[deliverable/linux.git] / net / ipv4 / inet_fragment.c

/*
 * inet fragments management
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 *              Authors:        Pavel Emelyanov <xemul@openvz.org>
 *                              Started as consolidation of ipv4/ip_fragment.c,
 *                              ipv6/reassembly. and ipv6 nf conntrack reassembly
 */

#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/random.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/slab.h>

#include <net/sock.h>
#include <net/inet_frag.h>
#include <net/inet_ecn.h>

#define INETFRAGS_EVICT_BUCKETS   128
#define INETFRAGS_EVICT_MAX       512

/* don't rebuild inetfrag table with new secret more often than this */
#define INETFRAGS_MIN_REBUILD_INTERVAL (5 * HZ)

/* Given the OR values of all fragments, apply RFC 3168 5.3 requirements
 * Value : 0xff if frame should be dropped.
 *         0 or INET_ECN_CE value, to be ORed in to final iph->tos field
 */
const u8 ip_frag_ecn_table[16] = {
        /* at least one fragment had CE, and others ECT_0 or ECT_1 */
        [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0]                      = INET_ECN_CE,
        [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1]                      = INET_ECN_CE,
        [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1]   = INET_ECN_CE,

        /* invalid combinations : drop frame */
        [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff,
        [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff,
        [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff,
        [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
        [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff,
        [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff,
        [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
};
EXPORT_SYMBOL(ip_frag_ecn_table);

static unsigned int
inet_frag_hashfn(const struct inet_frags *f, const struct inet_frag_queue *q)
{
        return f->hashfn(q) & (INETFRAGS_HASHSZ - 1);
}

static bool inet_frag_may_rebuild(struct inet_frags *f)
{
        return time_after(jiffies,
               f->last_rebuild_jiffies + INETFRAGS_MIN_REBUILD_INTERVAL);
}

static void inet_frag_secret_rebuild(struct inet_frags *f)
{
        int i;

        write_seqlock_bh(&f->rnd_seqlock);

        if (!inet_frag_may_rebuild(f))
                goto out;

        get_random_bytes(&f->rnd, sizeof(u32));

        for (i = 0; i < INETFRAGS_HASHSZ; i++) {
                struct inet_frag_bucket *hb;
                struct inet_frag_queue *q;
                struct hlist_node *n;

                hb = &f->hash[i];
                spin_lock(&hb->chain_lock);

                hlist_for_each_entry_safe(q, n, &hb->chain, list) {
                        unsigned int hval = inet_frag_hashfn(f, q);

                        if (hval != i) {
                                struct inet_frag_bucket *hb_dest;

                                hlist_del(&q->list);

                                /* Relink to new hash chain. */
                                hb_dest = &f->hash[hval];

                                /* This is the only place where we take
                                 * another chain_lock while already holding
                                 * one.  As this will not run concurrently,
                                 * we cannot deadlock on hb_dest lock below, if its
                                 * already locked it will be released soon since
                                 * other caller cannot be waiting for hb lock
                                 * that we've taken above.
                                 */
                                spin_lock_nested(&hb_dest->chain_lock,
                                                 SINGLE_DEPTH_NESTING);
                                hlist_add_head(&q->list, &hb_dest->chain);
                                spin_unlock(&hb_dest->chain_lock);
                        }
                }
                spin_unlock(&hb->chain_lock);
        }

        f->rebuild = false;
        f->last_rebuild_jiffies = jiffies;
out:
        write_sequnlock_bh(&f->rnd_seqlock);
}

static bool inet_fragq_should_evict(const struct inet_frag_queue *q)
{
        return q->net->low_thresh == 0 ||
               frag_mem_limit(q->net) >= q->net->low_thresh;
}

static unsigned int
inet_evict_bucket(struct inet_frags *f, struct inet_frag_bucket *hb)
{
        struct inet_frag_queue *fq;
        struct hlist_node *n;
        unsigned int evicted = 0;
        HLIST_HEAD(expired);

evict_again:
        spin_lock(&hb->chain_lock);

        hlist_for_each_entry_safe(fq, n, &hb->chain, list) {
                if (!inet_fragq_should_evict(fq))
                        continue;

                if (!del_timer(&fq->timer)) {
                        /* q expiring right now thus increment its refcount so
                         * it won't be freed under us and wait until the timer
                         * has finished executing then destroy it
                         */
                        atomic_inc(&fq->refcnt);
                        spin_unlock(&hb->chain_lock);
                        del_timer_sync(&fq->timer);
                        WARN_ON(atomic_read(&fq->refcnt) != 1);
                        inet_frag_put(fq, f);
                        goto evict_again;
                }

                /* suppress xmit of (icmp) error packet */
                fq->flags &= ~INET_FRAG_FIRST_IN;
                fq->flags |= INET_FRAG_EVICTED;
                hlist_del(&fq->list);
                hlist_add_head(&fq->list, &expired);
                ++evicted;
        }

        spin_unlock(&hb->chain_lock);

        hlist_for_each_entry_safe(fq, n, &expired, list)
                f->frag_expire((unsigned long) fq);

        return evicted;
}

static void inet_frag_worker(struct work_struct *work)
{
        unsigned int budget = INETFRAGS_EVICT_BUCKETS;
        unsigned int i, evicted = 0;
        struct inet_frags *f;

        f = container_of(work, struct inet_frags, frags_work);

        BUILD_BUG_ON(INETFRAGS_EVICT_BUCKETS >= INETFRAGS_HASHSZ);

        local_bh_disable();

        for (i = ACCESS_ONCE(f->next_bucket); budget; --budget) {
                evicted += inet_evict_bucket(f, &f->hash[i]);
                i = (i + 1) & (INETFRAGS_HASHSZ - 1);
                if (evicted > INETFRAGS_EVICT_MAX)
                        break;
        }

        f->next_bucket = i;

        local_bh_enable();

        if (f->rebuild && inet_frag_may_rebuild(f))
                inet_frag_secret_rebuild(f);
}

static void inet_frag_schedule_worker(struct inet_frags *f)
{
        if (unlikely(!work_pending(&f->frags_work)))
                schedule_work(&f->frags_work);
}

void inet_frags_init(struct inet_frags *f)
{
        int i;

        INIT_WORK(&f->frags_work, inet_frag_worker);

        for (i = 0; i < INETFRAGS_HASHSZ; i++) {
                struct inet_frag_bucket *hb = &f->hash[i];

                spin_lock_init(&hb->chain_lock);
                INIT_HLIST_HEAD(&hb->chain);
        }

        seqlock_init(&f->rnd_seqlock);
        f->last_rebuild_jiffies = 0;
}
EXPORT_SYMBOL(inet_frags_init);

void inet_frags_init_net(struct netns_frags *nf)
{
        init_frag_mem_limit(nf);
}
EXPORT_SYMBOL(inet_frags_init_net);

void inet_frags_fini(struct inet_frags *f)
{
        cancel_work_sync(&f->frags_work);
}
EXPORT_SYMBOL(inet_frags_fini);

void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
{
        unsigned int seq;
        int i;

        nf->low_thresh = 0;
        local_bh_disable();

evict_again:
        seq = read_seqbegin(&f->rnd_seqlock);

        for (i = 0; i < INETFRAGS_HASHSZ ; i++)
                inet_evict_bucket(f, &f->hash[i]);

        if (read_seqretry(&f->rnd_seqlock, seq))
                goto evict_again;

        local_bh_enable();

        percpu_counter_destroy(&nf->mem);
}
EXPORT_SYMBOL(inet_frags_exit_net);

static struct inet_frag_bucket *
get_frag_bucket_locked(struct inet_frag_queue *fq, struct inet_frags *f)
__acquires(hb->chain_lock)
{
        struct inet_frag_bucket *hb;
        unsigned int seq, hash;

 restart:
        seq = read_seqbegin(&f->rnd_seqlock);

        hash = inet_frag_hashfn(f, fq);
        hb = &f->hash[hash];

        spin_lock(&hb->chain_lock);
        if (read_seqretry(&f->rnd_seqlock, seq)) {
                spin_unlock(&hb->chain_lock);
                goto restart;
        }

        return hb;
}

static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
{
        struct inet_frag_bucket *hb;

        hb = get_frag_bucket_locked(fq, f);
        hlist_del(&fq->list);
        spin_unlock(&hb->chain_lock);
}

void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
{
        if (del_timer(&fq->timer))
                atomic_dec(&fq->refcnt);

        if (!(fq->flags & INET_FRAG_COMPLETE)) {
                fq_unlink(fq, f);
                atomic_dec(&fq->refcnt);
                fq->flags |= INET_FRAG_COMPLETE;
        }
}
EXPORT_SYMBOL(inet_frag_kill);

static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
                                  struct sk_buff *skb)
{
        if (f->skb_free)
                f->skb_free(skb);
        kfree_skb(skb);
}

void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f)
{
        struct sk_buff *fp;
        struct netns_frags *nf;
        unsigned int sum, sum_truesize = 0;

        WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
        WARN_ON(del_timer(&q->timer) != 0);

        /* Release all fragment data. */
        fp = q->fragments;
        nf = q->net;
        while (fp) {
                struct sk_buff *xp = fp->next;

                sum_truesize += fp->truesize;
                frag_kfree_skb(nf, f, fp);
                fp = xp;
        }
        sum = sum_truesize + f->qsize;
        sub_frag_mem_limit(q, sum);

        if (f->destructor)
                f->destructor(q);
        kfree(q);
}
EXPORT_SYMBOL(inet_frag_destroy);

static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
                                                struct inet_frag_queue *qp_in,
                                                struct inet_frags *f,
                                                void *arg)
{
        struct inet_frag_bucket *hb = get_frag_bucket_locked(qp_in, f);
        struct inet_frag_queue *qp;

#ifdef CONFIG_SMP
        /* With SMP race we have to recheck hash table, because
         * such entry could have been created on other cpu before
         * we acquired hash bucket lock.
         */
        hlist_for_each_entry(qp, &hb->chain, list) {
                if (qp->net == nf && f->match(qp, arg)) {
                        atomic_inc(&qp->refcnt);
                        spin_unlock(&hb->chain_lock);
                        qp_in->flags |= INET_FRAG_COMPLETE;
                        inet_frag_put(qp_in, f);
                        return qp;
                }
        }
#endif
        qp = qp_in;
        if (!mod_timer(&qp->timer, jiffies + nf->timeout))
                atomic_inc(&qp->refcnt);

        atomic_inc(&qp->refcnt);
        hlist_add_head(&qp->list, &hb->chain);

        spin_unlock(&hb->chain_lock);

        return qp;
}

static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
                                               struct inet_frags *f,
                                               void *arg)
{
        struct inet_frag_queue *q;

        if (frag_mem_limit(nf) > nf->high_thresh) {
                inet_frag_schedule_worker(f);
                return NULL;
        }

        q = kzalloc(f->qsize, GFP_ATOMIC);
        if (q == NULL)
                return NULL;

        q->net = nf;
        f->constructor(q, arg);
        add_frag_mem_limit(q, f->qsize);

        setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
        spin_lock_init(&q->lock);
        atomic_set(&q->refcnt, 1);

        return q;
}

static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
                                                struct inet_frags *f,
                                                void *arg)
{
        struct inet_frag_queue *q;

        q = inet_frag_alloc(nf, f, arg);
        if (q == NULL)
                return NULL;

        return inet_frag_intern(nf, q, f, arg);
}

struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
                                       struct inet_frags *f, void *key,
                                       unsigned int hash)
{
        struct inet_frag_bucket *hb;
        struct inet_frag_queue *q;
        int depth = 0;

        if (frag_mem_limit(nf) > nf->low_thresh)
                inet_frag_schedule_worker(f);

        hash &= (INETFRAGS_HASHSZ - 1);
        hb = &f->hash[hash];

        spin_lock(&hb->chain_lock);
        hlist_for_each_entry(q, &hb->chain, list) {
                if (q->net == nf && f->match(q, key)) {
                        atomic_inc(&q->refcnt);
                        spin_unlock(&hb->chain_lock);
                        return q;
                }
                depth++;
        }
        spin_unlock(&hb->chain_lock);

        if (depth <= INETFRAGS_MAXDEPTH)
                return inet_frag_create(nf, f, key);

        if (inet_frag_may_rebuild(f)) {
                if (!f->rebuild)
                        f->rebuild = true;
                inet_frag_schedule_worker(f);
        }

        return ERR_PTR(-ENOBUFS);
}
EXPORT_SYMBOL(inet_frag_find);

void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
                                   const char *prefix)
{
        static const char msg[] = "inet_frag_find: Fragment hash bucket"
                " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH)
                ". Dropping fragment.\n";

        if (PTR_ERR(q) == -ENOBUFS)
                LIMIT_NETDEBUG(KERN_WARNING "%s%s", prefix, msg);
}
EXPORT_SYMBOL(inet_frag_maybe_warn_overflow);