xref: /linux/net/core/dst.c (revision 0be3ff0c) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * net/core/dst.c	Protocol independent destination cache.
4  *
5  * Authors:		Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
6  *
7  */
8 
9 #include <linux/bitops.h>
10 #include <linux/errno.h>
11 #include <linux/init.h>
12 #include <linux/kernel.h>
13 #include <linux/workqueue.h>
14 #include <linux/mm.h>
15 #include <linux/module.h>
16 #include <linux/slab.h>
17 #include <linux/netdevice.h>
18 #include <linux/skbuff.h>
19 #include <linux/string.h>
20 #include <linux/types.h>
21 #include <net/net_namespace.h>
22 #include <linux/sched.h>
23 #include <linux/prefetch.h>
24 #include <net/lwtunnel.h>
25 #include <net/xfrm.h>
26 
27 #include <net/dst.h>
28 #include <net/dst_metadata.h>
29 
30 int dst_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb)
31 {
32 	kfree_skb(skb);
33 	return 0;
34 }
35 EXPORT_SYMBOL(dst_discard_out);
36 
37 const struct dst_metrics dst_default_metrics = {
38 	/* This initializer is needed to force linker to place this variable
39 	 * into const section. Otherwise it might end into bss section.
40 	 * We really want to avoid false sharing on this variable, and catch
41 	 * any writes on it.
42 	 */
43 	.refcnt = REFCOUNT_INIT(1),
44 };
45 EXPORT_SYMBOL(dst_default_metrics);
46 
47 void dst_init(struct dst_entry *dst, struct dst_ops *ops,
48 	      struct net_device *dev, int initial_ref, int initial_obsolete,
49 	      unsigned short flags)
50 {
51 	dst->dev = dev;
52 	dev_hold_track(dev, &dst->dev_tracker, GFP_ATOMIC);
53 	dst->ops = ops;
54 	dst_init_metrics(dst, dst_default_metrics.metrics, true);
55 	dst->expires = 0UL;
56 #ifdef CONFIG_XFRM
57 	dst->xfrm = NULL;
58 #endif
59 	dst->input = dst_discard;
60 	dst->output = dst_discard_out;
61 	dst->error = 0;
62 	dst->obsolete = initial_obsolete;
63 	dst->header_len = 0;
64 	dst->trailer_len = 0;
65 #ifdef CONFIG_IP_ROUTE_CLASSID
66 	dst->tclassid = 0;
67 #endif
68 	dst->lwtstate = NULL;
69 	atomic_set(&dst->__refcnt, initial_ref);
70 	dst->__use = 0;
71 	dst->lastuse = jiffies;
72 	dst->flags = flags;
73 	if (!(flags & DST_NOCOUNT))
74 		dst_entries_add(ops, 1);
75 }
76 EXPORT_SYMBOL(dst_init);
77 
78 void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
79 		int initial_ref, int initial_obsolete, unsigned short flags)
80 {
81 	struct dst_entry *dst;
82 
83 	if (ops->gc &&
84 	    !(flags & DST_NOCOUNT) &&
85 	    dst_entries_get_fast(ops) > ops->gc_thresh) {
86 		if (ops->gc(ops)) {
87 			pr_notice_ratelimited("Route cache is full: consider increasing sysctl net.ipv6.route.max_size.\n");
88 			return NULL;
89 		}
90 	}
91 
92 	dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC);
93 	if (!dst)
94 		return NULL;
95 
96 	dst_init(dst, ops, dev, initial_ref, initial_obsolete, flags);
97 
98 	return dst;
99 }
100 EXPORT_SYMBOL(dst_alloc);
101 
102 struct dst_entry *dst_destroy(struct dst_entry * dst)
103 {
104 	struct dst_entry *child = NULL;
105 
106 	smp_rmb();
107 
108 #ifdef CONFIG_XFRM
109 	if (dst->xfrm) {
110 		struct xfrm_dst *xdst = (struct xfrm_dst *) dst;
111 
112 		child = xdst->child;
113 	}
114 #endif
115 	if (!(dst->flags & DST_NOCOUNT))
116 		dst_entries_add(dst->ops, -1);
117 
118 	if (dst->ops->destroy)
119 		dst->ops->destroy(dst);
120 	dev_put_track(dst->dev, &dst->dev_tracker);
121 
122 	lwtstate_put(dst->lwtstate);
123 
124 	if (dst->flags & DST_METADATA)
125 		metadata_dst_free((struct metadata_dst *)dst);
126 	else
127 		kmem_cache_free(dst->ops->kmem_cachep, dst);
128 
129 	dst = child;
130 	if (dst)
131 		dst_release_immediate(dst);
132 	return NULL;
133 }
134 EXPORT_SYMBOL(dst_destroy);
135 
136 static void dst_destroy_rcu(struct rcu_head *head)
137 {
138 	struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
139 
140 	dst = dst_destroy(dst);
141 }
142 
143 /* Operations to mark dst as DEAD and clean up the net device referenced
144  * by dst:
145  * 1. put the dst under blackhole interface and discard all tx/rx packets
146  *    on this route.
147  * 2. release the net_device
148  * This function should be called when removing routes from the fib tree
149  * in preparation for a NETDEV_DOWN/NETDEV_UNREGISTER event and also to
150  * make the next dst_ops->check() fail.
151  */
152 void dst_dev_put(struct dst_entry *dst)
153 {
154 	struct net_device *dev = dst->dev;
155 
156 	dst->obsolete = DST_OBSOLETE_DEAD;
157 	if (dst->ops->ifdown)
158 		dst->ops->ifdown(dst, dev, true);
159 	dst->input = dst_discard;
160 	dst->output = dst_discard_out;
161 	dst->dev = blackhole_netdev;
162 	dev_replace_track(dev, blackhole_netdev, &dst->dev_tracker,
163 			  GFP_ATOMIC);
164 }
165 EXPORT_SYMBOL(dst_dev_put);
166 
167 void dst_release(struct dst_entry *dst)
168 {
169 	if (dst) {
170 		int newrefcnt;
171 
172 		newrefcnt = atomic_dec_return(&dst->__refcnt);
173 		if (WARN_ONCE(newrefcnt < 0, "dst_release underflow"))
174 			net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
175 					     __func__, dst, newrefcnt);
176 		if (!newrefcnt)
177 			call_rcu(&dst->rcu_head, dst_destroy_rcu);
178 	}
179 }
180 EXPORT_SYMBOL(dst_release);
181 
182 void dst_release_immediate(struct dst_entry *dst)
183 {
184 	if (dst) {
185 		int newrefcnt;
186 
187 		newrefcnt = atomic_dec_return(&dst->__refcnt);
188 		if (WARN_ONCE(newrefcnt < 0, "dst_release_immediate underflow"))
189 			net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
190 					     __func__, dst, newrefcnt);
191 		if (!newrefcnt)
192 			dst_destroy(dst);
193 	}
194 }
195 EXPORT_SYMBOL(dst_release_immediate);
196 
197 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old)
198 {
199 	struct dst_metrics *p = kmalloc(sizeof(*p), GFP_ATOMIC);
200 
201 	if (p) {
202 		struct dst_metrics *old_p = (struct dst_metrics *)__DST_METRICS_PTR(old);
203 		unsigned long prev, new;
204 
205 		refcount_set(&p->refcnt, 1);
206 		memcpy(p->metrics, old_p->metrics, sizeof(p->metrics));
207 
208 		new = (unsigned long) p;
209 		prev = cmpxchg(&dst->_metrics, old, new);
210 
211 		if (prev != old) {
212 			kfree(p);
213 			p = (struct dst_metrics *)__DST_METRICS_PTR(prev);
214 			if (prev & DST_METRICS_READ_ONLY)
215 				p = NULL;
216 		} else if (prev & DST_METRICS_REFCOUNTED) {
217 			if (refcount_dec_and_test(&old_p->refcnt))
218 				kfree(old_p);
219 		}
220 	}
221 	BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0);
222 	return (u32 *)p;
223 }
224 EXPORT_SYMBOL(dst_cow_metrics_generic);
225 
226 /* Caller asserts that dst_metrics_read_only(dst) is false.  */
227 void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old)
228 {
229 	unsigned long prev, new;
230 
231 	new = ((unsigned long) &dst_default_metrics) | DST_METRICS_READ_ONLY;
232 	prev = cmpxchg(&dst->_metrics, old, new);
233 	if (prev == old)
234 		kfree(__DST_METRICS_PTR(old));
235 }
236 EXPORT_SYMBOL(__dst_destroy_metrics_generic);
237 
238 struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie)
239 {
240 	return NULL;
241 }
242 
243 u32 *dst_blackhole_cow_metrics(struct dst_entry *dst, unsigned long old)
244 {
245 	return NULL;
246 }
247 
248 struct neighbour *dst_blackhole_neigh_lookup(const struct dst_entry *dst,
249 					     struct sk_buff *skb,
250 					     const void *daddr)
251 {
252 	return NULL;
253 }
254 
255 void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
256 			       struct sk_buff *skb, u32 mtu,
257 			       bool confirm_neigh)
258 {
259 }
260 EXPORT_SYMBOL_GPL(dst_blackhole_update_pmtu);
261 
262 void dst_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
263 			    struct sk_buff *skb)
264 {
265 }
266 EXPORT_SYMBOL_GPL(dst_blackhole_redirect);
267 
268 unsigned int dst_blackhole_mtu(const struct dst_entry *dst)
269 {
270 	unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
271 
272 	return mtu ? : dst->dev->mtu;
273 }
274 EXPORT_SYMBOL_GPL(dst_blackhole_mtu);
275 
276 static struct dst_ops dst_blackhole_ops = {
277 	.family		= AF_UNSPEC,
278 	.neigh_lookup	= dst_blackhole_neigh_lookup,
279 	.check		= dst_blackhole_check,
280 	.cow_metrics	= dst_blackhole_cow_metrics,
281 	.update_pmtu	= dst_blackhole_update_pmtu,
282 	.redirect	= dst_blackhole_redirect,
283 	.mtu		= dst_blackhole_mtu,
284 };
285 
286 static void __metadata_dst_init(struct metadata_dst *md_dst,
287 				enum metadata_type type, u8 optslen)
288 {
289 	struct dst_entry *dst;
290 
291 	dst = &md_dst->dst;
292 	dst_init(dst, &dst_blackhole_ops, NULL, 1, DST_OBSOLETE_NONE,
293 		 DST_METADATA | DST_NOCOUNT);
294 	memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst));
295 	md_dst->type = type;
296 }
297 
298 struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type,
299 					gfp_t flags)
300 {
301 	struct metadata_dst *md_dst;
302 
303 	md_dst = kmalloc(sizeof(*md_dst) + optslen, flags);
304 	if (!md_dst)
305 		return NULL;
306 
307 	__metadata_dst_init(md_dst, type, optslen);
308 
309 	return md_dst;
310 }
311 EXPORT_SYMBOL_GPL(metadata_dst_alloc);
312 
313 void metadata_dst_free(struct metadata_dst *md_dst)
314 {
315 #ifdef CONFIG_DST_CACHE
316 	if (md_dst->type == METADATA_IP_TUNNEL)
317 		dst_cache_destroy(&md_dst->u.tun_info.dst_cache);
318 #endif
319 	kfree(md_dst);
320 }
321 EXPORT_SYMBOL_GPL(metadata_dst_free);
322 
323 struct metadata_dst __percpu *
324 metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags)
325 {
326 	int cpu;
327 	struct metadata_dst __percpu *md_dst;
328 
329 	md_dst = __alloc_percpu_gfp(sizeof(struct metadata_dst) + optslen,
330 				    __alignof__(struct metadata_dst), flags);
331 	if (!md_dst)
332 		return NULL;
333 
334 	for_each_possible_cpu(cpu)
335 		__metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen);
336 
337 	return md_dst;
338 }
339 EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);
340 
341 void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst)
342 {
343 #ifdef CONFIG_DST_CACHE
344 	int cpu;
345 
346 	for_each_possible_cpu(cpu) {
347 		struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu);
348 
349 		if (one_md_dst->type == METADATA_IP_TUNNEL)
350 			dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache);
351 	}
352 #endif
353 	free_percpu(md_dst);
354 }
355 EXPORT_SYMBOL_GPL(metadata_dst_free_percpu);
356