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 /* Given the OR values of all fragments, apply RFC 3168 5.3 requirements
  32  * Value : 0xff if frame should be dropped.
  33  *         0 or INET_ECN_CE value, to be ORed in to final iph->tos field
  34  */
  35 const u8 ip_frag_ecn_table[16] = {
  36         /* at least one fragment had CE, and others ECT_0 or ECT_1 */
  37         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0]                      = INET_ECN_CE,
  38         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1]                      = INET_ECN_CE,
  39         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1]   = INET_ECN_CE,
  40
  41         /* invalid combinations : drop frame */
  42         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff,
  43         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff,
  44         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff,
  45         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
  46         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff,
  47         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff,
  48         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
  49 };
  50 EXPORT_SYMBOL(ip_frag_ecn_table);
  51
  52 static unsigned int
  53 inet_frag_hashfn(const struct inet_frags *f, const struct inet_frag_queue *q)
  54 {
  55         return f->hashfn(q) & (INETFRAGS_HASHSZ - 1);
  56 }
  57
  58 static void inet_frag_secret_rebuild(unsigned long dummy)
  59 {
  60         struct inet_frags *f = (struct inet_frags *)dummy;
  61         unsigned long now = jiffies;
  62         int i;
  63
  64         /* Per bucket lock NOT needed here, due to write lock protection */
  65         write_lock(&f->lock);
  66
  67         get_random_bytes(&f->rnd, sizeof(u32));
  68         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
  69                 struct inet_frag_bucket *hb;
  70                 struct inet_frag_queue *q;
  71                 struct hlist_node *n;
  72
  73                 hb = &f->hash[i];
  74                 hlist_for_each_entry_safe(q, n, &hb->chain, list) {
  75                         unsigned int hval = inet_frag_hashfn(f, q);
  76
  77                         if (hval != i) {
  78                                 struct inet_frag_bucket *hb_dest;
  79
  80                                 hlist_del(&q->list);
  81
  82                                 /* Relink to new hash chain. */
  83                                 hb_dest = &f->hash[hval];
  84                                 hlist_add_head(&q->list, &hb_dest->chain);
  85                         }
  86                 }
  87         }
  88         write_unlock(&f->lock);
  89
  90         mod_timer(&f->secret_timer, now + f->secret_interval);
  91 }
  92
  93 static bool inet_fragq_should_evict(const struct inet_frag_queue *q)
  94 {
  95         return q->net->low_thresh == 0 ||
  96                frag_mem_limit(q->net) >= q->net->low_thresh;
  97 }
  98
  99 static unsigned int
 100 inet_evict_bucket(struct inet_frags *f, struct inet_frag_bucket *hb)
 101 {
 102         struct inet_frag_queue *fq;
 103         struct hlist_node *n;
 104         unsigned int evicted = 0;
 105         HLIST_HEAD(expired);
 106
 107 evict_again:
 108         spin_lock(&hb->chain_lock);
 109
 110         hlist_for_each_entry_safe(fq, n, &hb->chain, list) {
 111                 if (!inet_fragq_should_evict(fq))
 112                         continue;
 113
 114                 if (!del_timer(&fq->timer)) {
 115                         /* q expiring right now thus increment its refcount so
 116                          * it won't be freed under us and wait until the timer
 117                          * has finished executing then destroy it
 118                          */
 119                         atomic_inc(&fq->refcnt);
 120                         spin_unlock(&hb->chain_lock);
 121                         del_timer_sync(&fq->timer);
 122                         WARN_ON(atomic_read(&fq->refcnt) != 1);
 123                         inet_frag_put(fq, f);
 124                         goto evict_again;
 125                 }
 126
 127                 /* suppress xmit of (icmp) error packet */
 128                 fq->last_in &= ~INET_FRAG_FIRST_IN;
 129                 fq->last_in |= INET_FRAG_EVICTED;
 130                 hlist_del(&fq->list);
 131                 hlist_add_head(&fq->list, &expired);
 132                 ++evicted;
 133         }
 134
 135         spin_unlock(&hb->chain_lock);
 136
 137         hlist_for_each_entry_safe(fq, n, &expired, list)
 138                 f->frag_expire((unsigned long) fq);
 139
 140         return evicted;
 141 }
 142
 143 static void inet_frag_worker(struct work_struct *work)
 144 {
 145         unsigned int budget = INETFRAGS_EVICT_BUCKETS;
 146         unsigned int i, evicted = 0;
 147         struct inet_frags *f;
 148
 149         f = container_of(work, struct inet_frags, frags_work);
 150
 151         BUILD_BUG_ON(INETFRAGS_EVICT_BUCKETS >= INETFRAGS_HASHSZ);
 152
 153         read_lock_bh(&f->lock);
 154
 155         for (i = ACCESS_ONCE(f->next_bucket); budget; --budget) {
 156                 evicted += inet_evict_bucket(f, &f->hash[i]);
 157                 i = (i + 1) & (INETFRAGS_HASHSZ - 1);
 158                 if (evicted > INETFRAGS_EVICT_MAX)
 159                         break;
 160         }
 161
 162         f->next_bucket = i;
 163
 164         read_unlock_bh(&f->lock);
 165 }
 166
 167 static void inet_frag_schedule_worker(struct inet_frags *f)
 168 {
 169         if (unlikely(!work_pending(&f->frags_work)))
 170                 schedule_work(&f->frags_work);
 171 }
 172
 173 void inet_frags_init(struct inet_frags *f)
 174 {
 175         int i;
 176
 177         INIT_WORK(&f->frags_work, inet_frag_worker);
 178
 179         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
 180                 struct inet_frag_bucket *hb = &f->hash[i];
 181
 182                 spin_lock_init(&hb->chain_lock);
 183                 INIT_HLIST_HEAD(&hb->chain);
 184         }
 185         rwlock_init(&f->lock);
 186
 187         setup_timer(&f->secret_timer, inet_frag_secret_rebuild,
 188                         (unsigned long)f);
 189         f->secret_timer.expires = jiffies + f->secret_interval;
 190         add_timer(&f->secret_timer);
 191 }
 192 EXPORT_SYMBOL(inet_frags_init);
 193
 194 void inet_frags_init_net(struct netns_frags *nf)
 195 {
 196         init_frag_mem_limit(nf);
 197 }
 198 EXPORT_SYMBOL(inet_frags_init_net);
 199
 200 void inet_frags_fini(struct inet_frags *f)
 201 {
 202         del_timer(&f->secret_timer);
 203         cancel_work_sync(&f->frags_work);
 204 }
 205 EXPORT_SYMBOL(inet_frags_fini);
 206
 207 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
 208 {
 209         int i;
 210
 211         nf->low_thresh = 0;
 212
 213         read_lock_bh(&f->lock);
 214
 215         for (i = 0; i < INETFRAGS_HASHSZ ; i++)
 216                 inet_evict_bucket(f, &f->hash[i]);
 217
 218         read_unlock_bh(&f->lock);
 219
 220         percpu_counter_destroy(&nf->mem);
 221 }
 222 EXPORT_SYMBOL(inet_frags_exit_net);
 223
 224 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
 225 {
 226         struct inet_frag_bucket *hb;
 227         unsigned int hash;
 228
 229         read_lock(&f->lock);
 230         hash = inet_frag_hashfn(f, fq);
 231         hb = &f->hash[hash];
 232
 233         spin_lock(&hb->chain_lock);
 234         hlist_del(&fq->list);
 235         spin_unlock(&hb->chain_lock);
 236
 237         read_unlock(&f->lock);
 238 }
 239
 240 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 241 {
 242         if (del_timer(&fq->timer))
 243                 atomic_dec(&fq->refcnt);
 244
 245         if (!(fq->last_in & INET_FRAG_COMPLETE)) {
 246                 fq_unlink(fq, f);
 247                 atomic_dec(&fq->refcnt);
 248                 fq->last_in |= INET_FRAG_COMPLETE;
 249         }
 250 }
 251 EXPORT_SYMBOL(inet_frag_kill);
 252
 253 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 254                 struct sk_buff *skb)
 255 {
 256         if (f->skb_free)
 257                 f->skb_free(skb);
 258         kfree_skb(skb);
 259 }
 260
 261 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f)
 262 {
 263         struct sk_buff *fp;
 264         struct netns_frags *nf;
 265         unsigned int sum, sum_truesize = 0;
 266
 267         WARN_ON(!(q->last_in & INET_FRAG_COMPLETE));
 268         WARN_ON(del_timer(&q->timer) != 0);
 269
 270         /* Release all fragment data. */
 271         fp = q->fragments;
 272         nf = q->net;
 273         while (fp) {
 274                 struct sk_buff *xp = fp->next;
 275
 276                 sum_truesize += fp->truesize;
 277                 frag_kfree_skb(nf, f, fp);
 278                 fp = xp;
 279         }
 280         sum = sum_truesize + f->qsize;
 281         sub_frag_mem_limit(q, sum);
 282
 283         if (f->destructor)
 284                 f->destructor(q);
 285         kfree(q);
 286 }
 287 EXPORT_SYMBOL(inet_frag_destroy);
 288
 289 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 290                 struct inet_frag_queue *qp_in, struct inet_frags *f,
 291                 void *arg)
 292 {
 293         struct inet_frag_bucket *hb;
 294         struct inet_frag_queue *qp;
 295         unsigned int hash;
 296
 297         read_lock(&f->lock); /* Protects against hash rebuild */
 298         /*
 299          * While we stayed w/o the lock other CPU could update
 300          * the rnd seed, so we need to re-calculate the hash
 301          * chain. Fortunatelly the qp_in can be used to get one.
 302          */
 303         hash = inet_frag_hashfn(f, qp_in);
 304         hb = &f->hash[hash];
 305         spin_lock(&hb->chain_lock);
 306
 307 #ifdef CONFIG_SMP
 308         /* With SMP race we have to recheck hash table, because
 309          * such entry could be created on other cpu, while we
 310          * released the hash bucket lock.
 311          */
 312         hlist_for_each_entry(qp, &hb->chain, list) {
 313                 if (qp->net == nf && f->match(qp, arg)) {
 314                         atomic_inc(&qp->refcnt);
 315                         spin_unlock(&hb->chain_lock);
 316                         read_unlock(&f->lock);
 317                         qp_in->last_in |= INET_FRAG_COMPLETE;
 318                         inet_frag_put(qp_in, f);
 319                         return qp;
 320                 }
 321         }
 322 #endif
 323         qp = qp_in;
 324         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 325                 atomic_inc(&qp->refcnt);
 326
 327         atomic_inc(&qp->refcnt);
 328         hlist_add_head(&qp->list, &hb->chain);
 329
 330         spin_unlock(&hb->chain_lock);
 331         read_unlock(&f->lock);
 332
 333         return qp;
 334 }
 335
 336 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 337                 struct inet_frags *f, void *arg)
 338 {
 339         struct inet_frag_queue *q;
 340
 341         if (frag_mem_limit(nf) > nf->high_thresh) {
 342                 inet_frag_schedule_worker(f);
 343                 return NULL;
 344         }
 345
 346         q = kzalloc(f->qsize, GFP_ATOMIC);
 347         if (q == NULL)
 348                 return NULL;
 349
 350         q->net = nf;
 351         f->constructor(q, arg);
 352         add_frag_mem_limit(q, f->qsize);
 353
 354         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 355         spin_lock_init(&q->lock);
 356         atomic_set(&q->refcnt, 1);
 357
 358         return q;
 359 }
 360
 361 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 362                 struct inet_frags *f, void *arg)
 363 {
 364         struct inet_frag_queue *q;
 365
 366         q = inet_frag_alloc(nf, f, arg);
 367         if (q == NULL)
 368                 return NULL;
 369
 370         return inet_frag_intern(nf, q, f, arg);
 371 }
 372
 373 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 374                 struct inet_frags *f, void *key, unsigned int hash)
 375         __releases(&f->lock)
 376 {
 377         struct inet_frag_bucket *hb;
 378         struct inet_frag_queue *q;
 379         int depth = 0;
 380
 381         if (frag_mem_limit(nf) > nf->low_thresh)
 382                 inet_frag_schedule_worker(f);
 383
 384         hash &= (INETFRAGS_HASHSZ - 1);
 385         hb = &f->hash[hash];
 386
 387         spin_lock(&hb->chain_lock);
 388         hlist_for_each_entry(q, &hb->chain, list) {
 389                 if (q->net == nf && f->match(q, key)) {
 390                         atomic_inc(&q->refcnt);
 391                         spin_unlock(&hb->chain_lock);
 392                         read_unlock(&f->lock);
 393                         return q;
 394                 }
 395                 depth++;
 396         }
 397         spin_unlock(&hb->chain_lock);
 398         read_unlock(&f->lock);
 399
 400         if (depth <= INETFRAGS_MAXDEPTH)
 401                 return inet_frag_create(nf, f, key);
 402         else
 403                 return ERR_PTR(-ENOBUFS);
 404 }
 405 EXPORT_SYMBOL(inet_frag_find);
 406
 407 void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
 408                                    const char *prefix)
 409 {
 410         static const char msg[] = "inet_frag_find: Fragment hash bucket"
 411                 " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH)
 412                 ". Dropping fragment.\n";
 413
 414         if (PTR_ERR(q) == -ENOBUFS)
 415                 LIMIT_NETDEBUG(KERN_WARNING "%s%s", prefix, msg);
 416 }
 417 EXPORT_SYMBOL(inet_frag_maybe_warn_overflow);