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