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         f->nqueues = 0;
  67         atomic_set(&f->mem, 0);
  68
  69         setup_timer(&f->secret_timer, inet_frag_secret_rebuild,
  70                         (unsigned long)f);
  71         f->secret_timer.expires = jiffies + f->ctl->secret_interval;
  72         add_timer(&f->secret_timer);
  73 }
  74 EXPORT_SYMBOL(inet_frags_init);
  75
  76 void inet_frags_fini(struct inet_frags *f)
  77 {
  78         del_timer(&f->secret_timer);
  79 }
  80 EXPORT_SYMBOL(inet_frags_fini);
  81
  82 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
  83 {
  84         write_lock(&f->lock);
  85         hlist_del(&fq->list);
  86         list_del(&fq->lru_list);
  87         f->nqueues--;
  88         write_unlock(&f->lock);
  89 }
  90
  91 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
  92 {
  93         if (del_timer(&fq->timer))
  94                 atomic_dec(&fq->refcnt);
  95
  96         if (!(fq->last_in & COMPLETE)) {
  97                 fq_unlink(fq, f);
  98                 atomic_dec(&fq->refcnt);
  99                 fq->last_in |= COMPLETE;
 100         }
 101 }
 102
 103 EXPORT_SYMBOL(inet_frag_kill);
 104
 105 static inline void frag_kfree_skb(struct inet_frags *f, struct sk_buff *skb,
 106                                                 int *work)
 107 {
 108         if (work)
 109                 *work -= skb->truesize;
 110
 111         atomic_sub(skb->truesize, &f->mem);
 112         if (f->skb_free)
 113                 f->skb_free(skb);
 114         kfree_skb(skb);
 115 }
 116
 117 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f,
 118                                         int *work)
 119 {
 120         struct sk_buff *fp;
 121
 122         BUG_TRAP(q->last_in & COMPLETE);
 123         BUG_TRAP(del_timer(&q->timer) == 0);
 124
 125         /* Release all fragment data. */
 126         fp = q->fragments;
 127         while (fp) {
 128                 struct sk_buff *xp = fp->next;
 129
 130                 frag_kfree_skb(f, fp, work);
 131                 fp = xp;
 132         }
 133
 134         if (work)
 135                 *work -= f->qsize;
 136         atomic_sub(f->qsize, &f->mem);
 137
 138         if (f->destructor)
 139                 f->destructor(q);
 140         kfree(q);
 141
 142 }
 143 EXPORT_SYMBOL(inet_frag_destroy);
 144
 145 int inet_frag_evictor(struct inet_frags *f)
 146 {
 147         struct inet_frag_queue *q;
 148         int work, evicted = 0;
 149
 150         work = atomic_read(&f->mem) - f->ctl->low_thresh;
 151         while (work > 0) {
 152                 read_lock(&f->lock);
 153                 if (list_empty(&f->lru_list)) {
 154                         read_unlock(&f->lock);
 155                         break;
 156                 }
 157
 158                 q = list_first_entry(&f->lru_list,
 159                                 struct inet_frag_queue, lru_list);
 160                 atomic_inc(&q->refcnt);
 161                 read_unlock(&f->lock);
 162
 163                 spin_lock(&q->lock);
 164                 if (!(q->last_in & COMPLETE))
 165                         inet_frag_kill(q, f);
 166                 spin_unlock(&q->lock);
 167
 168                 if (atomic_dec_and_test(&q->refcnt))
 169                         inet_frag_destroy(q, f, &work);
 170                 evicted++;
 171         }
 172
 173         return evicted;
 174 }
 175 EXPORT_SYMBOL(inet_frag_evictor);
 176
 177 static struct inet_frag_queue *inet_frag_intern(struct inet_frag_queue *qp_in,
 178                 struct inet_frags *f, unsigned int hash, void *arg)
 179 {
 180         struct inet_frag_queue *qp;
 181 #ifdef CONFIG_SMP
 182         struct hlist_node *n;
 183 #endif
 184
 185         write_lock(&f->lock);
 186 #ifdef CONFIG_SMP
 187         /* With SMP race we have to recheck hash table, because
 188          * such entry could be created on other cpu, while we
 189          * promoted read lock to write lock.
 190          */
 191         hlist_for_each_entry(qp, n, &f->hash[hash], list) {
 192                 if (f->match(qp, arg)) {
 193                         atomic_inc(&qp->refcnt);
 194                         write_unlock(&f->lock);
 195                         qp_in->last_in |= COMPLETE;
 196                         inet_frag_put(qp_in, f);
 197                         return qp;
 198                 }
 199         }
 200 #endif
 201         qp = qp_in;
 202         if (!mod_timer(&qp->timer, jiffies + f->ctl->timeout))
 203                 atomic_inc(&qp->refcnt);
 204
 205         atomic_inc(&qp->refcnt);
 206         hlist_add_head(&qp->list, &f->hash[hash]);
 207         list_add_tail(&qp->lru_list, &f->lru_list);
 208         f->nqueues++;
 209         write_unlock(&f->lock);
 210         return qp;
 211 }
 212
 213 static struct inet_frag_queue *inet_frag_alloc(struct inet_frags *f, void *arg)
 214 {
 215         struct inet_frag_queue *q;
 216
 217         q = kzalloc(f->qsize, GFP_ATOMIC);
 218         if (q == NULL)
 219                 return NULL;
 220
 221         f->constructor(q, arg);
 222         atomic_add(f->qsize, &f->mem);
 223         setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
 224         spin_lock_init(&q->lock);
 225         atomic_set(&q->refcnt, 1);
 226
 227         return q;
 228 }
 229
 230 static struct inet_frag_queue *inet_frag_create(struct inet_frags *f,
 231                 void *arg, unsigned int hash)
 232 {
 233         struct inet_frag_queue *q;
 234
 235         q = inet_frag_alloc(f, arg);
 236         if (q == NULL)
 237                 return NULL;
 238
 239         return inet_frag_intern(q, f, hash, arg);
 240 }
 241
 242 struct inet_frag_queue *inet_frag_find(struct inet_frags *f, void *key,
 243                 unsigned int hash)
 244 {
 245         struct inet_frag_queue *q;
 246         struct hlist_node *n;
 247
 248         read_lock(&f->lock);
 249         hlist_for_each_entry(q, n, &f->hash[hash], list) {
 250                 if (f->match(q, key)) {
 251                         atomic_inc(&q->refcnt);
 252                         read_unlock(&f->lock);
 253                         return q;
 254                 }
 255         }
 256         read_unlock(&f->lock);
 257
 258         return inet_frag_create(f, key, hash);
 259 }
 260 EXPORT_SYMBOL(inet_frag_find);