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 *p, *n;
  37
  38                 hlist_for_each_entry_safe(q, p, 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         atomic_set(&nf->mem, 0);
  77         INIT_LIST_HEAD(&nf->lru_list);
  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 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
  88 {
  89         nf->low_thresh = 0;
  90
  91         local_bh_disable();
  92         inet_frag_evictor(nf, f, true);
  93         local_bh_enable();
  94 }
  95 EXPORT_SYMBOL(inet_frags_exit_net);
  96
  97 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
  98 {
  99         write_lock(&f->lock);
 100         hlist_del(&fq->list);
 101         list_del(&fq->lru_list);
 102         fq->net->nqueues--;
 103         write_unlock(&f->lock);
 104 }
 105
 106 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
 107 {
 108         if (del_timer(&fq->timer))
 109                 atomic_dec(&fq->refcnt);
 110
 111         if (!(fq->last_in & INET_FRAG_COMPLETE)) {
 112                 fq_unlink(fq, f);
 113                 atomic_dec(&fq->refcnt);
 114                 fq->last_in |= INET_FRAG_COMPLETE;
 115         }
 116 }
 117 EXPORT_SYMBOL(inet_frag_kill);
 118
 119 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
 120                 struct sk_buff *skb, int *work)
 121 {
 122         if (work)
 123                 *work -= skb->truesize;
 124
 125         atomic_sub(skb->truesize, &nf->mem);
 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
 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                 frag_kfree_skb(nf, f, fp, work);
 147                 fp = xp;
 148         }
 149
 150         if (work)
 151                 *work -= f->qsize;
 152         atomic_sub(f->qsize, &nf->mem);
 153
 154         if (f->destructor)
 155                 f->destructor(q);
 156         kfree(q);
 157
 158 }
 159 EXPORT_SYMBOL(inet_frag_destroy);
 160
 161 int inet_frag_evictor(struct netns_frags *nf, struct inet_frags *f, bool force)
 162 {
 163         struct inet_frag_queue *q;
 164         int work, evicted = 0;
 165
 166         if (!force) {
 167                 if (atomic_read(&nf->mem) <= nf->high_thresh)
 168                         return 0;
 169         }
 170
 171         work = atomic_read(&nf->mem) - nf->low_thresh;
 172         while (work > 0) {
 173                 read_lock(&f->lock);
 174                 if (list_empty(&nf->lru_list)) {
 175                         read_unlock(&f->lock);
 176                         break;
 177                 }
 178
 179                 q = list_first_entry(&nf->lru_list,
 180                                 struct inet_frag_queue, lru_list);
 181                 atomic_inc(&q->refcnt);
 182                 read_unlock(&f->lock);
 183
 184                 spin_lock(&q->lock);
 185                 if (!(q->last_in & INET_FRAG_COMPLETE))
 186                         inet_frag_kill(q, f);
 187                 spin_unlock(&q->lock);
 188
 189                 if (atomic_dec_and_test(&q->refcnt))
 190                         inet_frag_destroy(q, f, &work);
 191                 evicted++;
 192         }
 193
 194         return evicted;
 195 }
 196 EXPORT_SYMBOL(inet_frag_evictor);
 197
 198 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
 199                 struct inet_frag_queue *qp_in, struct inet_frags *f,
 200                 void *arg)
 201 {
 202         struct inet_frag_queue *qp;
 203 #ifdef CONFIG_SMP
 204         struct hlist_node *n;
 205 #endif
 206         unsigned int hash;
 207
 208         write_lock(&f->lock);
 209         /*
 210          * While we stayed w/o the lock other CPU could update
 211          * the rnd seed, so we need to re-calculate the hash
 212          * chain. Fortunatelly the qp_in can be used to get one.
 213          */
 214         hash = f->hashfn(qp_in);
 215 #ifdef CONFIG_SMP
 216         /* With SMP race we have to recheck hash table, because
 217          * such entry could be created on other cpu, while we
 218          * promoted read lock to write lock.
 219          */
 220         hlist_for_each_entry(qp, n, &f->hash[hash], list) {
 221                 if (qp->net == nf && f->match(qp, arg)) {
 222                         atomic_inc(&qp->refcnt);
 223                         write_unlock(&f->lock);
 224                         qp_in->last_in |= INET_FRAG_COMPLETE;
 225                         inet_frag_put(qp_in, f);
 226                         return qp;
 227                 }
 228         }
 229 #endif
 230         qp = qp_in;
 231         if (!mod_timer(&qp->timer, jiffies + nf->timeout))
 232                 atomic_inc(&qp->refcnt);
 233
 234         atomic_inc(&qp->refcnt);
 235         hlist_add_head(&qp->list, &f->hash[hash]);
 236         list_add_tail(&qp->lru_list, &nf->lru_list);
 237         nf->nqueues++;
 238         write_unlock(&f->lock);
 239         return qp;
 240 }
 241
 242 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
 243                 struct inet_frags *f, void *arg)
 244 {
 245         struct inet_frag_queue *q;
 246
 247         q = kzalloc(f->qsize, GFP_ATOMIC);
 248         if (q == NULL)
 249                 return NULL;
 250
 251         q->net = nf;
 252         f->constructor(q, arg);
 253         atomic_add(f->qsize, &nf->mem);
 254         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 255         spin_lock_init(&q->lock);
 256         atomic_set(&q->refcnt, 1);
 257
 258         return q;
 259 }
 260
 261 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
 262                 struct inet_frags *f, void *arg)
 263 {
 264         struct inet_frag_queue *q;
 265
 266         q = inet_frag_alloc(nf, f, arg);
 267         if (q == NULL)
 268                 return NULL;
 269
 270         return inet_frag_intern(nf, q, f, arg);
 271 }
 272
 273 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
 274                 struct inet_frags *f, void *key, unsigned int hash)
 275         __releases(&f->lock)
 276 {
 277         struct inet_frag_queue *q;
 278         struct hlist_node *n;
 279
 280         hlist_for_each_entry(q, n, &f->hash[hash], list) {
 281                 if (q->net == nf && f->match(q, key)) {
 282                         atomic_inc(&q->refcnt);
 283                         read_unlock(&f->lock);
 284                         return q;
 285                 }
 286         }
 287         read_unlock(&f->lock);
 288
 289         return inet_frag_create(nf, f, key);
 290 }
 291 EXPORT_SYMBOL(inet_frag_find);