xref: /openbmc/linux/net/core/dst.c (revision 4cff79e9) 
1 /*
2  * net/core/dst.c	Protocol independent destination cache.
3  *
4  * Authors:		Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
5  *
6  */
7 
8 #include <linux/bitops.h>
9 #include <linux/errno.h>
10 #include <linux/init.h>
11 #include <linux/kernel.h>
12 #include <linux/workqueue.h>
13 #include <linux/mm.h>
14 #include <linux/module.h>
15 #include <linux/slab.h>
16 #include <linux/netdevice.h>
17 #include <linux/skbuff.h>
18 #include <linux/string.h>
19 #include <linux/types.h>
20 #include <net/net_namespace.h>
21 #include <linux/sched.h>
22 #include <linux/prefetch.h>
23 #include <net/lwtunnel.h>
24 #include <net/xfrm.h>
25 
26 #include <net/dst.h>
27 #include <net/dst_metadata.h>
28 
29 /*
30  * Theory of operations:
31  * 1) We use a list, protected by a spinlock, to add
32  *    new entries from both BH and non-BH context.
33  * 2) In order to keep spinlock held for a small delay,
34  *    we use a second list where are stored long lived
35  *    entries, that are handled by the garbage collect thread
36  *    fired by a workqueue.
37  * 3) This list is guarded by a mutex,
38  *    so that the gc_task and dst_dev_event() can be synchronized.
39  */
40 
41 /*
42  * We want to keep lock & list close together
43  * to dirty as few cache lines as possible in __dst_free().
44  * As this is not a very strong hint, we dont force an alignment on SMP.
45  */
46 int dst_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb)
47 {
48 	kfree_skb(skb);
49 	return 0;
50 }
51 EXPORT_SYMBOL(dst_discard_out);
52 
53 const struct dst_metrics dst_default_metrics = {
54 	/* This initializer is needed to force linker to place this variable
55 	 * into const section. Otherwise it might end into bss section.
56 	 * We really want to avoid false sharing on this variable, and catch
57 	 * any writes on it.
58 	 */
59 	.refcnt = REFCOUNT_INIT(1),
60 };
61 
62 void dst_init(struct dst_entry *dst, struct dst_ops *ops,
63 	      struct net_device *dev, int initial_ref, int initial_obsolete,
64 	      unsigned short flags)
65 {
66 	dst->dev = dev;
67 	if (dev)
68 		dev_hold(dev);
69 	dst->ops = ops;
70 	dst_init_metrics(dst, dst_default_metrics.metrics, true);
71 	dst->expires = 0UL;
72 #ifdef CONFIG_XFRM
73 	dst->xfrm = NULL;
74 #endif
75 	dst->input = dst_discard;
76 	dst->output = dst_discard_out;
77 	dst->error = 0;
78 	dst->obsolete = initial_obsolete;
79 	dst->header_len = 0;
80 	dst->trailer_len = 0;
81 #ifdef CONFIG_IP_ROUTE_CLASSID
82 	dst->tclassid = 0;
83 #endif
84 	dst->lwtstate = NULL;
85 	atomic_set(&dst->__refcnt, initial_ref);
86 	dst->__use = 0;
87 	dst->lastuse = jiffies;
88 	dst->flags = flags;
89 	if (!(flags & DST_NOCOUNT))
90 		dst_entries_add(ops, 1);
91 }
92 EXPORT_SYMBOL(dst_init);
93 
94 void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
95 		int initial_ref, int initial_obsolete, unsigned short flags)
96 {
97 	struct dst_entry *dst;
98 
99 	if (ops->gc && dst_entries_get_fast(ops) > ops->gc_thresh) {
100 		if (ops->gc(ops))
101 			return NULL;
102 	}
103 
104 	dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC);
105 	if (!dst)
106 		return NULL;
107 
108 	dst_init(dst, ops, dev, initial_ref, initial_obsolete, flags);
109 
110 	return dst;
111 }
112 EXPORT_SYMBOL(dst_alloc);
113 
114 struct dst_entry *dst_destroy(struct dst_entry * dst)
115 {
116 	struct dst_entry *child = NULL;
117 
118 	smp_rmb();
119 
120 #ifdef CONFIG_XFRM
121 	if (dst->xfrm) {
122 		struct xfrm_dst *xdst = (struct xfrm_dst *) dst;
123 
124 		child = xdst->child;
125 	}
126 #endif
127 	if (!(dst->flags & DST_NOCOUNT))
128 		dst_entries_add(dst->ops, -1);
129 
130 	if (dst->ops->destroy)
131 		dst->ops->destroy(dst);
132 	if (dst->dev)
133 		dev_put(dst->dev);
134 
135 	lwtstate_put(dst->lwtstate);
136 
137 	if (dst->flags & DST_METADATA)
138 		metadata_dst_free((struct metadata_dst *)dst);
139 	else
140 		kmem_cache_free(dst->ops->kmem_cachep, dst);
141 
142 	dst = child;
143 	if (dst)
144 		dst_release_immediate(dst);
145 	return NULL;
146 }
147 EXPORT_SYMBOL(dst_destroy);
148 
149 static void dst_destroy_rcu(struct rcu_head *head)
150 {
151 	struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
152 
153 	dst = dst_destroy(dst);
154 }
155 
156 /* Operations to mark dst as DEAD and clean up the net device referenced
157  * by dst:
158  * 1. put the dst under loopback interface and discard all tx/rx packets
159  *    on this route.
160  * 2. release the net_device
161  * This function should be called when removing routes from the fib tree
162  * in preparation for a NETDEV_DOWN/NETDEV_UNREGISTER event and also to
163  * make the next dst_ops->check() fail.
164  */
165 void dst_dev_put(struct dst_entry *dst)
166 {
167 	struct net_device *dev = dst->dev;
168 
169 	dst->obsolete = DST_OBSOLETE_DEAD;
170 	if (dst->ops->ifdown)
171 		dst->ops->ifdown(dst, dev, true);
172 	dst->input = dst_discard;
173 	dst->output = dst_discard_out;
174 	dst->dev = dev_net(dst->dev)->loopback_dev;
175 	dev_hold(dst->dev);
176 	dev_put(dev);
177 }
178 EXPORT_SYMBOL(dst_dev_put);
179 
180 void dst_release(struct dst_entry *dst)
181 {
182 	if (dst) {
183 		int newrefcnt;
184 
185 		newrefcnt = atomic_dec_return(&dst->__refcnt);
186 		if (unlikely(newrefcnt < 0))
187 			net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
188 					     __func__, dst, newrefcnt);
189 		if (!newrefcnt)
190 			call_rcu(&dst->rcu_head, dst_destroy_rcu);
191 	}
192 }
193 EXPORT_SYMBOL(dst_release);
194 
195 void dst_release_immediate(struct dst_entry *dst)
196 {
197 	if (dst) {
198 		int newrefcnt;
199 
200 		newrefcnt = atomic_dec_return(&dst->__refcnt);
201 		if (unlikely(newrefcnt < 0))
202 			net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
203 					     __func__, dst, newrefcnt);
204 		if (!newrefcnt)
205 			dst_destroy(dst);
206 	}
207 }
208 EXPORT_SYMBOL(dst_release_immediate);
209 
210 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old)
211 {
212 	struct dst_metrics *p = kmalloc(sizeof(*p), GFP_ATOMIC);
213 
214 	if (p) {
215 		struct dst_metrics *old_p = (struct dst_metrics *)__DST_METRICS_PTR(old);
216 		unsigned long prev, new;
217 
218 		refcount_set(&p->refcnt, 1);
219 		memcpy(p->metrics, old_p->metrics, sizeof(p->metrics));
220 
221 		new = (unsigned long) p;
222 		prev = cmpxchg(&dst->_metrics, old, new);
223 
224 		if (prev != old) {
225 			kfree(p);
226 			p = (struct dst_metrics *)__DST_METRICS_PTR(prev);
227 			if (prev & DST_METRICS_READ_ONLY)
228 				p = NULL;
229 		} else if (prev & DST_METRICS_REFCOUNTED) {
230 			if (refcount_dec_and_test(&old_p->refcnt))
231 				kfree(old_p);
232 		}
233 	}
234 	BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0);
235 	return (u32 *)p;
236 }
237 EXPORT_SYMBOL(dst_cow_metrics_generic);
238 
239 /* Caller asserts that dst_metrics_read_only(dst) is false.  */
240 void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old)
241 {
242 	unsigned long prev, new;
243 
244 	new = ((unsigned long) &dst_default_metrics) | DST_METRICS_READ_ONLY;
245 	prev = cmpxchg(&dst->_metrics, old, new);
246 	if (prev == old)
247 		kfree(__DST_METRICS_PTR(old));
248 }
249 EXPORT_SYMBOL(__dst_destroy_metrics_generic);
250 
251 static struct dst_ops md_dst_ops = {
252 	.family =		AF_UNSPEC,
253 };
254 
255 static int dst_md_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb)
256 {
257 	WARN_ONCE(1, "Attempting to call output on metadata dst\n");
258 	kfree_skb(skb);
259 	return 0;
260 }
261 
262 static int dst_md_discard(struct sk_buff *skb)
263 {
264 	WARN_ONCE(1, "Attempting to call input on metadata dst\n");
265 	kfree_skb(skb);
266 	return 0;
267 }
268 
269 static void __metadata_dst_init(struct metadata_dst *md_dst,
270 				enum metadata_type type, u8 optslen)
271 
272 {
273 	struct dst_entry *dst;
274 
275 	dst = &md_dst->dst;
276 	dst_init(dst, &md_dst_ops, NULL, 1, DST_OBSOLETE_NONE,
277 		 DST_METADATA | DST_NOCOUNT);
278 
279 	dst->input = dst_md_discard;
280 	dst->output = dst_md_discard_out;
281 
282 	memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst));
283 	md_dst->type = type;
284 }
285 
286 struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type,
287 					gfp_t flags)
288 {
289 	struct metadata_dst *md_dst;
290 
291 	md_dst = kmalloc(sizeof(*md_dst) + optslen, flags);
292 	if (!md_dst)
293 		return NULL;
294 
295 	__metadata_dst_init(md_dst, type, optslen);
296 
297 	return md_dst;
298 }
299 EXPORT_SYMBOL_GPL(metadata_dst_alloc);
300 
301 void metadata_dst_free(struct metadata_dst *md_dst)
302 {
303 #ifdef CONFIG_DST_CACHE
304 	if (md_dst->type == METADATA_IP_TUNNEL)
305 		dst_cache_destroy(&md_dst->u.tun_info.dst_cache);
306 #endif
307 	kfree(md_dst);
308 }
309 
310 struct metadata_dst __percpu *
311 metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags)
312 {
313 	int cpu;
314 	struct metadata_dst __percpu *md_dst;
315 
316 	md_dst = __alloc_percpu_gfp(sizeof(struct metadata_dst) + optslen,
317 				    __alignof__(struct metadata_dst), flags);
318 	if (!md_dst)
319 		return NULL;
320 
321 	for_each_possible_cpu(cpu)
322 		__metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen);
323 
324 	return md_dst;
325 }
326 EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);
327 
328 void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst)
329 {
330 #ifdef CONFIG_DST_CACHE
331 	int cpu;
332 
333 	for_each_possible_cpu(cpu) {
334 		struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu);
335 
336 		if (one_md_dst->type == METADATA_IP_TUNNEL)
337 			dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache);
338 	}
339 #endif
340 	free_percpu(md_dst);
341 }
342 EXPORT_SYMBOL_GPL(metadata_dst_free_percpu);
343