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 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
  87 {
  88         nf->low_thresh = 0;
  89         inet_frag_evictor(nf, f);
  90 }
  91 EXPORT_SYMBOL(inet_frags_exit_net);
  92
  93 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
  94 {
  95         write_lock(&f->lock);
  96         hlist_del(&fq->list);
  97         list_del(&fq->lru_list);
  98         fq->net->nqueues--;
  99         write_unlock(&f->lock);
 100 }
 101
 102 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 103 {
 104         if (del_timer(&fq->timer))
 105                 atomic_dec(&fq->refcnt);
 106
 107         if (!(fq->last_in & INET_FRAG_COMPLETE)) {
 108                 fq_unlink(fq, f);
 109                 atomic_dec(&fq->refcnt);
 110                 fq->last_in |= INET_FRAG_COMPLETE;
 111         }
 112 }
 113
 114 EXPORT_SYMBOL(inet_frag_kill);
 115
 116 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 117                 struct sk_buff *skb, int *work)
 118 {
 119         if (work)
 120                 *work -= skb->truesize;
 121
 122         atomic_sub(skb->truesize, &nf->mem);
 123         if (f->skb_free)
 124                 f->skb_free(skb);
 125         kfree_skb(skb);
 126 }
 127
 128 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f,
 129                                         int *work)
 130 {
 131         struct sk_buff *fp;
 132         struct netns_frags *nf;
 133
 134         BUG_TRAP(q->last_in & INET_FRAG_COMPLETE);
 135         BUG_TRAP(del_timer(&q->timer) == 0);
 136
 137         /* Release all fragment data. */
 138         fp = q->fragments;
 139         nf = q->net;
 140         while (fp) {
 141                 struct sk_buff *xp = fp->next;
 142
 143                 frag_kfree_skb(nf, f, fp, work);
 144                 fp = xp;
 145         }
 146
 147         if (work)
 148                 *work -= f->qsize;
 149         atomic_sub(f->qsize, &nf->mem);
 150
 151         if (f->destructor)
 152                 f->destructor(q);
 153         kfree(q);
 154
 155 }
 156 EXPORT_SYMBOL(inet_frag_destroy);
 157
 158 int inet_frag_evictor(struct netns_frags *nf, struct inet_frags *f)
 159 {
 160         struct inet_frag_queue *q;
 161         int work, evicted = 0;
 162
 163         work = atomic_read(&nf->mem) - nf->low_thresh;
 164         while (work > 0) {
 165                 read_lock(&f->lock);
 166                 if (list_empty(&nf->lru_list)) {
 167                         read_unlock(&f->lock);
 168                         break;
 169                 }
 170
 171                 q = list_first_entry(&nf->lru_list,
 172                                 struct inet_frag_queue, lru_list);
 173                 atomic_inc(&q->refcnt);
 174                 read_unlock(&f->lock);
 175
 176                 spin_lock(&q->lock);
 177                 if (!(q->last_in & INET_FRAG_COMPLETE))
 178                         inet_frag_kill(q, f);
 179                 spin_unlock(&q->lock);
 180
 181                 if (atomic_dec_and_test(&q->refcnt))
 182                         inet_frag_destroy(q, f, &work);
 183                 evicted++;
 184         }
 185
 186         return evicted;
 187 }
 188 EXPORT_SYMBOL(inet_frag_evictor);
 189
 190 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 191                 struct inet_frag_queue *qp_in, struct inet_frags *f,
 192                 unsigned int hash, void *arg)
 193 {
 194         struct inet_frag_queue *qp;
 195 #ifdef CONFIG_SMP
 196         struct hlist_node *n;
 197 #endif
 198
 199         write_lock(&f->lock);
 200 #ifdef CONFIG_SMP
 201         /* With SMP race we have to recheck hash table, because
 202          * such entry could be created on other cpu, while we
 203          * promoted read lock to write lock.
 204          */
 205         hlist_for_each_entry(qp, n, &f->hash[hash], list) {
 206                 if (qp->net == nf && f->match(qp, arg)) {
 207                         atomic_inc(&qp->refcnt);
 208                         write_unlock(&f->lock);
 209                         qp_in->last_in |= INET_FRAG_COMPLETE;
 210                         inet_frag_put(qp_in, f);
 211                         return qp;
 212                 }
 213         }
 214 #endif
 215         qp = qp_in;
 216         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 217                 atomic_inc(&qp->refcnt);
 218
 219         atomic_inc(&qp->refcnt);
 220         hlist_add_head(&qp->list, &f->hash[hash]);
 221         list_add_tail(&qp->lru_list, &nf->lru_list);
 222         nf->nqueues++;
 223         write_unlock(&f->lock);
 224         return qp;
 225 }
 226
 227 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 228                 struct inet_frags *f, void *arg)
 229 {
 230         struct inet_frag_queue *q;
 231
 232         q = kzalloc(f->qsize, GFP_ATOMIC);
 233         if (q == NULL)
 234                 return NULL;
 235
 236         f->constructor(q, arg);
 237         atomic_add(f->qsize, &nf->mem);
 238         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 239         spin_lock_init(&q->lock);
 240         atomic_set(&q->refcnt, 1);
 241         q->net = nf;
 242
 243         return q;
 244 }
 245
 246 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 247                 struct inet_frags *f, void *arg, unsigned int hash)
 248 {
 249         struct inet_frag_queue *q;
 250
 251         q = inet_frag_alloc(nf, f, arg);
 252         if (q == NULL)
 253                 return NULL;
 254
 255         return inet_frag_intern(nf, q, f, hash, arg);
 256 }
 257
 258 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 259                 struct inet_frags *f, void *key, unsigned int hash)
 260 {
 261         struct inet_frag_queue *q;
 262         struct hlist_node *n;
 263
 264         read_lock(&f->lock);
 265         hlist_for_each_entry(q, n, &f->hash[hash], list) {
 266                 if (q->net == nf && f->match(q, key)) {
 267                         atomic_inc(&q->refcnt);
 268                         read_unlock(&f->lock);
 269                         return q;
 270                 }
 271         }
 272         read_unlock(&f->lock);
 273
 274         return inet_frag_create(nf, f, key, hash);
 275 }
 276 EXPORT_SYMBOL(inet_frag_find);