linux/net/ipv4/inet_fragment.c
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   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
  26static 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
  54void 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}
  71EXPORT_SYMBOL(inet_frags_init);
  72
  73void 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}
  79EXPORT_SYMBOL(inet_frags_init_net);
  80
  81void inet_frags_fini(struct inet_frags *f)
  82{
  83        del_timer(&f->secret_timer);
  84}
  85EXPORT_SYMBOL(inet_frags_fini);
  86
  87void 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}
  95EXPORT_SYMBOL(inet_frags_exit_net);
  96
  97static 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
 106void 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}
 117EXPORT_SYMBOL(inet_frag_kill);
 118
 119static 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
 131void 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}
 159EXPORT_SYMBOL(inet_frag_destroy);
 160
 161int 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}
 196EXPORT_SYMBOL(inet_frag_evictor);
 197
 198static 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
 242static 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
 261static 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
 273struct 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}
 291EXPORT_SYMBOL(inet_frag_find);
 292
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