root/net/ipv4/netfilter/nf_nat_proto_sctp.c

DEFINITIONS

1. sctp_unique_tuple
2. sctp_manip_pkt
3. nf_nat_proto_sctp_init
4. nf_nat_proto_sctp_exit

/*
 * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
 *
 * 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/ip.h>
#include <linux/sctp.h>
#include <net/sctp/checksum.h>

#include <net/netfilter/nf_nat_protocol.h>

static u_int16_t nf_sctp_port_rover;

static bool
sctp_unique_tuple(struct nf_conntrack_tuple *tuple,
                  const struct nf_nat_range *range,
                  enum nf_nat_manip_type maniptype,
                  const struct nf_conn *ct)
{
        return nf_nat_proto_unique_tuple(tuple, range, maniptype, ct,
                                         &nf_sctp_port_rover);
}

static bool
sctp_manip_pkt(struct sk_buff *skb,
               unsigned int iphdroff,
               const struct nf_conntrack_tuple *tuple,
               enum nf_nat_manip_type maniptype)
{
        const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
        sctp_sctphdr_t *hdr;
        unsigned int hdroff = iphdroff + iph->ihl*4;
        __be32 oldip, newip;
        __be32 crc32;

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

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

        if (maniptype == IP_NAT_MANIP_SRC) {
                /* Get rid of src ip and src pt */
                oldip = iph->saddr;
                newip = tuple->src.u3.ip;
                hdr->source = tuple->src.u.sctp.port;
        } else {
                /* Get rid of dst ip and dst pt */
                oldip = iph->daddr;
                newip = tuple->dst.u3.ip;
                hdr->dest = tuple->dst.u.sctp.port;
        }

        crc32 = sctp_start_cksum((u8 *)hdr, skb_headlen(skb) - hdroff);
        for (skb = skb_shinfo(skb)->frag_list; skb; skb = skb->next)
                crc32 = sctp_update_cksum((u8 *)skb->data, skb_headlen(skb),
                                          crc32);
        crc32 = sctp_end_cksum(crc32);
        hdr->checksum = crc32;

        return true;
}

static const struct nf_nat_protocol nf_nat_protocol_sctp = {
        .protonum               = IPPROTO_SCTP,
        .me                     = THIS_MODULE,
        .manip_pkt              = sctp_manip_pkt,
        .in_range               = nf_nat_proto_in_range,
        .unique_tuple           = sctp_unique_tuple,
#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
        .range_to_nlattr        = nf_nat_proto_range_to_nlattr,
        .nlattr_to_range        = nf_nat_proto_nlattr_to_range,
#endif
};

static int __init nf_nat_proto_sctp_init(void)
{
        return nf_nat_protocol_register(&nf_nat_protocol_sctp);
}

static void __exit nf_nat_proto_sctp_exit(void)
{
        nf_nat_protocol_unregister(&nf_nat_protocol_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 <kaber@trash.net>");