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_ref,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_ref, 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, initial_ref);
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_ref,int initial_obsolete,unsigned short flags)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 &&
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_ref, initial_obsolete, flags);
94 
95 	return dst;
96 }
97 EXPORT_SYMBOL(dst_alloc);
98 
dst_destroy(struct dst_entry * dst)99 struct 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->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 	return NULL;
130 }
131 EXPORT_SYMBOL(dst_destroy);
132 
dst_destroy_rcu(struct rcu_head * head)133 static 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  */
dst_dev_put(struct dst_entry * dst)149 void 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(dev, blackhole_netdev, &dst->dev_tracker,
160 			   GFP_ATOMIC);
161 }
162 EXPORT_SYMBOL(dst_dev_put);
163 
dst_release(struct dst_entry * dst)164 void dst_release(struct dst_entry *dst)
165 {
166 	if (dst && rcuref_put(&dst->__rcuref))
167 		call_rcu_hurry(&dst->rcu_head, dst_destroy_rcu);
168 }
169 EXPORT_SYMBOL(dst_release);
170 
dst_release_immediate(struct dst_entry * dst)171 void dst_release_immediate(struct dst_entry *dst)
172 {
173 	if (dst && rcuref_put(&dst->__rcuref))
174 		dst_destroy(dst);
175 }
176 EXPORT_SYMBOL(dst_release_immediate);
177 
dst_cow_metrics_generic(struct dst_entry * dst,unsigned long old)178 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old)
179 {
180 	struct dst_metrics *p = kmalloc(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(&p->refcnt, 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(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(&old_p->refcnt))
199 				kfree(old_p);
200 		}
201 	}
202 	BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0);
203 	return (u32 *)p;
204 }
205 EXPORT_SYMBOL(dst_cow_metrics_generic);
206 
207 /* Caller asserts that dst_metrics_read_only(dst) is false.  */
__dst_destroy_metrics_generic(struct dst_entry * dst,unsigned long old)208 void __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 }
217 EXPORT_SYMBOL(__dst_destroy_metrics_generic);
218 
dst_blackhole_check(struct dst_entry * dst,u32 cookie)219 struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie)
220 {
221 	return NULL;
222 }
223 
dst_blackhole_cow_metrics(struct dst_entry * dst,unsigned long old)224 u32 *dst_blackhole_cow_metrics(struct dst_entry *dst, unsigned long old)
225 {
226 	return NULL;
227 }
228 
dst_blackhole_neigh_lookup(const struct dst_entry * dst,struct sk_buff * skb,const void * daddr)229 struct 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 
dst_blackhole_update_pmtu(struct dst_entry * dst,struct sock * sk,struct sk_buff * skb,u32 mtu,bool confirm_neigh)236 void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
237 			       struct sk_buff *skb, u32 mtu,
238 			       bool confirm_neigh)
239 {
240 }
241 EXPORT_SYMBOL_GPL(dst_blackhole_update_pmtu);
242 
dst_blackhole_redirect(struct dst_entry * dst,struct sock * sk,struct sk_buff * skb)243 void dst_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
244 			    struct sk_buff *skb)
245 {
246 }
247 EXPORT_SYMBOL_GPL(dst_blackhole_redirect);
248 
dst_blackhole_mtu(const struct dst_entry * dst)249 unsigned 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 }
255 EXPORT_SYMBOL_GPL(dst_blackhole_mtu);
256 
257 static 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 
__metadata_dst_init(struct metadata_dst * md_dst,enum metadata_type type,u8 optslen)267 static 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, 1, 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 
metadata_dst_alloc(u8 optslen,enum metadata_type type,gfp_t flags)279 struct 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(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 }
292 EXPORT_SYMBOL_GPL(metadata_dst_alloc);
293 
metadata_dst_free(struct metadata_dst * md_dst)294 void 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(&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(md_dst);
303 }
304 EXPORT_SYMBOL_GPL(metadata_dst_free);
305 
306 struct metadata_dst __percpu *
metadata_dst_alloc_percpu(u8 optslen,enum metadata_type type,gfp_t flags)307 metadata_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(sizeof(struct metadata_dst) + optslen,
313 				    __alignof__(struct metadata_dst), 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 }
322 EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);
323 
metadata_dst_free_percpu(struct metadata_dst __percpu * md_dst)324 void 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(&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(md_dst);
339 }
340 EXPORT_SYMBOL_GPL(metadata_dst_free_percpu);
341