ebt_ip.c

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/*
 *  ebt_ip
 *
 *  Authors:
 *  Bart De Schuymer <[email protected]>
 *
 *  April, 2002
 *
 *  Changes:
 *    added ip-sport and ip-dport
 *    Innominate Security Technologies AG <[email protected]>
 *    September, 2002
 */
#include <linux/ip.h>
#include <net/ip.h>
#include <linux/in.h>
#include <linux/module.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_ip.h>

struct tcpudphdr {
    __be16 src;
    __be16 dst;
};

static bool
ebt_ip_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
    const struct ebt_ip_info *info = par->matchinfo;
    const struct iphdr *ih;
    struct iphdr _iph;
    const struct tcpudphdr *pptr;
    struct tcpudphdr _ports;

    ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
    if (ih == NULL)
        return false;
    if (info->bitmask & EBT_IP_TOS &&
       FWINV(info->tos != ih->tos, EBT_IP_TOS))
        return false;
    if (info->bitmask & EBT_IP_SOURCE &&
       FWINV((ih->saddr & info->smsk) !=
       info->saddr, EBT_IP_SOURCE))
        return false;
    if ((info->bitmask & EBT_IP_DEST) &&
       FWINV((ih->daddr & info->dmsk) !=
       info->daddr, EBT_IP_DEST))
        return false;
    if (info->bitmask & EBT_IP_PROTO) {
        if (FWINV(info->protocol != ih->protocol, EBT_IP_PROTO))
            return false;
        if (!(info->bitmask & EBT_IP_DPORT) &&
            !(info->bitmask & EBT_IP_SPORT))
            return true;
        if (ntohs(ih->frag_off) & IP_OFFSET)
            return false;
        pptr = skb_header_pointer(skb, ih->ihl*4,
                      sizeof(_ports), &_ports);
        if (pptr == NULL)
            return false;
        if (info->bitmask & EBT_IP_DPORT) {
            u32 dst = ntohs(pptr->dst);
            if (FWINV(dst < info->dport[0] ||
                  dst > info->dport[1],
                  EBT_IP_DPORT))
            return false;
        }
        if (info->bitmask & EBT_IP_SPORT) {
            u32 src = ntohs(pptr->src);
            if (FWINV(src < info->sport[0] ||
                  src > info->sport[1],
                  EBT_IP_SPORT))
            return false;
        }
    }
    return true;
}

static int ebt_ip_mt_check(const struct xt_mtchk_param *par)
{
    const struct ebt_ip_info *info = par->matchinfo;
    const struct ebt_entry *e = par->entryinfo;

    if (e->ethproto != htons(ETH_P_IP) ||
       e->invflags & EBT_IPROTO)
        return -EINVAL;
    if (info->bitmask & ~EBT_IP_MASK || info->invflags & ~EBT_IP_MASK)
        return -EINVAL;
    if (info->bitmask & (EBT_IP_DPORT | EBT_IP_SPORT)) {
        if (info->invflags & EBT_IP_PROTO)
            return -EINVAL;
        if (info->protocol != IPPROTO_TCP &&
            info->protocol != IPPROTO_UDP &&
            info->protocol != IPPROTO_UDPLITE &&
            info->protocol != IPPROTO_SCTP &&
            info->protocol != IPPROTO_DCCP)
             return -EINVAL;
    }
    if (info->bitmask & EBT_IP_DPORT && info->dport[0] > info->dport[1])
        return -EINVAL;
    if (info->bitmask & EBT_IP_SPORT && info->sport[0] > info->sport[1])
        return -EINVAL;
    return 0;
}

static struct xt_match ebt_ip_mt_reg __read_mostly = {
    .name       = "ip",
    .revision   = 0,
    .family     = NFPROTO_BRIDGE,
    .match      = ebt_ip_mt,
    .checkentry = ebt_ip_mt_check,
    .matchsize  = sizeof(struct ebt_ip_info),
    .me     = THIS_MODULE,
};

static int __init ebt_ip_init(void)
{
    return xt_register_match(&ebt_ip_mt_reg);
}

static void __exit ebt_ip_fini(void)
{
    xt_unregister_match(&ebt_ip_mt_reg);
}

module_init(ebt_ip_init);
module_exit(ebt_ip_fini);
MODULE_DESCRIPTION("Ebtables: IPv4 protocol packet match");
MODULE_LICENSE("GPL");