST_METRICS_READ_ONLY           0x1UL
117 #define DST_METRICS_FLAGS               0x3UL
118 #define __DST_METRICS_PTR(Y)    \
119         ((u32 *)((Y) & ~DST_METRICS_FLAGS))
120 #define DST_METRICS_PTR(X)      __DST_METRICS_PTR((X)->_metrics)
121 
122 static inline bool dst_metrics_read_only(const struct dst_entry *dst)
123 {
124         return dst->_metrics & DST_METRICS_READ_ONLY;
125 }
126 
127 void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old);
128 
129 static inline void dst_destroy_metrics_generic(struct dst_entry *dst)
130 {
131         unsigned long val = dst->_metrics;
132         if (!(val & DST_METRICS_READ_ONLY))
133                 __dst_destroy_metrics_generic(dst, val);
134 }
135 
136 static inline u32 *dst_metrics_write_ptr(struct dst_entry *dst)
137 {
138         unsigned long p = dst->_metrics;
139 
140         BUG_ON(!p);
141 
142         if (p & DST_METRICS_READ_ONLY)
143                 return dst->ops->cow_metrics(dst, p);
144         return __DST_METRICS_PTR(p);
145 }
146 
147 /* This may only be invoked before the entry has reached global
148  * visibility.
149  */
150 static inline void dst_init_metrics(struct dst_entry *dst,
151                                     const u32 *src_metrics,
152                                     bool read_only)
153 {
154         dst->_metrics = ((unsigned long) src_metrics) |
155                 (read_only ? DST_METRICS_READ_ONLY : 0);
156 }
157 
158 static inline void dst_copy_metrics(struct dst_entry *dest, const struct dst_entry *src)
159 {
160         u32 *dst_metrics = dst_metrics_write_ptr(dest);
161 
162         if (dst_metrics) {
163                 u32 *src_metrics = DST_METRICS_PTR(src);
164 
165                 memcpy(dst_metrics, src_metrics, RTAX_MAX * sizeof(u32));
166         }
167 }
168 
169 static inline u32 *dst_metrics_ptr(struct dst_entry *dst)
170 {
171         return DST_METRICS_PTR(dst);
172 }
173 
174 static inline u32
175 dst_metric_raw(const struct dst_entry *dst, const int metric)
176 {
177         u32 *p = DST_METRICS_PTR(dst);
178 
179         return p[metric-1];
180 }
181 
182 static inline u32
183 dst_metric(const struct dst_entry *dst, const int metric)
184 {
185         WARN_ON_ONCE(metric == RTAX_HOPLIMIT ||
186                      metric == RTAX_ADVMSS ||
187                      metric == RTAX_MTU);
188         return dst_metric_raw(dst, metric);
189 }
190 
191 static inline u32
192 dst_metric_advmss(const struct dst_entry *dst)
193 {
194         u32 advmss = dst_metric_raw(dst, RTAX_ADVMSS);
195 
196         if (!advmss)
197                 advmss = dst->ops->default_advmss(dst);
198 
199         return advmss;
200 }
201 
202 static inline void dst_metric_set(struct dst_entry *dst, int metric, u32 val)
203 {
204         u32 *p = dst_metrics_write_ptr(dst);
205 
206         if (p)
207                 p[metric-1] = val;
208 }
209 
210 /* Kernel-internal feature bits that are unallocated in user space. */
211 #define DST_FEATURE_ECN_CA      (1 << 31)
212 
213 #define DST_FEATURE_MASK        (DST_FEATURE_ECN_CA)
214 #define DST_FEATURE_ECN_MASK    (DST_FEATURE_ECN_CA | RTAX_FEATURE_ECN)
215 
216 static inline u32
217 dst_feature(const struct dst_entry *dst, u32 feature)
218 {
219         return dst_metric(dst, RTAX_FEATURES) & feature;
220 }
221 
222 static inline u32 dst_mtu(const struct dst_entry *dst)
223 {
224         return dst->ops->mtu(dst);
225 }
226 
227 /* RTT metrics are stored in milliseconds for user ABI, but used as jiffies */
228 static inline unsigned long dst_metric_rtt(const struct dst_entry *dst, int metric)
229 {
230         return msecs_to_jiffies(dst_metric(dst, metric));
231 }
232 
233 static inline u32
234 dst_allfrag(const struct dst_entry *dst)
235 {
236         int ret = dst_feature(dst,  RTAX_FEATURE_ALLFRAG);
237         return ret;
238 }
239 
240 static inline int
241 dst_metric_locked(const struct dst_entry *dst, int metric)
242 {
243         return dst_metric(dst, RTAX_LOCK) & (1<<metric);
244 }
245 
246 static inline void dst_hold(struct dst_entry *dst)
247 {
248         /*
249          * If your kernel compilation stops here, please check
250          * __pad_to_align_refcnt declaration in struct dst_entry
251          */
252         BUILD_BUG_ON(offsetof(struct dst_entry, __refcnt) & 63);
253         atomic_inc(&dst->__refcnt);
254 }
255 
256 static inline void dst_use(struct dst_entry *dst, unsigned long time)
257 {
258         dst_hold(dst);
259         dst->__use++;
260         dst->lastuse = time;
261 }
262 
263 static inline void dst_use_noref(struct dst_entry *dst, unsigned long time)
264 {
265         dst->__use++;
266         dst->lastuse = time;
267 }
268 
269 static inline struct dst_entry *dst_clone(struct dst_entry *dst)
270 {
271         if (dst)
272                 atomic_inc(&dst->__refcnt);
273         return dst;
274 }
275 
276 void dst_release(struct dst_entry *dst);
277 
278 static inline void refdst_drop(unsigned long refdst)
279 {
280         if (!(refdst & SKB_DST_NOREF))
281                 dst_release((struct dst_entry *)(refdst & SKB_DST_PTRMASK));
282 }
283 
284 /**
285  * skb_dst_drop - drops skb dst
286  * @skb: buffer
287  *
288  * Drops dst reference count if a reference was taken.
289  */
290 static inline void skb_dst_drop(struct sk_buff *skb)
291 {
292         if (skb->_skb_refdst) {
293                 refdst_drop(skb->_skb_refdst);
294                 skb->_skb_refdst = 0UL;
295         }
296 }
297 
298 static inline void __skb_dst_copy(struct sk_buff *nskb, unsigned long refdst)
299 {
300         nskb->_skb_refdst = refdst;
301         if (!(nskb->_skb_refdst & SKB_DST_NOREF))
302                 dst_clone(skb_dst(nskb));
303 }
304 
305 static inline void skb_dst_copy(struct sk_buff *nskb, const struct sk_buff *oskb)
306 {
307         __skb_dst_copy(nskb, oskb->_skb_refdst);
308 }
309 
310 /**
311  * skb_dst_force - makes sure skb dst is refcounted
312  * @skb: buffer
313  *
314  * If dst is not yet refcounted, let's do it
315  */
316 static inline void skb_dst_force(struct sk_buff *skb)
317 {
318         if (skb_dst_is_noref(skb)) {
319                 WARN_ON(!rcu_read_lock_held());
320                 skb->_skb_refdst &= ~SKB_DST_NOREF;
321                 dst_clone(skb_dst(skb));
322         }
323 }
324 
325 /**
326  * dst_hold_safe - Take a reference on a dst if possible
327  * @dst: pointer to dst entry
328  *
329  * This helper returns false if it could not safely
330  * take a reference on a dst.
331  */
332 static inline bool dst_hold_safe(struct dst_entry *dst)
333 {
334         if (dst->flags & DST_NOCACHE)
335                 return atomic_inc_not_zero(&dst->__refcnt);
336         dst_hold(dst);
337         return true;
338 }
339 
340 /**
341  * skb_dst_force_safe - makes sure skb dst is refcounted
342  * @skb: buffer
343  *
344  * If dst is not yet refcounted and not destroyed, grab a ref on it.
345  */
346 static inline void skb_dst_force_safe(struct sk_buff *skb)
347 {
348         if (skb_dst_is_noref(skb)) {
349                 struct dst_entry *dst = skb_dst(skb);
350 
351                 if (!dst_hold_safe(dst))
352                         dst = NULL;
353 
354                 skb->_skb_refdst = (unsigned long)dst;
355         }
356 }
357 
358 
359 /**
360  *      __skb_tunnel_rx - prepare skb for rx reinsert
361  *      @skb: buffer
362  *      @dev: tunnel device
363  *      @net: netns for packet i/o
364  *
365  *      After decapsulation, packet is going to re-enter (netif_rx()) our stack,
366  *      so make some cleanups. (no accounting done)
367  */
368 static inline void __skb_tunnel_rx(struct sk_buff *skb, struct net_device *dev,
369                                    struct net *net)
370 {
371         skb->dev = dev;
372 
373         /*
374          * Clear hash so that we can recalulate the hash for the
375          * encapsulated packet, unless we have already determine the hash
376          * over the L4 4-tuple.
377          */
378         skb_clear_hash_if_not_l4(skb);
379         skb_set_queue_mapping(skb, 0);
380         skb_scrub_packet(skb, !net_eq(net, dev_net(dev)));
381 }
382 
383 /**
384  *      skb_tunnel_rx - prepare skb for rx reinsert
385  *      @skb: buffer
386  *      @dev: tunnel device
387  *
388  *      After decapsulation, packet is going to re-enter (netif_rx()) our stack,
389  *      so make some cleanups, and perform accounting.
390  *      Note: this accounting is not SMP safe.
391  */
392 static inline void skb_tunnel_rx(struct sk_buff *skb, struct net_device *dev,
393                                  struct net *net)
394 {
395         /* TODO : stats should be SMP safe */
396         dev->stats.rx_packets++;
397         dev->stats.rx_bytes += skb->len;
398         __skb_tunnel_rx(skb, dev, net);
399 }
400 
401 int dst_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb);
402 static inline int dst_discard(struct sk_buff *skb)
403 {
404         return dst_discard_out(&init_net, skb->sk, skb);
405 }
406 void *dst_alloc(struct dst_ops *ops, struct net_device *dev, int initial_ref,
407                 int initial_obsolete, unsigned short flags);
408 void dst_init(struct dst_entry *dst, struct dst_ops *ops,
409               struct net_device *dev, int initial_ref, int initial_obsolete,
410               unsigned short flags);
411 void __dst_free(struct dst_entry *dst);
412 struct dst_entry *dst_destroy(struct dst_entry *dst);
413 
414 static inline void dst_free(struct dst_entry *dst)
415 {
416         if (dst->obsolete > 0)
417                 return;
418         if (!atomic_read(&dst->__refcnt)) {
419                 dst = dst_destroy(dst);
420                 if (!dst)
421                         return;
422         }
423         __dst_free(dst);
424 }
425 
426 static inline void dst_rcu_free(struct rcu_head *head)
427 {
428         struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
429         dst_free(dst);
430 }
431 
432 static inline void dst_confirm(struct dst_entry *dst)
433 {
434         dst->pending_confirm = 1;
435 }
436 
437 static inline int dst_neigh_output(struct dst_entry *dst, struct neighbour *n,
438                                    struct sk_buff *skb)
439 {
440         const struct hh_cache *hh;
441 
442         if (dst->pending_confirm) {
443                 unsigned long now = jiffies;
444 
445                 dst->pending_confirm = 0;
446                 /* avoid dirtying neighbour */
447                 if (n->confirmed != now)
448                         n->confirmed = now;
449         }
450 
451         hh = &n->hh;
452         if ((n->nud_state & NUD_CONNECTED) && hh->hh_len)
453                 return neigh_hh_output(hh, skb);
454         else
455                 return n->output(n, skb);
456 }
457 
458 static inline struct neighbour *dst_neigh_lookup(const struct dst_entry *dst, const void *daddr)
459 {
460         struct neighbour *n = dst->ops->neigh_lookup(dst, NULL, daddr);
461         return IS_ERR(n) ? NULL : n;
462 }
463 
464 static inline struct neighbour *dst_neigh_lookup_skb(const struct dst_entry *dst,
465                                                      struct sk_buff *skb)
466 {
467         struct neighbour *n =  dst->ops->neigh_lookup(dst, skb, NULL);
468         return IS_ERR(n) ? NULL : n;
469 }
470 
471 static inline void dst_link_failure(struct sk_buff *skb)
472 {
473         struct dst_entry *dst = skb_dst(skb);
474         if (dst && dst->ops && dst->ops->link_failure)
475                 dst->ops->link_failure(skb);
476 }
477 
478 static inline void dst_set_expires(struct dst_entry *dst, int timeout)
479 {
480         unsigned long expires = jiffies + timeout;
481 
482         if (expires == 0)
483                 expires = 1;
484 
485         if (dst->expires == 0 || time_before(expires, dst->expires))
486                 dst->expires = expires;
487 }
488 
489 /* Output packet to network from transport.  */
490 static inline int dst_output(struct net *net, struct sock *sk, struct sk_buff *skb)
491 {
492         return skb_dst(skb)->output(net, sk, skb);
493 }
494 
495 /* Input packet from network to transport.  */
496 static inline int dst_input(struct sk_buff *skb)
497 {
498         return skb_dst(skb)->input(skb);
499 }
500 
501 static inline struct dst_entry *dst_check(struct dst_entry *dst, u32 cookie)
502 {
503         if (dst->obsolete)
504                 dst = dst->ops->check(dst, cookie);
505         return dst;
506 }
507 
508 void dst_subsys_init(void);
509 
510 /* Flags for xfrm_lookup flags argument. */
511 enum {
512         XFRM_LOOKUP_ICMP = 1 << 0,
513         XFRM_LOOKUP_QUEUE = 1 << 1,
514         XFRM_LOOKUP_KEEP_DST_REF = 1 << 2,
515 };
516 
517 struct flowi;
518 #ifndef CONFIG_XFRM
519 static inline struct dst_entry *xfrm_lookup(struct net *net,
520                                             struct dst_entry *dst_orig,
521                                             const struct flowi *fl,
522                                             const struct sock *sk,
523                                             int flags)
524 {
525         return dst_orig;
526 }
527 
528 static inline struct dst_entry *xfrm_lookup_route(struct net *net,
529                                                   struct dst_entry *dst_orig,
530                                                   const struct flowi *fl,
531                                                   const struct sock *sk,
532                                                   int flags)
533 {
534         return dst_orig;
535 }
536 
537 static inline struct xfrm_state *dst_xfrm(const struct dst_entry *dst)
538 {
539         return NULL;
540 }
541 
542 #else
543 struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
544                               const struct flowi *fl, const struct sock *sk,
545                               int flags);
546 
547 struct dst_entry *xfrm_lookup_route(struct net *net, struct dst_entry *dst_orig,
548                                     const struct flowi *fl, const struct sock *sk,
549                                     int flags);
550 
551 /* skb attached with this dst needs transformation if dst->xfrm is valid */
552 static inline struct xfrm_state *dst_xfrm(const struct dst_entry *dst)
553 {
554         return dst->xfrm;
555 }
556 #endif
557 
558 #endif /* _NET_DST_H */
559 

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