net/core/dst.c

   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         dst->obsolete = DST_OBSOLETE_DEAD;
 149         if (dst->ops->ifdown)
 150                 dst->ops->ifdown(dst, dev);
 151         dst->input = dst_discard;
 152         dst->output = dst_discard_out;
 153         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                 dst_count_dec(dst);
 169                 call_rcu_hurry(&dst->rcu_head, dst_destroy_rcu);
 170         }
 171 }
 172 EXPORT_SYMBOL(dst_release);
 173
 174 void dst_release_immediate(struct dst_entry *dst)
 175 {
 176         if (dst && rcuref_put(&dst->__rcuref)) {
 177                 dst_count_dec(dst);
 178                 dst_destroy(dst);
 179         }
 180 }
 181 EXPORT_SYMBOL(dst_release_immediate);
 182
 183 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old)
 184 {
 185         struct dst_metrics *p = kmalloc(sizeof(*p), GFP_ATOMIC);
 186
 187         if (p) {
 188                 struct dst_metrics *old_p = (struct dst_metrics *)__DST_METRICS_PTR(old);
 189                 unsigned long prev, new;
 190
 191                 refcount_set(&p->refcnt, 1);
 192                 memcpy(p->metrics, old_p->metrics, sizeof(p->metrics));
 193
 194                 new = (unsigned long) p;
 195                 prev = cmpxchg(&dst->_metrics, old, new);
 196
 197                 if (prev != old) {
 198                         kfree(p);
 199                         p = (struct dst_metrics *)__DST_METRICS_PTR(prev);
 200                         if (prev & DST_METRICS_READ_ONLY)
 201                                 p = NULL;
 202                 } else if (prev & DST_METRICS_REFCOUNTED) {
 203                         if (refcount_dec_and_test(&old_p->refcnt))
 204                                 kfree(old_p);
 205                 }
 206         }
 207         BUILD_BUG_ON(offsetof(struct dst_metrics, metrics) != 0);
 208         return (u32 *)p;
 209 }
 210 EXPORT_SYMBOL(dst_cow_metrics_generic);
 211
 212 /* Caller asserts that dst_metrics_read_only(dst) is false.  */
 213 void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old)
 214 {
 215         unsigned long prev, new;
 216
 217         new = ((unsigned long) &dst_default_metrics) | DST_METRICS_READ_ONLY;
 218         prev = cmpxchg(&dst->_metrics, old, new);
 219         if (prev == old)
 220                 kfree(__DST_METRICS_PTR(old));
 221 }
 222 EXPORT_SYMBOL(__dst_destroy_metrics_generic);
 223
 224 struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie)
 225 {
 226         return NULL;
 227 }
 228
 229 u32 *dst_blackhole_cow_metrics(struct dst_entry *dst, unsigned long old)
 230 {
 231         return NULL;
 232 }
 233
 234 struct neighbour *dst_blackhole_neigh_lookup(const struct dst_entry *dst,
 235                                              struct sk_buff *skb,
 236                                              const void *daddr)
 237 {
 238         return NULL;
 239 }
 240
 241 void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
 242                                struct sk_buff *skb, u32 mtu,
 243                                bool confirm_neigh)
 244 {
 245 }
 246 EXPORT_SYMBOL_GPL(dst_blackhole_update_pmtu);
 247
 248 void dst_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
 249                             struct sk_buff *skb)
 250 {
 251 }
 252 EXPORT_SYMBOL_GPL(dst_blackhole_redirect);
 253
 254 unsigned int dst_blackhole_mtu(const struct dst_entry *dst)
 255 {
 256         unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
 257
 258         return mtu ? : dst->dev->mtu;
 259 }
 260 EXPORT_SYMBOL_GPL(dst_blackhole_mtu);
 261
 262 static struct dst_ops dst_blackhole_ops = {
 263         .family         = AF_UNSPEC,
 264         .neigh_lookup   = dst_blackhole_neigh_lookup,
 265         .check          = dst_blackhole_check,
 266         .cow_metrics    = dst_blackhole_cow_metrics,
 267         .update_pmtu    = dst_blackhole_update_pmtu,
 268         .redirect       = dst_blackhole_redirect,
 269         .mtu            = dst_blackhole_mtu,
 270 };
 271
 272 static void __metadata_dst_init(struct metadata_dst *md_dst,
 273                                 enum metadata_type type, u8 optslen)
 274 {
 275         struct dst_entry *dst;
 276
 277         dst = &md_dst->dst;
 278         dst_init(dst, &dst_blackhole_ops, NULL, DST_OBSOLETE_NONE,
 279                  DST_METADATA | DST_NOCOUNT);
 280         memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst));
 281         md_dst->type = type;
 282 }
 283
 284 struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type,
 285                                         gfp_t flags)
 286 {
 287         struct metadata_dst *md_dst;
 288
 289         md_dst = kmalloc(sizeof(*md_dst) + optslen, flags);
 290         if (!md_dst)
 291                 return NULL;
 292
 293         __metadata_dst_init(md_dst, type, optslen);
 294
 295         return md_dst;
 296 }
 297 EXPORT_SYMBOL_GPL(metadata_dst_alloc);
 298
 299 void metadata_dst_free(struct metadata_dst *md_dst)
 300 {
 301 #ifdef CONFIG_DST_CACHE
 302         if (md_dst->type == METADATA_IP_TUNNEL)
 303                 dst_cache_destroy(&md_dst->u.tun_info.dst_cache);
 304 #endif
 305         if (md_dst->type == METADATA_XFRM)
 306                 dst_release(md_dst->u.xfrm_info.dst_orig);
 307         kfree(md_dst);
 308 }
 309 EXPORT_SYMBOL_GPL(metadata_dst_free);
 310
 311 struct metadata_dst __percpu *
 312 metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags)
 313 {
 314         int cpu;
 315         struct metadata_dst __percpu *md_dst;
 316
 317         md_dst = __alloc_percpu_gfp(sizeof(struct metadata_dst) + optslen,
 318                                     __alignof__(struct metadata_dst), flags);
 319         if (!md_dst)
 320                 return NULL;
 321
 322         for_each_possible_cpu(cpu)
 323                 __metadata_dst_init(per_cpu_ptr(md_dst, cpu), type, optslen);
 324
 325         return md_dst;
 326 }
 327 EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);
 328
 329 void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst)
 330 {
 331         int cpu;
 332
 333         for_each_possible_cpu(cpu) {
 334                 struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu);
 335
 336 #ifdef CONFIG_DST_CACHE
 337                 if (one_md_dst->type == METADATA_IP_TUNNEL)
 338                         dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache);
 339 #endif
 340                 if (one_md_dst->type == METADATA_XFRM)
 341                         dst_release(one_md_dst->u.xfrm_info.dst_orig);
 342         }
 343         free_percpu(md_dst);
 344 }
 345 EXPORT_SYMBOL_GPL(metadata_dst_free_percpu);