dst.c

  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, &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->rt_uncached_list = NULL;
 72	dst->__use = 0;
 73	dst->lastuse = jiffies;
 74	dst->flags = flags;
 75	if (!(flags & DST_NOCOUNT))
 76		dst_entries_add(ops, 1);
 77}
 78EXPORT_SYMBOL(dst_init);
 79
 80void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
 81		int initial_obsolete, unsigned short flags)
 82{
 83	struct dst_entry *dst;
 84
 85	if (ops->gc &&
 86	    !(flags & DST_NOCOUNT) &&
 87	    dst_entries_get_fast(ops) > ops->gc_thresh)
 88		ops->gc(ops);
 89
 90	dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC);
 91	if (!dst)
 92		return NULL;
 93
 94	dst_init(dst, ops, dev, initial_obsolete, flags);
 95
 96	return dst;
 97}
 98EXPORT_SYMBOL(dst_alloc);
 99
100static void dst_destroy(struct dst_entry *dst)
101{
102	struct dst_entry *child = NULL;
103
104	smp_rmb();
105
106#ifdef CONFIG_XFRM
107	if (dst->xfrm) {
108		struct xfrm_dst *xdst = (struct xfrm_dst *) dst;
109
110		child = xdst->child;
111	}
112#endif
113	if (dst->ops->destroy)
114		dst->ops->destroy(dst);
115	netdev_put(dst->dev, &dst->dev_tracker);
116
117	lwtstate_put(dst->lwtstate);
118
119	if (dst->flags & DST_METADATA)
120		metadata_dst_free((struct metadata_dst *)dst);
121	else
122		kmem_cache_free(dst->ops->kmem_cachep, dst);
123
124	dst = child;
125	if (dst)
126		dst_release_immediate(dst);
127}
128
129static void dst_destroy_rcu(struct rcu_head *head)
130{
131	struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
132
133	dst_destroy(dst);
134}
135
136/* Operations to mark dst as DEAD and clean up the net device referenced
137 * by dst:
138 * 1. put the dst under blackhole interface and discard all tx/rx packets
139 *    on this route.
140 * 2. release the net_device
141 * This function should be called when removing routes from the fib tree
142 * in preparation for a NETDEV_DOWN/NETDEV_UNREGISTER event and also to
143 * make the next dst_ops->check() fail.
144 */
145void dst_dev_put(struct dst_entry *dst)
146{
147	struct net_device *dev = dst->dev;
148
149	WRITE_ONCE(dst->obsolete, DST_OBSOLETE_DEAD);
150	if (dst->ops->ifdown)
151		dst->ops->ifdown(dst, dev);
152	WRITE_ONCE(dst->input, dst_discard);
153	WRITE_ONCE(dst->output, dst_discard_out);
154	rcu_assign_pointer(dst->dev_rcu, blackhole_netdev);
155	netdev_ref_replace(dev, blackhole_netdev, &dst->dev_tracker,
156			   GFP_ATOMIC);
157}
158EXPORT_SYMBOL(dst_dev_put);
159
160static void dst_count_dec(struct dst_entry *dst)
161{
162	if (!(dst->flags & DST_NOCOUNT))
163		dst_entries_add(dst->ops, -1);
164}
165
166void dst_release(struct dst_entry *dst)
167{
168	if (dst && rcuref_put(&dst->__rcuref)) {
169#ifdef CONFIG_DST_CACHE
170		if (dst->flags & DST_METADATA) {
171			struct metadata_dst *md_dst = (struct metadata_dst *)dst;
172
173			if (md_dst->type == METADATA_IP_TUNNEL)
174				dst_cache_reset_now(&md_dst->u.tun_info.dst_cache);
175		}
176#endif
177		dst_count_dec(dst);
178		call_rcu_hurry(&dst->rcu_head, dst_destroy_rcu);
179	}
180}
181EXPORT_SYMBOL(dst_release);
182
183void dst_release_immediate(struct dst_entry *dst)
184{
185	if (dst && rcuref_put(&dst->__rcuref)) {
186		dst_count_dec(dst);
187		dst_destroy(dst);
188	}
189}
190EXPORT_SYMBOL(dst_release_immediate);
191
192u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old)
193{
194	struct dst_metrics *p = kmalloc(sizeof(*p), GFP_ATOMIC);
195
196	if (p) {
197		struct dst_metrics *old_p = (struct dst_metrics *)__DST_METRICS_PTR(old);
198		unsigned long prev, new;
199
200		refcount_set(&p->refcnt, 1);
201		memcpy(p->metrics, old_p->metrics, sizeof(p->metrics));
202
203		new = (unsigned long) p;
204		prev = cmpxchg(&dst->_metrics, old, new);
205
206		if (prev != old) {
207			kfree(p);
208			p = (struct dst_metrics *)__DST_METRICS_PTR(prev);
209			if (prev & DST_METRICS_READ_ONLY)
210				p = NULL;
211		} else if (prev & DST_METRICS_REFCOUNTED) {
212			if (refcount_dec_and_test(&old_p->refcnt))
213				kfree(old_p);
214		}
215	}
216	BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0);
217	return (u32 *)p;
218}
219EXPORT_SYMBOL(dst_cow_metrics_generic);
220
221/* Caller asserts that dst_metrics_read_only(dst) is false.  */
222void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old)
223{
224	unsigned long prev, new;
225
226	new = ((unsigned long) &dst_default_metrics) | DST_METRICS_READ_ONLY;
227	prev = cmpxchg(&dst->_metrics, old, new);
228	if (prev == old)
229		kfree(__DST_METRICS_PTR(old));
230}
231EXPORT_SYMBOL(__dst_destroy_metrics_generic);
232
233struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie)
234{
235	return NULL;
236}
237
238u32 *dst_blackhole_cow_metrics(struct dst_entry *dst, unsigned long old)
239{
240	return NULL;
241}
242
243struct neighbour *dst_blackhole_neigh_lookup(const struct dst_entry *dst,
244					     struct sk_buff *skb,
245					     const void *daddr)
246{
247	return NULL;
248}
249
250void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
251			       struct sk_buff *skb, u32 mtu,
252			       bool confirm_neigh)
253{
254}
255EXPORT_SYMBOL_GPL(dst_blackhole_update_pmtu);
256
257void dst_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
258			    struct sk_buff *skb)
259{
260}
261EXPORT_SYMBOL_GPL(dst_blackhole_redirect);
262
263unsigned int dst_blackhole_mtu(const struct dst_entry *dst)
264{
265	unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
266
267	return mtu ? : dst_dev(dst)->mtu;
268}
269EXPORT_SYMBOL_GPL(dst_blackhole_mtu);
270
271static struct dst_ops dst_blackhole_ops = {
272	.family		= AF_UNSPEC,
273	.neigh_lookup	= dst_blackhole_neigh_lookup,
274	.check		= dst_blackhole_check,
275	.cow_metrics	= dst_blackhole_cow_metrics,
276	.update_pmtu	= dst_blackhole_update_pmtu,
277	.redirect	= dst_blackhole_redirect,
278	.mtu		= dst_blackhole_mtu,
279};
280
281static void __metadata_dst_init(struct metadata_dst *md_dst,
282				enum metadata_type type, u8 optslen)
283{
284	struct dst_entry *dst;
285
286	dst = &md_dst->dst;
287	dst_init(dst, &dst_blackhole_ops, NULL, DST_OBSOLETE_NONE,
288		 DST_METADATA | DST_NOCOUNT);
289	memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst));
290	md_dst->type = type;
291}
292
293struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type,
294					gfp_t flags)
295{
296	struct metadata_dst *md_dst;
297
298	md_dst = kmalloc(struct_size(md_dst, u.tun_info.options, optslen),
299			 flags);
300	if (!md_dst)
301		return NULL;
302
303	__metadata_dst_init(md_dst, type, optslen);
304
305	return md_dst;
306}
307EXPORT_SYMBOL_GPL(metadata_dst_alloc);
308
309void metadata_dst_free(struct metadata_dst *md_dst)
310{
311#ifdef CONFIG_DST_CACHE
312	if (md_dst->type == METADATA_IP_TUNNEL)
313		dst_cache_destroy(&md_dst->u.tun_info.dst_cache);
314#endif
315	if (md_dst->type == METADATA_XFRM)
316		dst_release(md_dst->u.xfrm_info.dst_orig);
317	kfree(md_dst);
318}
319EXPORT_SYMBOL_GPL(metadata_dst_free);
320
321struct metadata_dst __percpu *
322metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags)
323{
324	int cpu;
325	struct metadata_dst __percpu *md_dst;
326
327	md_dst = __alloc_percpu_gfp(struct_size(md_dst, u.tun_info.options,
328						optslen),
329				    __alignof__(struct metadata_dst), flags);
330	if (!md_dst)
331		return NULL;
332
333	for_each_possible_cpu(cpu)
334		__metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen);
335
336	return md_dst;
337}
338EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);
339
340void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst)
341{
342	int cpu;
343
344	for_each_possible_cpu(cpu) {
345		struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu);
346
347#ifdef CONFIG_DST_CACHE
348		if (one_md_dst->type == METADATA_IP_TUNNEL)
349			dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache);
350#endif
351		if (one_md_dst->type == METADATA_XFRM)
352			dst_release(one_md_dst->u.xfrm_info.dst_orig);
353	}
354	free_percpu(md_dst);
355}
356EXPORT_SYMBOL_GPL(metadata_dst_free_percpu);