xref: /linux/net/core/dst.c (revision 52338415) 
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 	if (dev)
53 		dev_hold(dev);
54 	dst->ops = ops;
55 	dst_init_metrics(dst, dst_default_metrics.metrics, true);
56 	dst->expires = 0UL;
57 #ifdef CONFIG_XFRM
58 	dst->xfrm = NULL;
59 #endif
60 	dst->input = dst_discard;
61 	dst->output = dst_discard_out;
62 	dst->error = 0;
63 	dst->obsolete = initial_obsolete;
64 	dst->header_len = 0;
65 	dst->trailer_len = 0;
66 #ifdef CONFIG_IP_ROUTE_CLASSID
67 	dst->tclassid = 0;
68 #endif
69 	dst->lwtstate = NULL;
70 	atomic_set(&dst->__refcnt, initial_ref);
71 	dst->__use = 0;
72 	dst->lastuse = jiffies;
73 	dst->flags = flags;
74 	if (!(flags & DST_NOCOUNT))
75 		dst_entries_add(ops, 1);
76 }
77 EXPORT_SYMBOL(dst_init);
78 
79 void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
80 		int initial_ref, int initial_obsolete, unsigned short flags)
81 {
82 	struct dst_entry *dst;
83 
84 	if (ops->gc && dst_entries_get_fast(ops) > ops->gc_thresh) {
85 		if (ops->gc(ops)) {
86 			printk_ratelimited(KERN_NOTICE "Route cache is full: "
87 					   "consider increasing sysctl "
88 					   "net.ipv[4|6].route.max_size.\n");
89 			return NULL;
90 		}
91 	}
92 
93 	dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC);
94 	if (!dst)
95 		return NULL;
96 
97 	dst_init(dst, ops, dev, initial_ref, initial_obsolete, flags);
98 
99 	return dst;
100 }
101 EXPORT_SYMBOL(dst_alloc);
102 
103 struct dst_entry *dst_destroy(struct dst_entry * dst)
104 {
105 	struct dst_entry *child = NULL;
106 
107 	smp_rmb();
108 
109 #ifdef CONFIG_XFRM
110 	if (dst->xfrm) {
111 		struct xfrm_dst *xdst = (struct xfrm_dst *) dst;
112 
113 		child = xdst->child;
114 	}
115 #endif
116 	if (!(dst->flags & DST_NOCOUNT))
117 		dst_entries_add(dst->ops, -1);
118 
119 	if (dst->ops->destroy)
120 		dst->ops->destroy(dst);
121 	if (dst->dev)
122 		dev_put(dst->dev);
123 
124 	lwtstate_put(dst->lwtstate);
125 
126 	if (dst->flags & DST_METADATA)
127 		metadata_dst_free((struct metadata_dst *)dst);
128 	else
129 		kmem_cache_free(dst->ops->kmem_cachep, dst);
130 
131 	dst = child;
132 	if (dst)
133 		dst_release_immediate(dst);
134 	return NULL;
135 }
136 EXPORT_SYMBOL(dst_destroy);
137 
138 static void dst_destroy_rcu(struct rcu_head *head)
139 {
140 	struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
141 
142 	dst = dst_destroy(dst);
143 }
144 
145 /* Operations to mark dst as DEAD and clean up the net device referenced
146  * by dst:
147  * 1. put the dst under loopback interface and discard all tx/rx packets
148  *    on this route.
149  * 2. release the net_device
150  * This function should be called when removing routes from the fib tree
151  * in preparation for a NETDEV_DOWN/NETDEV_UNREGISTER event and also to
152  * make the next dst_ops->check() fail.
153  */
154 void dst_dev_put(struct dst_entry *dst)
155 {
156 	struct net_device *dev = dst->dev;
157 
158 	dst->obsolete = DST_OBSOLETE_DEAD;
159 	if (dst->ops->ifdown)
160 		dst->ops->ifdown(dst, dev, true);
161 	dst->input = dst_discard;
162 	dst->output = dst_discard_out;
163 	dst->dev = blackhole_netdev;
164 	dev_hold(dst->dev);
165 	dev_put(dev);
166 }
167 EXPORT_SYMBOL(dst_dev_put);
168 
169 void dst_release(struct dst_entry *dst)
170 {
171 	if (dst) {
172 		int newrefcnt;
173 
174 		newrefcnt = atomic_dec_return(&dst->__refcnt);
175 		if (WARN_ONCE(newrefcnt < 0, "dst_release underflow"))
176 			net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
177 					     __func__, dst, newrefcnt);
178 		if (!newrefcnt)
179 			call_rcu(&dst->rcu_head, dst_destroy_rcu);
180 	}
181 }
182 EXPORT_SYMBOL(dst_release);
183 
184 void dst_release_immediate(struct dst_entry *dst)
185 {
186 	if (dst) {
187 		int newrefcnt;
188 
189 		newrefcnt = atomic_dec_return(&dst->__refcnt);
190 		if (WARN_ONCE(newrefcnt < 0, "dst_release_immediate underflow"))
191 			net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
192 					     __func__, dst, newrefcnt);
193 		if (!newrefcnt)
194 			dst_destroy(dst);
195 	}
196 }
197 EXPORT_SYMBOL(dst_release_immediate);
198 
199 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old)
200 {
201 	struct dst_metrics *p = kmalloc(sizeof(*p), GFP_ATOMIC);
202 
203 	if (p) {
204 		struct dst_metrics *old_p = (struct dst_metrics *)__DST_METRICS_PTR(old);
205 		unsigned long prev, new;
206 
207 		refcount_set(&p->refcnt, 1);
208 		memcpy(p->metrics, old_p->metrics, sizeof(p->metrics));
209 
210 		new = (unsigned long) p;
211 		prev = cmpxchg(&dst->_metrics, old, new);
212 
213 		if (prev != old) {
214 			kfree(p);
215 			p = (struct dst_metrics *)__DST_METRICS_PTR(prev);
216 			if (prev & DST_METRICS_READ_ONLY)
217 				p = NULL;
218 		} else if (prev & DST_METRICS_REFCOUNTED) {
219 			if (refcount_dec_and_test(&old_p->refcnt))
220 				kfree(old_p);
221 		}
222 	}
223 	BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0);
224 	return (u32 *)p;
225 }
226 EXPORT_SYMBOL(dst_cow_metrics_generic);
227 
228 /* Caller asserts that dst_metrics_read_only(dst) is false.  */
229 void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old)
230 {
231 	unsigned long prev, new;
232 
233 	new = ((unsigned long) &dst_default_metrics) | DST_METRICS_READ_ONLY;
234 	prev = cmpxchg(&dst->_metrics, old, new);
235 	if (prev == old)
236 		kfree(__DST_METRICS_PTR(old));
237 }
238 EXPORT_SYMBOL(__dst_destroy_metrics_generic);
239 
240 static struct dst_ops md_dst_ops = {
241 	.family =		AF_UNSPEC,
242 };
243 
244 static int dst_md_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb)
245 {
246 	WARN_ONCE(1, "Attempting to call output on metadata dst\n");
247 	kfree_skb(skb);
248 	return 0;
249 }
250 
251 static int dst_md_discard(struct sk_buff *skb)
252 {
253 	WARN_ONCE(1, "Attempting to call input on metadata dst\n");
254 	kfree_skb(skb);
255 	return 0;
256 }
257 
258 static void __metadata_dst_init(struct metadata_dst *md_dst,
259 				enum metadata_type type, u8 optslen)
260 
261 {
262 	struct dst_entry *dst;
263 
264 	dst = &md_dst->dst;
265 	dst_init(dst, &md_dst_ops, NULL, 1, DST_OBSOLETE_NONE,
266 		 DST_METADATA | DST_NOCOUNT);
267 
268 	dst->input = dst_md_discard;
269 	dst->output = dst_md_discard_out;
270 
271 	memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst));
272 	md_dst->type = type;
273 }
274 
275 struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type,
276 					gfp_t flags)
277 {
278 	struct metadata_dst *md_dst;
279 
280 	md_dst = kmalloc(sizeof(*md_dst) + optslen, flags);
281 	if (!md_dst)
282 		return NULL;
283 
284 	__metadata_dst_init(md_dst, type, optslen);
285 
286 	return md_dst;
287 }
288 EXPORT_SYMBOL_GPL(metadata_dst_alloc);
289 
290 void metadata_dst_free(struct metadata_dst *md_dst)
291 {
292 #ifdef CONFIG_DST_CACHE
293 	if (md_dst->type == METADATA_IP_TUNNEL)
294 		dst_cache_destroy(&md_dst->u.tun_info.dst_cache);
295 #endif
296 	kfree(md_dst);
297 }
298 EXPORT_SYMBOL_GPL(metadata_dst_free);
299 
300 struct metadata_dst __percpu *
301 metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags)
302 {
303 	int cpu;
304 	struct metadata_dst __percpu *md_dst;
305 
306 	md_dst = __alloc_percpu_gfp(sizeof(struct metadata_dst) + optslen,
307 				    __alignof__(struct metadata_dst), flags);
308 	if (!md_dst)
309 		return NULL;
310 
311 	for_each_possible_cpu(cpu)
312 		__metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen);
313 
314 	return md_dst;
315 }
316 EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);
317 
318 void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst)
319 {
320 #ifdef CONFIG_DST_CACHE
321 	int cpu;
322 
323 	for_each_possible_cpu(cpu) {
324 		struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu);
325 
326 		if (one_md_dst->type == METADATA_IP_TUNNEL)
327 			dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache);
328 	}
329 #endif
330 	free_percpu(md_dst);
331 }
332 EXPORT_SYMBOL_GPL(metadata_dst_free_percpu);
333