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