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