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/inet_frag.h>
  25
  26 static void inet_frag_secret_rebuild(unsigned long dummy)
  27 {
  28         struct inet_frags *f = (struct inet_frags *)dummy;
  29         unsigned long now = jiffies;
  30         int i;
  31
  32         write_lock(&f->lock);
  33         get_random_bytes(&f->rnd, sizeof(u32));
  34         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
  35                 struct inet_frag_queue *q;
  36                 struct hlist_node *n;
  37
  38                 hlist_for_each_entry_safe(q, n, &f->hash[i], list) {
  39                         unsigned int hval = f->hashfn(q);
  40
  41                         if (hval != i) {
  42                                 hlist_del(&q->list);
  43
  44                                 /* Relink to new hash chain. */
  45                                 hlist_add_head(&q->list, &f->hash[hval]);
  46                         }
  47                 }
  48         }
  49         write_unlock(&f->lock);
  50
  51         mod_timer(&f->secret_timer, now + f->secret_interval);
  52 }
  53
  54 void inet_frags_init(struct inet_frags *f)
  55 {
  56         int i;
  57
  58         for (i = 0; i < INETFRAGS_HASHSZ; i++)
  59                 INIT_HLIST_HEAD(&f->hash[i]);
  60
  61         rwlock_init(&f->lock);
  62
  63         f->rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
  64                                    (jiffies ^ (jiffies >> 6)));
  65
  66         setup_timer(&f->secret_timer, inet_frag_secret_rebuild,
  67                         (unsigned long)f);
  68         f->secret_timer.expires = jiffies + f->secret_interval;
  69         add_timer(&f->secret_timer);
  70 }
  71 EXPORT_SYMBOL(inet_frags_init);
  72
  73 void inet_frags_init_net(struct netns_frags *nf)
  74 {
  75         nf->nqueues = 0;
  76         init_frag_mem_limit(nf);
  77         INIT_LIST_HEAD(&nf->lru_list);
  78         spin_lock_init(&nf->lru_lock);
  79 }
  80 EXPORT_SYMBOL(inet_frags_init_net);
  81
  82 void inet_frags_fini(struct inet_frags *f)
  83 {
  84         del_timer(&f->secret_timer);
  85 }
  86 EXPORT_SYMBOL(inet_frags_fini);
  87
  88 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
  89 {
  90         nf->low_thresh = 0;
  91
  92         local_bh_disable();
  93         inet_frag_evictor(nf, f, true);
  94         local_bh_enable();
  95
  96         percpu_counter_destroy(&nf->mem);
  97 }
  98 EXPORT_SYMBOL(inet_frags_exit_net);
  99
 100 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
 101 {
 102         write_lock(&f->lock);
 103         hlist_del(&fq->list);
 104         fq->net->nqueues--;
 105         write_unlock(&f->lock);
 106         inet_frag_lru_del(fq);
 107 }
 108
 109 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 110 {
 111         if (del_timer(&fq->timer))
 112                 atomic_dec(&fq->refcnt);
 113
 114         if (!(fq->last_in & INET_FRAG_COMPLETE)) {
 115                 fq_unlink(fq, f);
 116                 atomic_dec(&fq->refcnt);
 117                 fq->last_in |= INET_FRAG_COMPLETE;
 118         }
 119 }
 120 EXPORT_SYMBOL(inet_frag_kill);
 121
 122 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 123                 struct sk_buff *skb)
 124 {
 125         if (f->skb_free)
 126                 f->skb_free(skb);
 127         kfree_skb(skb);
 128 }
 129
 130 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f,
 131                                         int *work)
 132 {
 133         struct sk_buff *fp;
 134         struct netns_frags *nf;
 135         unsigned int sum, sum_truesize = 0;
 136
 137         WARN_ON(!(q->last_in & INET_FRAG_COMPLETE));
 138         WARN_ON(del_timer(&q->timer) != 0);
 139
 140         /* Release all fragment data. */
 141         fp = q->fragments;
 142         nf = q->net;
 143         while (fp) {
 144                 struct sk_buff *xp = fp->next;
 145
 146                 sum_truesize += fp->truesize;
 147                 frag_kfree_skb(nf, f, fp);
 148                 fp = xp;
 149         }
 150         sum = sum_truesize + f->qsize;
 151         if (work)
 152                 *work -= sum;
 153         sub_frag_mem_limit(q, sum);
 154
 155         if (f->destructor)
 156                 f->destructor(q);
 157         kfree(q);
 158
 159 }
 160 EXPORT_SYMBOL(inet_frag_destroy);
 161
 162 int inet_frag_evictor(struct netns_frags *nf, struct inet_frags *f, bool force)
 163 {
 164         struct inet_frag_queue *q;
 165         int work, evicted = 0;
 166
 167         if (!force) {
 168                 if (frag_mem_limit(nf) <= nf->high_thresh)
 169                         return 0;
 170         }
 171
 172         work = frag_mem_limit(nf) - nf->low_thresh;
 173         while (work > 0) {
 174                 spin_lock(&nf->lru_lock);
 175
 176                 if (list_empty(&nf->lru_list)) {
 177                         spin_unlock(&nf->lru_lock);
 178                         break;
 179                 }
 180
 181                 q = list_first_entry(&nf->lru_list,
 182                                 struct inet_frag_queue, lru_list);
 183                 atomic_inc(&q->refcnt);
 184                 spin_unlock(&nf->lru_lock);
 185
 186                 spin_lock(&q->lock);
 187                 if (!(q->last_in & INET_FRAG_COMPLETE))
 188                         inet_frag_kill(q, f);
 189                 spin_unlock(&q->lock);
 190
 191                 if (atomic_dec_and_test(&q->refcnt))
 192                         inet_frag_destroy(q, f, &work);
 193                 evicted++;
 194         }
 195
 196         return evicted;
 197 }
 198 EXPORT_SYMBOL(inet_frag_evictor);
 199
 200 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 201                 struct inet_frag_queue *qp_in, struct inet_frags *f,
 202                 void *arg)
 203 {
 204         struct inet_frag_queue *qp;
 205 #ifdef CONFIG_SMP
 206 #endif
 207         unsigned int hash;
 208
 209         write_lock(&f->lock);
 210         /*
 211          * While we stayed w/o the lock other CPU could update
 212          * the rnd seed, so we need to re-calculate the hash
 213          * chain. Fortunatelly the qp_in can be used to get one.
 214          */
 215         hash = f->hashfn(qp_in);
 216 #ifdef CONFIG_SMP
 217         /* With SMP race we have to recheck hash table, because
 218          * such entry could be created on other cpu, while we
 219          * promoted read lock to write lock.
 220          */
 221         hlist_for_each_entry(qp, &f->hash[hash], list) {
 222                 if (qp->net == nf && f->match(qp, arg)) {
 223                         atomic_inc(&qp->refcnt);
 224                         write_unlock(&f->lock);
 225                         qp_in->last_in |= INET_FRAG_COMPLETE;
 226                         inet_frag_put(qp_in, f);
 227                         return qp;
 228                 }
 229         }
 230 #endif
 231         qp = qp_in;
 232         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 233                 atomic_inc(&qp->refcnt);
 234
 235         atomic_inc(&qp->refcnt);
 236         hlist_add_head(&qp->list, &f->hash[hash]);
 237         nf->nqueues++;
 238         write_unlock(&f->lock);
 239         inet_frag_lru_add(nf, qp);
 240         return qp;
 241 }
 242
 243 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 244                 struct inet_frags *f, void *arg)
 245 {
 246         struct inet_frag_queue *q;
 247
 248         q = kzalloc(f->qsize, GFP_ATOMIC);
 249         if (q == NULL)
 250                 return NULL;
 251
 252         q->net = nf;
 253         f->constructor(q, arg);
 254         add_frag_mem_limit(q, f->qsize);
 255
 256         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 257         spin_lock_init(&q->lock);
 258         atomic_set(&q->refcnt, 1);
 259
 260         return q;
 261 }
 262
 263 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 264                 struct inet_frags *f, void *arg)
 265 {
 266         struct inet_frag_queue *q;
 267
 268         q = inet_frag_alloc(nf, f, arg);
 269         if (q == NULL)
 270                 return NULL;
 271
 272         return inet_frag_intern(nf, q, f, arg);
 273 }
 274
 275 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 276                 struct inet_frags *f, void *key, unsigned int hash)
 277         __releases(&f->lock)
 278 {
 279         struct inet_frag_queue *q;
 280
 281         hlist_for_each_entry(q, &f->hash[hash], list) {
 282                 if (q->net == nf && f->match(q, key)) {
 283                         atomic_inc(&q->refcnt);
 284                         read_unlock(&f->lock);
 285                         return q;
 286                 }
 287         }
 288         read_unlock(&f->lock);
 289
 290         return inet_frag_create(nf, f, key);
 291 }
 292 EXPORT_SYMBOL(inet_frag_find);