xt_CT.c

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/*
 * Copyright (c) 2010 Patrick McHardy <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/skbuff.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_CT.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_ecache.h>
#include <net/netfilter/nf_conntrack_timeout.h>
#include <net/netfilter/nf_conntrack_zones.h>

static unsigned int xt_ct_target_v0(struct sk_buff *skb,
                    const struct xt_action_param *par)
{
    const struct xt_ct_target_info *info = par->targinfo;
    struct nf_conn *ct = info->ct;

    /* Previously seen (loopback)? Ignore. */
    if (skb->nfct != NULL)
        return XT_CONTINUE;

    atomic_inc(&ct->ct_general.use);
    skb->nfct = &ct->ct_general;
    skb->nfctinfo = IP_CT_NEW;

    return XT_CONTINUE;
}

static unsigned int xt_ct_target_v1(struct sk_buff *skb,
                    const struct xt_action_param *par)
{
    const struct xt_ct_target_info_v1 *info = par->targinfo;
    struct nf_conn *ct = info->ct;

    /* Previously seen (loopback)? Ignore. */
    if (skb->nfct != NULL)
        return XT_CONTINUE;

    atomic_inc(&ct->ct_general.use);
    skb->nfct = &ct->ct_general;
    skb->nfctinfo = IP_CT_NEW;

    return XT_CONTINUE;
}

static u8 xt_ct_find_proto(const struct xt_tgchk_param *par)
{
    if (par->family == NFPROTO_IPV4) {
        const struct ipt_entry *e = par->entryinfo;

        if (e->ip.invflags & IPT_INV_PROTO)
            return 0;
        return e->ip.proto;
    } else if (par->family == NFPROTO_IPV6) {
        const struct ip6t_entry *e = par->entryinfo;

        if (e->ipv6.invflags & IP6T_INV_PROTO)
            return 0;
        return e->ipv6.proto;
    } else
        return 0;
}

static int
xt_ct_set_helper(struct nf_conn *ct, const char *helper_name,
         const struct xt_tgchk_param *par)
{
    struct nf_conntrack_helper *helper;
    struct nf_conn_help *help;
    u8 proto;

    proto = xt_ct_find_proto(par);
    if (!proto) {
        pr_info("You must specify a L4 protocol, and not use "
            "inversions on it.\n");
        return -ENOENT;
    }

    helper = nf_conntrack_helper_try_module_get(helper_name, par->family,
                            proto);
    if (helper == NULL) {
        pr_info("No such helper \"%s\"\n", helper_name);
        return -ENOENT;
    }

    help = nf_ct_helper_ext_add(ct, helper, GFP_KERNEL);
    if (help == NULL) {
        module_put(helper->me);
        return -ENOMEM;
    }

    help->helper = helper;
    return 0;
}

static int xt_ct_tg_check_v0(const struct xt_tgchk_param *par)
{
    struct xt_ct_target_info *info = par->targinfo;
    struct nf_conntrack_tuple t;
    struct nf_conn *ct;
    int ret;

    if (info->flags & ~XT_CT_NOTRACK)
        return -EINVAL;

    if (info->flags & XT_CT_NOTRACK) {
        ct = nf_ct_untracked_get();
        atomic_inc(&ct->ct_general.use);
        goto out;
    }

#ifndef CONFIG_NF_CONNTRACK_ZONES
    if (info->zone)
        goto err1;
#endif

    ret = nf_ct_l3proto_try_module_get(par->family);
    if (ret < 0)
        goto err1;

    memset(&t, 0, sizeof(t));
    ct = nf_conntrack_alloc(par->net, info->zone, &t, &t, GFP_KERNEL);
    ret = PTR_ERR(ct);
    if (IS_ERR(ct))
        goto err2;

    ret = 0;
    if ((info->ct_events || info->exp_events) &&
        !nf_ct_ecache_ext_add(ct, info->ct_events, info->exp_events,
                  GFP_KERNEL))
        goto err3;

    if (info->helper[0]) {
        ret = xt_ct_set_helper(ct, info->helper, par);
        if (ret < 0)
            goto err3;
    }

    __set_bit(IPS_TEMPLATE_BIT, &ct->status);
    __set_bit(IPS_CONFIRMED_BIT, &ct->status);
out:
    info->ct = ct;
    return 0;

err3:
    nf_conntrack_free(ct);
err2:
    nf_ct_l3proto_module_put(par->family);
err1:
    return ret;
}

#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
static void __xt_ct_tg_timeout_put(struct ctnl_timeout *timeout)
{
    typeof(nf_ct_timeout_put_hook) timeout_put;

    timeout_put = rcu_dereference(nf_ct_timeout_put_hook);
    if (timeout_put)
        timeout_put(timeout);
}
#endif

static int
xt_ct_set_timeout(struct nf_conn *ct, const struct xt_tgchk_param *par,
          const char *timeout_name)
{
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
    typeof(nf_ct_timeout_find_get_hook) timeout_find_get;
    struct ctnl_timeout *timeout;
    struct nf_conn_timeout *timeout_ext;
    struct nf_conntrack_l4proto *l4proto;
    int ret = 0;
    u8 proto;

    rcu_read_lock();
    timeout_find_get = rcu_dereference(nf_ct_timeout_find_get_hook);
    if (timeout_find_get == NULL) {
        ret = -ENOENT;
        pr_info("Timeout policy base is empty\n");
        goto out;
    }

    proto = xt_ct_find_proto(par);
    if (!proto) {
        ret = -EINVAL;
        pr_info("You must specify a L4 protocol, and not use "
            "inversions on it.\n");
        goto out;
    }

    timeout = timeout_find_get(timeout_name);
    if (timeout == NULL) {
        ret = -ENOENT;
        pr_info("No such timeout policy \"%s\"\n", timeout_name);
        goto out;
    }

    if (timeout->l3num != par->family) {
        ret = -EINVAL;
        pr_info("Timeout policy `%s' can only be used by L3 protocol "
            "number %d\n", timeout_name, timeout->l3num);
        goto err_put_timeout;
    }
    /* Make sure the timeout policy matches any existing protocol tracker,
     * otherwise default to generic.
     */
    l4proto = __nf_ct_l4proto_find(par->family, proto);
    if (timeout->l4proto->l4proto != l4proto->l4proto) {
        ret = -EINVAL;
        pr_info("Timeout policy `%s' can only be used by L4 protocol "
            "number %d\n",
            timeout_name, timeout->l4proto->l4proto);
        goto err_put_timeout;
    }
    timeout_ext = nf_ct_timeout_ext_add(ct, timeout, GFP_ATOMIC);
    if (timeout_ext == NULL)
        ret = -ENOMEM;

err_put_timeout:
    __xt_ct_tg_timeout_put(timeout);
out:
    rcu_read_unlock();
    return ret;
#else
    return -EOPNOTSUPP;
#endif
}

static int xt_ct_tg_check_v1(const struct xt_tgchk_param *par)
{
    struct xt_ct_target_info_v1 *info = par->targinfo;
    struct nf_conntrack_tuple t;
    struct nf_conn *ct;
    int ret;

    if (info->flags & ~XT_CT_NOTRACK)
        return -EINVAL;

    if (info->flags & XT_CT_NOTRACK) {
        ct = nf_ct_untracked_get();
        atomic_inc(&ct->ct_general.use);
        goto out;
    }

#ifndef CONFIG_NF_CONNTRACK_ZONES
    if (info->zone)
        goto err1;
#endif

    ret = nf_ct_l3proto_try_module_get(par->family);
    if (ret < 0)
        goto err1;

    memset(&t, 0, sizeof(t));
    ct = nf_conntrack_alloc(par->net, info->zone, &t, &t, GFP_KERNEL);
    ret = PTR_ERR(ct);
    if (IS_ERR(ct))
        goto err2;

    ret = 0;
    if ((info->ct_events || info->exp_events) &&
        !nf_ct_ecache_ext_add(ct, info->ct_events, info->exp_events,
                  GFP_KERNEL))
        goto err3;

    if (info->helper[0]) {
        ret = xt_ct_set_helper(ct, info->helper, par);
        if (ret < 0)
            goto err3;
    }

    if (info->timeout[0]) {
        ret = xt_ct_set_timeout(ct, par, info->timeout);
        if (ret < 0)
            goto err3;
    }

    __set_bit(IPS_TEMPLATE_BIT, &ct->status);
    __set_bit(IPS_CONFIRMED_BIT, &ct->status);
out:
    info->ct = ct;
    return 0;

err3:
    nf_conntrack_free(ct);
err2:
    nf_ct_l3proto_module_put(par->family);
err1:
    return ret;
}

static void xt_ct_tg_destroy_v0(const struct xt_tgdtor_param *par)
{
    struct xt_ct_target_info *info = par->targinfo;
    struct nf_conn *ct = info->ct;
    struct nf_conn_help *help;

    if (!nf_ct_is_untracked(ct)) {
        help = nfct_help(ct);
        if (help)
            module_put(help->helper->me);

        nf_ct_l3proto_module_put(par->family);
    }
    nf_ct_put(info->ct);
}

static void xt_ct_destroy_timeout(struct nf_conn *ct)
{
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
    struct nf_conn_timeout *timeout_ext;
    typeof(nf_ct_timeout_put_hook) timeout_put;

    rcu_read_lock();
    timeout_put = rcu_dereference(nf_ct_timeout_put_hook);

    if (timeout_put) {
        timeout_ext = nf_ct_timeout_find(ct);
        if (timeout_ext)
            timeout_put(timeout_ext->timeout);
    }
    rcu_read_unlock();
#endif
}

static void xt_ct_tg_destroy_v1(const struct xt_tgdtor_param *par)
{
    struct xt_ct_target_info_v1 *info = par->targinfo;
    struct nf_conn *ct = info->ct;
    struct nf_conn_help *help;

    if (!nf_ct_is_untracked(ct)) {
        help = nfct_help(ct);
        if (help)
            module_put(help->helper->me);

        nf_ct_l3proto_module_put(par->family);

        xt_ct_destroy_timeout(ct);
    }
    nf_ct_put(info->ct);
}

static struct xt_target xt_ct_tg_reg[] __read_mostly = {
    {
        .name       = "CT",
        .family     = NFPROTO_UNSPEC,
        .targetsize = sizeof(struct xt_ct_target_info),
        .checkentry = xt_ct_tg_check_v0,
        .destroy    = xt_ct_tg_destroy_v0,
        .target     = xt_ct_target_v0,
        .table      = "raw",
        .me     = THIS_MODULE,
    },
    {
        .name       = "CT",
        .family     = NFPROTO_UNSPEC,
        .revision   = 1,
        .targetsize = sizeof(struct xt_ct_target_info_v1),
        .checkentry = xt_ct_tg_check_v1,
        .destroy    = xt_ct_tg_destroy_v1,
        .target     = xt_ct_target_v1,
        .table      = "raw",
        .me     = THIS_MODULE,
    },
};

static int __init xt_ct_tg_init(void)
{
    return xt_register_targets(xt_ct_tg_reg, ARRAY_SIZE(xt_ct_tg_reg));
}

static void __exit xt_ct_tg_exit(void)
{
    xt_unregister_targets(xt_ct_tg_reg, ARRAY_SIZE(xt_ct_tg_reg));
}

module_init(xt_ct_tg_init);
module_exit(xt_ct_tg_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Xtables: connection tracking target");
MODULE_ALIAS("ipt_CT");
MODULE_ALIAS("ip6t_CT");