1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * net/core/dst.c Protocol independent destination cache. 4 * 5 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> 6 * 7 */ 8 9 #include <linux/bitops.h> 10 #include <linux/errno.h> 11 #include <linux/init.h> 12 #include <linux/kernel.h> 13 #include <linux/workqueue.h> 14 #include <linux/mm.h> 15 #include <linux/module.h> 16 #include <linux/slab.h> 17 #include <linux/netdevice.h> 18 #include <linux/skbuff.h> 19 #include <linux/string.h> 20 #include <linux/types.h> 21 #include <net/net_namespace.h> 22 #include <linux/sched.h> 23 #include <linux/prefetch.h> 24 #include <net/lwtunnel.h> 25 #include <net/xfrm.h> 26 27 #include <net/dst.h> 28 #include <net/dst_metadata.h> 29 30 int dst_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb) 31 { 32 kfree_skb(skb); 33 return 0; 34 } 35 EXPORT_SYMBOL(dst_discard_out); 36 37 const struct dst_metrics dst_default_metrics = { 38 /* This initializer is needed to force linker to place this variable 39 * into const section. Otherwise it might end into bss section. 40 * We really want to avoid false sharing on this variable, and catch 41 * any writes on it. 42 */ 43 .refcnt = REFCOUNT_INIT(1), 44 }; 45 EXPORT_SYMBOL(dst_default_metrics); 46 47 void dst_init(struct dst_entry *dst, struct dst_ops *ops, 48 struct net_device *dev, int initial_ref, int initial_obsolete, 49 unsigned short flags) 50 { 51 dst->dev = dev; 52 dev_hold_track(dev, &dst->dev_tracker, GFP_ATOMIC); 53 dst->ops = ops; 54 dst_init_metrics(dst, dst_default_metrics.metrics, true); 55 dst->expires = 0UL; 56 #ifdef CONFIG_XFRM 57 dst->xfrm = NULL; 58 #endif 59 dst->input = dst_discard; 60 dst->output = dst_discard_out; 61 dst->error = 0; 62 dst->obsolete = initial_obsolete; 63 dst->header_len = 0; 64 dst->trailer_len = 0; 65 #ifdef CONFIG_IP_ROUTE_CLASSID 66 dst->tclassid = 0; 67 #endif 68 dst->lwtstate = NULL; 69 atomic_set(&dst->__refcnt, initial_ref); 70 dst->__use = 0; 71 dst->lastuse = jiffies; 72 dst->flags = flags; 73 if (!(flags & DST_NOCOUNT)) 74 dst_entries_add(ops, 1); 75 } 76 EXPORT_SYMBOL(dst_init); 77 78 void *dst_alloc(struct dst_ops *ops, struct net_device *dev, 79 int initial_ref, int initial_obsolete, unsigned short flags) 80 { 81 struct dst_entry *dst; 82 83 if (ops->gc && 84 !(flags & DST_NOCOUNT) && 85 dst_entries_get_fast(ops) > ops->gc_thresh) { 86 if (ops->gc(ops)) { 87 pr_notice_ratelimited("Route cache is full: consider increasing sysctl net.ipv6.route.max_size.\n"); 88 return NULL; 89 } 90 } 91 92 dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC); 93 if (!dst) 94 return NULL; 95 96 dst_init(dst, ops, dev, initial_ref, initial_obsolete, flags); 97 98 return dst; 99 } 100 EXPORT_SYMBOL(dst_alloc); 101 102 struct dst_entry *dst_destroy(struct dst_entry * dst) 103 { 104 struct dst_entry *child = NULL; 105 106 smp_rmb(); 107 108 #ifdef CONFIG_XFRM 109 if (dst->xfrm) { 110 struct xfrm_dst *xdst = (struct xfrm_dst *) dst; 111 112 child = xdst->child; 113 } 114 #endif 115 if (!(dst->flags & DST_NOCOUNT)) 116 dst_entries_add(dst->ops, -1); 117 118 if (dst->ops->destroy) 119 dst->ops->destroy(dst); 120 dev_put_track(dst->dev, &dst->dev_tracker); 121 122 lwtstate_put(dst->lwtstate); 123 124 if (dst->flags & DST_METADATA) 125 metadata_dst_free((struct metadata_dst *)dst); 126 else 127 kmem_cache_free(dst->ops->kmem_cachep, dst); 128 129 dst = child; 130 if (dst) 131 dst_release_immediate(dst); 132 return NULL; 133 } 134 EXPORT_SYMBOL(dst_destroy); 135 136 static void dst_destroy_rcu(struct rcu_head *head) 137 { 138 struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head); 139 140 dst = dst_destroy(dst); 141 } 142 143 /* Operations to mark dst as DEAD and clean up the net device referenced 144 * by dst: 145 * 1. put the dst under blackhole interface and discard all tx/rx packets 146 * on this route. 147 * 2. release the net_device 148 * This function should be called when removing routes from the fib tree 149 * in preparation for a NETDEV_DOWN/NETDEV_UNREGISTER event and also to 150 * make the next dst_ops->check() fail. 151 */ 152 void dst_dev_put(struct dst_entry *dst) 153 { 154 struct net_device *dev = dst->dev; 155 156 dst->obsolete = DST_OBSOLETE_DEAD; 157 if (dst->ops->ifdown) 158 dst->ops->ifdown(dst, dev, true); 159 dst->input = dst_discard; 160 dst->output = dst_discard_out; 161 dst->dev = blackhole_netdev; 162 dev_replace_track(dev, blackhole_netdev, &dst->dev_tracker, 163 GFP_ATOMIC); 164 } 165 EXPORT_SYMBOL(dst_dev_put); 166 167 void dst_release(struct dst_entry *dst) 168 { 169 if (dst) { 170 int newrefcnt; 171 172 newrefcnt = atomic_dec_return(&dst->__refcnt); 173 if (WARN_ONCE(newrefcnt < 0, "dst_release underflow")) 174 net_warn_ratelimited("%s: dst:%p refcnt:%d\n", 175 __func__, dst, newrefcnt); 176 if (!newrefcnt) 177 call_rcu(&dst->rcu_head, dst_destroy_rcu); 178 } 179 } 180 EXPORT_SYMBOL(dst_release); 181 182 void dst_release_immediate(struct dst_entry *dst) 183 { 184 if (dst) { 185 int newrefcnt; 186 187 newrefcnt = atomic_dec_return(&dst->__refcnt); 188 if (WARN_ONCE(newrefcnt < 0, "dst_release_immediate underflow")) 189 net_warn_ratelimited("%s: dst:%p refcnt:%d\n", 190 __func__, dst, newrefcnt); 191 if (!newrefcnt) 192 dst_destroy(dst); 193 } 194 } 195 EXPORT_SYMBOL(dst_release_immediate); 196 197 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old) 198 { 199 struct dst_metrics *p = kmalloc(sizeof(*p), GFP_ATOMIC); 200 201 if (p) { 202 struct dst_metrics *old_p = (struct dst_metrics *)__DST_METRICS_PTR(old); 203 unsigned long prev, new; 204 205 refcount_set(&p->refcnt, 1); 206 memcpy(p->metrics, old_p->metrics, sizeof(p->metrics)); 207 208 new = (unsigned long) p; 209 prev = cmpxchg(&dst->_metrics, old, new); 210 211 if (prev != old) { 212 kfree(p); 213 p = (struct dst_metrics *)__DST_METRICS_PTR(prev); 214 if (prev & DST_METRICS_READ_ONLY) 215 p = NULL; 216 } else if (prev & DST_METRICS_REFCOUNTED) { 217 if (refcount_dec_and_test(&old_p->refcnt)) 218 kfree(old_p); 219 } 220 } 221 BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0); 222 return (u32 *)p; 223 } 224 EXPORT_SYMBOL(dst_cow_metrics_generic); 225 226 /* Caller asserts that dst_metrics_read_only(dst) is false. */ 227 void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old) 228 { 229 unsigned long prev, new; 230 231 new = ((unsigned long) &dst_default_metrics) | DST_METRICS_READ_ONLY; 232 prev = cmpxchg(&dst->_metrics, old, new); 233 if (prev == old) 234 kfree(__DST_METRICS_PTR(old)); 235 } 236 EXPORT_SYMBOL(__dst_destroy_metrics_generic); 237 238 struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie) 239 { 240 return NULL; 241 } 242 243 u32 *dst_blackhole_cow_metrics(struct dst_entry *dst, unsigned long old) 244 { 245 return NULL; 246 } 247 248 struct neighbour *dst_blackhole_neigh_lookup(const struct dst_entry *dst, 249 struct sk_buff *skb, 250 const void *daddr) 251 { 252 return NULL; 253 } 254 255 void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk, 256 struct sk_buff *skb, u32 mtu, 257 bool confirm_neigh) 258 { 259 } 260 EXPORT_SYMBOL_GPL(dst_blackhole_update_pmtu); 261 262 void dst_blackhole_redirect(struct dst_entry *dst, struct sock *sk, 263 struct sk_buff *skb) 264 { 265 } 266 EXPORT_SYMBOL_GPL(dst_blackhole_redirect); 267 268 unsigned int dst_blackhole_mtu(const struct dst_entry *dst) 269 { 270 unsigned int mtu = dst_metric_raw(dst, RTAX_MTU); 271 272 return mtu ? : dst->dev->mtu; 273 } 274 EXPORT_SYMBOL_GPL(dst_blackhole_mtu); 275 276 static struct dst_ops dst_blackhole_ops = { 277 .family = AF_UNSPEC, 278 .neigh_lookup = dst_blackhole_neigh_lookup, 279 .check = dst_blackhole_check, 280 .cow_metrics = dst_blackhole_cow_metrics, 281 .update_pmtu = dst_blackhole_update_pmtu, 282 .redirect = dst_blackhole_redirect, 283 .mtu = dst_blackhole_mtu, 284 }; 285 286 static void __metadata_dst_init(struct metadata_dst *md_dst, 287 enum metadata_type type, u8 optslen) 288 { 289 struct dst_entry *dst; 290 291 dst = &md_dst->dst; 292 dst_init(dst, &dst_blackhole_ops, NULL, 1, DST_OBSOLETE_NONE, 293 DST_METADATA | DST_NOCOUNT); 294 memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst)); 295 md_dst->type = type; 296 } 297 298 struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type, 299 gfp_t flags) 300 { 301 struct metadata_dst *md_dst; 302 303 md_dst = kmalloc(sizeof(*md_dst) + optslen, flags); 304 if (!md_dst) 305 return NULL; 306 307 __metadata_dst_init(md_dst, type, optslen); 308 309 return md_dst; 310 } 311 EXPORT_SYMBOL_GPL(metadata_dst_alloc); 312 313 void metadata_dst_free(struct metadata_dst *md_dst) 314 { 315 #ifdef CONFIG_DST_CACHE 316 if (md_dst->type == METADATA_IP_TUNNEL) 317 dst_cache_destroy(&md_dst->u.tun_info.dst_cache); 318 #endif 319 kfree(md_dst); 320 } 321 EXPORT_SYMBOL_GPL(metadata_dst_free); 322 323 struct metadata_dst __percpu * 324 metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags) 325 { 326 int cpu; 327 struct metadata_dst __percpu *md_dst; 328 329 md_dst = __alloc_percpu_gfp(sizeof(struct metadata_dst) + optslen, 330 __alignof__(struct metadata_dst), flags); 331 if (!md_dst) 332 return NULL; 333 334 for_each_possible_cpu(cpu) 335 __metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen); 336 337 return md_dst; 338 } 339 EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu); 340 341 void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst) 342 { 343 #ifdef CONFIG_DST_CACHE 344 int cpu; 345 346 for_each_possible_cpu(cpu) { 347 struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu); 348 349 if (one_md_dst->type == METADATA_IP_TUNNEL) 350 dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache); 351 } 352 #endif 353 free_percpu(md_dst); 354 } 355 EXPORT_SYMBOL_GPL(metadata_dst_free_percpu); 356