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 /* Given the OR values of all fragments, apply RFC 3168 5.3 requirements
  29  * Value : 0xff if frame should be dropped.
  30  *         0 or INET_ECN_CE value, to be ORed in to final iph->tos field
  31  */
  32 const u8 ip_frag_ecn_table[16] = {
  33         /* at least one fragment had CE, and others ECT_0 or ECT_1 */
  34         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0]                      = INET_ECN_CE,
  35         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1]                      = INET_ECN_CE,
  36         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1]   = INET_ECN_CE,
  37
  38         /* invalid combinations : drop frame */
  39         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff,
  40         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff,
  41         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff,
  42         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
  43         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff,
  44         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff,
  45         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
  46 };
  47 EXPORT_SYMBOL(ip_frag_ecn_table);
  48
  49 static void inet_frag_secret_rebuild(unsigned long dummy)
  50 {
  51         struct inet_frags *f = (struct inet_frags *)dummy;
  52         unsigned long now = jiffies;
  53         int i;
  54
  55         /* Per bucket lock NOT needed here, due to write lock protection */
  56         write_lock(&f->lock);
  57
  58         get_random_bytes(&f->rnd, sizeof(u32));
  59         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
  60                 struct inet_frag_bucket *hb;
  61                 struct inet_frag_queue *q;
  62                 struct hlist_node *n;
  63
  64                 hb = &f->hash[i];
  65                 hlist_for_each_entry_safe(q, n, &hb->chain, list) {
  66                         unsigned int hval = f->hashfn(q);
  67
  68                         if (hval != i) {
  69                                 struct inet_frag_bucket *hb_dest;
  70
  71                                 hlist_del(&q->list);
  72
  73                                 /* Relink to new hash chain. */
  74                                 hb_dest = &f->hash[hval];
  75                                 hlist_add_head(&q->list, &hb_dest->chain);
  76                         }
  77                 }
  78         }
  79         write_unlock(&f->lock);
  80
  81         mod_timer(&f->secret_timer, now + f->secret_interval);
  82 }
  83
  84 void inet_frags_init(struct inet_frags *f)
  85 {
  86         int i;
  87
  88         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
  89                 struct inet_frag_bucket *hb = &f->hash[i];
  90
  91                 spin_lock_init(&hb->chain_lock);
  92                 INIT_HLIST_HEAD(&hb->chain);
  93         }
  94         rwlock_init(&f->lock);
  95
  96         f->rnd = (u32) ((totalram_pages ^ (totalram_pages >> 7)) ^
  97                                    (jiffies ^ (jiffies >> 6)));
  98
  99         setup_timer(&f->secret_timer, inet_frag_secret_rebuild,
 100                         (unsigned long)f);
 101         f->secret_timer.expires = jiffies + f->secret_interval;
 102         add_timer(&f->secret_timer);
 103 }
 104 EXPORT_SYMBOL(inet_frags_init);
 105
 106 void inet_frags_init_net(struct netns_frags *nf)
 107 {
 108         nf->nqueues = 0;
 109         init_frag_mem_limit(nf);
 110         INIT_LIST_HEAD(&nf->lru_list);
 111         spin_lock_init(&nf->lru_lock);
 112 }
 113 EXPORT_SYMBOL(inet_frags_init_net);
 114
 115 void inet_frags_fini(struct inet_frags *f)
 116 {
 117         del_timer(&f->secret_timer);
 118 }
 119 EXPORT_SYMBOL(inet_frags_fini);
 120
 121 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
 122 {
 123         nf->low_thresh = 0;
 124
 125         local_bh_disable();
 126         inet_frag_evictor(nf, f, true);
 127         local_bh_enable();
 128
 129         percpu_counter_destroy(&nf->mem);
 130 }
 131 EXPORT_SYMBOL(inet_frags_exit_net);
 132
 133 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
 134 {
 135         struct inet_frag_bucket *hb;
 136         unsigned int hash;
 137
 138         read_lock(&f->lock);
 139         hash = f->hashfn(fq);
 140         hb = &f->hash[hash];
 141
 142         spin_lock(&hb->chain_lock);
 143         hlist_del(&fq->list);
 144         spin_unlock(&hb->chain_lock);
 145
 146         read_unlock(&f->lock);
 147         inet_frag_lru_del(fq);
 148 }
 149
 150 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 151 {
 152         if (del_timer(&fq->timer))
 153                 atomic_dec(&fq->refcnt);
 154
 155         if (!(fq->last_in & INET_FRAG_COMPLETE)) {
 156                 fq_unlink(fq, f);
 157                 atomic_dec(&fq->refcnt);
 158                 fq->last_in |= INET_FRAG_COMPLETE;
 159         }
 160 }
 161 EXPORT_SYMBOL(inet_frag_kill);
 162
 163 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 164                 struct sk_buff *skb)
 165 {
 166         if (f->skb_free)
 167                 f->skb_free(skb);
 168         kfree_skb(skb);
 169 }
 170
 171 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f,
 172                                         int *work)
 173 {
 174         struct sk_buff *fp;
 175         struct netns_frags *nf;
 176         unsigned int sum, sum_truesize = 0;
 177
 178         WARN_ON(!(q->last_in & INET_FRAG_COMPLETE));
 179         WARN_ON(del_timer(&q->timer) != 0);
 180
 181         /* Release all fragment data. */
 182         fp = q->fragments;
 183         nf = q->net;
 184         while (fp) {
 185                 struct sk_buff *xp = fp->next;
 186
 187                 sum_truesize += fp->truesize;
 188                 frag_kfree_skb(nf, f, fp);
 189                 fp = xp;
 190         }
 191         sum = sum_truesize + f->qsize;
 192         if (work)
 193                 *work -= sum;
 194         sub_frag_mem_limit(q, sum);
 195
 196         if (f->destructor)
 197                 f->destructor(q);
 198         kfree(q);
 199
 200 }
 201 EXPORT_SYMBOL(inet_frag_destroy);
 202
 203 int inet_frag_evictor(struct netns_frags *nf, struct inet_frags *f, bool force)
 204 {
 205         struct inet_frag_queue *q;
 206         int work, evicted = 0;
 207
 208         if (!force) {
 209                 if (frag_mem_limit(nf) <= nf->high_thresh)
 210                         return 0;
 211         }
 212
 213         work = frag_mem_limit(nf) - nf->low_thresh;
 214         while (work > 0) {
 215                 spin_lock(&nf->lru_lock);
 216
 217                 if (list_empty(&nf->lru_list)) {
 218                         spin_unlock(&nf->lru_lock);
 219                         break;
 220                 }
 221
 222                 q = list_first_entry(&nf->lru_list,
 223                                 struct inet_frag_queue, lru_list);
 224                 atomic_inc(&q->refcnt);
 225                 /* Remove q from list to avoid several CPUs grabbing it */
 226                 list_del_init(&q->lru_list);
 227
 228                 spin_unlock(&nf->lru_lock);
 229
 230                 spin_lock(&q->lock);
 231                 if (!(q->last_in & INET_FRAG_COMPLETE))
 232                         inet_frag_kill(q, f);
 233                 spin_unlock(&q->lock);
 234
 235                 if (atomic_dec_and_test(&q->refcnt))
 236                         inet_frag_destroy(q, f, &work);
 237                 evicted++;
 238         }
 239
 240         return evicted;
 241 }
 242 EXPORT_SYMBOL(inet_frag_evictor);
 243
 244 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 245                 struct inet_frag_queue *qp_in, struct inet_frags *f,
 246                 void *arg)
 247 {
 248         struct inet_frag_bucket *hb;
 249         struct inet_frag_queue *qp;
 250         unsigned int hash;
 251
 252         read_lock(&f->lock); /* Protects against hash rebuild */
 253         /*
 254          * While we stayed w/o the lock other CPU could update
 255          * the rnd seed, so we need to re-calculate the hash
 256          * chain. Fortunatelly the qp_in can be used to get one.
 257          */
 258         hash = f->hashfn(qp_in);
 259         hb = &f->hash[hash];
 260         spin_lock(&hb->chain_lock);
 261
 262 #ifdef CONFIG_SMP
 263         /* With SMP race we have to recheck hash table, because
 264          * such entry could be created on other cpu, while we
 265          * released the hash bucket lock.
 266          */
 267         hlist_for_each_entry(qp, &hb->chain, list) {
 268                 if (qp->net == nf && f->match(qp, arg)) {
 269                         atomic_inc(&qp->refcnt);
 270                         spin_unlock(&hb->chain_lock);
 271                         read_unlock(&f->lock);
 272                         qp_in->last_in |= INET_FRAG_COMPLETE;
 273                         inet_frag_put(qp_in, f);
 274                         return qp;
 275                 }
 276         }
 277 #endif
 278         qp = qp_in;
 279         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 280                 atomic_inc(&qp->refcnt);
 281
 282         atomic_inc(&qp->refcnt);
 283         hlist_add_head(&qp->list, &hb->chain);
 284         spin_unlock(&hb->chain_lock);
 285         read_unlock(&f->lock);
 286         inet_frag_lru_add(nf, qp);
 287         return qp;
 288 }
 289
 290 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 291                 struct inet_frags *f, void *arg)
 292 {
 293         struct inet_frag_queue *q;
 294
 295         q = kzalloc(f->qsize, GFP_ATOMIC);
 296         if (q == NULL)
 297                 return NULL;
 298
 299         q->net = nf;
 300         f->constructor(q, arg);
 301         add_frag_mem_limit(q, f->qsize);
 302
 303         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 304         spin_lock_init(&q->lock);
 305         atomic_set(&q->refcnt, 1);
 306         INIT_LIST_HEAD(&q->lru_list);
 307
 308         return q;
 309 }
 310
 311 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 312                 struct inet_frags *f, void *arg)
 313 {
 314         struct inet_frag_queue *q;
 315
 316         q = inet_frag_alloc(nf, f, arg);
 317         if (q == NULL)
 318                 return NULL;
 319
 320         return inet_frag_intern(nf, q, f, arg);
 321 }
 322
 323 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 324                 struct inet_frags *f, void *key, unsigned int hash)
 325         __releases(&f->lock)
 326 {
 327         struct inet_frag_bucket *hb;
 328         struct inet_frag_queue *q;
 329         int depth = 0;
 330
 331         hb = &f->hash[hash];
 332
 333         spin_lock(&hb->chain_lock);
 334         hlist_for_each_entry(q, &hb->chain, list) {
 335                 if (q->net == nf && f->match(q, key)) {
 336                         atomic_inc(&q->refcnt);
 337                         spin_unlock(&hb->chain_lock);
 338                         read_unlock(&f->lock);
 339                         return q;
 340                 }
 341                 depth++;
 342         }
 343         spin_unlock(&hb->chain_lock);
 344         read_unlock(&f->lock);
 345
 346         if (depth <= INETFRAGS_MAXDEPTH)
 347                 return inet_frag_create(nf, f, key);
 348         else
 349                 return ERR_PTR(-ENOBUFS);
 350 }
 351 EXPORT_SYMBOL(inet_frag_find);
 352
 353 void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
 354                                    const char *prefix)
 355 {
 356         static const char msg[] = "inet_frag_find: Fragment hash bucket"
 357                 " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH)
 358                 ". Dropping fragment.\n";
 359
 360         if (PTR_ERR(q) == -ENOBUFS)
 361                 LIMIT_NETDEBUG(KERN_WARNING "%s%s", prefix, msg);
 362 }
 363 EXPORT_SYMBOL(inet_frag_maybe_warn_overflow);