nf_nat_proto_dccp.c

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/*
 * DCCP NAT protocol helper
 *
 * Copyright (c) 2005, 2006, 2008 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.
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/skbuff.h>
#include <linux/dccp.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_l3proto.h>
#include <net/netfilter/nf_nat_l4proto.h>

static u_int16_t dccp_port_rover;

static void
dccp_unique_tuple(const struct nf_nat_l3proto *l3proto,
          struct nf_conntrack_tuple *tuple,
          const struct nf_nat_range *range,
          enum nf_nat_manip_type maniptype,
          const struct nf_conn *ct)
{
    nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,
                    &dccp_port_rover);
}

static bool
dccp_manip_pkt(struct sk_buff *skb,
           const struct nf_nat_l3proto *l3proto,
           unsigned int iphdroff, unsigned int hdroff,
           const struct nf_conntrack_tuple *tuple,
           enum nf_nat_manip_type maniptype)
{
    struct dccp_hdr *hdr;
    __be16 *portptr, oldport, newport;
    int hdrsize = 8; /* DCCP connection tracking guarantees this much */

    if (skb->len >= hdroff + sizeof(struct dccp_hdr))
        hdrsize = sizeof(struct dccp_hdr);

    if (!skb_make_writable(skb, hdroff + hdrsize))
        return false;

    hdr = (struct dccp_hdr *)(skb->data + hdroff);

    if (maniptype == NF_NAT_MANIP_SRC) {
        newport = tuple->src.u.dccp.port;
        portptr = &hdr->dccph_sport;
    } else {
        newport = tuple->dst.u.dccp.port;
        portptr = &hdr->dccph_dport;
    }

    oldport = *portptr;
    *portptr = newport;

    if (hdrsize < sizeof(*hdr))
        return true;

    l3proto->csum_update(skb, iphdroff, &hdr->dccph_checksum,
                 tuple, maniptype);
    inet_proto_csum_replace2(&hdr->dccph_checksum, skb, oldport, newport,
                 0);
    return true;
}

static const struct nf_nat_l4proto nf_nat_l4proto_dccp = {
    .l4proto        = IPPROTO_DCCP,
    .manip_pkt      = dccp_manip_pkt,
    .in_range       = nf_nat_l4proto_in_range,
    .unique_tuple       = dccp_unique_tuple,
#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
    .nlattr_to_range    = nf_nat_l4proto_nlattr_to_range,
#endif
};

static int __init nf_nat_proto_dccp_init(void)
{
    int err;

    err = nf_nat_l4proto_register(NFPROTO_IPV4, &nf_nat_l4proto_dccp);
    if (err < 0)
        goto err1;
    err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_dccp);
    if (err < 0)
        goto err2;
    return 0;

err2:
    nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_dccp);
err1:
    return err;
}

static void __exit nf_nat_proto_dccp_fini(void)
{
    nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_dccp);
    nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_dccp);

}

module_init(nf_nat_proto_dccp_init);
module_exit(nf_nat_proto_dccp_fini);

MODULE_AUTHOR("Patrick McHardy <[email protected]>");
MODULE_DESCRIPTION("DCCP NAT protocol helper");
MODULE_LICENSE("GPL");