act_ipt.c

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/*
 * net/sched/ipt.c     iptables target interface
 *
 *TODO: Add other tables. For now we only support the ipv4 table targets
 *
 *      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.
 *
 * Copyright:   Jamal Hadi Salim (2002-4)
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <linux/tc_act/tc_ipt.h>
#include <net/tc_act/tc_ipt.h>

#include <linux/netfilter_ipv4/ip_tables.h>


#define IPT_TAB_MASK     15
static struct tcf_common *tcf_ipt_ht[IPT_TAB_MASK + 1];
static u32 ipt_idx_gen;
static DEFINE_RWLOCK(ipt_lock);

static struct tcf_hashinfo ipt_hash_info = {
    .htab   =   tcf_ipt_ht,
    .hmask  =   IPT_TAB_MASK,
    .lock   =   &ipt_lock,
};

static int ipt_init_target(struct xt_entry_target *t, char *table, unsigned int hook)
{
    struct xt_tgchk_param par;
    struct xt_target *target;
    int ret = 0;

    target = xt_request_find_target(AF_INET, t->u.user.name,
                    t->u.user.revision);
    if (IS_ERR(target))
        return PTR_ERR(target);

    t->u.kernel.target = target;
    par.table     = table;
    par.entryinfo = NULL;
    par.target    = target;
    par.targinfo  = t->data;
    par.hook_mask = hook;
    par.family    = NFPROTO_IPV4;

    ret = xt_check_target(&par, t->u.target_size - sizeof(*t), 0, false);
    if (ret < 0) {
        module_put(t->u.kernel.target->me);
        return ret;
    }
    return 0;
}

static void ipt_destroy_target(struct xt_entry_target *t)
{
    struct xt_tgdtor_param par = {
        .target   = t->u.kernel.target,
        .targinfo = t->data,
    };
    if (par.target->destroy != NULL)
        par.target->destroy(&par);
    module_put(par.target->me);
}

static int tcf_ipt_release(struct tcf_ipt *ipt, int bind)
{
    int ret = 0;
    if (ipt) {
        if (bind)
            ipt->tcf_bindcnt--;
        ipt->tcf_refcnt--;
        if (ipt->tcf_bindcnt <= 0 && ipt->tcf_refcnt <= 0) {
            ipt_destroy_target(ipt->tcfi_t);
            kfree(ipt->tcfi_tname);
            kfree(ipt->tcfi_t);
            tcf_hash_destroy(&ipt->common, &ipt_hash_info);
            ret = ACT_P_DELETED;
        }
    }
    return ret;
}

static const struct nla_policy ipt_policy[TCA_IPT_MAX + 1] = {
    [TCA_IPT_TABLE] = { .type = NLA_STRING, .len = IFNAMSIZ },
    [TCA_IPT_HOOK]  = { .type = NLA_U32 },
    [TCA_IPT_INDEX] = { .type = NLA_U32 },
    [TCA_IPT_TARG]  = { .len = sizeof(struct xt_entry_target) },
};

static int tcf_ipt_init(struct nlattr *nla, struct nlattr *est,
            struct tc_action *a, int ovr, int bind)
{
    struct nlattr *tb[TCA_IPT_MAX + 1];
    struct tcf_ipt *ipt;
    struct tcf_common *pc;
    struct xt_entry_target *td, *t;
    char *tname;
    int ret = 0, err;
    u32 hook = 0;
    u32 index = 0;

    if (nla == NULL)
        return -EINVAL;

    err = nla_parse_nested(tb, TCA_IPT_MAX, nla, ipt_policy);
    if (err < 0)
        return err;

    if (tb[TCA_IPT_HOOK] == NULL)
        return -EINVAL;
    if (tb[TCA_IPT_TARG] == NULL)
        return -EINVAL;

    td = (struct xt_entry_target *)nla_data(tb[TCA_IPT_TARG]);
    if (nla_len(tb[TCA_IPT_TARG]) < td->u.target_size)
        return -EINVAL;

    if (tb[TCA_IPT_INDEX] != NULL)
        index = nla_get_u32(tb[TCA_IPT_INDEX]);

    pc = tcf_hash_check(index, a, bind, &ipt_hash_info);
    if (!pc) {
        pc = tcf_hash_create(index, est, a, sizeof(*ipt), bind,
                     &ipt_idx_gen, &ipt_hash_info);
        if (IS_ERR(pc))
            return PTR_ERR(pc);
        ret = ACT_P_CREATED;
    } else {
        if (!ovr) {
            tcf_ipt_release(to_ipt(pc), bind);
            return -EEXIST;
        }
    }
    ipt = to_ipt(pc);

    hook = nla_get_u32(tb[TCA_IPT_HOOK]);

    err = -ENOMEM;
    tname = kmalloc(IFNAMSIZ, GFP_KERNEL);
    if (unlikely(!tname))
        goto err1;
    if (tb[TCA_IPT_TABLE] == NULL ||
        nla_strlcpy(tname, tb[TCA_IPT_TABLE], IFNAMSIZ) >= IFNAMSIZ)
        strcpy(tname, "mangle");

    t = kmemdup(td, td->u.target_size, GFP_KERNEL);
    if (unlikely(!t))
        goto err2;

    err = ipt_init_target(t, tname, hook);
    if (err < 0)
        goto err3;

    spin_lock_bh(&ipt->tcf_lock);
    if (ret != ACT_P_CREATED) {
        ipt_destroy_target(ipt->tcfi_t);
        kfree(ipt->tcfi_tname);
        kfree(ipt->tcfi_t);
    }
    ipt->tcfi_tname = tname;
    ipt->tcfi_t     = t;
    ipt->tcfi_hook  = hook;
    spin_unlock_bh(&ipt->tcf_lock);
    if (ret == ACT_P_CREATED)
        tcf_hash_insert(pc, &ipt_hash_info);
    return ret;

err3:
    kfree(t);
err2:
    kfree(tname);
err1:
    if (ret == ACT_P_CREATED) {
        if (est)
            gen_kill_estimator(&pc->tcfc_bstats,
                       &pc->tcfc_rate_est);
        kfree_rcu(pc, tcfc_rcu);
    }
    return err;
}

static int tcf_ipt_cleanup(struct tc_action *a, int bind)
{
    struct tcf_ipt *ipt = a->priv;
    return tcf_ipt_release(ipt, bind);
}

static int tcf_ipt(struct sk_buff *skb, const struct tc_action *a,
           struct tcf_result *res)
{
    int ret = 0, result = 0;
    struct tcf_ipt *ipt = a->priv;
    struct xt_action_param par;

    if (skb_cloned(skb)) {
        if (pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
            return TC_ACT_UNSPEC;
    }

    spin_lock(&ipt->tcf_lock);

    ipt->tcf_tm.lastuse = jiffies;
    bstats_update(&ipt->tcf_bstats, skb);

    /* yes, we have to worry about both in and out dev
     * worry later - danger - this API seems to have changed
     * from earlier kernels
     */
    par.in       = skb->dev;
    par.out      = NULL;
    par.hooknum  = ipt->tcfi_hook;
    par.target   = ipt->tcfi_t->u.kernel.target;
    par.targinfo = ipt->tcfi_t->data;
    ret = par.target->target(skb, &par);

    switch (ret) {
    case NF_ACCEPT:
        result = TC_ACT_OK;
        break;
    case NF_DROP:
        result = TC_ACT_SHOT;
        ipt->tcf_qstats.drops++;
        break;
    case XT_CONTINUE:
        result = TC_ACT_PIPE;
        break;
    default:
        net_notice_ratelimited("tc filter: Bogus netfilter code %d assume ACCEPT\n",
                       ret);
        result = TC_POLICE_OK;
        break;
    }
    spin_unlock(&ipt->tcf_lock);
    return result;

}

static int tcf_ipt_dump(struct sk_buff *skb, struct tc_action *a, int bind, int ref)
{
    unsigned char *b = skb_tail_pointer(skb);
    struct tcf_ipt *ipt = a->priv;
    struct xt_entry_target *t;
    struct tcf_t tm;
    struct tc_cnt c;

    /* for simple targets kernel size == user size
     * user name = target name
     * for foolproof you need to not assume this
     */

    t = kmemdup(ipt->tcfi_t, ipt->tcfi_t->u.user.target_size, GFP_ATOMIC);
    if (unlikely(!t))
        goto nla_put_failure;

    c.bindcnt = ipt->tcf_bindcnt - bind;
    c.refcnt = ipt->tcf_refcnt - ref;
    strcpy(t->u.user.name, ipt->tcfi_t->u.kernel.target->name);

    if (nla_put(skb, TCA_IPT_TARG, ipt->tcfi_t->u.user.target_size, t) ||
        nla_put_u32(skb, TCA_IPT_INDEX, ipt->tcf_index) ||
        nla_put_u32(skb, TCA_IPT_HOOK, ipt->tcfi_hook) ||
        nla_put(skb, TCA_IPT_CNT, sizeof(struct tc_cnt), &c) ||
        nla_put_string(skb, TCA_IPT_TABLE, ipt->tcfi_tname))
        goto nla_put_failure;
    tm.install = jiffies_to_clock_t(jiffies - ipt->tcf_tm.install);
    tm.lastuse = jiffies_to_clock_t(jiffies - ipt->tcf_tm.lastuse);
    tm.expires = jiffies_to_clock_t(ipt->tcf_tm.expires);
    if (nla_put(skb, TCA_IPT_TM, sizeof (tm), &tm))
        goto nla_put_failure;
    kfree(t);
    return skb->len;

nla_put_failure:
    nlmsg_trim(skb, b);
    kfree(t);
    return -1;
}

static struct tc_action_ops act_ipt_ops = {
    .kind       =   "ipt",
    .hinfo      =   &ipt_hash_info,
    .type       =   TCA_ACT_IPT,
    .capab      =   TCA_CAP_NONE,
    .owner      =   THIS_MODULE,
    .act        =   tcf_ipt,
    .dump       =   tcf_ipt_dump,
    .cleanup    =   tcf_ipt_cleanup,
    .lookup     =   tcf_hash_search,
    .init       =   tcf_ipt_init,
    .walk       =   tcf_generic_walker
};

MODULE_AUTHOR("Jamal Hadi Salim(2002-4)");
MODULE_DESCRIPTION("Iptables target actions");
MODULE_LICENSE("GPL");

static int __init ipt_init_module(void)
{
    return tcf_register_action(&act_ipt_ops);
}

static void __exit ipt_cleanup_module(void)
{
    tcf_unregister_action(&act_ipt_ops);
}

module_init(ipt_init_module);
module_exit(ipt_cleanup_module);