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