nf_nat_proto_sctp.c

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/*
 * Copyright (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/sctp.h>
#include <linux/module.h>
#include <net/sctp/checksum.h>

#include <net/netfilter/nf_nat_l4proto.h>

static u_int16_t nf_sctp_port_rover;

static void
sctp_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,
                    &nf_sctp_port_rover);
}

static bool
sctp_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 sk_buff *frag;
    sctp_sctphdr_t *hdr;
    __be32 crc32;

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

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

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

    crc32 = sctp_start_cksum((u8 *)hdr, skb_headlen(skb) - hdroff);
    skb_walk_frags(skb, frag)
        crc32 = sctp_update_cksum((u8 *)frag->data, skb_headlen(frag),
                      crc32);
    crc32 = sctp_end_cksum(crc32);
    hdr->checksum = crc32;

    return true;
}

static const struct nf_nat_l4proto nf_nat_l4proto_sctp = {
    .l4proto        = IPPROTO_SCTP,
    .manip_pkt      = sctp_manip_pkt,
    .in_range       = nf_nat_l4proto_in_range,
    .unique_tuple       = sctp_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_sctp_init(void)
{
    int err;

    err = nf_nat_l4proto_register(NFPROTO_IPV4, &nf_nat_l4proto_sctp);
    if (err < 0)
        goto err1;
    err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_sctp);
    if (err < 0)
        goto err2;
    return 0;

err2:
    nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_sctp);
err1:
    return err;
}

static void __exit nf_nat_proto_sctp_exit(void)
{
    nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_sctp);
    nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_sctp);
}

module_init(nf_nat_proto_sctp_init);
module_exit(nf_nat_proto_sctp_exit);

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