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 #include <linux/rhashtable.h>
  24
  25 #include <net/sock.h>
  26 #include <net/inet_frag.h>
  27 #include <net/inet_ecn.h>
  28
  29 /* Given the OR values of all fragments, apply RFC 3168 5.3 requirements
  30  * Value : 0xff if frame should be dropped.
  31  *         0 or INET_ECN_CE value, to be ORed in to final iph->tos field
  32  */
  33 const u8 ip_frag_ecn_table[16] = {
  34         /* at least one fragment had CE, and others ECT_0 or ECT_1 */
  35         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0]                      = INET_ECN_CE,
  36         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1]                      = INET_ECN_CE,
  37         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1]   = INET_ECN_CE,
  38
  39         /* invalid combinations : drop frame */
  40         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff,
  41         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff,
  42         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff,
  43         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
  44         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff,
  45         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff,
  46         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
  47 };
  48 EXPORT_SYMBOL(ip_frag_ecn_table);
  49
  50 int inet_frags_init(struct inet_frags *f)
  51 {
  52         f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0,
  53                                             NULL);
  54         if (!f->frags_cachep)
  55                 return -ENOMEM;
  56
  57         return 0;
  58 }
  59 EXPORT_SYMBOL(inet_frags_init);
  60
  61 void inet_frags_fini(struct inet_frags *f)
  62 {
  63         /* We must wait that all inet_frag_destroy_rcu() have completed. */
  64         rcu_barrier();
  65
  66         kmem_cache_destroy(f->frags_cachep);
  67         f->frags_cachep = NULL;
  68 }
  69 EXPORT_SYMBOL(inet_frags_fini);
  70
  71 static void inet_frags_free_cb(void *ptr, void *arg)
  72 {
  73         struct inet_frag_queue *fq = ptr;
  74
  75         /* If we can not cancel the timer, it means this frag_queue
  76          * is already disappearing, we have nothing to do.
  77          * Otherwise, we own a refcount until the end of this function.
  78          */
  79         if (!del_timer(&fq->timer))
  80                 return;
  81
  82         spin_lock_bh(&fq->lock);
  83         if (!(fq->flags & INET_FRAG_COMPLETE)) {
  84                 fq->flags |= INET_FRAG_COMPLETE;
  85                 refcount_dec(&fq->refcnt);
  86         }
  87         spin_unlock_bh(&fq->lock);
  88
  89         inet_frag_put(fq);
  90 }
  91
  92 void inet_frags_exit_net(struct netns_frags *nf)
  93 {
  94         nf->high_thresh = 0; /* prevent creation of new frags */
  95
  96         rhashtable_free_and_destroy(&nf->rhashtable, inet_frags_free_cb, NULL);
  97 }
  98 EXPORT_SYMBOL(inet_frags_exit_net);
  99
 100 void inet_frag_kill(struct inet_frag_queue *fq)
 101 {
 102         if (del_timer(&fq->timer))
 103                 refcount_dec(&fq->refcnt);
 104
 105         if (!(fq->flags & INET_FRAG_COMPLETE)) {
 106                 struct netns_frags *nf = fq->net;
 107
 108                 fq->flags |= INET_FRAG_COMPLETE;
 109                 rhashtable_remove_fast(&nf->rhashtable, &fq->node, nf->f->rhash_params);
 110                 refcount_dec(&fq->refcnt);
 111         }
 112 }
 113 EXPORT_SYMBOL(inet_frag_kill);
 114
 115 static void inet_frag_destroy_rcu(struct rcu_head *head)
 116 {
 117         struct inet_frag_queue *q = container_of(head, struct inet_frag_queue,
 118                                                  rcu);
 119         struct inet_frags *f = q->net->f;
 120
 121         if (f->destructor)
 122                 f->destructor(q);
 123         kmem_cache_free(f->frags_cachep, q);
 124 }
 125
 126 void inet_frag_destroy(struct inet_frag_queue *q)
 127 {
 128         struct sk_buff *fp;
 129         struct netns_frags *nf;
 130         unsigned int sum, sum_truesize = 0;
 131         struct inet_frags *f;
 132
 133         WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
 134         WARN_ON(del_timer(&q->timer) != 0);
 135
 136         /* Release all fragment data. */
 137         fp = q->fragments;
 138         nf = q->net;
 139         f = nf->f;
 140         if (fp) {
 141                 do {
 142                         struct sk_buff *xp = fp->next;
 143
 144                         sum_truesize += fp->truesize;
 145                         kfree_skb(fp);
 146                         fp = xp;
 147                 } while (fp);
 148         } else {
 149                 sum_truesize = inet_frag_rbtree_purge(&q->rb_fragments);
 150         }
 151         sum = sum_truesize + f->qsize;
 152
 153         call_rcu(&q->rcu, inet_frag_destroy_rcu);
 154
 155         sub_frag_mem_limit(nf, sum);
 156 }
 157 EXPORT_SYMBOL(inet_frag_destroy);
 158
 159 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 160                                                struct inet_frags *f,
 161                                                void *arg)
 162 {
 163         struct inet_frag_queue *q;
 164
 165         q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC);
 166         if (!q)
 167                 return NULL;
 168
 169         q->net = nf;
 170         f->constructor(q, arg);
 171         add_frag_mem_limit(nf, f->qsize);
 172
 173         timer_setup(&q->timer, f->frag_expire, 0);
 174         spin_lock_init(&q->lock);
 175         refcount_set(&q->refcnt, 3);
 176
 177         return q;
 178 }
 179
 180 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 181                                                 void *arg,
 182                                                 struct inet_frag_queue **prev)
 183 {
 184         struct inet_frags *f = nf->f;
 185         struct inet_frag_queue *q;
 186
 187         q = inet_frag_alloc(nf, f, arg);
 188         if (!q) {
 189                 *prev = ERR_PTR(-ENOMEM);
 190                 return NULL;
 191         }
 192         mod_timer(&q->timer, jiffies + nf->timeout);
 193
 194         *prev = rhashtable_lookup_get_insert_key(&nf->rhashtable, &q->key,
 195                                                  &q->node, f->rhash_params);
 196         if (*prev) {
 197                 q->flags |= INET_FRAG_COMPLETE;
 198                 inet_frag_kill(q);
 199                 inet_frag_destroy(q);
 200                 return NULL;
 201         }
 202         return q;
 203 }
 204
 205 /* TODO : call from rcu_read_lock() and no longer use refcount_inc_not_zero() */
 206 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf, void *key)
 207 {
 208         struct inet_frag_queue *fq = NULL, *prev;
 209
 210         if (!nf->high_thresh || frag_mem_limit(nf) > nf->high_thresh)
 211                 return NULL;
 212
 213         rcu_read_lock();
 214
 215         prev = rhashtable_lookup(&nf->rhashtable, key, nf->f->rhash_params);
 216         if (!prev)
 217                 fq = inet_frag_create(nf, key, &prev);
 218         if (prev && !IS_ERR(prev)) {
 219                 fq = prev;
 220                 if (!refcount_inc_not_zero(&fq->refcnt))
 221                         fq = NULL;
 222         }
 223         rcu_read_unlock();
 224         return fq;
 225 }
 226 EXPORT_SYMBOL(inet_frag_find);