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