net/ipv4/inet_fragment.c

   1 /*
   2  * inet fragments management
   3  *
   4  *              This program is free software; you can redistribute it and/or
   5  *              modify it under the terms of the GNU General Public License
   6  *              as published by the Free Software Foundation; either version
   7  *              2 of the License, or (at your option) any later version.
   8  *
   9  *              Authors:        Pavel Emelyanov <xemul@openvz.org>
  10  *                              Started as consolidation of ipv4/ip_fragment.c,
  11  *                              ipv6/reassembly. and ipv6 nf conntrack reassembly
  12  */
  13
  14 #include <linux/list.h>
  15 #include <linux/spinlock.h>
  16 #include <linux/module.h>
  17 #include <linux/timer.h>
  18 #include <linux/mm.h>
  19 #include <linux/random.h>
  20 #include <linux/skbuff.h>
  21 #include <linux/rtnetlink.h>
  22 #include <linux/slab.h>
  23
  24 #include <net/sock.h>
  25 #include <net/inet_frag.h>
  26 #include <net/inet_ecn.h>
  27
  28 #define INETFRAGS_EVICT_BUCKETS   128
  29 #define INETFRAGS_EVICT_MAX       512
  30
  31 /* don't rebuild inetfrag table with new secret more often than this */
  32 #define INETFRAGS_MIN_REBUILD_INTERVAL (5 * HZ)
  33
  34 /* Given the OR values of all fragments, apply RFC 3168 5.3 requirements
  35  * Value : 0xff if frame should be dropped.
  36  *         0 or INET_ECN_CE value, to be ORed in to final iph->tos field
  37  */
  38 const u8 ip_frag_ecn_table[16] = {
  39         /* at least one fragment had CE, and others ECT_0 or ECT_1 */
  40         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0]                      = INET_ECN_CE,
  41         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1]                      = INET_ECN_CE,
  42         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1]   = INET_ECN_CE,
  43
  44         /* invalid combinations : drop frame */
  45         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff,
  46         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff,
  47         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff,
  48         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
  49         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff,
  50         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff,
  51         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
  52 };
  53 EXPORT_SYMBOL(ip_frag_ecn_table);
  54
  55 static unsigned int
  56 inet_frag_hashfn(const struct inet_frags *f, const struct inet_frag_queue *q)
  57 {
  58         return f->hashfn(q) & (INETFRAGS_HASHSZ - 1);
  59 }
  60
  61 static bool inet_frag_may_rebuild(struct inet_frags *f)
  62 {
  63         return time_after(jiffies,
  64                f->last_rebuild_jiffies + INETFRAGS_MIN_REBUILD_INTERVAL);
  65 }
  66
  67 static void inet_frag_secret_rebuild(struct inet_frags *f)
  68 {
  69         int i;
  70
  71         write_seqlock_bh(&f->rnd_seqlock);
  72
  73         if (!inet_frag_may_rebuild(f))
  74                 goto out;
  75
  76         get_random_bytes(&f->rnd, sizeof(u32));
  77
  78         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
  79                 struct inet_frag_bucket *hb;
  80                 struct inet_frag_queue *q;
  81                 struct hlist_node *n;
  82
  83                 hb = &f->hash[i];
  84                 spin_lock(&hb->chain_lock);
  85
  86                 hlist_for_each_entry_safe(q, n, &hb->chain, list) {
  87                         unsigned int hval = inet_frag_hashfn(f, q);
  88
  89                         if (hval != i) {
  90                                 struct inet_frag_bucket *hb_dest;
  91
  92                                 hlist_del(&q->list);
  93
  94                                 /* Relink to new hash chain. */
  95                                 hb_dest = &f->hash[hval];
  96
  97                                 /* This is the only place where we take
  98                                  * another chain_lock while already holding
  99                                  * one.  As this will not run concurrently,
 100                                  * we cannot deadlock on hb_dest lock below, if its
 101                                  * already locked it will be released soon since
 102                                  * other caller cannot be waiting for hb lock
 103                                  * that we've taken above.
 104                                  */
 105                                 spin_lock_nested(&hb_dest->chain_lock,
 106                                                  SINGLE_DEPTH_NESTING);
 107                                 hlist_add_head(&q->list, &hb_dest->chain);
 108                                 spin_unlock(&hb_dest->chain_lock);
 109                         }
 110                 }
 111                 spin_unlock(&hb->chain_lock);
 112         }
 113
 114         f->rebuild = false;
 115         f->last_rebuild_jiffies = jiffies;
 116 out:
 117         write_sequnlock_bh(&f->rnd_seqlock);
 118 }
 119
 120 static bool inet_fragq_should_evict(const struct inet_frag_queue *q)
 121 {
 122         return q->net->low_thresh == 0 ||
 123                frag_mem_limit(q->net) >= q->net->low_thresh;
 124 }
 125
 126 static unsigned int
 127 inet_evict_bucket(struct inet_frags *f, struct inet_frag_bucket *hb)
 128 {
 129         struct inet_frag_queue *fq;
 130         struct hlist_node *n;
 131         unsigned int evicted = 0;
 132         HLIST_HEAD(expired);
 133
 134         spin_lock(&hb->chain_lock);
 135
 136         hlist_for_each_entry_safe(fq, n, &hb->chain, list) {
 137                 if (!inet_fragq_should_evict(fq))
 138                         continue;
 139
 140                 if (!del_timer(&fq->timer))
 141                         continue;
 142
 143                 hlist_add_head(&fq->list_evictor, &expired);
 144                 ++evicted;
 145         }
 146
 147         spin_unlock(&hb->chain_lock);
 148
 149         hlist_for_each_entry_safe(fq, n, &expired, list_evictor)
 150                 f->frag_expire((unsigned long) fq);
 151
 152         return evicted;
 153 }
 154
 155 static void inet_frag_worker(struct work_struct *work)
 156 {
 157         unsigned int budget = INETFRAGS_EVICT_BUCKETS;
 158         unsigned int i, evicted = 0;
 159         struct inet_frags *f;
 160
 161         f = container_of(work, struct inet_frags, frags_work);
 162
 163         BUILD_BUG_ON(INETFRAGS_EVICT_BUCKETS >= INETFRAGS_HASHSZ);
 164
 165         local_bh_disable();
 166
 167         for (i = ACCESS_ONCE(f->next_bucket); budget; --budget) {
 168                 evicted += inet_evict_bucket(f, &f->hash[i]);
 169                 i = (i + 1) & (INETFRAGS_HASHSZ - 1);
 170                 if (evicted > INETFRAGS_EVICT_MAX)
 171                         break;
 172         }
 173
 174         f->next_bucket = i;
 175
 176         local_bh_enable();
 177
 178         if (f->rebuild && inet_frag_may_rebuild(f))
 179                 inet_frag_secret_rebuild(f);
 180 }
 181
 182 static void inet_frag_schedule_worker(struct inet_frags *f)
 183 {
 184         if (unlikely(!work_pending(&f->frags_work)))
 185                 schedule_work(&f->frags_work);
 186 }
 187
 188 int inet_frags_init(struct inet_frags *f)
 189 {
 190         int i;
 191
 192         INIT_WORK(&f->frags_work, inet_frag_worker);
 193
 194         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
 195                 struct inet_frag_bucket *hb = &f->hash[i];
 196
 197                 spin_lock_init(&hb->chain_lock);
 198                 INIT_HLIST_HEAD(&hb->chain);
 199         }
 200
 201         seqlock_init(&f->rnd_seqlock);
 202         f->last_rebuild_jiffies = 0;
 203         f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0,
 204                                             NULL);
 205         if (!f->frags_cachep)
 206                 return -ENOMEM;
 207
 208         return 0;
 209 }
 210 EXPORT_SYMBOL(inet_frags_init);
 211
 212 void inet_frags_init_net(struct netns_frags *nf)
 213 {
 214         init_frag_mem_limit(nf);
 215 }
 216 EXPORT_SYMBOL(inet_frags_init_net);
 217
 218 void inet_frags_fini(struct inet_frags *f)
 219 {
 220         cancel_work_sync(&f->frags_work);
 221         kmem_cache_destroy(f->frags_cachep);
 222 }
 223 EXPORT_SYMBOL(inet_frags_fini);
 224
 225 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
 226 {
 227         unsigned int seq;
 228         int i;
 229
 230         nf->low_thresh = 0;
 231
 232 evict_again:
 233         local_bh_disable();
 234         seq = read_seqbegin(&f->rnd_seqlock);
 235
 236         for (i = 0; i < INETFRAGS_HASHSZ ; i++)
 237                 inet_evict_bucket(f, &f->hash[i]);
 238
 239         local_bh_enable();
 240         cond_resched();
 241
 242         if (read_seqretry(&f->rnd_seqlock, seq) ||
 243             percpu_counter_sum(&nf->mem))
 244                 goto evict_again;
 245
 246         percpu_counter_destroy(&nf->mem);
 247 }
 248 EXPORT_SYMBOL(inet_frags_exit_net);
 249
 250 static struct inet_frag_bucket *
 251 get_frag_bucket_locked(struct inet_frag_queue *fq, struct inet_frags *f)
 252 __acquires(hb->chain_lock)
 253 {
 254         struct inet_frag_bucket *hb;
 255         unsigned int seq, hash;
 256
 257  restart:
 258         seq = read_seqbegin(&f->rnd_seqlock);
 259
 260         hash = inet_frag_hashfn(f, fq);
 261         hb = &f->hash[hash];
 262
 263         spin_lock(&hb->chain_lock);
 264         if (read_seqretry(&f->rnd_seqlock, seq)) {
 265                 spin_unlock(&hb->chain_lock);
 266                 goto restart;
 267         }
 268
 269         return hb;
 270 }
 271
 272 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
 273 {
 274         struct inet_frag_bucket *hb;
 275
 276         hb = get_frag_bucket_locked(fq, f);
 277         hlist_del(&fq->list);
 278         fq->flags |= INET_FRAG_COMPLETE;
 279         spin_unlock(&hb->chain_lock);
 280 }
 281
 282 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 283 {
 284         if (del_timer(&fq->timer))
 285                 atomic_dec(&fq->refcnt);
 286
 287         if (!(fq->flags & INET_FRAG_COMPLETE)) {
 288                 fq_unlink(fq, f);
 289                 atomic_dec(&fq->refcnt);
 290         }
 291 }
 292 EXPORT_SYMBOL(inet_frag_kill);
 293
 294 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 295                                   struct sk_buff *skb)
 296 {
 297         if (f->skb_free)
 298                 f->skb_free(skb);
 299         kfree_skb(skb);
 300 }
 301
 302 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f)
 303 {
 304         struct sk_buff *fp;
 305         struct netns_frags *nf;
 306         unsigned int sum, sum_truesize = 0;
 307
 308         WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
 309         WARN_ON(del_timer(&q->timer) != 0);
 310
 311         /* Release all fragment data. */
 312         fp = q->fragments;
 313         nf = q->net;
 314         while (fp) {
 315                 struct sk_buff *xp = fp->next;
 316
 317                 sum_truesize += fp->truesize;
 318                 frag_kfree_skb(nf, f, fp);
 319                 fp = xp;
 320         }
 321         sum = sum_truesize + f->qsize;
 322
 323         if (f->destructor)
 324                 f->destructor(q);
 325         kmem_cache_free(f->frags_cachep, q);
 326
 327         sub_frag_mem_limit(nf, sum);
 328 }
 329 EXPORT_SYMBOL(inet_frag_destroy);
 330
 331 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 332                                                 struct inet_frag_queue *qp_in,
 333                                                 struct inet_frags *f,
 334                                                 void *arg)
 335 {
 336         struct inet_frag_bucket *hb = get_frag_bucket_locked(qp_in, f);
 337         struct inet_frag_queue *qp;
 338
 339 #ifdef CONFIG_SMP
 340         /* With SMP race we have to recheck hash table, because
 341          * such entry could have been created on other cpu before
 342          * we acquired hash bucket lock.
 343          */
 344         hlist_for_each_entry(qp, &hb->chain, list) {
 345                 if (qp->net == nf && f->match(qp, arg)) {
 346                         atomic_inc(&qp->refcnt);
 347                         spin_unlock(&hb->chain_lock);
 348                         qp_in->flags |= INET_FRAG_COMPLETE;
 349                         inet_frag_put(qp_in, f);
 350                         return qp;
 351                 }
 352         }
 353 #endif
 354         qp = qp_in;
 355         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 356                 atomic_inc(&qp->refcnt);
 357
 358         atomic_inc(&qp->refcnt);
 359         hlist_add_head(&qp->list, &hb->chain);
 360
 361         spin_unlock(&hb->chain_lock);
 362
 363         return qp;
 364 }
 365
 366 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 367                                                struct inet_frags *f,
 368                                                void *arg)
 369 {
 370         struct inet_frag_queue *q;
 371
 372         if (frag_mem_limit(nf) > nf->high_thresh) {
 373                 inet_frag_schedule_worker(f);
 374                 return NULL;
 375         }
 376
 377         q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC);
 378         if (!q)
 379                 return NULL;
 380
 381         q->net = nf;
 382         f->constructor(q, arg);
 383         add_frag_mem_limit(nf, f->qsize);
 384
 385         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 386         spin_lock_init(&q->lock);
 387         atomic_set(&q->refcnt, 1);
 388
 389         return q;
 390 }
 391
 392 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 393                                                 struct inet_frags *f,
 394                                                 void *arg)
 395 {
 396         struct inet_frag_queue *q;
 397
 398         q = inet_frag_alloc(nf, f, arg);
 399         if (!q)
 400                 return NULL;
 401
 402         return inet_frag_intern(nf, q, f, arg);
 403 }
 404
 405 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 406                                        struct inet_frags *f, void *key,
 407                                        unsigned int hash)
 408 {
 409         struct inet_frag_bucket *hb;
 410         struct inet_frag_queue *q;
 411         int depth = 0;
 412
 413         if (frag_mem_limit(nf) > nf->low_thresh)
 414                 inet_frag_schedule_worker(f);
 415
 416         hash &= (INETFRAGS_HASHSZ - 1);
 417         hb = &f->hash[hash];
 418
 419         spin_lock(&hb->chain_lock);
 420         hlist_for_each_entry(q, &hb->chain, list) {
 421                 if (q->net == nf && f->match(q, key)) {
 422                         atomic_inc(&q->refcnt);
 423                         spin_unlock(&hb->chain_lock);
 424                         return q;
 425                 }
 426                 depth++;
 427         }
 428         spin_unlock(&hb->chain_lock);
 429
 430         if (depth <= INETFRAGS_MAXDEPTH)
 431                 return inet_frag_create(nf, f, key);
 432
 433         if (inet_frag_may_rebuild(f)) {
 434                 if (!f->rebuild)
 435                         f->rebuild = true;
 436                 inet_frag_schedule_worker(f);
 437         }
 438
 439         return ERR_PTR(-ENOBUFS);
 440 }
 441 EXPORT_SYMBOL(inet_frag_find);
 442
 443 void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
 444                                    const char *prefix)
 445 {
 446         static const char msg[] = "inet_frag_find: Fragment hash bucket"
 447                 " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH)
 448                 ". Dropping fragment.\n";
 449
 450         if (PTR_ERR(q) == -ENOBUFS)
 451                 net_dbg_ratelimited("%s%s", prefix, msg);
 452 }
 453 EXPORT_SYMBOL(inet_frag_maybe_warn_overflow);