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TOMOYO Linux Cross Reference
Linux/net/core/dst.c

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  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                         printk_ratelimited(KERN_NOTICE "Route cache is full: "
103                                            "consider increasing sysctl "
104                                            "net.ipv[4|6].route.max_size.\n");
105                         return NULL;
106                 }
107         }
108 
109         dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC);
110         if (!dst)
111                 return NULL;
112 
113         dst_init(dst, ops, dev, initial_ref, initial_obsolete, flags);
114 
115         return dst;
116 }
117 EXPORT_SYMBOL(dst_alloc);
118 
119 struct dst_entry *dst_destroy(struct dst_entry * dst)
120 {
121         struct dst_entry *child = NULL;
122 
123         smp_rmb();
124 
125 #ifdef CONFIG_XFRM
126         if (dst->xfrm) {
127                 struct xfrm_dst *xdst = (struct xfrm_dst *) dst;
128 
129                 child = xdst->child;
130         }
131 #endif
132         if (!(dst->flags & DST_NOCOUNT))
133                 dst_entries_add(dst->ops, -1);
134 
135         if (dst->ops->destroy)
136                 dst->ops->destroy(dst);
137         if (dst->dev)
138                 dev_put(dst->dev);
139 
140         lwtstate_put(dst->lwtstate);
141 
142         if (dst->flags & DST_METADATA)
143                 metadata_dst_free((struct metadata_dst *)dst);
144         else
145                 kmem_cache_free(dst->ops->kmem_cachep, dst);
146 
147         dst = child;
148         if (dst)
149                 dst_release_immediate(dst);
150         return NULL;
151 }
152 EXPORT_SYMBOL(dst_destroy);
153 
154 static void dst_destroy_rcu(struct rcu_head *head)
155 {
156         struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
157 
158         dst = dst_destroy(dst);
159 }
160 
161 /* Operations to mark dst as DEAD and clean up the net device referenced
162  * by dst:
163  * 1. put the dst under loopback interface and discard all tx/rx packets
164  *    on this route.
165  * 2. release the net_device
166  * This function should be called when removing routes from the fib tree
167  * in preparation for a NETDEV_DOWN/NETDEV_UNREGISTER event and also to
168  * make the next dst_ops->check() fail.
169  */
170 void dst_dev_put(struct dst_entry *dst)
171 {
172         struct net_device *dev = dst->dev;
173 
174         dst->obsolete = DST_OBSOLETE_DEAD;
175         if (dst->ops->ifdown)
176                 dst->ops->ifdown(dst, dev, true);
177         dst->input = dst_discard;
178         dst->output = dst_discard_out;
179         dst->dev = dev_net(dst->dev)->loopback_dev;
180         dev_hold(dst->dev);
181         dev_put(dev);
182 }
183 EXPORT_SYMBOL(dst_dev_put);
184 
185 void dst_release(struct dst_entry *dst)
186 {
187         if (dst) {
188                 int newrefcnt;
189 
190                 newrefcnt = atomic_dec_return(&dst->__refcnt);
191                 if (unlikely(newrefcnt < 0))
192                         net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
193                                              __func__, dst, newrefcnt);
194                 if (!newrefcnt)
195                         call_rcu(&dst->rcu_head, dst_destroy_rcu);
196         }
197 }
198 EXPORT_SYMBOL(dst_release);
199 
200 void dst_release_immediate(struct dst_entry *dst)
201 {
202         if (dst) {
203                 int newrefcnt;
204 
205                 newrefcnt = atomic_dec_return(&dst->__refcnt);
206                 if (unlikely(newrefcnt < 0))
207                         net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
208                                              __func__, dst, newrefcnt);
209                 if (!newrefcnt)
210                         dst_destroy(dst);
211         }
212 }
213 EXPORT_SYMBOL(dst_release_immediate);
214 
215 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old)
216 {
217         struct dst_metrics *p = kmalloc(sizeof(*p), GFP_ATOMIC);
218 
219         if (p) {
220                 struct dst_metrics *old_p = (struct dst_metrics *)__DST_METRICS_PTR(old);
221                 unsigned long prev, new;
222 
223                 refcount_set(&p->refcnt, 1);
224                 memcpy(p->metrics, old_p->metrics, sizeof(p->metrics));
225 
226                 new = (unsigned long) p;
227                 prev = cmpxchg(&dst->_metrics, old, new);
228 
229                 if (prev != old) {
230                         kfree(p);
231                         p = (struct dst_metrics *)__DST_METRICS_PTR(prev);
232                         if (prev & DST_METRICS_READ_ONLY)
233                                 p = NULL;
234                 } else if (prev & DST_METRICS_REFCOUNTED) {
235                         if (refcount_dec_and_test(&old_p->refcnt))
236                                 kfree(old_p);
237                 }
238         }
239         BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0);
240         return (u32 *)p;
241 }
242 EXPORT_SYMBOL(dst_cow_metrics_generic);
243 
244 /* Caller asserts that dst_metrics_read_only(dst) is false.  */
245 void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old)
246 {
247         unsigned long prev, new;
248 
249         new = ((unsigned long) &dst_default_metrics) | DST_METRICS_READ_ONLY;
250         prev = cmpxchg(&dst->_metrics, old, new);
251         if (prev == old)
252                 kfree(__DST_METRICS_PTR(old));
253 }
254 EXPORT_SYMBOL(__dst_destroy_metrics_generic);
255 
256 static struct dst_ops md_dst_ops = {
257         .family =               AF_UNSPEC,
258 };
259 
260 static int dst_md_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb)
261 {
262         WARN_ONCE(1, "Attempting to call output on metadata dst\n");
263         kfree_skb(skb);
264         return 0;
265 }
266 
267 static int dst_md_discard(struct sk_buff *skb)
268 {
269         WARN_ONCE(1, "Attempting to call input on metadata dst\n");
270         kfree_skb(skb);
271         return 0;
272 }
273 
274 static void __metadata_dst_init(struct metadata_dst *md_dst,
275                                 enum metadata_type type, u8 optslen)
276 
277 {
278         struct dst_entry *dst;
279 
280         dst = &md_dst->dst;
281         dst_init(dst, &md_dst_ops, NULL, 1, DST_OBSOLETE_NONE,
282                  DST_METADATA | DST_NOCOUNT);
283 
284         dst->input = dst_md_discard;
285         dst->output = dst_md_discard_out;
286 
287         memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst));
288         md_dst->type = type;
289 }
290 
291 struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type,
292                                         gfp_t flags)
293 {
294         struct metadata_dst *md_dst;
295 
296         md_dst = kmalloc(sizeof(*md_dst) + optslen, flags);
297         if (!md_dst)
298                 return NULL;
299 
300         __metadata_dst_init(md_dst, type, optslen);
301 
302         return md_dst;
303 }
304 EXPORT_SYMBOL_GPL(metadata_dst_alloc);
305 
306 void metadata_dst_free(struct metadata_dst *md_dst)
307 {
308 #ifdef CONFIG_DST_CACHE
309         if (md_dst->type == METADATA_IP_TUNNEL)
310                 dst_cache_destroy(&md_dst->u.tun_info.dst_cache);
311 #endif
312         kfree(md_dst);
313 }
314 EXPORT_SYMBOL_GPL(metadata_dst_free);
315 
316 struct metadata_dst __percpu *
317 metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags)
318 {
319         int cpu;
320         struct metadata_dst __percpu *md_dst;
321 
322         md_dst = __alloc_percpu_gfp(sizeof(struct metadata_dst) + optslen,
323                                     __alignof__(struct metadata_dst), flags);
324         if (!md_dst)
325                 return NULL;
326 
327         for_each_possible_cpu(cpu)
328                 __metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen);
329 
330         return md_dst;
331 }
332 EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);
333 
334 void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst)
335 {
336 #ifdef CONFIG_DST_CACHE
337         int cpu;
338 
339         for_each_possible_cpu(cpu) {
340                 struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu);
341 
342                 if (one_md_dst->type == METADATA_IP_TUNNEL)
343                         dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache);
344         }
345 #endif
346         free_percpu(md_dst);
347 }
348 EXPORT_SYMBOL_GPL(metadata_dst_free_percpu);
349 

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