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
dst_discard_out(struct net * net,struct sock * sk,struct sk_buff * skb)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
dst_init(struct dst_entry * dst,struct dst_ops * ops,struct net_device * dev,int initial_obsolete,unsigned short flags)47 void dst_init(struct dst_entry *dst, struct dst_ops *ops,
48 struct net_device *dev, int initial_obsolete,
49 unsigned short flags)
50 {
51 dst->dev = dev;
52 netdev_hold(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 rcuref_init(&dst->__rcuref, 1);
70 INIT_LIST_HEAD(&dst->rt_uncached);
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
dst_alloc(struct dst_ops * ops,struct net_device * dev,int initial_obsolete,unsigned short flags)79 void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
80 int initial_obsolete, unsigned short flags)
81 {
82 struct dst_entry *dst;
83
84 if (ops->gc &&
85 !(flags & DST_NOCOUNT) &&
86 dst_entries_get_fast(ops) > ops->gc_thresh)
87 ops->gc(ops);
88
89 dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC);
90 if (!dst)
91 return NULL;
92
93 dst_init(dst, ops, dev, initial_obsolete, flags);
94
95 return dst;
96 }
97 EXPORT_SYMBOL(dst_alloc);
98
dst_destroy(struct dst_entry * dst)99 static void dst_destroy(struct dst_entry *dst)
100 {
101 struct dst_entry *child = NULL;
102
103 smp_rmb();
104
105 #ifdef CONFIG_XFRM
106 if (dst->xfrm) {
107 struct xfrm_dst *xdst = (struct xfrm_dst *) dst;
108
109 child = xdst->child;
110 }
111 #endif
112 if (!(dst->flags & DST_NOCOUNT))
113 dst_entries_add(dst->ops, -1);
114
115 if (dst->ops->destroy)
116 dst->ops->destroy(dst);
117 netdev_put(dst->dev, &dst->dev_tracker);
118
119 lwtstate_put(dst->lwtstate);
120
121 if (dst->flags & DST_METADATA)
122 metadata_dst_free((struct metadata_dst *)dst);
123 else
124 kmem_cache_free(dst->ops->kmem_cachep, dst);
125
126 dst = child;
127 if (dst)
128 dst_release_immediate(dst);
129 }
130
dst_destroy_rcu(struct rcu_head * head)131 static void dst_destroy_rcu(struct rcu_head *head)
132 {
133 struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
134
135 dst_destroy(dst);
136 }
137
138 /* Operations to mark dst as DEAD and clean up the net device referenced
139 * by dst:
140 * 1. put the dst under blackhole interface and discard all tx/rx packets
141 * on this route.
142 * 2. release the net_device
143 * This function should be called when removing routes from the fib tree
144 * in preparation for a NETDEV_DOWN/NETDEV_UNREGISTER event and also to
145 * make the next dst_ops->check() fail.
146 */
dst_dev_put(struct dst_entry * dst)147 void dst_dev_put(struct dst_entry *dst)
148 {
149 struct net_device *dev = dst->dev;
150
151 dst->obsolete = DST_OBSOLETE_DEAD;
152 if (dst->ops->ifdown)
153 dst->ops->ifdown(dst, dev);
154 dst->input = dst_discard;
155 dst->output = dst_discard_out;
156 dst->dev = blackhole_netdev;
157 netdev_ref_replace(dev, blackhole_netdev, &dst->dev_tracker,
158 GFP_ATOMIC);
159 }
160 EXPORT_SYMBOL(dst_dev_put);
161
dst_release(struct dst_entry * dst)162 void dst_release(struct dst_entry *dst)
163 {
164 if (dst && rcuref_put(&dst->__rcuref))
165 call_rcu_hurry(&dst->rcu_head, dst_destroy_rcu);
166 }
167 EXPORT_SYMBOL(dst_release);
168
dst_release_immediate(struct dst_entry * dst)169 void dst_release_immediate(struct dst_entry *dst)
170 {
171 if (dst && rcuref_put(&dst->__rcuref))
172 dst_destroy(dst);
173 }
174 EXPORT_SYMBOL(dst_release_immediate);
175
dst_cow_metrics_generic(struct dst_entry * dst,unsigned long old)176 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old)
177 {
178 struct dst_metrics *p = kmalloc(sizeof(*p), GFP_ATOMIC);
179
180 if (p) {
181 struct dst_metrics *old_p = (struct dst_metrics *)__DST_METRICS_PTR(old);
182 unsigned long prev, new;
183
184 refcount_set(&p->refcnt, 1);
185 memcpy(p->metrics, old_p->metrics, sizeof(p->metrics));
186
187 new = (unsigned long) p;
188 prev = cmpxchg(&dst->_metrics, old, new);
189
190 if (prev != old) {
191 kfree(p);
192 p = (struct dst_metrics *)__DST_METRICS_PTR(prev);
193 if (prev & DST_METRICS_READ_ONLY)
194 p = NULL;
195 } else if (prev & DST_METRICS_REFCOUNTED) {
196 if (refcount_dec_and_test(&old_p->refcnt))
197 kfree(old_p);
198 }
199 }
200 BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0);
201 return (u32 *)p;
202 }
203 EXPORT_SYMBOL(dst_cow_metrics_generic);
204
205 /* Caller asserts that dst_metrics_read_only(dst) is false. */
__dst_destroy_metrics_generic(struct dst_entry * dst,unsigned long old)206 void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old)
207 {
208 unsigned long prev, new;
209
210 new = ((unsigned long) &dst_default_metrics) | DST_METRICS_READ_ONLY;
211 prev = cmpxchg(&dst->_metrics, old, new);
212 if (prev == old)
213 kfree(__DST_METRICS_PTR(old));
214 }
215 EXPORT_SYMBOL(__dst_destroy_metrics_generic);
216
dst_blackhole_check(struct dst_entry * dst,u32 cookie)217 struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie)
218 {
219 return NULL;
220 }
221
dst_blackhole_cow_metrics(struct dst_entry * dst,unsigned long old)222 u32 *dst_blackhole_cow_metrics(struct dst_entry *dst, unsigned long old)
223 {
224 return NULL;
225 }
226
dst_blackhole_neigh_lookup(const struct dst_entry * dst,struct sk_buff * skb,const void * daddr)227 struct neighbour *dst_blackhole_neigh_lookup(const struct dst_entry *dst,
228 struct sk_buff *skb,
229 const void *daddr)
230 {
231 return NULL;
232 }
233
dst_blackhole_update_pmtu(struct dst_entry * dst,struct sock * sk,struct sk_buff * skb,u32 mtu,bool confirm_neigh)234 void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
235 struct sk_buff *skb, u32 mtu,
236 bool confirm_neigh)
237 {
238 }
239 EXPORT_SYMBOL_GPL(dst_blackhole_update_pmtu);
240
dst_blackhole_redirect(struct dst_entry * dst,struct sock * sk,struct sk_buff * skb)241 void dst_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
242 struct sk_buff *skb)
243 {
244 }
245 EXPORT_SYMBOL_GPL(dst_blackhole_redirect);
246
dst_blackhole_mtu(const struct dst_entry * dst)247 unsigned int dst_blackhole_mtu(const struct dst_entry *dst)
248 {
249 unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
250
251 return mtu ? : dst->dev->mtu;
252 }
253 EXPORT_SYMBOL_GPL(dst_blackhole_mtu);
254
255 static struct dst_ops dst_blackhole_ops = {
256 .family = AF_UNSPEC,
257 .neigh_lookup = dst_blackhole_neigh_lookup,
258 .check = dst_blackhole_check,
259 .cow_metrics = dst_blackhole_cow_metrics,
260 .update_pmtu = dst_blackhole_update_pmtu,
261 .redirect = dst_blackhole_redirect,
262 .mtu = dst_blackhole_mtu,
263 };
264
__metadata_dst_init(struct metadata_dst * md_dst,enum metadata_type type,u8 optslen)265 static void __metadata_dst_init(struct metadata_dst *md_dst,
266 enum metadata_type type, u8 optslen)
267 {
268 struct dst_entry *dst;
269
270 dst = &md_dst->dst;
271 dst_init(dst, &dst_blackhole_ops, NULL, DST_OBSOLETE_NONE,
272 DST_METADATA | DST_NOCOUNT);
273 memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst));
274 md_dst->type = type;
275 }
276
metadata_dst_alloc(u8 optslen,enum metadata_type type,gfp_t flags)277 struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type,
278 gfp_t flags)
279 {
280 struct metadata_dst *md_dst;
281
282 md_dst = kmalloc(sizeof(*md_dst) + optslen, flags);
283 if (!md_dst)
284 return NULL;
285
286 __metadata_dst_init(md_dst, type, optslen);
287
288 return md_dst;
289 }
290 EXPORT_SYMBOL_GPL(metadata_dst_alloc);
291
metadata_dst_free(struct metadata_dst * md_dst)292 void metadata_dst_free(struct metadata_dst *md_dst)
293 {
294 #ifdef CONFIG_DST_CACHE
295 if (md_dst->type == METADATA_IP_TUNNEL)
296 dst_cache_destroy(&md_dst->u.tun_info.dst_cache);
297 #endif
298 if (md_dst->type == METADATA_XFRM)
299 dst_release(md_dst->u.xfrm_info.dst_orig);
300 kfree(md_dst);
301 }
302 EXPORT_SYMBOL_GPL(metadata_dst_free);
303
304 struct metadata_dst __percpu *
metadata_dst_alloc_percpu(u8 optslen,enum metadata_type type,gfp_t flags)305 metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags)
306 {
307 int cpu;
308 struct metadata_dst __percpu *md_dst;
309
310 md_dst = __alloc_percpu_gfp(sizeof(struct metadata_dst) + optslen,
311 __alignof__(struct metadata_dst), flags);
312 if (!md_dst)
313 return NULL;
314
315 for_each_possible_cpu(cpu)
316 __metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen);
317
318 return md_dst;
319 }
320 EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);
321
metadata_dst_free_percpu(struct metadata_dst __percpu * md_dst)322 void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst)
323 {
324 int cpu;
325
326 for_each_possible_cpu(cpu) {
327 struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu);
328
329 #ifdef CONFIG_DST_CACHE
330 if (one_md_dst->type == METADATA_IP_TUNNEL)
331 dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache);
332 #endif
333 if (one_md_dst->type == METADATA_XFRM)
334 dst_release(one_md_dst->u.xfrm_info.dst_orig);
335 }
336 free_percpu(md_dst);
337 }
338 EXPORT_SYMBOL_GPL(metadata_dst_free_percpu);
339