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
30int dst_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb)
31{
32 kfree_skb(skb);
33 return 0;
34}
35EXPORT_SYMBOL(dst_discard_out);
36
37const 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};
45EXPORT_SYMBOL(dst_default_metrics);
46
47void 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, tracker: &dst->dev_tracker, GFP_ATOMIC);
53 dst->ops = ops;
54 dst_init_metrics(dst, src_metrics: dst_default_metrics.metrics, read_only: 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(ref: &dst->__rcuref, cnt: 1);
70 INIT_LIST_HEAD(list: &dst->rt_uncached);
71 dst->__use = 0;
72 dst->lastuse = jiffies;
73 dst->flags = flags;
74 if (!(flags & DST_NOCOUNT))
75 dst_entries_add(dst: ops, val: 1);
76}
77EXPORT_SYMBOL(dst_init);
78
79void *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(dst: ops) > ops->gc_thresh)
87 ops->gc(ops);
88
89 dst = kmem_cache_alloc(cachep: 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}
97EXPORT_SYMBOL(dst_alloc);
98
99struct dst_entry *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: dst->ops, val: -1);
114
115 if (dst->ops->destroy)
116 dst->ops->destroy(dst);
117 netdev_put(dev: dst->dev, tracker: &dst->dev_tracker);
118
119 lwtstate_put(lws: dst->lwtstate);
120
121 if (dst->flags & DST_METADATA)
122 metadata_dst_free((struct metadata_dst *)dst);
123 else
124 kmem_cache_free(s: dst->ops->kmem_cachep, objp: dst);
125
126 dst = child;
127 if (dst)
128 dst_release_immediate(dst);
129 return NULL;
130}
131EXPORT_SYMBOL(dst_destroy);
132
133static void dst_destroy_rcu(struct rcu_head *head)
134{
135 struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
136
137 dst = dst_destroy(dst);
138}
139
140/* Operations to mark dst as DEAD and clean up the net device referenced
141 * by dst:
142 * 1. put the dst under blackhole interface and discard all tx/rx packets
143 * on this route.
144 * 2. release the net_device
145 * This function should be called when removing routes from the fib tree
146 * in preparation for a NETDEV_DOWN/NETDEV_UNREGISTER event and also to
147 * make the next dst_ops->check() fail.
148 */
149void dst_dev_put(struct dst_entry *dst)
150{
151 struct net_device *dev = dst->dev;
152
153 dst->obsolete = DST_OBSOLETE_DEAD;
154 if (dst->ops->ifdown)
155 dst->ops->ifdown(dst, dev);
156 dst->input = dst_discard;
157 dst->output = dst_discard_out;
158 dst->dev = blackhole_netdev;
159 netdev_ref_replace(odev: dev, ndev: blackhole_netdev, tracker: &dst->dev_tracker,
160 GFP_ATOMIC);
161}
162EXPORT_SYMBOL(dst_dev_put);
163
164void dst_release(struct dst_entry *dst)
165{
166 if (dst && rcuref_put(ref: &dst->__rcuref))
167 call_rcu_hurry(head: &dst->rcu_head, func: dst_destroy_rcu);
168}
169EXPORT_SYMBOL(dst_release);
170
171void dst_release_immediate(struct dst_entry *dst)
172{
173 if (dst && rcuref_put(ref: &dst->__rcuref))
174 dst_destroy(dst);
175}
176EXPORT_SYMBOL(dst_release_immediate);
177
178u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old)
179{
180 struct dst_metrics *p = kmalloc(size: sizeof(*p), GFP_ATOMIC);
181
182 if (p) {
183 struct dst_metrics *old_p = (struct dst_metrics *)__DST_METRICS_PTR(old);
184 unsigned long prev, new;
185
186 refcount_set(r: &p->refcnt, n: 1);
187 memcpy(p->metrics, old_p->metrics, sizeof(p->metrics));
188
189 new = (unsigned long) p;
190 prev = cmpxchg(&dst->_metrics, old, new);
191
192 if (prev != old) {
193 kfree(objp: p);
194 p = (struct dst_metrics *)__DST_METRICS_PTR(prev);
195 if (prev & DST_METRICS_READ_ONLY)
196 p = NULL;
197 } else if (prev & DST_METRICS_REFCOUNTED) {
198 if (refcount_dec_and_test(r: &old_p->refcnt))
199 kfree(objp: old_p);
200 }
201 }
202 BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0);
203 return (u32 *)p;
204}
205EXPORT_SYMBOL(dst_cow_metrics_generic);
206
207/* Caller asserts that dst_metrics_read_only(dst) is false. */
208void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old)
209{
210 unsigned long prev, new;
211
212 new = ((unsigned long) &dst_default_metrics) | DST_METRICS_READ_ONLY;
213 prev = cmpxchg(&dst->_metrics, old, new);
214 if (prev == old)
215 kfree(__DST_METRICS_PTR(old));
216}
217EXPORT_SYMBOL(__dst_destroy_metrics_generic);
218
219struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie)
220{
221 return NULL;
222}
223
224u32 *dst_blackhole_cow_metrics(struct dst_entry *dst, unsigned long old)
225{
226 return NULL;
227}
228
229struct neighbour *dst_blackhole_neigh_lookup(const struct dst_entry *dst,
230 struct sk_buff *skb,
231 const void *daddr)
232{
233 return NULL;
234}
235
236void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
237 struct sk_buff *skb, u32 mtu,
238 bool confirm_neigh)
239{
240}
241EXPORT_SYMBOL_GPL(dst_blackhole_update_pmtu);
242
243void dst_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
244 struct sk_buff *skb)
245{
246}
247EXPORT_SYMBOL_GPL(dst_blackhole_redirect);
248
249unsigned int dst_blackhole_mtu(const struct dst_entry *dst)
250{
251 unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
252
253 return mtu ? : dst->dev->mtu;
254}
255EXPORT_SYMBOL_GPL(dst_blackhole_mtu);
256
257static struct dst_ops dst_blackhole_ops = {
258 .family = AF_UNSPEC,
259 .neigh_lookup = dst_blackhole_neigh_lookup,
260 .check = dst_blackhole_check,
261 .cow_metrics = dst_blackhole_cow_metrics,
262 .update_pmtu = dst_blackhole_update_pmtu,
263 .redirect = dst_blackhole_redirect,
264 .mtu = dst_blackhole_mtu,
265};
266
267static void __metadata_dst_init(struct metadata_dst *md_dst,
268 enum metadata_type type, u8 optslen)
269{
270 struct dst_entry *dst;
271
272 dst = &md_dst->dst;
273 dst_init(dst, &dst_blackhole_ops, NULL, DST_OBSOLETE_NONE,
274 DST_METADATA | DST_NOCOUNT);
275 memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst));
276 md_dst->type = type;
277}
278
279struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type,
280 gfp_t flags)
281{
282 struct metadata_dst *md_dst;
283
284 md_dst = kmalloc(size: sizeof(*md_dst) + optslen, flags);
285 if (!md_dst)
286 return NULL;
287
288 __metadata_dst_init(md_dst, type, optslen);
289
290 return md_dst;
291}
292EXPORT_SYMBOL_GPL(metadata_dst_alloc);
293
294void metadata_dst_free(struct metadata_dst *md_dst)
295{
296#ifdef CONFIG_DST_CACHE
297 if (md_dst->type == METADATA_IP_TUNNEL)
298 dst_cache_destroy(dst_cache: &md_dst->u.tun_info.dst_cache);
299#endif
300 if (md_dst->type == METADATA_XFRM)
301 dst_release(md_dst->u.xfrm_info.dst_orig);
302 kfree(objp: md_dst);
303}
304EXPORT_SYMBOL_GPL(metadata_dst_free);
305
306struct metadata_dst __percpu *
307metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags)
308{
309 int cpu;
310 struct metadata_dst __percpu *md_dst;
311
312 md_dst = __alloc_percpu_gfp(size: sizeof(struct metadata_dst) + optslen,
313 align: __alignof__(struct metadata_dst), gfp: flags);
314 if (!md_dst)
315 return NULL;
316
317 for_each_possible_cpu(cpu)
318 __metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen);
319
320 return md_dst;
321}
322EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);
323
324void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst)
325{
326 int cpu;
327
328 for_each_possible_cpu(cpu) {
329 struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu);
330
331#ifdef CONFIG_DST_CACHE
332 if (one_md_dst->type == METADATA_IP_TUNNEL)
333 dst_cache_destroy(dst_cache: &one_md_dst->u.tun_info.dst_cache);
334#endif
335 if (one_md_dst->type == METADATA_XFRM)
336 dst_release(one_md_dst->u.xfrm_info.dst_orig);
337 }
338 free_percpu(pdata: md_dst);
339}
340EXPORT_SYMBOL_GPL(metadata_dst_free_percpu);
341

source code of linux/net/core/dst.c