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
99static 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: 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}
130
131static 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 */
147void 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(odev: dev, ndev: blackhole_netdev, tracker: &dst->dev_tracker,
158 GFP_ATOMIC);
159}
160EXPORT_SYMBOL(dst_dev_put);
161
162void dst_release(struct dst_entry *dst)
163{
164 if (dst && rcuref_put(ref: &dst->__rcuref))
165 call_rcu_hurry(head: &dst->rcu_head, func: dst_destroy_rcu);
166}
167EXPORT_SYMBOL(dst_release);
168
169void dst_release_immediate(struct dst_entry *dst)
170{
171 if (dst && rcuref_put(ref: &dst->__rcuref))
172 dst_destroy(dst);
173}
174EXPORT_SYMBOL(dst_release_immediate);
175
176u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old)
177{
178 struct dst_metrics *p = kmalloc(size: 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(r: &p->refcnt, n: 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(objp: 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(r: &old_p->refcnt))
197 kfree(objp: old_p);
198 }
199 }
200 BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0);
201 return (u32 *)p;
202}
203EXPORT_SYMBOL(dst_cow_metrics_generic);
204
205/* Caller asserts that dst_metrics_read_only(dst) is false. */
206void __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}
215EXPORT_SYMBOL(__dst_destroy_metrics_generic);
216
217struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie)
218{
219 return NULL;
220}
221
222u32 *dst_blackhole_cow_metrics(struct dst_entry *dst, unsigned long old)
223{
224 return NULL;
225}
226
227struct 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
234void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
235 struct sk_buff *skb, u32 mtu,
236 bool confirm_neigh)
237{
238}
239EXPORT_SYMBOL_GPL(dst_blackhole_update_pmtu);
240
241void dst_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
242 struct sk_buff *skb)
243{
244}
245EXPORT_SYMBOL_GPL(dst_blackhole_redirect);
246
247unsigned 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}
253EXPORT_SYMBOL_GPL(dst_blackhole_mtu);
254
255static 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
265static 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
277struct 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(size: 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}
290EXPORT_SYMBOL_GPL(metadata_dst_alloc);
291
292void 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(dst_cache: &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(objp: md_dst);
301}
302EXPORT_SYMBOL_GPL(metadata_dst_free);
303
304struct metadata_dst __percpu *
305metadata_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(size: sizeof(struct metadata_dst) + optslen,
311 align: __alignof__(struct metadata_dst), gfp: 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}
320EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);
321
322void 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(dst_cache: &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(pdata: md_dst);
337}
338EXPORT_SYMBOL_GPL(metadata_dst_free_percpu);
339

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