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
  23 #include <net/inet_frag.h>
  24
  25 static void inet_frag_secret_rebuild(unsigned long dummy)
  26 {
  27         struct inet_frags *f = (struct inet_frags *)dummy;
  28         unsigned long now = jiffies;
  29         int i;
  30
  31         write_lock(&f->lock);
  32         get_random_bytes(&f->rnd, sizeof(u32));
  33         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
  34                 struct inet_frag_queue *q;
  35                 struct hlist_node *p, *n;
  36
  37                 hlist_for_each_entry_safe(q, p, n, &f->hash[i], list) {
  38                         unsigned int hval = f->hashfn(q);
  39
  40                         if (hval != i) {
  41                                 hlist_del(&q->list);
  42
  43                                 /* Relink to new hash chain. */
  44                                 hlist_add_head(&q->list, &f->hash[hval]);
  45                         }
  46                 }
  47         }
  48         write_unlock(&f->lock);
  49
  50         mod_timer(&f->secret_timer, now + f->secret_interval);
  51 }
  52
  53 void inet_frags_init(struct inet_frags *f)
  54 {
  55         int i;
  56
  57         for (i = 0; i < INETFRAGS_HASHSZ; i++)
  58                 INIT_HLIST_HEAD(&f->hash[i]);
  59
  60         rwlock_init(&f->lock);
  61
  62         f->rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
  63                                    (jiffies ^ (jiffies >> 6)));
  64
  65         setup_timer(&f->secret_timer, inet_frag_secret_rebuild,
  66                         (unsigned long)f);
  67         f->secret_timer.expires = jiffies + f->secret_interval;
  68         add_timer(&f->secret_timer);
  69 }
  70 EXPORT_SYMBOL(inet_frags_init);
  71
  72 void inet_frags_init_net(struct netns_frags *nf)
  73 {
  74         nf->nqueues = 0;
  75         atomic_set(&nf->mem, 0);
  76         INIT_LIST_HEAD(&nf->lru_list);
  77 }
  78 EXPORT_SYMBOL(inet_frags_init_net);
  79
  80 void inet_frags_fini(struct inet_frags *f)
  81 {
  82         del_timer(&f->secret_timer);
  83 }
  84 EXPORT_SYMBOL(inet_frags_fini);
  85
  86 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
  87 {
  88         write_lock(&f->lock);
  89         hlist_del(&fq->list);
  90         list_del(&fq->lru_list);
  91         fq->net->nqueues--;
  92         write_unlock(&f->lock);
  93 }
  94
  95 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
  96 {
  97         if (del_timer(&fq->timer))
  98                 atomic_dec(&fq->refcnt);
  99
 100         if (!(fq->last_in & COMPLETE)) {
 101                 fq_unlink(fq, f);
 102                 atomic_dec(&fq->refcnt);
 103                 fq->last_in |= COMPLETE;
 104         }
 105 }
 106
 107 EXPORT_SYMBOL(inet_frag_kill);
 108
 109 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 110                 struct sk_buff *skb, int *work)
 111 {
 112         if (work)
 113                 *work -= skb->truesize;
 114
 115         atomic_sub(skb->truesize, &nf->mem);
 116         if (f->skb_free)
 117                 f->skb_free(skb);
 118         kfree_skb(skb);
 119 }
 120
 121 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f,
 122                                         int *work)
 123 {
 124         struct sk_buff *fp;
 125         struct netns_frags *nf;
 126
 127         BUG_TRAP(q->last_in & COMPLETE);
 128         BUG_TRAP(del_timer(&q->timer) == 0);
 129
 130         /* Release all fragment data. */
 131         fp = q->fragments;
 132         nf = q->net;
 133         while (fp) {
 134                 struct sk_buff *xp = fp->next;
 135
 136                 frag_kfree_skb(nf, f, fp, work);
 137                 fp = xp;
 138         }
 139
 140         if (work)
 141                 *work -= f->qsize;
 142         atomic_sub(f->qsize, &nf->mem);
 143
 144         if (f->destructor)
 145                 f->destructor(q);
 146         kfree(q);
 147
 148 }
 149 EXPORT_SYMBOL(inet_frag_destroy);
 150
 151 int inet_frag_evictor(struct netns_frags *nf, struct inet_frags *f)
 152 {
 153         struct inet_frag_queue *q;
 154         int work, evicted = 0;
 155
 156         work = atomic_read(&nf->mem) - nf->low_thresh;
 157         while (work > 0) {
 158                 read_lock(&f->lock);
 159                 if (list_empty(&nf->lru_list)) {
 160                         read_unlock(&f->lock);
 161                         break;
 162                 }
 163
 164                 q = list_first_entry(&nf->lru_list,
 165                                 struct inet_frag_queue, lru_list);
 166                 atomic_inc(&q->refcnt);
 167                 read_unlock(&f->lock);
 168
 169                 spin_lock(&q->lock);
 170                 if (!(q->last_in & COMPLETE))
 171                         inet_frag_kill(q, f);
 172                 spin_unlock(&q->lock);
 173
 174                 if (atomic_dec_and_test(&q->refcnt))
 175                         inet_frag_destroy(q, f, &work);
 176                 evicted++;
 177         }
 178
 179         return evicted;
 180 }
 181 EXPORT_SYMBOL(inet_frag_evictor);
 182
 183 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 184                 struct inet_frag_queue *qp_in, struct inet_frags *f,
 185                 unsigned int hash, void *arg)
 186 {
 187         struct inet_frag_queue *qp;
 188 #ifdef CONFIG_SMP
 189         struct hlist_node *n;
 190 #endif
 191
 192         write_lock(&f->lock);
 193 #ifdef CONFIG_SMP
 194         /* With SMP race we have to recheck hash table, because
 195          * such entry could be created on other cpu, while we
 196          * promoted read lock to write lock.
 197          */
 198         hlist_for_each_entry(qp, n, &f->hash[hash], list) {
 199                 if (qp->net == nf && f->match(qp, arg)) {
 200                         atomic_inc(&qp->refcnt);
 201                         write_unlock(&f->lock);
 202                         qp_in->last_in |= COMPLETE;
 203                         inet_frag_put(qp_in, f);
 204                         return qp;
 205                 }
 206         }
 207 #endif
 208         qp = qp_in;
 209         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 210                 atomic_inc(&qp->refcnt);
 211
 212         atomic_inc(&qp->refcnt);
 213         hlist_add_head(&qp->list, &f->hash[hash]);
 214         list_add_tail(&qp->lru_list, &nf->lru_list);
 215         nf->nqueues++;
 216         write_unlock(&f->lock);
 217         return qp;
 218 }
 219
 220 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 221                 struct inet_frags *f, void *arg)
 222 {
 223         struct inet_frag_queue *q;
 224
 225         q = kzalloc(f->qsize, GFP_ATOMIC);
 226         if (q == NULL)
 227                 return NULL;
 228
 229         f->constructor(q, arg);
 230         atomic_add(f->qsize, &nf->mem);
 231         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 232         spin_lock_init(&q->lock);
 233         atomic_set(&q->refcnt, 1);
 234         q->net = nf;
 235
 236         return q;
 237 }
 238
 239 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 240                 struct inet_frags *f, void *arg, unsigned int hash)
 241 {
 242         struct inet_frag_queue *q;
 243
 244         q = inet_frag_alloc(nf, f, arg);
 245         if (q == NULL)
 246                 return NULL;
 247
 248         return inet_frag_intern(nf, q, f, hash, arg);
 249 }
 250
 251 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 252                 struct inet_frags *f, void *key, unsigned int hash)
 253 {
 254         struct inet_frag_queue *q;
 255         struct hlist_node *n;
 256
 257         read_lock(&f->lock);
 258         hlist_for_each_entry(q, n, &f->hash[hash], list) {
 259                 if (q->net == nf && f->match(q, key)) {
 260                         atomic_inc(&q->refcnt);
 261                         read_unlock(&f->lock);
 262                         return q;
 263                 }
 264         }
 265         read_unlock(&f->lock);
 266
 267         return inet_frag_create(nf, f, key, hash);
 268 }
 269 EXPORT_SYMBOL(inet_frag_find);