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         write_lock(&f->lock);
  56         get_random_bytes(&f->rnd, sizeof(u32));
  57         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
  58                 struct inet_frag_queue *q;
  59                 struct hlist_node *n;
  60
  61                 hlist_for_each_entry_safe(q, n, &f->hash[i], list) {
  62                         unsigned int hval = f->hashfn(q);
  63
  64                         if (hval != i) {
  65                                 hlist_del(&q->list);
  66
  67                                 /* Relink to new hash chain. */
  68                                 hlist_add_head(&q->list, &f->hash[hval]);
  69                         }
  70                 }
  71         }
  72         write_unlock(&f->lock);
  73
  74         mod_timer(&f->secret_timer, now + f->secret_interval);
  75 }
  76
  77 void inet_frags_init(struct inet_frags *f)
  78 {
  79         int i;
  80
  81         for (i = 0; i < INETFRAGS_HASHSZ; i++)
  82                 INIT_HLIST_HEAD(&f->hash[i]);
  83
  84         rwlock_init(&f->lock);
  85
  86         f->rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
  87                                    (jiffies ^ (jiffies >> 6)));
  88
  89         setup_timer(&f->secret_timer, inet_frag_secret_rebuild,
  90                         (unsigned long)f);
  91         f->secret_timer.expires = jiffies + f->secret_interval;
  92         add_timer(&f->secret_timer);
  93 }
  94 EXPORT_SYMBOL(inet_frags_init);
  95
  96 void inet_frags_init_net(struct netns_frags *nf)
  97 {
  98         nf->nqueues = 0;
  99         init_frag_mem_limit(nf);
 100         INIT_LIST_HEAD(&nf->lru_list);
 101         spin_lock_init(&nf->lru_lock);
 102 }
 103 EXPORT_SYMBOL(inet_frags_init_net);
 104
 105 void inet_frags_fini(struct inet_frags *f)
 106 {
 107         del_timer(&f->secret_timer);
 108 }
 109 EXPORT_SYMBOL(inet_frags_fini);
 110
 111 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
 112 {
 113         nf->low_thresh = 0;
 114
 115         local_bh_disable();
 116         inet_frag_evictor(nf, f, true);
 117         local_bh_enable();
 118
 119         percpu_counter_destroy(&nf->mem);
 120 }
 121 EXPORT_SYMBOL(inet_frags_exit_net);
 122
 123 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
 124 {
 125         write_lock(&f->lock);
 126         hlist_del(&fq->list);
 127         write_unlock(&f->lock);
 128         inet_frag_lru_del(fq);
 129 }
 130
 131 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 132 {
 133         if (del_timer(&fq->timer))
 134                 atomic_dec(&fq->refcnt);
 135
 136         if (!(fq->last_in & INET_FRAG_COMPLETE)) {
 137                 fq_unlink(fq, f);
 138                 atomic_dec(&fq->refcnt);
 139                 fq->last_in |= INET_FRAG_COMPLETE;
 140         }
 141 }
 142 EXPORT_SYMBOL(inet_frag_kill);
 143
 144 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 145                 struct sk_buff *skb)
 146 {
 147         if (f->skb_free)
 148                 f->skb_free(skb);
 149         kfree_skb(skb);
 150 }
 151
 152 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f,
 153                                         int *work)
 154 {
 155         struct sk_buff *fp;
 156         struct netns_frags *nf;
 157         unsigned int sum, sum_truesize = 0;
 158
 159         WARN_ON(!(q->last_in & INET_FRAG_COMPLETE));
 160         WARN_ON(del_timer(&q->timer) != 0);
 161
 162         /* Release all fragment data. */
 163         fp = q->fragments;
 164         nf = q->net;
 165         while (fp) {
 166                 struct sk_buff *xp = fp->next;
 167
 168                 sum_truesize += fp->truesize;
 169                 frag_kfree_skb(nf, f, fp);
 170                 fp = xp;
 171         }
 172         sum = sum_truesize + f->qsize;
 173         if (work)
 174                 *work -= sum;
 175         sub_frag_mem_limit(q, sum);
 176
 177         if (f->destructor)
 178                 f->destructor(q);
 179         kfree(q);
 180
 181 }
 182 EXPORT_SYMBOL(inet_frag_destroy);
 183
 184 int inet_frag_evictor(struct netns_frags *nf, struct inet_frags *f, bool force)
 185 {
 186         struct inet_frag_queue *q;
 187         int work, evicted = 0;
 188
 189         if (!force) {
 190                 if (frag_mem_limit(nf) <= nf->high_thresh)
 191                         return 0;
 192         }
 193
 194         work = frag_mem_limit(nf) - nf->low_thresh;
 195         while (work > 0) {
 196                 spin_lock(&nf->lru_lock);
 197
 198                 if (list_empty(&nf->lru_list)) {
 199                         spin_unlock(&nf->lru_lock);
 200                         break;
 201                 }
 202
 203                 q = list_first_entry(&nf->lru_list,
 204                                 struct inet_frag_queue, lru_list);
 205                 atomic_inc(&q->refcnt);
 206                 /* Remove q from list to avoid several CPUs grabbing it */
 207                 list_del_init(&q->lru_list);
 208
 209                 spin_unlock(&nf->lru_lock);
 210
 211                 spin_lock(&q->lock);
 212                 if (!(q->last_in & INET_FRAG_COMPLETE))
 213                         inet_frag_kill(q, f);
 214                 spin_unlock(&q->lock);
 215
 216                 if (atomic_dec_and_test(&q->refcnt))
 217                         inet_frag_destroy(q, f, &work);
 218                 evicted++;
 219         }
 220
 221         return evicted;
 222 }
 223 EXPORT_SYMBOL(inet_frag_evictor);
 224
 225 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 226                 struct inet_frag_queue *qp_in, struct inet_frags *f,
 227                 void *arg)
 228 {
 229         struct inet_frag_queue *qp;
 230 #ifdef CONFIG_SMP
 231 #endif
 232         unsigned int hash;
 233
 234         write_lock(&f->lock);
 235         /*
 236          * While we stayed w/o the lock other CPU could update
 237          * the rnd seed, so we need to re-calculate the hash
 238          * chain. Fortunatelly the qp_in can be used to get one.
 239          */
 240         hash = f->hashfn(qp_in);
 241 #ifdef CONFIG_SMP
 242         /* With SMP race we have to recheck hash table, because
 243          * such entry could be created on other cpu, while we
 244          * promoted read lock to write lock.
 245          */
 246         hlist_for_each_entry(qp, &f->hash[hash], list) {
 247                 if (qp->net == nf && f->match(qp, arg)) {
 248                         atomic_inc(&qp->refcnt);
 249                         write_unlock(&f->lock);
 250                         qp_in->last_in |= INET_FRAG_COMPLETE;
 251                         inet_frag_put(qp_in, f);
 252                         return qp;
 253                 }
 254         }
 255 #endif
 256         qp = qp_in;
 257         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 258                 atomic_inc(&qp->refcnt);
 259
 260         atomic_inc(&qp->refcnt);
 261         hlist_add_head(&qp->list, &f->hash[hash]);
 262         write_unlock(&f->lock);
 263         inet_frag_lru_add(nf, qp);
 264         return qp;
 265 }
 266
 267 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 268                 struct inet_frags *f, void *arg)
 269 {
 270         struct inet_frag_queue *q;
 271
 272         q = kzalloc(f->qsize, GFP_ATOMIC);
 273         if (q == NULL)
 274                 return NULL;
 275
 276         q->net = nf;
 277         f->constructor(q, arg);
 278         add_frag_mem_limit(q, f->qsize);
 279
 280         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 281         spin_lock_init(&q->lock);
 282         atomic_set(&q->refcnt, 1);
 283
 284         return q;
 285 }
 286
 287 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 288                 struct inet_frags *f, void *arg)
 289 {
 290         struct inet_frag_queue *q;
 291
 292         q = inet_frag_alloc(nf, f, arg);
 293         if (q == NULL)
 294                 return NULL;
 295
 296         return inet_frag_intern(nf, q, f, arg);
 297 }
 298
 299 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 300                 struct inet_frags *f, void *key, unsigned int hash)
 301         __releases(&f->lock)
 302 {
 303         struct inet_frag_queue *q;
 304         int depth = 0;
 305
 306         hlist_for_each_entry(q, &f->hash[hash], list) {
 307                 if (q->net == nf && f->match(q, key)) {
 308                         atomic_inc(&q->refcnt);
 309                         read_unlock(&f->lock);
 310                         return q;
 311                 }
 312                 depth++;
 313         }
 314         read_unlock(&f->lock);
 315
 316         if (depth <= INETFRAGS_MAXDEPTH)
 317                 return inet_frag_create(nf, f, key);
 318         else
 319                 return ERR_PTR(-ENOBUFS);
 320 }
 321 EXPORT_SYMBOL(inet_frag_find);
 322
 323 void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
 324                                    const char *prefix)
 325 {
 326         static const char msg[] = "inet_frag_find: Fragment hash bucket"
 327                 " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH)
 328                 ". Dropping fragment.\n";
 329
 330         if (PTR_ERR(q) == -ENOBUFS)
 331                 LIMIT_NETDEBUG(KERN_WARNING "%s%s", prefix, msg);
 332 }
 333 EXPORT_SYMBOL(inet_frag_maybe_warn_overflow);