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         /* Per bucket lock NOT needed here, due to write lock protection */
  72         write_lock_bh(&f->lock);
  73
  74         if (!inet_frag_may_rebuild(f))
  75                 goto out;
  76
  77         get_random_bytes(&f->rnd, sizeof(u32));
  78
  79         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
  80                 struct inet_frag_bucket *hb;
  81                 struct inet_frag_queue *q;
  82                 struct hlist_node *n;
  83
  84                 hb = &f->hash[i];
  85                 hlist_for_each_entry_safe(q, n, &hb->chain, list) {
  86                         unsigned int hval = inet_frag_hashfn(f, q);
  87
  88                         if (hval != i) {
  89                                 struct inet_frag_bucket *hb_dest;
  90
  91                                 hlist_del(&q->list);
  92
  93                                 /* Relink to new hash chain. */
  94                                 hb_dest = &f->hash[hval];
  95                                 hlist_add_head(&q->list, &hb_dest->chain);
  96                         }
  97                 }
  98         }
  99
 100         f->rebuild = false;
 101         f->last_rebuild_jiffies = jiffies;
 102 out:
 103         write_unlock_bh(&f->lock);
 104 }
 105
 106 static bool inet_fragq_should_evict(const struct inet_frag_queue *q)
 107 {
 108         return q->net->low_thresh == 0 ||
 109                frag_mem_limit(q->net) >= q->net->low_thresh;
 110 }
 111
 112 static unsigned int
 113 inet_evict_bucket(struct inet_frags *f, struct inet_frag_bucket *hb)
 114 {
 115         struct inet_frag_queue *fq;
 116         struct hlist_node *n;
 117         unsigned int evicted = 0;
 118         HLIST_HEAD(expired);
 119
 120 evict_again:
 121         spin_lock(&hb->chain_lock);
 122
 123         hlist_for_each_entry_safe(fq, n, &hb->chain, list) {
 124                 if (!inet_fragq_should_evict(fq))
 125                         continue;
 126
 127                 if (!del_timer(&fq->timer)) {
 128                         /* q expiring right now thus increment its refcount so
 129                          * it won't be freed under us and wait until the timer
 130                          * has finished executing then destroy it
 131                          */
 132                         atomic_inc(&fq->refcnt);
 133                         spin_unlock(&hb->chain_lock);
 134                         del_timer_sync(&fq->timer);
 135                         WARN_ON(atomic_read(&fq->refcnt) != 1);
 136                         inet_frag_put(fq, f);
 137                         goto evict_again;
 138                 }
 139
 140                 /* suppress xmit of (icmp) error packet */
 141                 fq->last_in &= ~INET_FRAG_FIRST_IN;
 142                 fq->last_in |= INET_FRAG_EVICTED;
 143                 hlist_del(&fq->list);
 144                 hlist_add_head(&fq->list, &expired);
 145                 ++evicted;
 146         }
 147
 148         spin_unlock(&hb->chain_lock);
 149
 150         hlist_for_each_entry_safe(fq, n, &expired, list)
 151                 f->frag_expire((unsigned long) fq);
 152
 153         return evicted;
 154 }
 155
 156 static void inet_frag_worker(struct work_struct *work)
 157 {
 158         unsigned int budget = INETFRAGS_EVICT_BUCKETS;
 159         unsigned int i, evicted = 0;
 160         struct inet_frags *f;
 161
 162         f = container_of(work, struct inet_frags, frags_work);
 163
 164         BUILD_BUG_ON(INETFRAGS_EVICT_BUCKETS >= INETFRAGS_HASHSZ);
 165
 166         read_lock_bh(&f->lock);
 167
 168         for (i = ACCESS_ONCE(f->next_bucket); budget; --budget) {
 169                 evicted += inet_evict_bucket(f, &f->hash[i]);
 170                 i = (i + 1) & (INETFRAGS_HASHSZ - 1);
 171                 if (evicted > INETFRAGS_EVICT_MAX)
 172                         break;
 173         }
 174
 175         f->next_bucket = i;
 176
 177         read_unlock_bh(&f->lock);
 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 void 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         rwlock_init(&f->lock);
 201         f->last_rebuild_jiffies = 0;
 202 }
 203 EXPORT_SYMBOL(inet_frags_init);
 204
 205 void inet_frags_init_net(struct netns_frags *nf)
 206 {
 207         init_frag_mem_limit(nf);
 208 }
 209 EXPORT_SYMBOL(inet_frags_init_net);
 210
 211 void inet_frags_fini(struct inet_frags *f)
 212 {
 213         cancel_work_sync(&f->frags_work);
 214 }
 215 EXPORT_SYMBOL(inet_frags_fini);
 216
 217 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
 218 {
 219         int i;
 220
 221         nf->low_thresh = 0;
 222
 223         read_lock_bh(&f->lock);
 224
 225         for (i = 0; i < INETFRAGS_HASHSZ ; i++)
 226                 inet_evict_bucket(f, &f->hash[i]);
 227
 228         read_unlock_bh(&f->lock);
 229
 230         percpu_counter_destroy(&nf->mem);
 231 }
 232 EXPORT_SYMBOL(inet_frags_exit_net);
 233
 234 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
 235 {
 236         struct inet_frag_bucket *hb;
 237         unsigned int hash;
 238
 239         read_lock(&f->lock);
 240         hash = inet_frag_hashfn(f, fq);
 241         hb = &f->hash[hash];
 242
 243         spin_lock(&hb->chain_lock);
 244         hlist_del(&fq->list);
 245         spin_unlock(&hb->chain_lock);
 246
 247         read_unlock(&f->lock);
 248 }
 249
 250 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 251 {
 252         if (del_timer(&fq->timer))
 253                 atomic_dec(&fq->refcnt);
 254
 255         if (!(fq->last_in & INET_FRAG_COMPLETE)) {
 256                 fq_unlink(fq, f);
 257                 atomic_dec(&fq->refcnt);
 258                 fq->last_in |= INET_FRAG_COMPLETE;
 259         }
 260 }
 261 EXPORT_SYMBOL(inet_frag_kill);
 262
 263 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 264                 struct sk_buff *skb)
 265 {
 266         if (f->skb_free)
 267                 f->skb_free(skb);
 268         kfree_skb(skb);
 269 }
 270
 271 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f)
 272 {
 273         struct sk_buff *fp;
 274         struct netns_frags *nf;
 275         unsigned int sum, sum_truesize = 0;
 276
 277         WARN_ON(!(q->last_in & INET_FRAG_COMPLETE));
 278         WARN_ON(del_timer(&q->timer) != 0);
 279
 280         /* Release all fragment data. */
 281         fp = q->fragments;
 282         nf = q->net;
 283         while (fp) {
 284                 struct sk_buff *xp = fp->next;
 285
 286                 sum_truesize += fp->truesize;
 287                 frag_kfree_skb(nf, f, fp);
 288                 fp = xp;
 289         }
 290         sum = sum_truesize + f->qsize;
 291         sub_frag_mem_limit(q, sum);
 292
 293         if (f->destructor)
 294                 f->destructor(q);
 295         kfree(q);
 296 }
 297 EXPORT_SYMBOL(inet_frag_destroy);
 298
 299 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 300                 struct inet_frag_queue *qp_in, struct inet_frags *f,
 301                 void *arg)
 302 {
 303         struct inet_frag_bucket *hb;
 304         struct inet_frag_queue *qp;
 305         unsigned int hash;
 306
 307         read_lock(&f->lock); /* Protects against hash rebuild */
 308         /*
 309          * While we stayed w/o the lock other CPU could update
 310          * the rnd seed, so we need to re-calculate the hash
 311          * chain. Fortunatelly the qp_in can be used to get one.
 312          */
 313         hash = inet_frag_hashfn(f, qp_in);
 314         hb = &f->hash[hash];
 315         spin_lock(&hb->chain_lock);
 316
 317 #ifdef CONFIG_SMP
 318         /* With SMP race we have to recheck hash table, because
 319          * such entry could be created on other cpu, while we
 320          * released the hash bucket lock.
 321          */
 322         hlist_for_each_entry(qp, &hb->chain, list) {
 323                 if (qp->net == nf && f->match(qp, arg)) {
 324                         atomic_inc(&qp->refcnt);
 325                         spin_unlock(&hb->chain_lock);
 326                         read_unlock(&f->lock);
 327                         qp_in->last_in |= INET_FRAG_COMPLETE;
 328                         inet_frag_put(qp_in, f);
 329                         return qp;
 330                 }
 331         }
 332 #endif
 333         qp = qp_in;
 334         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 335                 atomic_inc(&qp->refcnt);
 336
 337         atomic_inc(&qp->refcnt);
 338         hlist_add_head(&qp->list, &hb->chain);
 339
 340         spin_unlock(&hb->chain_lock);
 341         read_unlock(&f->lock);
 342
 343         return qp;
 344 }
 345
 346 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 347                 struct inet_frags *f, void *arg)
 348 {
 349         struct inet_frag_queue *q;
 350
 351         if (frag_mem_limit(nf) > nf->high_thresh) {
 352                 inet_frag_schedule_worker(f);
 353                 return NULL;
 354         }
 355
 356         q = kzalloc(f->qsize, GFP_ATOMIC);
 357         if (q == NULL)
 358                 return NULL;
 359
 360         q->net = nf;
 361         f->constructor(q, arg);
 362         add_frag_mem_limit(q, f->qsize);
 363
 364         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 365         spin_lock_init(&q->lock);
 366         atomic_set(&q->refcnt, 1);
 367
 368         return q;
 369 }
 370
 371 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 372                 struct inet_frags *f, void *arg)
 373 {
 374         struct inet_frag_queue *q;
 375
 376         q = inet_frag_alloc(nf, f, arg);
 377         if (q == NULL)
 378                 return NULL;
 379
 380         return inet_frag_intern(nf, q, f, arg);
 381 }
 382
 383 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 384                 struct inet_frags *f, void *key, unsigned int hash)
 385         __releases(&f->lock)
 386 {
 387         struct inet_frag_bucket *hb;
 388         struct inet_frag_queue *q;
 389         int depth = 0;
 390
 391         if (frag_mem_limit(nf) > nf->low_thresh)
 392                 inet_frag_schedule_worker(f);
 393
 394         hash &= (INETFRAGS_HASHSZ - 1);
 395         hb = &f->hash[hash];
 396
 397         spin_lock(&hb->chain_lock);
 398         hlist_for_each_entry(q, &hb->chain, list) {
 399                 if (q->net == nf && f->match(q, key)) {
 400                         atomic_inc(&q->refcnt);
 401                         spin_unlock(&hb->chain_lock);
 402                         read_unlock(&f->lock);
 403                         return q;
 404                 }
 405                 depth++;
 406         }
 407         spin_unlock(&hb->chain_lock);
 408         read_unlock(&f->lock);
 409
 410         if (depth <= INETFRAGS_MAXDEPTH)
 411                 return inet_frag_create(nf, f, key);
 412
 413         if (inet_frag_may_rebuild(f)) {
 414                 f->rebuild = true;
 415                 inet_frag_schedule_worker(f);
 416         }
 417
 418         return ERR_PTR(-ENOBUFS);
 419 }
 420 EXPORT_SYMBOL(inet_frag_find);
 421
 422 void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
 423                                    const char *prefix)
 424 {
 425         static const char msg[] = "inet_frag_find: Fragment hash bucket"
 426                 " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH)
 427                 ". Dropping fragment.\n";
 428
 429         if (PTR_ERR(q) == -ENOBUFS)
 430                 LIMIT_NETDEBUG(KERN_WARNING "%s%s", prefix, msg);
 431 }
 432 EXPORT_SYMBOL(inet_frag_maybe_warn_overflow);