nf_nat_proto_udplite.c

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/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 Netfilter Core Team <[email protected]>
 * (C) 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/types.h>
#include <linux/init.h>
#include <linux/udp.h>

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

static u16 udplite_port_rover;

static void
udplite_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,
                    &udplite_port_rover);
}

static bool
udplite_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 udphdr *hdr;
    __be16 *portptr, newport;

    if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
        return false;

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

    if (maniptype == NF_NAT_MANIP_SRC) {
        /* Get rid of source port */
        newport = tuple->src.u.udp.port;
        portptr = &hdr->source;
    } else {
        /* Get rid of dst port */
        newport = tuple->dst.u.udp.port;
        portptr = &hdr->dest;
    }

    l3proto->csum_update(skb, iphdroff, &hdr->check, tuple, maniptype);
    inet_proto_csum_replace2(&hdr->check, skb, *portptr, newport, 0);
    if (!hdr->check)
        hdr->check = CSUM_MANGLED_0;

    *portptr = newport;
    return true;
}

static const struct nf_nat_l4proto nf_nat_l4proto_udplite = {
    .l4proto        = IPPROTO_UDPLITE,
    .manip_pkt      = udplite_manip_pkt,
    .in_range       = nf_nat_l4proto_in_range,
    .unique_tuple       = udplite_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_udplite_init(void)
{
    int err;

    err = nf_nat_l4proto_register(NFPROTO_IPV4, &nf_nat_l4proto_udplite);
    if (err < 0)
        goto err1;
    err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_udplite);
    if (err < 0)
        goto err2;
    return 0;

err2:
    nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_udplite);
err1:
    return err;
}

static void __exit nf_nat_proto_udplite_fini(void)
{
    nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_udplite);
    nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_udplite);
}

module_init(nf_nat_proto_udplite_init);
module_exit(nf_nat_proto_udplite_fini);

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