xref: /linux/include/net/dst.h (revision 56d06fa29edd58c448766014afd833b7ff51247b) 
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 static inline u32 dst_tclassid(const struct sk_buff *skb)
402 {
403 #ifdef CONFIG_IP_ROUTE_CLASSID
404 	const struct dst_entry *dst;
405 
406 	dst = skb_dst(skb);
407 	if (dst)
408 		return dst->tclassid;
409 #endif
410 	return 0;
411 }
412 
413 int dst_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb);
414 static inline int dst_discard(struct sk_buff *skb)
415 {
416 	return dst_discard_out(&init_net, skb->sk, skb);
417 }
418 void *dst_alloc(struct dst_ops *ops, struct net_device *dev, int initial_ref,
419 		int initial_obsolete, unsigned short flags);
420 void dst_init(struct dst_entry *dst, struct dst_ops *ops,
421 	      struct net_device *dev, int initial_ref, int initial_obsolete,
422 	      unsigned short flags);
423 void __dst_free(struct dst_entry *dst);
424 struct dst_entry *dst_destroy(struct dst_entry *dst);
425 
426 static inline void dst_free(struct dst_entry *dst)
427 {
428 	if (dst->obsolete > 0)
429 		return;
430 	if (!atomic_read(&dst->__refcnt)) {
431 		dst = dst_destroy(dst);
432 		if (!dst)
433 			return;
434 	}
435 	__dst_free(dst);
436 }
437 
438 static inline void dst_rcu_free(struct rcu_head *head)
439 {
440 	struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
441 	dst_free(dst);
442 }
443 
444 static inline void dst_confirm(struct dst_entry *dst)
445 {
446 	dst->pending_confirm = 1;
447 }
448 
449 static inline int dst_neigh_output(struct dst_entry *dst, struct neighbour *n,
450 				   struct sk_buff *skb)
451 {
452 	const struct hh_cache *hh;
453 
454 	if (dst->pending_confirm) {
455 		unsigned long now = jiffies;
456 
457 		dst->pending_confirm = 0;
458 		/* avoid dirtying neighbour */
459 		if (n->confirmed != now)
460 			n->confirmed = now;
461 	}
462 
463 	hh = &n->hh;
464 	if ((n->nud_state & NUD_CONNECTED) && hh->hh_len)
465 		return neigh_hh_output(hh, skb);
466 	else
467 		return n->output(n, skb);
468 }
469 
470 static inline struct neighbour *dst_neigh_lookup(const struct dst_entry *dst, const void *daddr)
471 {
472 	struct neighbour *n = dst->ops->neigh_lookup(dst, NULL, daddr);
473 	return IS_ERR(n) ? NULL : n;
474 }
475 
476 static inline struct neighbour *dst_neigh_lookup_skb(const struct dst_entry *dst,
477 						     struct sk_buff *skb)
478 {
479 	struct neighbour *n =  dst->ops->neigh_lookup(dst, skb, NULL);
480 	return IS_ERR(n) ? NULL : n;
481 }
482 
483 static inline void dst_link_failure(struct sk_buff *skb)
484 {
485 	struct dst_entry *dst = skb_dst(skb);
486 	if (dst && dst->ops && dst->ops->link_failure)
487 		dst->ops->link_failure(skb);
488 }
489 
490 static inline void dst_set_expires(struct dst_entry *dst, int timeout)
491 {
492 	unsigned long expires = jiffies + timeout;
493 
494 	if (expires == 0)
495 		expires = 1;
496 
497 	if (dst->expires == 0 || time_before(expires, dst->expires))
498 		dst->expires = expires;
499 }
500 
501 /* Output packet to network from transport.  */
502 static inline int dst_output(struct net *net, struct sock *sk, struct sk_buff *skb)
503 {
504 	return skb_dst(skb)->output(net, sk, skb);
505 }
506 
507 /* Input packet from network to transport.  */
508 static inline int dst_input(struct sk_buff *skb)
509 {
510 	return skb_dst(skb)->input(skb);
511 }
512 
513 static inline struct dst_entry *dst_check(struct dst_entry *dst, u32 cookie)
514 {
515 	if (dst->obsolete)
516 		dst = dst->ops->check(dst, cookie);
517 	return dst;
518 }
519 
520 void dst_subsys_init(void);
521 
522 /* Flags for xfrm_lookup flags argument. */
523 enum {
524 	XFRM_LOOKUP_ICMP = 1 << 0,
525 	XFRM_LOOKUP_QUEUE = 1 << 1,
526 	XFRM_LOOKUP_KEEP_DST_REF = 1 << 2,
527 };
528 
529 struct flowi;
530 #ifndef CONFIG_XFRM
531 static inline struct dst_entry *xfrm_lookup(struct net *net,
532 					    struct dst_entry *dst_orig,
533 					    const struct flowi *fl,
534 					    const struct sock *sk,
535 					    int flags)
536 {
537 	return dst_orig;
538 }
539 
540 static inline struct dst_entry *xfrm_lookup_route(struct net *net,
541 						  struct dst_entry *dst_orig,
542 						  const struct flowi *fl,
543 						  const struct sock *sk,
544 						  int flags)
545 {
546 	return dst_orig;
547 }
548 
549 static inline struct xfrm_state *dst_xfrm(const struct dst_entry *dst)
550 {
551 	return NULL;
552 }
553 
554 #else
555 struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
556 			      const struct flowi *fl, const struct sock *sk,
557 			      int flags);
558 
559 struct dst_entry *xfrm_lookup_route(struct net *net, struct dst_entry *dst_orig,
560 				    const struct flowi *fl, const struct sock *sk,
561 				    int flags);
562 
563 /* skb attached with this dst needs transformation if dst->xfrm is valid */
564 static inline struct xfrm_state *dst_xfrm(const struct dst_entry *dst)
565 {
566 	return dst->xfrm;
567 }
568 #endif
569 
570 #endif /* _NET_DST_H */
571