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 } 310 311 struct metadata_dst __percpu * 312 metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags) 313 { 314 int cpu; 315 struct metadata_dst __percpu *md_dst; 316 317 md_dst = __alloc_percpu_gfp(sizeof(struct metadata_dst) + optslen, 318 __alignof__(struct metadata_dst), flags); 319 if (!md_dst) 320 return NULL; 321 322 for_each_possible_cpu(cpu) 323 __metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen); 324 325 return md_dst; 326 } 327 EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu); 328 329 void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst) 330 { 331 #ifdef CONFIG_DST_CACHE 332 int cpu; 333 334 for_each_possible_cpu(cpu) { 335 struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu); 336 337 if (one_md_dst->type == METADATA_IP_TUNNEL) 338 dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache); 339 } 340 #endif 341 free_percpu(md_dst); 342 } 343 EXPORT_SYMBOL_GPL(metadata_dst_free_percpu); 344