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 int inet_frags_init(struct inet_frags *f)
  50 {
  51         f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0,
  52                                             NULL);
  53         if (!f->frags_cachep)
  54                 return -ENOMEM;
  55
  56         return 0;
  57 }
  58 EXPORT_SYMBOL(inet_frags_init);
  59
  60 void inet_frags_fini(struct inet_frags *f)
  61 {
  62         /* We must wait that all inet_frag_destroy_rcu() have completed. */
  63         rcu_barrier();
  64
  65         kmem_cache_destroy(f->frags_cachep);
  66         f->frags_cachep = NULL;
  67 }
  68 EXPORT_SYMBOL(inet_frags_fini);
  69
  70 static void inet_frags_free_cb(void *ptr, void *arg)
  71 {
  72         struct inet_frag_queue *fq = ptr;
  73
  74         /* If we can not cancel the timer, it means this frag_queue
  75          * is already disappearing, we have nothing to do.
  76          * Otherwise, we own a refcount until the end of this function.
  77          */
  78         if (!del_timer(&fq->timer))
  79                 return;
  80
  81         spin_lock_bh(&fq->lock);
  82         if (!(fq->flags & INET_FRAG_COMPLETE)) {
  83                 fq->flags |= INET_FRAG_COMPLETE;
  84                 atomic_dec(&fq->refcnt);
  85         }
  86         spin_unlock_bh(&fq->lock);
  87
  88         inet_frag_put(fq);
  89 }
  90
  91 void inet_frags_exit_net(struct netns_frags *nf)
  92 {
  93         nf->high_thresh = 0; /* prevent creation of new frags */
  94
  95         rhashtable_free_and_destroy(&nf->rhashtable, inet_frags_free_cb, NULL);
  96 }
  97 EXPORT_SYMBOL(inet_frags_exit_net);
  98
  99 void inet_frag_kill(struct inet_frag_queue *fq)
 100 {
 101         if (del_timer(&fq->timer))
 102                 atomic_dec(&fq->refcnt);
 103
 104         if (!(fq->flags & INET_FRAG_COMPLETE)) {
 105                 struct netns_frags *nf = fq->net;
 106
 107                 fq->flags |= INET_FRAG_COMPLETE;
 108                 rhashtable_remove_fast(&nf->rhashtable, &fq->node, nf->f->rhash_params);
 109                 atomic_dec(&fq->refcnt);
 110         }
 111 }
 112 EXPORT_SYMBOL(inet_frag_kill);
 113
 114 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 115                                   struct sk_buff *skb)
 116 {
 117         if (f->skb_free)
 118                 f->skb_free(skb);
 119         kfree_skb(skb);
 120 }
 121
 122 static void inet_frag_destroy_rcu(struct rcu_head *head)
 123 {
 124         struct inet_frag_queue *q = container_of(head, struct inet_frag_queue,
 125                                                  rcu);
 126         struct inet_frags *f = q->net->f;
 127
 128         if (f->destructor)
 129                 f->destructor(q);
 130         kmem_cache_free(f->frags_cachep, q);
 131 }
 132
 133 void inet_frag_destroy(struct inet_frag_queue *q)
 134 {
 135         struct sk_buff *fp;
 136         struct netns_frags *nf;
 137         unsigned int sum, sum_truesize = 0;
 138         struct inet_frags *f;
 139
 140         WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
 141         WARN_ON(del_timer(&q->timer) != 0);
 142
 143         /* Release all fragment data. */
 144         fp = q->fragments;
 145         nf = q->net;
 146         f = nf->f;
 147         if (fp) {
 148                 do {
 149                         struct sk_buff *xp = fp->next;
 150
 151                         sum_truesize += fp->truesize;
 152                         frag_kfree_skb(nf, f, fp);
 153                         fp = xp;
 154                 } while (fp);
 155         } else {
 156                 sum_truesize = inet_frag_rbtree_purge(&q->rb_fragments);
 157         }
 158         sum = sum_truesize + f->qsize;
 159
 160         call_rcu(&q->rcu, inet_frag_destroy_rcu);
 161
 162         sub_frag_mem_limit(nf, sum);
 163 }
 164 EXPORT_SYMBOL(inet_frag_destroy);
 165
 166 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 167                                                struct inet_frags *f,
 168                                                void *arg)
 169 {
 170         struct inet_frag_queue *q;
 171
 172         if (!nf->high_thresh || frag_mem_limit(nf) > nf->high_thresh)
 173                 return NULL;
 174
 175         q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC);
 176         if (!q)
 177                 return NULL;
 178
 179         q->net = nf;
 180         f->constructor(q, arg);
 181         add_frag_mem_limit(nf, f->qsize);
 182
 183         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 184         spin_lock_init(&q->lock);
 185         atomic_set(&q->refcnt, 3);
 186
 187         return q;
 188 }
 189
 190 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 191                                                 void *arg,
 192                                                 struct inet_frag_queue **prev)
 193 {
 194         struct inet_frags *f = nf->f;
 195         struct inet_frag_queue *q;
 196
 197         q = inet_frag_alloc(nf, f, arg);
 198         if (!q) {
 199                 *prev = ERR_PTR(-ENOMEM);
 200                 return NULL;
 201         }
 202         mod_timer(&q->timer, jiffies + nf->timeout);
 203
 204         *prev = rhashtable_lookup_get_insert_key(&nf->rhashtable, &q->key,
 205                                                  &q->node, f->rhash_params);
 206         if (*prev) {
 207                 q->flags |= INET_FRAG_COMPLETE;
 208                 inet_frag_kill(q);
 209                 inet_frag_destroy(q);
 210                 return NULL;
 211         }
 212         return q;
 213 }
 214 EXPORT_SYMBOL(inet_frag_create);
 215
 216 /* TODO : call from rcu_read_lock() and no longer use refcount_inc_not_zero() */
 217 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf, void *key)
 218 {
 219         struct inet_frag_queue *fq = NULL, *prev;
 220
 221         rcu_read_lock();
 222         prev = rhashtable_lookup(&nf->rhashtable, key, nf->f->rhash_params);
 223         if (!prev)
 224                 fq = inet_frag_create(nf, key, &prev);
 225         if (prev && !IS_ERR(prev)) {
 226                 fq = prev;
 227                 if (!atomic_inc_not_zero(&fq->refcnt))
 228                         fq = NULL;
 229         }
 230         rcu_read_unlock();
 231         return fq;
 232 }
 233 EXPORT_SYMBOL(inet_frag_find);