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