xref: /openbmc/linux/net/core/dst.c (revision e6e8c82b) 
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 EXPORT_SYMBOL(dst_default_metrics);
62 
63 void dst_init(struct dst_entry *dst, struct dst_ops *ops,
64 	      struct net_device *dev, int initial_ref, int initial_obsolete,
65 	      unsigned short flags)
66 {
67 	dst->dev = dev;
68 	if (dev)
69 		dev_hold(dev);
70 	dst->ops = ops;
71 	dst_init_metrics(dst, dst_default_metrics.metrics, true);
72 	dst->expires = 0UL;
73 #ifdef CONFIG_XFRM
74 	dst->xfrm = NULL;
75 #endif
76 	dst->input = dst_discard;
77 	dst->output = dst_discard_out;
78 	dst->error = 0;
79 	dst->obsolete = initial_obsolete;
80 	dst->header_len = 0;
81 	dst->trailer_len = 0;
82 #ifdef CONFIG_IP_ROUTE_CLASSID
83 	dst->tclassid = 0;
84 #endif
85 	dst->lwtstate = NULL;
86 	atomic_set(&dst->__refcnt, initial_ref);
87 	dst->__use = 0;
88 	dst->lastuse = jiffies;
89 	dst->flags = flags;
90 	if (!(flags & DST_NOCOUNT))
91 		dst_entries_add(ops, 1);
92 }
93 EXPORT_SYMBOL(dst_init);
94 
95 void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
96 		int initial_ref, int initial_obsolete, unsigned short flags)
97 {
98 	struct dst_entry *dst;
99 
100 	if (ops->gc && dst_entries_get_fast(ops) > ops->gc_thresh) {
101 		if (ops->gc(ops))
102 			return NULL;
103 	}
104 
105 	dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC);
106 	if (!dst)
107 		return NULL;
108 
109 	dst_init(dst, ops, dev, initial_ref, initial_obsolete, flags);
110 
111 	return dst;
112 }
113 EXPORT_SYMBOL(dst_alloc);
114 
115 struct dst_entry *dst_destroy(struct dst_entry * dst)
116 {
117 	struct dst_entry *child = NULL;
118 
119 	smp_rmb();
120 
121 #ifdef CONFIG_XFRM
122 	if (dst->xfrm) {
123 		struct xfrm_dst *xdst = (struct xfrm_dst *) dst;
124 
125 		child = xdst->child;
126 	}
127 #endif
128 	if (!(dst->flags & DST_NOCOUNT))
129 		dst_entries_add(dst->ops, -1);
130 
131 	if (dst->ops->destroy)
132 		dst->ops->destroy(dst);
133 	if (dst->dev)
134 		dev_put(dst->dev);
135 
136 	lwtstate_put(dst->lwtstate);
137 
138 	if (dst->flags & DST_METADATA)
139 		metadata_dst_free((struct metadata_dst *)dst);
140 	else
141 		kmem_cache_free(dst->ops->kmem_cachep, dst);
142 
143 	dst = child;
144 	if (dst)
145 		dst_release_immediate(dst);
146 	return NULL;
147 }
148 EXPORT_SYMBOL(dst_destroy);
149 
150 static void dst_destroy_rcu(struct rcu_head *head)
151 {
152 	struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
153 
154 	dst = dst_destroy(dst);
155 }
156 
157 /* Operations to mark dst as DEAD and clean up the net device referenced
158  * by dst:
159  * 1. put the dst under loopback interface and discard all tx/rx packets
160  *    on this route.
161  * 2. release the net_device
162  * This function should be called when removing routes from the fib tree
163  * in preparation for a NETDEV_DOWN/NETDEV_UNREGISTER event and also to
164  * make the next dst_ops->check() fail.
165  */
166 void dst_dev_put(struct dst_entry *dst)
167 {
168 	struct net_device *dev = dst->dev;
169 
170 	dst->obsolete = DST_OBSOLETE_DEAD;
171 	if (dst->ops->ifdown)
172 		dst->ops->ifdown(dst, dev, true);
173 	dst->input = dst_discard;
174 	dst->output = dst_discard_out;
175 	dst->dev = dev_net(dst->dev)->loopback_dev;
176 	dev_hold(dst->dev);
177 	dev_put(dev);
178 }
179 EXPORT_SYMBOL(dst_dev_put);
180 
181 void dst_release(struct dst_entry *dst)
182 {
183 	if (dst) {
184 		int newrefcnt;
185 
186 		newrefcnt = atomic_dec_return(&dst->__refcnt);
187 		if (unlikely(newrefcnt < 0))
188 			net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
189 					     __func__, dst, newrefcnt);
190 		if (!newrefcnt)
191 			call_rcu(&dst->rcu_head, dst_destroy_rcu);
192 	}
193 }
194 EXPORT_SYMBOL(dst_release);
195 
196 void dst_release_immediate(struct dst_entry *dst)
197 {
198 	if (dst) {
199 		int newrefcnt;
200 
201 		newrefcnt = atomic_dec_return(&dst->__refcnt);
202 		if (unlikely(newrefcnt < 0))
203 			net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
204 					     __func__, dst, newrefcnt);
205 		if (!newrefcnt)
206 			dst_destroy(dst);
207 	}
208 }
209 EXPORT_SYMBOL(dst_release_immediate);
210 
211 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old)
212 {
213 	struct dst_metrics *p = kmalloc(sizeof(*p), GFP_ATOMIC);
214 
215 	if (p) {
216 		struct dst_metrics *old_p = (struct dst_metrics *)__DST_METRICS_PTR(old);
217 		unsigned long prev, new;
218 
219 		refcount_set(&p->refcnt, 1);
220 		memcpy(p->metrics, old_p->metrics, sizeof(p->metrics));
221 
222 		new = (unsigned long) p;
223 		prev = cmpxchg(&dst->_metrics, old, new);
224 
225 		if (prev != old) {
226 			kfree(p);
227 			p = (struct dst_metrics *)__DST_METRICS_PTR(prev);
228 			if (prev & DST_METRICS_READ_ONLY)
229 				p = NULL;
230 		} else if (prev & DST_METRICS_REFCOUNTED) {
231 			if (refcount_dec_and_test(&old_p->refcnt))
232 				kfree(old_p);
233 		}
234 	}
235 	BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0);
236 	return (u32 *)p;
237 }
238 EXPORT_SYMBOL(dst_cow_metrics_generic);
239 
240 /* Caller asserts that dst_metrics_read_only(dst) is false.  */
241 void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old)
242 {
243 	unsigned long prev, new;
244 
245 	new = ((unsigned long) &dst_default_metrics) | DST_METRICS_READ_ONLY;
246 	prev = cmpxchg(&dst->_metrics, old, new);
247 	if (prev == old)
248 		kfree(__DST_METRICS_PTR(old));
249 }
250 EXPORT_SYMBOL(__dst_destroy_metrics_generic);
251 
252 static struct dst_ops md_dst_ops = {
253 	.family =		AF_UNSPEC,
254 };
255 
256 static int dst_md_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb)
257 {
258 	WARN_ONCE(1, "Attempting to call output on metadata dst\n");
259 	kfree_skb(skb);
260 	return 0;
261 }
262 
263 static int dst_md_discard(struct sk_buff *skb)
264 {
265 	WARN_ONCE(1, "Attempting to call input on metadata dst\n");
266 	kfree_skb(skb);
267 	return 0;
268 }
269 
270 static void __metadata_dst_init(struct metadata_dst *md_dst,
271 				enum metadata_type type, u8 optslen)
272 
273 {
274 	struct dst_entry *dst;
275 
276 	dst = &md_dst->dst;
277 	dst_init(dst, &md_dst_ops, NULL, 1, DST_OBSOLETE_NONE,
278 		 DST_METADATA | DST_NOCOUNT);
279 
280 	dst->input = dst_md_discard;
281 	dst->output = dst_md_discard_out;
282 
283 	memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst));
284 	md_dst->type = type;
285 }
286 
287 struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type,
288 					gfp_t flags)
289 {
290 	struct metadata_dst *md_dst;
291 
292 	md_dst = kmalloc(sizeof(*md_dst) + optslen, flags);
293 	if (!md_dst)
294 		return NULL;
295 
296 	__metadata_dst_init(md_dst, type, optslen);
297 
298 	return md_dst;
299 }
300 EXPORT_SYMBOL_GPL(metadata_dst_alloc);
301 
302 void metadata_dst_free(struct metadata_dst *md_dst)
303 {
304 #ifdef CONFIG_DST_CACHE
305 	if (md_dst->type == METADATA_IP_TUNNEL)
306 		dst_cache_destroy(&md_dst->u.tun_info.dst_cache);
307 #endif
308 	kfree(md_dst);
309 }
310 EXPORT_SYMBOL_GPL(metadata_dst_free);
311 
312 struct metadata_dst __percpu *
313 metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags)
314 {
315 	int cpu;
316 	struct metadata_dst __percpu *md_dst;
317 
318 	md_dst = __alloc_percpu_gfp(sizeof(struct metadata_dst) + optslen,
319 				    __alignof__(struct metadata_dst), flags);
320 	if (!md_dst)
321 		return NULL;
322 
323 	for_each_possible_cpu(cpu)
324 		__metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen);
325 
326 	return md_dst;
327 }
328 EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);
329 
330 void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst)
331 {
332 #ifdef CONFIG_DST_CACHE
333 	int cpu;
334 
335 	for_each_possible_cpu(cpu) {
336 		struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu);
337 
338 		if (one_md_dst->type == METADATA_IP_TUNNEL)
339 			dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache);
340 	}
341 #endif
342 	free_percpu(md_dst);
343 }
344 EXPORT_SYMBOL_GPL(metadata_dst_free_percpu);
345