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 = READ_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_fini(struct inet_frags *f)
 213 {
 214         cancel_work_sync(&f->frags_work);
 215         kmem_cache_destroy(f->frags_cachep);
 216 }
 217 EXPORT_SYMBOL(inet_frags_fini);
 218
 219 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
 220 {
 221         unsigned int seq;
 222         int i;
 223
 224         nf->low_thresh = 0;
 225
 226 evict_again:
 227         local_bh_disable();
 228         seq = read_seqbegin(&f->rnd_seqlock);
 229
 230         for (i = 0; i < INETFRAGS_HASHSZ ; i++)
 231                 inet_evict_bucket(f, &f->hash[i]);
 232
 233         local_bh_enable();
 234         cond_resched();
 235
 236         if (read_seqretry(&f->rnd_seqlock, seq) ||
 237             sum_frag_mem_limit(nf))
 238                 goto evict_again;
 239 }
 240 EXPORT_SYMBOL(inet_frags_exit_net);
 241
 242 static struct inet_frag_bucket *
 243 get_frag_bucket_locked(struct inet_frag_queue *fq, struct inet_frags *f)
 244 __acquires(hb->chain_lock)
 245 {
 246         struct inet_frag_bucket *hb;
 247         unsigned int seq, hash;
 248
 249  restart:
 250         seq = read_seqbegin(&f->rnd_seqlock);
 251
 252         hash = inet_frag_hashfn(f, fq);
 253         hb = &f->hash[hash];
 254
 255         spin_lock(&hb->chain_lock);
 256         if (read_seqretry(&f->rnd_seqlock, seq)) {
 257                 spin_unlock(&hb->chain_lock);
 258                 goto restart;
 259         }
 260
 261         return hb;
 262 }
 263
 264 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
 265 {
 266         struct inet_frag_bucket *hb;
 267
 268         hb = get_frag_bucket_locked(fq, f);
 269         hlist_del(&fq->list);
 270         fq->flags |= INET_FRAG_COMPLETE;
 271         spin_unlock(&hb->chain_lock);
 272 }
 273
 274 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 275 {
 276         if (del_timer(&fq->timer))
 277                 refcount_dec(&fq->refcnt);
 278
 279         if (!(fq->flags & INET_FRAG_COMPLETE)) {
 280                 fq_unlink(fq, f);
 281                 refcount_dec(&fq->refcnt);
 282         }
 283 }
 284 EXPORT_SYMBOL(inet_frag_kill);
 285
 286 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f)
 287 {
 288         struct sk_buff *fp;
 289         struct netns_frags *nf;
 290         unsigned int sum, sum_truesize = 0;
 291
 292         WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
 293         WARN_ON(del_timer(&q->timer) != 0);
 294
 295         /* Release all fragment data. */
 296         fp = q->fragments;
 297         nf = q->net;
 298         while (fp) {
 299                 struct sk_buff *xp = fp->next;
 300
 301                 sum_truesize += fp->truesize;
 302                 kfree_skb(fp);
 303                 fp = xp;
 304         }
 305         sum = sum_truesize + f->qsize;
 306
 307         if (f->destructor)
 308                 f->destructor(q);
 309         kmem_cache_free(f->frags_cachep, q);
 310
 311         sub_frag_mem_limit(nf, sum);
 312 }
 313 EXPORT_SYMBOL(inet_frag_destroy);
 314
 315 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 316                                                 struct inet_frag_queue *qp_in,
 317                                                 struct inet_frags *f,
 318                                                 void *arg)
 319 {
 320         struct inet_frag_bucket *hb = get_frag_bucket_locked(qp_in, f);
 321         struct inet_frag_queue *qp;
 322
 323 #ifdef CONFIG_SMP
 324         /* With SMP race we have to recheck hash table, because
 325          * such entry could have been created on other cpu before
 326          * we acquired hash bucket lock.
 327          */
 328         hlist_for_each_entry(qp, &hb->chain, list) {
 329                 if (qp->net == nf && f->match(qp, arg)) {
 330                         refcount_inc(&qp->refcnt);
 331                         spin_unlock(&hb->chain_lock);
 332                         qp_in->flags |= INET_FRAG_COMPLETE;
 333                         inet_frag_put(qp_in, f);
 334                         return qp;
 335                 }
 336         }
 337 #endif
 338         qp = qp_in;
 339         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 340                 refcount_inc(&qp->refcnt);
 341
 342         refcount_inc(&qp->refcnt);
 343         hlist_add_head(&qp->list, &hb->chain);
 344
 345         spin_unlock(&hb->chain_lock);
 346
 347         return qp;
 348 }
 349
 350 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 351                                                struct inet_frags *f,
 352                                                void *arg)
 353 {
 354         struct inet_frag_queue *q;
 355
 356         if (!nf->high_thresh || frag_mem_limit(nf) > nf->high_thresh) {
 357                 inet_frag_schedule_worker(f);
 358                 return NULL;
 359         }
 360
 361         q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC);
 362         if (!q)
 363                 return NULL;
 364
 365         q->net = nf;
 366         f->constructor(q, arg);
 367         add_frag_mem_limit(nf, f->qsize);
 368
 369         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 370         spin_lock_init(&q->lock);
 371         refcount_set(&q->refcnt, 1);
 372
 373         return q;
 374 }
 375
 376 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 377                                                 struct inet_frags *f,
 378                                                 void *arg)
 379 {
 380         struct inet_frag_queue *q;
 381
 382         q = inet_frag_alloc(nf, f, arg);
 383         if (!q)
 384                 return NULL;
 385
 386         return inet_frag_intern(nf, q, f, arg);
 387 }
 388
 389 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 390                                        struct inet_frags *f, void *key,
 391                                        unsigned int hash)
 392 {
 393         struct inet_frag_bucket *hb;
 394         struct inet_frag_queue *q;
 395         int depth = 0;
 396
 397         if (frag_mem_limit(nf) > nf->low_thresh)
 398                 inet_frag_schedule_worker(f);
 399
 400         hash &= (INETFRAGS_HASHSZ - 1);
 401         hb = &f->hash[hash];
 402
 403         spin_lock(&hb->chain_lock);
 404         hlist_for_each_entry(q, &hb->chain, list) {
 405                 if (q->net == nf && f->match(q, key)) {
 406                         refcount_inc(&q->refcnt);
 407                         spin_unlock(&hb->chain_lock);
 408                         return q;
 409                 }
 410                 depth++;
 411         }
 412         spin_unlock(&hb->chain_lock);
 413
 414         if (depth <= INETFRAGS_MAXDEPTH)
 415                 return inet_frag_create(nf, f, key);
 416
 417         if (inet_frag_may_rebuild(f)) {
 418                 if (!f->rebuild)
 419                         f->rebuild = true;
 420                 inet_frag_schedule_worker(f);
 421         }
 422
 423         return ERR_PTR(-ENOBUFS);
 424 }
 425 EXPORT_SYMBOL(inet_frag_find);
 426
 427 void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
 428                                    const char *prefix)
 429 {
 430         static const char msg[] = "inet_frag_find: Fragment hash bucket"
 431                 " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH)
 432                 ". Dropping fragment.\n";
 433
 434         if (PTR_ERR(q) == -ENOBUFS)
 435                 net_dbg_ratelimited("%s%s", prefix, msg);
 436 }
 437 EXPORT_SYMBOL(inet_frag_maybe_warn_overflow);