inet_fragment.c

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/*
 * 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 <[email protected]>
 *              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/inet_frag.h>

static void inet_frag_secret_rebuild(unsigned long dummy)
{
    struct inet_frags *f = (struct inet_frags *)dummy;
    unsigned long now = jiffies;
    int i;

    write_lock(&f->lock);
    get_random_bytes(&f->rnd, sizeof(u32));
    for (i = 0; i < INETFRAGS_HASHSZ; i++) {
        struct inet_frag_queue *q;
        struct hlist_node *p, *n;

        hlist_for_each_entry_safe(q, p, n, &f->hash[i], list) {
            unsigned int hval = f->hashfn(q);

            if (hval != i) {
                hlist_del(&q->list);

                /* Relink to new hash chain. */
                hlist_add_head(&q->list, &f->hash[hval]);
            }
        }
    }
    write_unlock(&f->lock);

    mod_timer(&f->secret_timer, now + f->secret_interval);
}

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

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

    rwlock_init(&f->lock);

    f->rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
                   (jiffies ^ (jiffies >> 6)));

    setup_timer(&f->secret_timer, inet_frag_secret_rebuild,
            (unsigned long)f);
    f->secret_timer.expires = jiffies + f->secret_interval;
    add_timer(&f->secret_timer);
}
EXPORT_SYMBOL(inet_frags_init);

void inet_frags_init_net(struct netns_frags *nf)
{
    nf->nqueues = 0;
    atomic_set(&nf->mem, 0);
    INIT_LIST_HEAD(&nf->lru_list);
}
EXPORT_SYMBOL(inet_frags_init_net);

void inet_frags_fini(struct inet_frags *f)
{
    del_timer(&f->secret_timer);
}
EXPORT_SYMBOL(inet_frags_fini);

void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
{
    nf->low_thresh = 0;

    local_bh_disable();
    inet_frag_evictor(nf, f, true);
    local_bh_enable();
}
EXPORT_SYMBOL(inet_frags_exit_net);

static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
{
    write_lock(&f->lock);
    hlist_del(&fq->list);
    list_del(&fq->lru_list);
    fq->net->nqueues--;
    write_unlock(&f->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->last_in & INET_FRAG_COMPLETE)) {
        fq_unlink(fq, f);
        atomic_dec(&fq->refcnt);
        fq->last_in |= 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, int *work)
{
    if (work)
        *work -= skb->truesize;

    atomic_sub(skb->truesize, &nf->mem);
    if (f->skb_free)
        f->skb_free(skb);
    kfree_skb(skb);
}

void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f,
                    int *work)
{
    struct sk_buff *fp;
    struct netns_frags *nf;

    WARN_ON(!(q->last_in & 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;

        frag_kfree_skb(nf, f, fp, work);
        fp = xp;
    }

    if (work)
        *work -= f->qsize;
    atomic_sub(f->qsize, &nf->mem);

    if (f->destructor)
        f->destructor(q);
    kfree(q);

}
EXPORT_SYMBOL(inet_frag_destroy);

int inet_frag_evictor(struct netns_frags *nf, struct inet_frags *f, bool force)
{
    struct inet_frag_queue *q;
    int work, evicted = 0;

    if (!force) {
        if (atomic_read(&nf->mem) <= nf->high_thresh)
            return 0;
    }

    work = atomic_read(&nf->mem) - nf->low_thresh;
    while (work > 0) {
        read_lock(&f->lock);
        if (list_empty(&nf->lru_list)) {
            read_unlock(&f->lock);
            break;
        }

        q = list_first_entry(&nf->lru_list,
                struct inet_frag_queue, lru_list);
        atomic_inc(&q->refcnt);
        read_unlock(&f->lock);

        spin_lock(&q->lock);
        if (!(q->last_in & INET_FRAG_COMPLETE))
            inet_frag_kill(q, f);
        spin_unlock(&q->lock);

        if (atomic_dec_and_test(&q->refcnt))
            inet_frag_destroy(q, f, &work);
        evicted++;
    }

    return evicted;
}
EXPORT_SYMBOL(inet_frag_evictor);

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_queue *qp;
#ifdef CONFIG_SMP
    struct hlist_node *n;
#endif
    unsigned int hash;

    write_lock(&f->lock);
    /*
     * While we stayed w/o the lock other CPU could update
     * the rnd seed, so we need to re-calculate the hash
     * chain. Fortunatelly the qp_in can be used to get one.
     */
    hash = f->hashfn(qp_in);
#ifdef CONFIG_SMP
    /* With SMP race we have to recheck hash table, because
     * such entry could be created on other cpu, while we
     * promoted read lock to write lock.
     */
    hlist_for_each_entry(qp, n, &f->hash[hash], list) {
        if (qp->net == nf && f->match(qp, arg)) {
            atomic_inc(&qp->refcnt);
            write_unlock(&f->lock);
            qp_in->last_in |= 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, &f->hash[hash]);
    list_add_tail(&qp->lru_list, &nf->lru_list);
    nf->nqueues++;
    write_unlock(&f->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;

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

    q->net = nf;
    f->constructor(q, arg);
    atomic_add(f->qsize, &nf->mem);
    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)
    __releases(&f->lock)
{
    struct inet_frag_queue *q;
    struct hlist_node *n;

    hlist_for_each_entry(q, n, &f->hash[hash], list) {
        if (q->net == nf && f->match(q, key)) {
            atomic_inc(&q->refcnt);
            read_unlock(&f->lock);
            return q;
        }
    }
    read_unlock(&f->lock);

    return inet_frag_create(nf, f, key);
}
EXPORT_SYMBOL(inet_frag_find);