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 if (dev) 53 dev_hold(dev); 54 dst->ops = ops; 55 dst_init_metrics(dst, dst_default_metrics.metrics, true); 56 dst->expires = 0UL; 57 #ifdef CONFIG_XFRM 58 dst->xfrm = NULL; 59 #endif 60 dst->input = dst_discard; 61 dst->output = dst_discard_out; 62 dst->error = 0; 63 dst->obsolete = initial_obsolete; 64 dst->header_len = 0; 65 dst->trailer_len = 0; 66 #ifdef CONFIG_IP_ROUTE_CLASSID 67 dst->tclassid = 0; 68 #endif 69 dst->lwtstate = NULL; 70 atomic_set(&dst->__refcnt, initial_ref); 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_ref, 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 if (ops->gc(ops)) { 88 pr_notice_ratelimited("Route cache is full: consider increasing sysctl net.ipv6.route.max_size.\n"); 89 return NULL; 90 } 91 } 92 93 dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC); 94 if (!dst) 95 return NULL; 96 97 dst_init(dst, ops, dev, initial_ref, initial_obsolete, flags); 98 99 return dst; 100 } 101 EXPORT_SYMBOL(dst_alloc); 102 103 struct dst_entry *dst_destroy(struct dst_entry * dst) 104 { 105 struct dst_entry *child = NULL; 106 107 smp_rmb(); 108 109 #ifdef CONFIG_XFRM 110 if (dst->xfrm) { 111 struct xfrm_dst *xdst = (struct xfrm_dst *) dst; 112 113 child = xdst->child; 114 } 115 #endif 116 if (!(dst->flags & DST_NOCOUNT)) 117 dst_entries_add(dst->ops, -1); 118 119 if (dst->ops->destroy) 120 dst->ops->destroy(dst); 121 if (dst->dev) 122 dev_put(dst->dev); 123 124 lwtstate_put(dst->lwtstate); 125 126 if (dst->flags & DST_METADATA) 127 metadata_dst_free((struct metadata_dst *)dst); 128 else 129 kmem_cache_free(dst->ops->kmem_cachep, dst); 130 131 dst = child; 132 if (dst) 133 dst_release_immediate(dst); 134 return NULL; 135 } 136 EXPORT_SYMBOL(dst_destroy); 137 138 static void dst_destroy_rcu(struct rcu_head *head) 139 { 140 struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head); 141 142 dst = dst_destroy(dst); 143 } 144 145 /* Operations to mark dst as DEAD and clean up the net device referenced 146 * by dst: 147 * 1. put the dst under loopback interface and discard all tx/rx packets 148 * on this route. 149 * 2. release the net_device 150 * This function should be called when removing routes from the fib tree 151 * in preparation for a NETDEV_DOWN/NETDEV_UNREGISTER event and also to 152 * make the next dst_ops->check() fail. 153 */ 154 void dst_dev_put(struct dst_entry *dst) 155 { 156 struct net_device *dev = dst->dev; 157 158 dst->obsolete = DST_OBSOLETE_DEAD; 159 if (dst->ops->ifdown) 160 dst->ops->ifdown(dst, dev, true); 161 dst->input = dst_discard; 162 dst->output = dst_discard_out; 163 dst->dev = blackhole_netdev; 164 dev_hold(dst->dev); 165 dev_put(dev); 166 } 167 EXPORT_SYMBOL(dst_dev_put); 168 169 void dst_release(struct dst_entry *dst) 170 { 171 if (dst) { 172 int newrefcnt; 173 174 newrefcnt = atomic_dec_return(&dst->__refcnt); 175 if (WARN_ONCE(newrefcnt < 0, "dst_release underflow")) 176 net_warn_ratelimited("%s: dst:%p refcnt:%d\n", 177 __func__, dst, newrefcnt); 178 if (!newrefcnt) 179 call_rcu(&dst->rcu_head, dst_destroy_rcu); 180 } 181 } 182 EXPORT_SYMBOL(dst_release); 183 184 void dst_release_immediate(struct dst_entry *dst) 185 { 186 if (dst) { 187 int newrefcnt; 188 189 newrefcnt = atomic_dec_return(&dst->__refcnt); 190 if (WARN_ONCE(newrefcnt < 0, "dst_release_immediate underflow")) 191 net_warn_ratelimited("%s: dst:%p refcnt:%d\n", 192 __func__, dst, newrefcnt); 193 if (!newrefcnt) 194 dst_destroy(dst); 195 } 196 } 197 EXPORT_SYMBOL(dst_release_immediate); 198 199 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old) 200 { 201 struct dst_metrics *p = kmalloc(sizeof(*p), GFP_ATOMIC); 202 203 if (p) { 204 struct dst_metrics *old_p = (struct dst_metrics *)__DST_METRICS_PTR(old); 205 unsigned long prev, new; 206 207 refcount_set(&p->refcnt, 1); 208 memcpy(p->metrics, old_p->metrics, sizeof(p->metrics)); 209 210 new = (unsigned long) p; 211 prev = cmpxchg(&dst->_metrics, old, new); 212 213 if (prev != old) { 214 kfree(p); 215 p = (struct dst_metrics *)__DST_METRICS_PTR(prev); 216 if (prev & DST_METRICS_READ_ONLY) 217 p = NULL; 218 } else if (prev & DST_METRICS_REFCOUNTED) { 219 if (refcount_dec_and_test(&old_p->refcnt)) 220 kfree(old_p); 221 } 222 } 223 BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0); 224 return (u32 *)p; 225 } 226 EXPORT_SYMBOL(dst_cow_metrics_generic); 227 228 /* Caller asserts that dst_metrics_read_only(dst) is false. */ 229 void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old) 230 { 231 unsigned long prev, new; 232 233 new = ((unsigned long) &dst_default_metrics) | DST_METRICS_READ_ONLY; 234 prev = cmpxchg(&dst->_metrics, old, new); 235 if (prev == old) 236 kfree(__DST_METRICS_PTR(old)); 237 } 238 EXPORT_SYMBOL(__dst_destroy_metrics_generic); 239 240 static struct dst_ops md_dst_ops = { 241 .family = AF_UNSPEC, 242 }; 243 244 static int dst_md_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb) 245 { 246 WARN_ONCE(1, "Attempting to call output on metadata dst\n"); 247 kfree_skb(skb); 248 return 0; 249 } 250 251 static int dst_md_discard(struct sk_buff *skb) 252 { 253 WARN_ONCE(1, "Attempting to call input on metadata dst\n"); 254 kfree_skb(skb); 255 return 0; 256 } 257 258 static void __metadata_dst_init(struct metadata_dst *md_dst, 259 enum metadata_type type, u8 optslen) 260 261 { 262 struct dst_entry *dst; 263 264 dst = &md_dst->dst; 265 dst_init(dst, &md_dst_ops, NULL, 1, DST_OBSOLETE_NONE, 266 DST_METADATA | DST_NOCOUNT); 267 268 dst->input = dst_md_discard; 269 dst->output = dst_md_discard_out; 270 271 memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst)); 272 md_dst->type = type; 273 } 274 275 struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type, 276 gfp_t flags) 277 { 278 struct metadata_dst *md_dst; 279 280 md_dst = kmalloc(sizeof(*md_dst) + optslen, flags); 281 if (!md_dst) 282 return NULL; 283 284 __metadata_dst_init(md_dst, type, optslen); 285 286 return md_dst; 287 } 288 EXPORT_SYMBOL_GPL(metadata_dst_alloc); 289 290 void metadata_dst_free(struct metadata_dst *md_dst) 291 { 292 #ifdef CONFIG_DST_CACHE 293 if (md_dst->type == METADATA_IP_TUNNEL) 294 dst_cache_destroy(&md_dst->u.tun_info.dst_cache); 295 #endif 296 kfree(md_dst); 297 } 298 EXPORT_SYMBOL_GPL(metadata_dst_free); 299 300 struct metadata_dst __percpu * 301 metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags) 302 { 303 int cpu; 304 struct metadata_dst __percpu *md_dst; 305 306 md_dst = __alloc_percpu_gfp(sizeof(struct metadata_dst) + optslen, 307 __alignof__(struct metadata_dst), flags); 308 if (!md_dst) 309 return NULL; 310 311 for_each_possible_cpu(cpu) 312 __metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen); 313 314 return md_dst; 315 } 316 EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu); 317 318 void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst) 319 { 320 #ifdef CONFIG_DST_CACHE 321 int cpu; 322 323 for_each_possible_cpu(cpu) { 324 struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu); 325 326 if (one_md_dst->type == METADATA_IP_TUNNEL) 327 dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache); 328 } 329 #endif 330 free_percpu(md_dst); 331 } 332 EXPORT_SYMBOL_GPL(metadata_dst_free_percpu); 333