kernel/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_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             percpu_counter_sum(&nf->mem))
 238                 goto evict_again;
 239
 240         percpu_counter_destroy(&nf->mem);
 241 }
 242 EXPORT_SYMBOL(inet_frags_exit_net);
 243
 244 static struct inet_frag_bucket *
 245 get_frag_bucket_locked(struct inet_frag_queue *fq, struct inet_frags *f)
 246 __acquires(hb->chain_lock)
 247 {
 248         struct inet_frag_bucket *hb;
 249         unsigned int seq, hash;
 250
 251  restart:
 252         seq = read_seqbegin(&f->rnd_seqlock);
 253
 254         hash = inet_frag_hashfn(f, fq);
 255         hb = &f->hash[hash];
 256
 257         spin_lock(&hb->chain_lock);
 258         if (read_seqretry(&f->rnd_seqlock, seq)) {
 259                 spin_unlock(&hb->chain_lock);
 260                 goto restart;
 261         }
 262
 263         return hb;
 264 }
 265
 266 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
 267 {
 268         struct inet_frag_bucket *hb;
 269
 270         hb = get_frag_bucket_locked(fq, f);
 271         hlist_del(&fq->list);
 272         fq->flags |= INET_FRAG_COMPLETE;
 273         spin_unlock(&hb->chain_lock);
 274 }
 275
 276 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 277 {
 278         if (del_timer(&fq->timer))
 279                 atomic_dec(&fq->refcnt);
 280
 281         if (!(fq->flags & INET_FRAG_COMPLETE)) {
 282                 fq_unlink(fq, f);
 283                 atomic_dec(&fq->refcnt);
 284         }
 285 }
 286 EXPORT_SYMBOL(inet_frag_kill);
 287
 288 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 289                                   struct sk_buff *skb)
 290 {
 291         if (f->skb_free)
 292                 f->skb_free(skb);
 293         kfree_skb(skb);
 294 }
 295
 296 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f)
 297 {
 298         struct sk_buff *fp;
 299         struct netns_frags *nf;
 300         unsigned int sum, sum_truesize = 0;
 301
 302         WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
 303         WARN_ON(del_timer(&q->timer) != 0);
 304
 305         /* Release all fragment data. */
 306         fp = q->fragments;
 307         nf = q->net;
 308         while (fp) {
 309                 struct sk_buff *xp = fp->next;
 310
 311                 sum_truesize += fp->truesize;
 312                 frag_kfree_skb(nf, f, fp);
 313                 fp = xp;
 314         }
 315         sum = sum_truesize + f->qsize;
 316
 317         if (f->destructor)
 318                 f->destructor(q);
 319         kmem_cache_free(f->frags_cachep, q);
 320
 321         sub_frag_mem_limit(nf, sum);
 322 }
 323 EXPORT_SYMBOL(inet_frag_destroy);
 324
 325 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 326                                                 struct inet_frag_queue *qp_in,
 327                                                 struct inet_frags *f,
 328                                                 void *arg)
 329 {
 330         struct inet_frag_bucket *hb = get_frag_bucket_locked(qp_in, f);
 331         struct inet_frag_queue *qp;
 332
 333 #ifdef CONFIG_SMP
 334         /* With SMP race we have to recheck hash table, because
 335          * such entry could have been created on other cpu before
 336          * we acquired hash bucket lock.
 337          */
 338         hlist_for_each_entry(qp, &hb->chain, list) {
 339                 if (qp->net == nf && f->match(qp, arg)) {
 340                         atomic_inc(&qp->refcnt);
 341                         spin_unlock(&hb->chain_lock);
 342                         qp_in->flags |= INET_FRAG_COMPLETE;
 343                         inet_frag_put(qp_in, f);
 344                         return qp;
 345                 }
 346         }
 347 #endif
 348         qp = qp_in;
 349         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 350                 atomic_inc(&qp->refcnt);
 351
 352         atomic_inc(&qp->refcnt);
 353         hlist_add_head(&qp->list, &hb->chain);
 354
 355         spin_unlock(&hb->chain_lock);
 356
 357         return qp;
 358 }
 359
 360 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 361                                                struct inet_frags *f,
 362                                                void *arg)
 363 {
 364         struct inet_frag_queue *q;
 365
 366         if (frag_mem_limit(nf) > nf->high_thresh) {
 367                 inet_frag_schedule_worker(f);
 368                 return NULL;
 369         }
 370
 371         q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC);
 372         if (!q)
 373                 return NULL;
 374
 375         q->net = nf;
 376         f->constructor(q, arg);
 377         add_frag_mem_limit(nf, f->qsize);
 378
 379         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 380         spin_lock_init(&q->lock);
 381         atomic_set(&q->refcnt, 1);
 382
 383         return q;
 384 }
 385
 386 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 387                                                 struct inet_frags *f,
 388                                                 void *arg)
 389 {
 390         struct inet_frag_queue *q;
 391
 392         q = inet_frag_alloc(nf, f, arg);
 393         if (!q)
 394                 return NULL;
 395
 396         return inet_frag_intern(nf, q, f, arg);
 397 }
 398
 399 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 400                                        struct inet_frags *f, void *key,
 401                                        unsigned int hash)
 402 {
 403         struct inet_frag_bucket *hb;
 404         struct inet_frag_queue *q;
 405         int depth = 0;
 406
 407         if (frag_mem_limit(nf) > nf->low_thresh)
 408                 inet_frag_schedule_worker(f);
 409
 410         hash &= (INETFRAGS_HASHSZ - 1);
 411         hb = &f->hash[hash];
 412
 413         spin_lock(&hb->chain_lock);
 414         hlist_for_each_entry(q, &hb->chain, list) {
 415                 if (q->net == nf && f->match(q, key)) {
 416                         atomic_inc(&q->refcnt);
 417                         spin_unlock(&hb->chain_lock);
 418                         return q;
 419                 }
 420                 depth++;
 421         }
 422         spin_unlock(&hb->chain_lock);
 423
 424         if (depth <= INETFRAGS_MAXDEPTH)
 425                 return inet_frag_create(nf, f, key);
 426
 427         if (inet_frag_may_rebuild(f)) {
 428                 if (!f->rebuild)
 429                         f->rebuild = true;
 430                 inet_frag_schedule_worker(f);
 431         }
 432
 433         return ERR_PTR(-ENOBUFS);
 434 }
 435 EXPORT_SYMBOL(inet_frag_find);
 436
 437 void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
 438                                    const char *prefix)
 439 {
 440         static const char msg[] = "inet_frag_find: Fragment hash bucket"
 441                 " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH)
 442                 ". Dropping fragment.\n";
 443
 444         if (PTR_ERR(q) == -ENOBUFS)
 445                 net_dbg_ratelimited("%s%s", prefix, msg);
 446 }
 447 EXPORT_SYMBOL(inet_frag_maybe_warn_overflow);