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 evict_again:
 135         spin_lock(&hb->chain_lock);
 136
 137         hlist_for_each_entry_safe(fq, n, &hb->chain, list) {
 138                 if (!inet_fragq_should_evict(fq))
 139                         continue;
 140
 141                 if (!del_timer(&fq->timer)) {
 142                         /* q expiring right now thus increment its refcount so
 143                          * it won't be freed under us and wait until the timer
 144                          * has finished executing then destroy it
 145                          */
 146                         atomic_inc(&fq->refcnt);
 147                         spin_unlock(&hb->chain_lock);
 148                         del_timer_sync(&fq->timer);
 149                         inet_frag_put(fq, f);
 150                         goto evict_again;
 151                 }
 152
 153                 fq->flags |= INET_FRAG_EVICTED;
 154                 hlist_del(&fq->list);
 155                 hlist_add_head(&fq->list, &expired);
 156                 ++evicted;
 157         }
 158
 159         spin_unlock(&hb->chain_lock);
 160
 161         hlist_for_each_entry_safe(fq, n, &expired, list)
 162                 f->frag_expire((unsigned long) fq);
 163
 164         return evicted;
 165 }
 166
 167 static void inet_frag_worker(struct work_struct *work)
 168 {
 169         unsigned int budget = INETFRAGS_EVICT_BUCKETS;
 170         unsigned int i, evicted = 0;
 171         struct inet_frags *f;
 172
 173         f = container_of(work, struct inet_frags, frags_work);
 174
 175         BUILD_BUG_ON(INETFRAGS_EVICT_BUCKETS >= INETFRAGS_HASHSZ);
 176
 177         local_bh_disable();
 178
 179         for (i = ACCESS_ONCE(f->next_bucket); budget; --budget) {
 180                 evicted += inet_evict_bucket(f, &f->hash[i]);
 181                 i = (i + 1) & (INETFRAGS_HASHSZ - 1);
 182                 if (evicted > INETFRAGS_EVICT_MAX)
 183                         break;
 184         }
 185
 186         f->next_bucket = i;
 187
 188         local_bh_enable();
 189
 190         if (f->rebuild && inet_frag_may_rebuild(f))
 191                 inet_frag_secret_rebuild(f);
 192 }
 193
 194 static void inet_frag_schedule_worker(struct inet_frags *f)
 195 {
 196         if (unlikely(!work_pending(&f->frags_work)))
 197                 schedule_work(&f->frags_work);
 198 }
 199
 200 int inet_frags_init(struct inet_frags *f)
 201 {
 202         int i;
 203
 204         INIT_WORK(&f->frags_work, inet_frag_worker);
 205
 206         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
 207                 struct inet_frag_bucket *hb = &f->hash[i];
 208
 209                 spin_lock_init(&hb->chain_lock);
 210                 INIT_HLIST_HEAD(&hb->chain);
 211         }
 212
 213         seqlock_init(&f->rnd_seqlock);
 214         f->last_rebuild_jiffies = 0;
 215         f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0,
 216                                             NULL);
 217         if (!f->frags_cachep)
 218                 return -ENOMEM;
 219
 220         return 0;
 221 }
 222 EXPORT_SYMBOL(inet_frags_init);
 223
 224 void inet_frags_init_net(struct netns_frags *nf)
 225 {
 226         init_frag_mem_limit(nf);
 227 }
 228 EXPORT_SYMBOL(inet_frags_init_net);
 229
 230 void inet_frags_fini(struct inet_frags *f)
 231 {
 232         cancel_work_sync(&f->frags_work);
 233         kmem_cache_destroy(f->frags_cachep);
 234 }
 235 EXPORT_SYMBOL(inet_frags_fini);
 236
 237 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
 238 {
 239         unsigned int seq;
 240         int i;
 241
 242         nf->low_thresh = 0;
 243         local_bh_disable();
 244
 245 evict_again:
 246         seq = read_seqbegin(&f->rnd_seqlock);
 247
 248         for (i = 0; i < INETFRAGS_HASHSZ ; i++)
 249                 inet_evict_bucket(f, &f->hash[i]);
 250
 251         if (read_seqretry(&f->rnd_seqlock, seq))
 252                 goto evict_again;
 253
 254         local_bh_enable();
 255
 256         percpu_counter_destroy(&nf->mem);
 257 }
 258 EXPORT_SYMBOL(inet_frags_exit_net);
 259
 260 static struct inet_frag_bucket *
 261 get_frag_bucket_locked(struct inet_frag_queue *fq, struct inet_frags *f)
 262 __acquires(hb->chain_lock)
 263 {
 264         struct inet_frag_bucket *hb;
 265         unsigned int seq, hash;
 266
 267  restart:
 268         seq = read_seqbegin(&f->rnd_seqlock);
 269
 270         hash = inet_frag_hashfn(f, fq);
 271         hb = &f->hash[hash];
 272
 273         spin_lock(&hb->chain_lock);
 274         if (read_seqretry(&f->rnd_seqlock, seq)) {
 275                 spin_unlock(&hb->chain_lock);
 276                 goto restart;
 277         }
 278
 279         return hb;
 280 }
 281
 282 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
 283 {
 284         struct inet_frag_bucket *hb;
 285
 286         hb = get_frag_bucket_locked(fq, f);
 287         if (!(fq->flags & INET_FRAG_EVICTED))
 288                 hlist_del(&fq->list);
 289         spin_unlock(&hb->chain_lock);
 290 }
 291
 292 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 293 {
 294         if (del_timer(&fq->timer))
 295                 atomic_dec(&fq->refcnt);
 296
 297         if (!(fq->flags & INET_FRAG_COMPLETE)) {
 298                 fq_unlink(fq, f);
 299                 atomic_dec(&fq->refcnt);
 300                 fq->flags |= INET_FRAG_COMPLETE;
 301         }
 302 }
 303 EXPORT_SYMBOL(inet_frag_kill);
 304
 305 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 306                                   struct sk_buff *skb)
 307 {
 308         if (f->skb_free)
 309                 f->skb_free(skb);
 310         kfree_skb(skb);
 311 }
 312
 313 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f)
 314 {
 315         struct sk_buff *fp;
 316         struct netns_frags *nf;
 317         unsigned int sum, sum_truesize = 0;
 318
 319         WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
 320         WARN_ON(del_timer(&q->timer) != 0);
 321
 322         /* Release all fragment data. */
 323         fp = q->fragments;
 324         nf = q->net;
 325         while (fp) {
 326                 struct sk_buff *xp = fp->next;
 327
 328                 sum_truesize += fp->truesize;
 329                 frag_kfree_skb(nf, f, fp);
 330                 fp = xp;
 331         }
 332         sum = sum_truesize + f->qsize;
 333         sub_frag_mem_limit(q, sum);
 334
 335         if (f->destructor)
 336                 f->destructor(q);
 337         kmem_cache_free(f->frags_cachep, q);
 338 }
 339 EXPORT_SYMBOL(inet_frag_destroy);
 340
 341 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 342                                                 struct inet_frag_queue *qp_in,
 343                                                 struct inet_frags *f,
 344                                                 void *arg)
 345 {
 346         struct inet_frag_bucket *hb = get_frag_bucket_locked(qp_in, f);
 347         struct inet_frag_queue *qp;
 348
 349 #ifdef CONFIG_SMP
 350         /* With SMP race we have to recheck hash table, because
 351          * such entry could have been created on other cpu before
 352          * we acquired hash bucket lock.
 353          */
 354         hlist_for_each_entry(qp, &hb->chain, list) {
 355                 if (qp->net == nf && f->match(qp, arg)) {
 356                         atomic_inc(&qp->refcnt);
 357                         spin_unlock(&hb->chain_lock);
 358                         qp_in->flags |= INET_FRAG_COMPLETE;
 359                         inet_frag_put(qp_in, f);
 360                         return qp;
 361                 }
 362         }
 363 #endif
 364         qp = qp_in;
 365         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 366                 atomic_inc(&qp->refcnt);
 367
 368         atomic_inc(&qp->refcnt);
 369         hlist_add_head(&qp->list, &hb->chain);
 370
 371         spin_unlock(&hb->chain_lock);
 372
 373         return qp;
 374 }
 375
 376 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 377                                                struct inet_frags *f,
 378                                                void *arg)
 379 {
 380         struct inet_frag_queue *q;
 381
 382         if (frag_mem_limit(nf) > nf->high_thresh) {
 383                 inet_frag_schedule_worker(f);
 384                 return NULL;
 385         }
 386
 387         q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC);
 388         if (q == NULL)
 389                 return NULL;
 390
 391         q->net = nf;
 392         f->constructor(q, arg);
 393         add_frag_mem_limit(q, f->qsize);
 394
 395         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 396         spin_lock_init(&q->lock);
 397         atomic_set(&q->refcnt, 1);
 398
 399         return q;
 400 }
 401
 402 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 403                                                 struct inet_frags *f,
 404                                                 void *arg)
 405 {
 406         struct inet_frag_queue *q;
 407
 408         q = inet_frag_alloc(nf, f, arg);
 409         if (q == NULL)
 410                 return NULL;
 411
 412         return inet_frag_intern(nf, q, f, arg);
 413 }
 414
 415 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 416                                        struct inet_frags *f, void *key,
 417                                        unsigned int hash)
 418 {
 419         struct inet_frag_bucket *hb;
 420         struct inet_frag_queue *q;
 421         int depth = 0;
 422
 423         if (frag_mem_limit(nf) > nf->low_thresh)
 424                 inet_frag_schedule_worker(f);
 425
 426         hash &= (INETFRAGS_HASHSZ - 1);
 427         hb = &f->hash[hash];
 428
 429         spin_lock(&hb->chain_lock);
 430         hlist_for_each_entry(q, &hb->chain, list) {
 431                 if (q->net == nf && f->match(q, key)) {
 432                         atomic_inc(&q->refcnt);
 433                         spin_unlock(&hb->chain_lock);
 434                         return q;
 435                 }
 436                 depth++;
 437         }
 438         spin_unlock(&hb->chain_lock);
 439
 440         if (depth <= INETFRAGS_MAXDEPTH)
 441                 return inet_frag_create(nf, f, key);
 442
 443         if (inet_frag_may_rebuild(f)) {
 444                 if (!f->rebuild)
 445                         f->rebuild = true;
 446                 inet_frag_schedule_worker(f);
 447         }
 448
 449         return ERR_PTR(-ENOBUFS);
 450 }
 451 EXPORT_SYMBOL(inet_frag_find);
 452
 453 void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
 454                                    const char *prefix)
 455 {
 456         static const char msg[] = "inet_frag_find: Fragment hash bucket"
 457                 " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH)
 458                 ". Dropping fragment.\n";
 459
 460         if (PTR_ERR(q) == -ENOBUFS)
 461                 LIMIT_NETDEBUG(KERN_WARNING "%s%s", prefix, msg);
 462 }
 463 EXPORT_SYMBOL(inet_frag_maybe_warn_overflow);