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
  27 static void inet_frag_secret_rebuild(unsigned long dummy)
  28 {
  29         struct inet_frags *f = (struct inet_frags *)dummy;
  30         unsigned long now = jiffies;
  31         int i;
  32
  33         write_lock(&f->lock);
  34         get_random_bytes(&f->rnd, sizeof(u32));
  35         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
  36                 struct inet_frag_queue *q;
  37                 struct hlist_node *n;
  38
  39                 hlist_for_each_entry_safe(q, n, &f->hash[i], list) {
  40                         unsigned int hval = f->hashfn(q);
  41
  42                         if (hval != i) {
  43                                 hlist_del(&q->list);
  44
  45                                 /* Relink to new hash chain. */
  46                                 hlist_add_head(&q->list, &f->hash[hval]);
  47                         }
  48                 }
  49         }
  50         write_unlock(&f->lock);
  51
  52         mod_timer(&f->secret_timer, now + f->secret_interval);
  53 }
  54
  55 void inet_frags_init(struct inet_frags *f)
  56 {
  57         int i;
  58
  59         for (i = 0; i < INETFRAGS_HASHSZ; i++)
  60                 INIT_HLIST_HEAD(&f->hash[i]);
  61
  62         rwlock_init(&f->lock);
  63
  64         f->rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
  65                                    (jiffies ^ (jiffies >> 6)));
  66
  67         setup_timer(&f->secret_timer, inet_frag_secret_rebuild,
  68                         (unsigned long)f);
  69         f->secret_timer.expires = jiffies + f->secret_interval;
  70         add_timer(&f->secret_timer);
  71 }
  72 EXPORT_SYMBOL(inet_frags_init);
  73
  74 void inet_frags_init_net(struct netns_frags *nf)
  75 {
  76         nf->nqueues = 0;
  77         init_frag_mem_limit(nf);
  78         INIT_LIST_HEAD(&nf->lru_list);
  79         spin_lock_init(&nf->lru_lock);
  80 }
  81 EXPORT_SYMBOL(inet_frags_init_net);
  82
  83 void inet_frags_fini(struct inet_frags *f)
  84 {
  85         del_timer(&f->secret_timer);
  86 }
  87 EXPORT_SYMBOL(inet_frags_fini);
  88
  89 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
  90 {
  91         nf->low_thresh = 0;
  92
  93         local_bh_disable();
  94         inet_frag_evictor(nf, f, true);
  95         local_bh_enable();
  96
  97         percpu_counter_destroy(&nf->mem);
  98 }
  99 EXPORT_SYMBOL(inet_frags_exit_net);
 100
 101 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
 102 {
 103         write_lock(&f->lock);
 104         hlist_del(&fq->list);
 105         fq->net->nqueues--;
 106         write_unlock(&f->lock);
 107         inet_frag_lru_del(fq);
 108 }
 109
 110 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 111 {
 112         if (del_timer(&fq->timer))
 113                 atomic_dec(&fq->refcnt);
 114
 115         if (!(fq->last_in & INET_FRAG_COMPLETE)) {
 116                 fq_unlink(fq, f);
 117                 atomic_dec(&fq->refcnt);
 118                 fq->last_in |= INET_FRAG_COMPLETE;
 119         }
 120 }
 121 EXPORT_SYMBOL(inet_frag_kill);
 122
 123 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 124                 struct sk_buff *skb)
 125 {
 126         if (f->skb_free)
 127                 f->skb_free(skb);
 128         kfree_skb(skb);
 129 }
 130
 131 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f,
 132                                         int *work)
 133 {
 134         struct sk_buff *fp;
 135         struct netns_frags *nf;
 136         unsigned int sum, sum_truesize = 0;
 137
 138         WARN_ON(!(q->last_in & INET_FRAG_COMPLETE));
 139         WARN_ON(del_timer(&q->timer) != 0);
 140
 141         /* Release all fragment data. */
 142         fp = q->fragments;
 143         nf = q->net;
 144         while (fp) {
 145                 struct sk_buff *xp = fp->next;
 146
 147                 sum_truesize += fp->truesize;
 148                 frag_kfree_skb(nf, f, fp);
 149                 fp = xp;
 150         }
 151         sum = sum_truesize + f->qsize;
 152         if (work)
 153                 *work -= sum;
 154         sub_frag_mem_limit(q, sum);
 155
 156         if (f->destructor)
 157                 f->destructor(q);
 158         kfree(q);
 159
 160 }
 161 EXPORT_SYMBOL(inet_frag_destroy);
 162
 163 int inet_frag_evictor(struct netns_frags *nf, struct inet_frags *f, bool force)
 164 {
 165         struct inet_frag_queue *q;
 166         int work, evicted = 0;
 167
 168         if (!force) {
 169                 if (frag_mem_limit(nf) <= nf->high_thresh)
 170                         return 0;
 171         }
 172
 173         work = frag_mem_limit(nf) - nf->low_thresh;
 174         while (work > 0) {
 175                 spin_lock(&nf->lru_lock);
 176
 177                 if (list_empty(&nf->lru_list)) {
 178                         spin_unlock(&nf->lru_lock);
 179                         break;
 180                 }
 181
 182                 q = list_first_entry(&nf->lru_list,
 183                                 struct inet_frag_queue, lru_list);
 184                 atomic_inc(&q->refcnt);
 185                 spin_unlock(&nf->lru_lock);
 186
 187                 spin_lock(&q->lock);
 188                 if (!(q->last_in & INET_FRAG_COMPLETE))
 189                         inet_frag_kill(q, f);
 190                 spin_unlock(&q->lock);
 191
 192                 if (atomic_dec_and_test(&q->refcnt))
 193                         inet_frag_destroy(q, f, &work);
 194                 evicted++;
 195         }
 196
 197         return evicted;
 198 }
 199 EXPORT_SYMBOL(inet_frag_evictor);
 200
 201 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 202                 struct inet_frag_queue *qp_in, struct inet_frags *f,
 203                 void *arg)
 204 {
 205         struct inet_frag_queue *qp;
 206 #ifdef CONFIG_SMP
 207 #endif
 208         unsigned int hash;
 209
 210         write_lock(&f->lock);
 211         /*
 212          * While we stayed w/o the lock other CPU could update
 213          * the rnd seed, so we need to re-calculate the hash
 214          * chain. Fortunatelly the qp_in can be used to get one.
 215          */
 216         hash = f->hashfn(qp_in);
 217 #ifdef CONFIG_SMP
 218         /* With SMP race we have to recheck hash table, because
 219          * such entry could be created on other cpu, while we
 220          * promoted read lock to write lock.
 221          */
 222         hlist_for_each_entry(qp, &f->hash[hash], list) {
 223                 if (qp->net == nf && f->match(qp, arg)) {
 224                         atomic_inc(&qp->refcnt);
 225                         write_unlock(&f->lock);
 226                         qp_in->last_in |= INET_FRAG_COMPLETE;
 227                         inet_frag_put(qp_in, f);
 228                         return qp;
 229                 }
 230         }
 231 #endif
 232         qp = qp_in;
 233         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 234                 atomic_inc(&qp->refcnt);
 235
 236         atomic_inc(&qp->refcnt);
 237         hlist_add_head(&qp->list, &f->hash[hash]);
 238         nf->nqueues++;
 239         write_unlock(&f->lock);
 240         inet_frag_lru_add(nf, qp);
 241         return qp;
 242 }
 243
 244 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 245                 struct inet_frags *f, void *arg)
 246 {
 247         struct inet_frag_queue *q;
 248
 249         q = kzalloc(f->qsize, GFP_ATOMIC);
 250         if (q == NULL)
 251                 return NULL;
 252
 253         q->net = nf;
 254         f->constructor(q, arg);
 255         add_frag_mem_limit(q, f->qsize);
 256
 257         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 258         spin_lock_init(&q->lock);
 259         atomic_set(&q->refcnt, 1);
 260
 261         return q;
 262 }
 263
 264 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 265                 struct inet_frags *f, void *arg)
 266 {
 267         struct inet_frag_queue *q;
 268
 269         q = inet_frag_alloc(nf, f, arg);
 270         if (q == NULL)
 271                 return NULL;
 272
 273         return inet_frag_intern(nf, q, f, arg);
 274 }
 275
 276 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 277                 struct inet_frags *f, void *key, unsigned int hash)
 278         __releases(&f->lock)
 279 {
 280         struct inet_frag_queue *q;
 281         int depth = 0;
 282
 283         hlist_for_each_entry(q, &f->hash[hash], list) {
 284                 if (q->net == nf && f->match(q, key)) {
 285                         atomic_inc(&q->refcnt);
 286                         read_unlock(&f->lock);
 287                         return q;
 288                 }
 289                 depth++;
 290         }
 291         read_unlock(&f->lock);
 292
 293         if (depth <= INETFRAGS_MAXDEPTH)
 294                 return inet_frag_create(nf, f, key);
 295         else
 296                 return ERR_PTR(-ENOBUFS);
 297 }
 298 EXPORT_SYMBOL(inet_frag_find);
 299
 300 void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
 301                                    const char *prefix)
 302 {
 303         static const char msg[] = "inet_frag_find: Fragment hash bucket"
 304                 " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH)
 305                 ". Dropping fragment.\n";
 306
 307         if (PTR_ERR(q) == -ENOBUFS)
 308                 LIMIT_NETDEBUG(KERN_WARNING "%s%s", prefix, msg);
 309 }
 310 EXPORT_SYMBOL(inet_frag_maybe_warn_overflow);