xt_physdev.c

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/* Kernel module to match the bridge port in and
 * out device for IP packets coming into contact with a bridge. */

/* (C) 2001-2003 Bart De Schuymer <[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/skbuff.h>
#include <linux/netfilter_bridge.h>
#include <linux/netfilter/xt_physdev.h>
#include <linux/netfilter/x_tables.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Bart De Schuymer <[email protected]>");
MODULE_DESCRIPTION("Xtables: Bridge physical device match");
MODULE_ALIAS("ipt_physdev");
MODULE_ALIAS("ip6t_physdev");


static bool
physdev_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
    static const char nulldevname[IFNAMSIZ] __attribute__((aligned(sizeof(long))));
    const struct xt_physdev_info *info = par->matchinfo;
    unsigned long ret;
    const char *indev, *outdev;
    const struct nf_bridge_info *nf_bridge;

    /* Not a bridged IP packet or no info available yet:
     * LOCAL_OUT/mangle and LOCAL_OUT/nat don't know if
     * the destination device will be a bridge. */
    if (!(nf_bridge = skb->nf_bridge)) {
        /* Return MATCH if the invert flags of the used options are on */
        if ((info->bitmask & XT_PHYSDEV_OP_BRIDGED) &&
            !(info->invert & XT_PHYSDEV_OP_BRIDGED))
            return false;
        if ((info->bitmask & XT_PHYSDEV_OP_ISIN) &&
            !(info->invert & XT_PHYSDEV_OP_ISIN))
            return false;
        if ((info->bitmask & XT_PHYSDEV_OP_ISOUT) &&
            !(info->invert & XT_PHYSDEV_OP_ISOUT))
            return false;
        if ((info->bitmask & XT_PHYSDEV_OP_IN) &&
            !(info->invert & XT_PHYSDEV_OP_IN))
            return false;
        if ((info->bitmask & XT_PHYSDEV_OP_OUT) &&
            !(info->invert & XT_PHYSDEV_OP_OUT))
            return false;
        return true;
    }

    /* This only makes sense in the FORWARD and POSTROUTING chains */
    if ((info->bitmask & XT_PHYSDEV_OP_BRIDGED) &&
        (!!(nf_bridge->mask & BRNF_BRIDGED) ^
        !(info->invert & XT_PHYSDEV_OP_BRIDGED)))
        return false;

    if ((info->bitmask & XT_PHYSDEV_OP_ISIN &&
        (!nf_bridge->physindev ^ !!(info->invert & XT_PHYSDEV_OP_ISIN))) ||
        (info->bitmask & XT_PHYSDEV_OP_ISOUT &&
        (!nf_bridge->physoutdev ^ !!(info->invert & XT_PHYSDEV_OP_ISOUT))))
        return false;

    if (!(info->bitmask & XT_PHYSDEV_OP_IN))
        goto match_outdev;
    indev = nf_bridge->physindev ? nf_bridge->physindev->name : nulldevname;
    ret = ifname_compare_aligned(indev, info->physindev, info->in_mask);

    if (!ret ^ !(info->invert & XT_PHYSDEV_OP_IN))
        return false;

match_outdev:
    if (!(info->bitmask & XT_PHYSDEV_OP_OUT))
        return true;
    outdev = nf_bridge->physoutdev ?
         nf_bridge->physoutdev->name : nulldevname;
    ret = ifname_compare_aligned(outdev, info->physoutdev, info->out_mask);

    return (!!ret ^ !(info->invert & XT_PHYSDEV_OP_OUT));
}

static int physdev_mt_check(const struct xt_mtchk_param *par)
{
    const struct xt_physdev_info *info = par->matchinfo;

    if (!(info->bitmask & XT_PHYSDEV_OP_MASK) ||
        info->bitmask & ~XT_PHYSDEV_OP_MASK)
        return -EINVAL;
    if (info->bitmask & XT_PHYSDEV_OP_OUT &&
        (!(info->bitmask & XT_PHYSDEV_OP_BRIDGED) ||
         info->invert & XT_PHYSDEV_OP_BRIDGED) &&
        par->hook_mask & ((1 << NF_INET_LOCAL_OUT) |
        (1 << NF_INET_FORWARD) | (1 << NF_INET_POST_ROUTING))) {
        pr_info("using --physdev-out in the OUTPUT, FORWARD and "
            "POSTROUTING chains for non-bridged traffic is not "
            "supported anymore.\n");
        if (par->hook_mask & (1 << NF_INET_LOCAL_OUT))
            return -EINVAL;
    }
    return 0;
}

static struct xt_match physdev_mt_reg __read_mostly = {
    .name       = "physdev",
    .revision   = 0,
    .family     = NFPROTO_UNSPEC,
    .checkentry = physdev_mt_check,
    .match      = physdev_mt,
    .matchsize  = sizeof(struct xt_physdev_info),
    .me         = THIS_MODULE,
};

static int __init physdev_mt_init(void)
{
    return xt_register_match(&physdev_mt_reg);
}

static void __exit physdev_mt_exit(void)
{
    xt_unregister_match(&physdev_mt_reg);
}

module_init(physdev_mt_init);
module_exit(physdev_mt_exit);