linux/net/netfilter/nf_nat_proto_sctp.c
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   1/*
   2 * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
   3 *
   4 * This program is free software; you can redistribute it and/or modify
   5 * it under the terms of the GNU General Public License version 2 as
   6 * published by the Free Software Foundation.
   7 */
   8
   9#include <linux/types.h>
  10#include <linux/init.h>
  11#include <linux/sctp.h>
  12#include <linux/module.h>
  13#include <net/sctp/checksum.h>
  14
  15#include <net/netfilter/nf_nat_l4proto.h>
  16
  17static u_int16_t nf_sctp_port_rover;
  18
  19static void
  20sctp_unique_tuple(const struct nf_nat_l3proto *l3proto,
  21                  struct nf_conntrack_tuple *tuple,
  22                  const struct nf_nat_range *range,
  23                  enum nf_nat_manip_type maniptype,
  24                  const struct nf_conn *ct)
  25{
  26        nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,
  27                                    &nf_sctp_port_rover);
  28}
  29
  30static bool
  31sctp_manip_pkt(struct sk_buff *skb,
  32               const struct nf_nat_l3proto *l3proto,
  33               unsigned int iphdroff, unsigned int hdroff,
  34               const struct nf_conntrack_tuple *tuple,
  35               enum nf_nat_manip_type maniptype)
  36{
  37        struct sk_buff *frag;
  38        sctp_sctphdr_t *hdr;
  39        __u32 crc32;
  40
  41        if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
  42                return false;
  43
  44        hdr = (struct sctphdr *)(skb->data + hdroff);
  45
  46        if (maniptype == NF_NAT_MANIP_SRC) {
  47                /* Get rid of src port */
  48                hdr->source = tuple->src.u.sctp.port;
  49        } else {
  50                /* Get rid of dst port */
  51                hdr->dest = tuple->dst.u.sctp.port;
  52        }
  53
  54        crc32 = sctp_start_cksum((u8 *)hdr, skb_headlen(skb) - hdroff);
  55        skb_walk_frags(skb, frag)
  56                crc32 = sctp_update_cksum((u8 *)frag->data, skb_headlen(frag),
  57                                          crc32);
  58        hdr->checksum = sctp_end_cksum(crc32);
  59
  60        return true;
  61}
  62
  63static const struct nf_nat_l4proto nf_nat_l4proto_sctp = {
  64        .l4proto                = IPPROTO_SCTP,
  65        .manip_pkt              = sctp_manip_pkt,
  66        .in_range               = nf_nat_l4proto_in_range,
  67        .unique_tuple           = sctp_unique_tuple,
  68#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
  69        .nlattr_to_range        = nf_nat_l4proto_nlattr_to_range,
  70#endif
  71};
  72
  73static int __init nf_nat_proto_sctp_init(void)
  74{
  75        int err;
  76
  77        err = nf_nat_l4proto_register(NFPROTO_IPV4, &nf_nat_l4proto_sctp);
  78        if (err < 0)
  79                goto err1;
  80        err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_sctp);
  81        if (err < 0)
  82                goto err2;
  83        return 0;
  84
  85err2:
  86        nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_sctp);
  87err1:
  88        return err;
  89}
  90
  91static void __exit nf_nat_proto_sctp_exit(void)
  92{
  93        nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_sctp);
  94        nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_sctp);
  95}
  96
  97module_init(nf_nat_proto_sctp_init);
  98module_exit(nf_nat_proto_sctp_exit);
  99
 100MODULE_LICENSE("GPL");
 101MODULE_DESCRIPTION("SCTP NAT protocol helper");
 102MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
 103
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