inet_hashtables.c

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/*
 * INET     An implementation of the TCP/IP protocol suite for the LINUX
 *      operating system.  INET is implemented using the BSD Socket
 *      interface as the means of communication with the user level.
 *
 *      Generic INET transport hashtables
 *
 * Authors: Lotsa people, from code originally in tcp
 *
 *  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.
 */

#include <linux/module.h>
#include <linux/random.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/wait.h>

#include <net/inet_connection_sock.h>
#include <net/inet_hashtables.h>
#include <net/secure_seq.h>
#include <net/ip.h>

/*
 * Allocate and initialize a new local port bind bucket.
 * The bindhash mutex for snum's hash chain must be held here.
 */
struct inet_bind_bucket *inet_bind_bucket_create(struct kmem_cache *cachep,
                         struct net *net,
                         struct inet_bind_hashbucket *head,
                         const unsigned short snum)
{
    struct inet_bind_bucket *tb = kmem_cache_alloc(cachep, GFP_ATOMIC);

    if (tb != NULL) {
        write_pnet(&tb->ib_net, hold_net(net));
        tb->port      = snum;
        tb->fastreuse = 0;
        tb->num_owners = 0;
        INIT_HLIST_HEAD(&tb->owners);
        hlist_add_head(&tb->node, &head->chain);
    }
    return tb;
}

/*
 * Caller must hold hashbucket lock for this tb with local BH disabled
 */
void inet_bind_bucket_destroy(struct kmem_cache *cachep, struct inet_bind_bucket *tb)
{
    if (hlist_empty(&tb->owners)) {
        __hlist_del(&tb->node);
        release_net(ib_net(tb));
        kmem_cache_free(cachep, tb);
    }
}

void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
            const unsigned short snum)
{
    struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;

    atomic_inc(&hashinfo->bsockets);

    inet_sk(sk)->inet_num = snum;
    sk_add_bind_node(sk, &tb->owners);
    tb->num_owners++;
    inet_csk(sk)->icsk_bind_hash = tb;
}

/*
 * Get rid of any references to a local port held by the given sock.
 */
static void __inet_put_port(struct sock *sk)
{
    struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
    const int bhash = inet_bhashfn(sock_net(sk), inet_sk(sk)->inet_num,
            hashinfo->bhash_size);
    struct inet_bind_hashbucket *head = &hashinfo->bhash[bhash];
    struct inet_bind_bucket *tb;

    atomic_dec(&hashinfo->bsockets);

    spin_lock(&head->lock);
    tb = inet_csk(sk)->icsk_bind_hash;
    __sk_del_bind_node(sk);
    tb->num_owners--;
    inet_csk(sk)->icsk_bind_hash = NULL;
    inet_sk(sk)->inet_num = 0;
    inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
    spin_unlock(&head->lock);
}

void inet_put_port(struct sock *sk)
{
    local_bh_disable();
    __inet_put_port(sk);
    local_bh_enable();
}
EXPORT_SYMBOL(inet_put_port);

int __inet_inherit_port(struct sock *sk, struct sock *child)
{
    struct inet_hashinfo *table = sk->sk_prot->h.hashinfo;
    unsigned short port = inet_sk(child)->inet_num;
    const int bhash = inet_bhashfn(sock_net(sk), port,
            table->bhash_size);
    struct inet_bind_hashbucket *head = &table->bhash[bhash];
    struct inet_bind_bucket *tb;

    spin_lock(&head->lock);
    tb = inet_csk(sk)->icsk_bind_hash;
    if (tb->port != port) {
        /* NOTE: using tproxy and redirecting skbs to a proxy
         * on a different listener port breaks the assumption
         * that the listener socket's icsk_bind_hash is the same
         * as that of the child socket. We have to look up or
         * create a new bind bucket for the child here. */
        struct hlist_node *node;
        inet_bind_bucket_for_each(tb, node, &head->chain) {
            if (net_eq(ib_net(tb), sock_net(sk)) &&
                tb->port == port)
                break;
        }
        if (!node) {
            tb = inet_bind_bucket_create(table->bind_bucket_cachep,
                             sock_net(sk), head, port);
            if (!tb) {
                spin_unlock(&head->lock);
                return -ENOMEM;
            }
        }
    }
    inet_bind_hash(child, tb, port);
    spin_unlock(&head->lock);

    return 0;
}
EXPORT_SYMBOL_GPL(__inet_inherit_port);

static inline int compute_score(struct sock *sk, struct net *net,
                const unsigned short hnum, const __be32 daddr,
                const int dif)
{
    int score = -1;
    struct inet_sock *inet = inet_sk(sk);

    if (net_eq(sock_net(sk), net) && inet->inet_num == hnum &&
            !ipv6_only_sock(sk)) {
        __be32 rcv_saddr = inet->inet_rcv_saddr;
        score = sk->sk_family == PF_INET ? 1 : 0;
        if (rcv_saddr) {
            if (rcv_saddr != daddr)
                return -1;
            score += 2;
        }
        if (sk->sk_bound_dev_if) {
            if (sk->sk_bound_dev_if != dif)
                return -1;
            score += 2;
        }
    }
    return score;
}

/*
 * Don't inline this cruft. Here are some nice properties to exploit here. The
 * BSD API does not allow a listening sock to specify the remote port nor the
 * remote address for the connection. So always assume those are both
 * wildcarded during the search since they can never be otherwise.
 */


struct sock *__inet_lookup_listener(struct net *net,
                    struct inet_hashinfo *hashinfo,
                    const __be32 daddr, const unsigned short hnum,
                    const int dif)
{
    struct sock *sk, *result;
    struct hlist_nulls_node *node;
    unsigned int hash = inet_lhashfn(net, hnum);
    struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash];
    int score, hiscore;

    rcu_read_lock();
begin:
    result = NULL;
    hiscore = -1;
    sk_nulls_for_each_rcu(sk, node, &ilb->head) {
        score = compute_score(sk, net, hnum, daddr, dif);
        if (score > hiscore) {
            result = sk;
            hiscore = score;
        }
    }
    /*
     * if the nulls value we got at the end of this lookup is
     * not the expected one, we must restart lookup.
     * We probably met an item that was moved to another chain.
     */
    if (get_nulls_value(node) != hash + LISTENING_NULLS_BASE)
        goto begin;
    if (result) {
        if (unlikely(!atomic_inc_not_zero(&result->sk_refcnt)))
            result = NULL;
        else if (unlikely(compute_score(result, net, hnum, daddr,
                  dif) < hiscore)) {
            sock_put(result);
            goto begin;
        }
    }
    rcu_read_unlock();
    return result;
}
EXPORT_SYMBOL_GPL(__inet_lookup_listener);

struct sock *__inet_lookup_established(struct net *net,
                  struct inet_hashinfo *hashinfo,
                  const __be32 saddr, const __be16 sport,
                  const __be32 daddr, const u16 hnum,
                  const int dif)
{
    INET_ADDR_COOKIE(acookie, saddr, daddr)
    const __portpair ports = INET_COMBINED_PORTS(sport, hnum);
    struct sock *sk;
    const struct hlist_nulls_node *node;
    /* Optimize here for direct hit, only listening connections can
     * have wildcards anyways.
     */
    unsigned int hash = inet_ehashfn(net, daddr, hnum, saddr, sport);
    unsigned int slot = hash & hashinfo->ehash_mask;
    struct inet_ehash_bucket *head = &hashinfo->ehash[slot];

    rcu_read_lock();
begin:
    sk_nulls_for_each_rcu(sk, node, &head->chain) {
        if (INET_MATCH(sk, net, hash, acookie,
                    saddr, daddr, ports, dif)) {
            if (unlikely(!atomic_inc_not_zero(&sk->sk_refcnt)))
                goto begintw;
            if (unlikely(!INET_MATCH(sk, net, hash, acookie,
                saddr, daddr, ports, dif))) {
                sock_put(sk);
                goto begin;
            }
            goto out;
        }
    }
    /*
     * if the nulls value we got at the end of this lookup is
     * not the expected one, we must restart lookup.
     * We probably met an item that was moved to another chain.
     */
    if (get_nulls_value(node) != slot)
        goto begin;

begintw:
    /* Must check for a TIME_WAIT'er before going to listener hash. */
    sk_nulls_for_each_rcu(sk, node, &head->twchain) {
        if (INET_TW_MATCH(sk, net, hash, acookie,
                    saddr, daddr, ports, dif)) {
            if (unlikely(!atomic_inc_not_zero(&sk->sk_refcnt))) {
                sk = NULL;
                goto out;
            }
            if (unlikely(!INET_TW_MATCH(sk, net, hash, acookie,
                 saddr, daddr, ports, dif))) {
                sock_put(sk);
                goto begintw;
            }
            goto out;
        }
    }
    /*
     * if the nulls value we got at the end of this lookup is
     * not the expected one, we must restart lookup.
     * We probably met an item that was moved to another chain.
     */
    if (get_nulls_value(node) != slot)
        goto begintw;
    sk = NULL;
out:
    rcu_read_unlock();
    return sk;
}
EXPORT_SYMBOL_GPL(__inet_lookup_established);

/* called with local bh disabled */
static int __inet_check_established(struct inet_timewait_death_row *death_row,
                    struct sock *sk, __u16 lport,
                    struct inet_timewait_sock **twp)
{
    struct inet_hashinfo *hinfo = death_row->hashinfo;
    struct inet_sock *inet = inet_sk(sk);
    __be32 daddr = inet->inet_rcv_saddr;
    __be32 saddr = inet->inet_daddr;
    int dif = sk->sk_bound_dev_if;
    INET_ADDR_COOKIE(acookie, saddr, daddr)
    const __portpair ports = INET_COMBINED_PORTS(inet->inet_dport, lport);
    struct net *net = sock_net(sk);
    unsigned int hash = inet_ehashfn(net, daddr, lport,
                     saddr, inet->inet_dport);
    struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);
    spinlock_t *lock = inet_ehash_lockp(hinfo, hash);
    struct sock *sk2;
    const struct hlist_nulls_node *node;
    struct inet_timewait_sock *tw;
    int twrefcnt = 0;

    spin_lock(lock);

    /* Check TIME-WAIT sockets first. */
    sk_nulls_for_each(sk2, node, &head->twchain) {
        tw = inet_twsk(sk2);

        if (INET_TW_MATCH(sk2, net, hash, acookie,
                    saddr, daddr, ports, dif)) {
            if (twsk_unique(sk, sk2, twp))
                goto unique;
            else
                goto not_unique;
        }
    }
    tw = NULL;

    /* And established part... */
    sk_nulls_for_each(sk2, node, &head->chain) {
        if (INET_MATCH(sk2, net, hash, acookie,
                    saddr, daddr, ports, dif))
            goto not_unique;
    }

unique:
    /* Must record num and sport now. Otherwise we will see
     * in hash table socket with a funny identity. */
    inet->inet_num = lport;
    inet->inet_sport = htons(lport);
    sk->sk_hash = hash;
    WARN_ON(!sk_unhashed(sk));
    __sk_nulls_add_node_rcu(sk, &head->chain);
    if (tw) {
        twrefcnt = inet_twsk_unhash(tw);
        NET_INC_STATS_BH(net, LINUX_MIB_TIMEWAITRECYCLED);
    }
    spin_unlock(lock);
    if (twrefcnt)
        inet_twsk_put(tw);
    sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);

    if (twp) {
        *twp = tw;
    } else if (tw) {
        /* Silly. Should hash-dance instead... */
        inet_twsk_deschedule(tw, death_row);

        inet_twsk_put(tw);
    }
    return 0;

not_unique:
    spin_unlock(lock);
    return -EADDRNOTAVAIL;
}

static inline u32 inet_sk_port_offset(const struct sock *sk)
{
    const struct inet_sock *inet = inet_sk(sk);
    return secure_ipv4_port_ephemeral(inet->inet_rcv_saddr,
                      inet->inet_daddr,
                      inet->inet_dport);
}

int __inet_hash_nolisten(struct sock *sk, struct inet_timewait_sock *tw)
{
    struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
    struct hlist_nulls_head *list;
    spinlock_t *lock;
    struct inet_ehash_bucket *head;
    int twrefcnt = 0;

    WARN_ON(!sk_unhashed(sk));

    sk->sk_hash = inet_sk_ehashfn(sk);
    head = inet_ehash_bucket(hashinfo, sk->sk_hash);
    list = &head->chain;
    lock = inet_ehash_lockp(hashinfo, sk->sk_hash);

    spin_lock(lock);
    __sk_nulls_add_node_rcu(sk, list);
    if (tw) {
        WARN_ON(sk->sk_hash != tw->tw_hash);
        twrefcnt = inet_twsk_unhash(tw);
    }
    spin_unlock(lock);
    sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
    return twrefcnt;
}
EXPORT_SYMBOL_GPL(__inet_hash_nolisten);

static void __inet_hash(struct sock *sk)
{
    struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
    struct inet_listen_hashbucket *ilb;

    if (sk->sk_state != TCP_LISTEN) {
        __inet_hash_nolisten(sk, NULL);
        return;
    }

    WARN_ON(!sk_unhashed(sk));
    ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];

    spin_lock(&ilb->lock);
    __sk_nulls_add_node_rcu(sk, &ilb->head);
    sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
    spin_unlock(&ilb->lock);
}

void inet_hash(struct sock *sk)
{
    if (sk->sk_state != TCP_CLOSE) {
        local_bh_disable();
        __inet_hash(sk);
        local_bh_enable();
    }
}
EXPORT_SYMBOL_GPL(inet_hash);

void inet_unhash(struct sock *sk)
{
    struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
    spinlock_t *lock;
    int done;

    if (sk_unhashed(sk))
        return;

    if (sk->sk_state == TCP_LISTEN)
        lock = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)].lock;
    else
        lock = inet_ehash_lockp(hashinfo, sk->sk_hash);

    spin_lock_bh(lock);
    done =__sk_nulls_del_node_init_rcu(sk);
    if (done)
        sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
    spin_unlock_bh(lock);
}
EXPORT_SYMBOL_GPL(inet_unhash);

int __inet_hash_connect(struct inet_timewait_death_row *death_row,
        struct sock *sk, u32 port_offset,
        int (*check_established)(struct inet_timewait_death_row *,
            struct sock *, __u16, struct inet_timewait_sock **),
        int (*hash)(struct sock *sk, struct inet_timewait_sock *twp))
{
    struct inet_hashinfo *hinfo = death_row->hashinfo;
    const unsigned short snum = inet_sk(sk)->inet_num;
    struct inet_bind_hashbucket *head;
    struct inet_bind_bucket *tb;
    int ret;
    struct net *net = sock_net(sk);
    int twrefcnt = 1;

    if (!snum) {
        int i, remaining, low, high, port;
        static u32 hint;
        u32 offset = hint + port_offset;
        struct hlist_node *node;
        struct inet_timewait_sock *tw = NULL;

        inet_get_local_port_range(&low, &high);
        remaining = (high - low) + 1;

        local_bh_disable();
        for (i = 1; i <= remaining; i++) {
            port = low + (i + offset) % remaining;
            if (inet_is_reserved_local_port(port))
                continue;
            head = &hinfo->bhash[inet_bhashfn(net, port,
                    hinfo->bhash_size)];
            spin_lock(&head->lock);

            /* Does not bother with rcv_saddr checks,
             * because the established check is already
             * unique enough.
             */
            inet_bind_bucket_for_each(tb, node, &head->chain) {
                if (net_eq(ib_net(tb), net) &&
                    tb->port == port) {
                    if (tb->fastreuse >= 0)
                        goto next_port;
                    WARN_ON(hlist_empty(&tb->owners));
                    if (!check_established(death_row, sk,
                                port, &tw))
                        goto ok;
                    goto next_port;
                }
            }

            tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep,
                    net, head, port);
            if (!tb) {
                spin_unlock(&head->lock);
                break;
            }
            tb->fastreuse = -1;
            goto ok;

        next_port:
            spin_unlock(&head->lock);
        }
        local_bh_enable();

        return -EADDRNOTAVAIL;

ok:
        hint += i;

        /* Head lock still held and bh's disabled */
        inet_bind_hash(sk, tb, port);
        if (sk_unhashed(sk)) {
            inet_sk(sk)->inet_sport = htons(port);
            twrefcnt += hash(sk, tw);
        }
        if (tw)
            twrefcnt += inet_twsk_bind_unhash(tw, hinfo);
        spin_unlock(&head->lock);

        if (tw) {
            inet_twsk_deschedule(tw, death_row);
            while (twrefcnt) {
                twrefcnt--;
                inet_twsk_put(tw);
            }
        }

        ret = 0;
        goto out;
    }

    head = &hinfo->bhash[inet_bhashfn(net, snum, hinfo->bhash_size)];
    tb  = inet_csk(sk)->icsk_bind_hash;
    spin_lock_bh(&head->lock);
    if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) {
        hash(sk, NULL);
        spin_unlock_bh(&head->lock);
        return 0;
    } else {
        spin_unlock(&head->lock);
        /* No definite answer... Walk to established hash table */
        ret = check_established(death_row, sk, snum, NULL);
out:
        local_bh_enable();
        return ret;
    }
}

/*
 * Bind a port for a connect operation and hash it.
 */
int inet_hash_connect(struct inet_timewait_death_row *death_row,
              struct sock *sk)
{
    return __inet_hash_connect(death_row, sk, inet_sk_port_offset(sk),
            __inet_check_established, __inet_hash_nolisten);
}
EXPORT_SYMBOL_GPL(inet_hash_connect);

void inet_hashinfo_init(struct inet_hashinfo *h)
{
    int i;

    atomic_set(&h->bsockets, 0);
    for (i = 0; i < INET_LHTABLE_SIZE; i++) {
        spin_lock_init(&h->listening_hash[i].lock);
        INIT_HLIST_NULLS_HEAD(&h->listening_hash[i].head,
                      i + LISTENING_NULLS_BASE);
        }
}
EXPORT_SYMBOL_GPL(inet_hashinfo_init);