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_obsolete, 49 unsigned short flags) 50 { 51 dst->dev = dev; 52 netdev_hold(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 rcuref_init(&dst->__rcuref, 1); 70 INIT_LIST_HEAD(&dst->rt_uncached); 71 dst->rt_uncached_list = NULL; 72 dst->__use = 0; 73 dst->lastuse = jiffies; 74 dst->flags = flags; 75 if (!(flags & DST_NOCOUNT)) 76 dst_entries_add(ops, 1); 77 } 78 EXPORT_SYMBOL(dst_init); 79 80 void *dst_alloc(struct dst_ops *ops, struct net_device *dev, 81 int initial_obsolete, unsigned short flags) 82 { 83 struct dst_entry *dst; 84 85 if (ops->gc && 86 !(flags & DST_NOCOUNT) && 87 dst_entries_get_fast(ops) > ops->gc_thresh) 88 ops->gc(ops); 89 90 dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC); 91 if (!dst) 92 return NULL; 93 94 dst_init(dst, ops, dev, initial_obsolete, flags); 95 96 return dst; 97 } 98 EXPORT_SYMBOL(dst_alloc); 99 100 static void dst_destroy(struct dst_entry *dst) 101 { 102 struct dst_entry *child = NULL; 103 104 smp_rmb(); 105 106 #ifdef CONFIG_XFRM 107 if (dst->xfrm) { 108 struct xfrm_dst *xdst = (struct xfrm_dst *) dst; 109 110 child = xdst->child; 111 } 112 #endif 113 if (dst->ops->destroy) 114 dst->ops->destroy(dst); 115 netdev_put(dst->dev, &dst->dev_tracker); 116 117 lwtstate_put(dst->lwtstate); 118 119 if (dst->flags & DST_METADATA) 120 metadata_dst_free((struct metadata_dst *)dst); 121 else 122 kmem_cache_free(dst->ops->kmem_cachep, dst); 123 124 dst = child; 125 if (dst) 126 dst_release_immediate(dst); 127 } 128 129 static void dst_destroy_rcu(struct rcu_head *head) 130 { 131 struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head); 132 133 dst_destroy(dst); 134 } 135 136 /* Operations to mark dst as DEAD and clean up the net device referenced 137 * by dst: 138 * 1. put the dst under blackhole interface and discard all tx/rx packets 139 * on this route. 140 * 2. release the net_device 141 * This function should be called when removing routes from the fib tree 142 * in preparation for a NETDEV_DOWN/NETDEV_UNREGISTER event and also to 143 * make the next dst_ops->check() fail. 144 */ 145 void dst_dev_put(struct dst_entry *dst) 146 { 147 struct net_device *dev = dst->dev; 148 149 WRITE_ONCE(dst->obsolete, DST_OBSOLETE_DEAD); 150 if (dst->ops->ifdown) 151 dst->ops->ifdown(dst, dev); 152 WRITE_ONCE(dst->input, dst_discard); 153 WRITE_ONCE(dst->output, dst_discard_out); 154 rcu_assign_pointer(dst->dev_rcu, blackhole_netdev); 155 netdev_ref_replace(dev, blackhole_netdev, &dst->dev_tracker, 156 GFP_ATOMIC); 157 } 158 EXPORT_SYMBOL(dst_dev_put); 159 160 static void dst_count_dec(struct dst_entry *dst) 161 { 162 if (!(dst->flags & DST_NOCOUNT)) 163 dst_entries_add(dst->ops, -1); 164 } 165 166 void dst_release(struct dst_entry *dst) 167 { 168 if (dst && rcuref_put(&dst->__rcuref)) { 169 #ifdef CONFIG_DST_CACHE 170 if (dst->flags & DST_METADATA) { 171 struct metadata_dst *md_dst = (struct metadata_dst *)dst; 172 173 if (md_dst->type == METADATA_IP_TUNNEL) 174 dst_cache_reset_now(&md_dst->u.tun_info.dst_cache); 175 } 176 #endif 177 dst_count_dec(dst); 178 call_rcu_hurry(&dst->rcu_head, dst_destroy_rcu); 179 } 180 } 181 EXPORT_SYMBOL(dst_release); 182 183 void dst_release_immediate(struct dst_entry *dst) 184 { 185 if (dst && rcuref_put(&dst->__rcuref)) { 186 dst_count_dec(dst); 187 dst_destroy(dst); 188 } 189 } 190 EXPORT_SYMBOL(dst_release_immediate); 191 192 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old) 193 { 194 struct dst_metrics *p = kmalloc(sizeof(*p), GFP_ATOMIC); 195 196 if (p) { 197 struct dst_metrics *old_p = (struct dst_metrics *)__DST_METRICS_PTR(old); 198 unsigned long prev, new; 199 200 refcount_set(&p->refcnt, 1); 201 memcpy(p->metrics, old_p->metrics, sizeof(p->metrics)); 202 203 new = (unsigned long) p; 204 prev = cmpxchg(&dst->_metrics, old, new); 205 206 if (prev != old) { 207 kfree(p); 208 p = (struct dst_metrics *)__DST_METRICS_PTR(prev); 209 if (prev & DST_METRICS_READ_ONLY) 210 p = NULL; 211 } else if (prev & DST_METRICS_REFCOUNTED) { 212 if (refcount_dec_and_test(&old_p->refcnt)) 213 kfree(old_p); 214 } 215 } 216 BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0); 217 return (u32 *)p; 218 } 219 EXPORT_SYMBOL(dst_cow_metrics_generic); 220 221 /* Caller asserts that dst_metrics_read_only(dst) is false. */ 222 void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old) 223 { 224 unsigned long prev, new; 225 226 new = ((unsigned long) &dst_default_metrics) | DST_METRICS_READ_ONLY; 227 prev = cmpxchg(&dst->_metrics, old, new); 228 if (prev == old) 229 kfree(__DST_METRICS_PTR(old)); 230 } 231 EXPORT_SYMBOL(__dst_destroy_metrics_generic); 232 233 struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie) 234 { 235 return NULL; 236 } 237 238 u32 *dst_blackhole_cow_metrics(struct dst_entry *dst, unsigned long old) 239 { 240 return NULL; 241 } 242 243 struct neighbour *dst_blackhole_neigh_lookup(const struct dst_entry *dst, 244 struct sk_buff *skb, 245 const void *daddr) 246 { 247 return NULL; 248 } 249 250 void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk, 251 struct sk_buff *skb, u32 mtu, 252 bool confirm_neigh) 253 { 254 } 255 EXPORT_SYMBOL_GPL(dst_blackhole_update_pmtu); 256 257 void dst_blackhole_redirect(struct dst_entry *dst, struct sock *sk, 258 struct sk_buff *skb) 259 { 260 } 261 EXPORT_SYMBOL_GPL(dst_blackhole_redirect); 262 263 unsigned int dst_blackhole_mtu(const struct dst_entry *dst) 264 { 265 unsigned int mtu = dst_metric_raw(dst, RTAX_MTU); 266 267 return mtu ? : dst_dev(dst)->mtu; 268 } 269 EXPORT_SYMBOL_GPL(dst_blackhole_mtu); 270 271 static struct dst_ops dst_blackhole_ops = { 272 .family = AF_UNSPEC, 273 .neigh_lookup = dst_blackhole_neigh_lookup, 274 .check = dst_blackhole_check, 275 .cow_metrics = dst_blackhole_cow_metrics, 276 .update_pmtu = dst_blackhole_update_pmtu, 277 .redirect = dst_blackhole_redirect, 278 .mtu = dst_blackhole_mtu, 279 }; 280 281 static void __metadata_dst_init(struct metadata_dst *md_dst, 282 enum metadata_type type, u8 optslen) 283 { 284 struct dst_entry *dst; 285 286 dst = &md_dst->dst; 287 dst_init(dst, &dst_blackhole_ops, NULL, DST_OBSOLETE_NONE, 288 DST_METADATA | DST_NOCOUNT); 289 memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst)); 290 md_dst->type = type; 291 } 292 293 struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type, 294 gfp_t flags) 295 { 296 struct metadata_dst *md_dst; 297 298 md_dst = kmalloc(struct_size(md_dst, u.tun_info.options, optslen), 299 flags); 300 if (!md_dst) 301 return NULL; 302 303 __metadata_dst_init(md_dst, type, optslen); 304 305 return md_dst; 306 } 307 EXPORT_SYMBOL_GPL(metadata_dst_alloc); 308 309 void metadata_dst_free(struct metadata_dst *md_dst) 310 { 311 #ifdef CONFIG_DST_CACHE 312 if (md_dst->type == METADATA_IP_TUNNEL) 313 dst_cache_destroy(&md_dst->u.tun_info.dst_cache); 314 #endif 315 if (md_dst->type == METADATA_XFRM) 316 dst_release(md_dst->u.xfrm_info.dst_orig); 317 kfree(md_dst); 318 } 319 EXPORT_SYMBOL_GPL(metadata_dst_free); 320 321 struct metadata_dst __percpu * 322 metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags) 323 { 324 int cpu; 325 struct metadata_dst __percpu *md_dst; 326 327 md_dst = __alloc_percpu_gfp(struct_size(md_dst, u.tun_info.options, 328 optslen), 329 __alignof__(struct metadata_dst), flags); 330 if (!md_dst) 331 return NULL; 332 333 for_each_possible_cpu(cpu) 334 __metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen); 335 336 return md_dst; 337 } 338 EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu); 339 340 void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst) 341 { 342 int cpu; 343 344 for_each_possible_cpu(cpu) { 345 struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu); 346 347 #ifdef CONFIG_DST_CACHE 348 if (one_md_dst->type == METADATA_IP_TUNNEL) 349 dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache); 350 #endif 351 if (one_md_dst->type == METADATA_XFRM) 352 dst_release(one_md_dst->u.xfrm_info.dst_orig); 353 } 354 free_percpu(md_dst); 355 } 356 EXPORT_SYMBOL_GPL(metadata_dst_free_percpu); 357