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