net/ipv4/netfilter/nf_nat_proto_sctp.c

   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/ip.h>
  12 #include <linux/sctp.h>
  13 #include <linux/module.h>
  14 #include <net/sctp/checksum.h>
  15
  16 #include <net/netfilter/nf_nat_protocol.h>
  17
  18 static u_int16_t nf_sctp_port_rover;
  19
  20 static void
  21 sctp_unique_tuple(struct nf_conntrack_tuple *tuple,
  22                   const struct nf_nat_ipv4_range *range,
  23                   enum nf_nat_manip_type maniptype,
  24                   const struct nf_conn *ct)
  25 {
  26         nf_nat_proto_unique_tuple(tuple, range, maniptype, ct,
  27                                   &nf_sctp_port_rover);
  28 }
  29
  30 static bool
  31 sctp_manip_pkt(struct sk_buff *skb,
  32                unsigned int iphdroff,
  33                const struct nf_conntrack_tuple *tuple,
  34                enum nf_nat_manip_type maniptype)
  35 {
  36         const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
  37         struct sk_buff *frag;
  38         sctp_sctphdr_t *hdr;
  39         unsigned int hdroff = iphdroff + iph->ihl*4;
  40         __be32 oldip, newip;
  41         __be32 crc32;
  42
  43         if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
  44                 return false;
  45
  46         iph = (struct iphdr *)(skb->data + iphdroff);
  47         hdr = (struct sctphdr *)(skb->data + hdroff);
  48
  49         if (maniptype == NF_NAT_MANIP_SRC) {
  50                 /* Get rid of src ip and src pt */
  51                 oldip = iph->saddr;
  52                 newip = tuple->src.u3.ip;
  53                 hdr->source = tuple->src.u.sctp.port;
  54         } else {
  55                 /* Get rid of dst ip and dst pt */
  56                 oldip = iph->daddr;
  57                 newip = tuple->dst.u3.ip;
  58                 hdr->dest = tuple->dst.u.sctp.port;
  59         }
  60
  61         crc32 = sctp_start_cksum((u8 *)hdr, skb_headlen(skb) - hdroff);
  62         skb_walk_frags(skb, frag)
  63                 crc32 = sctp_update_cksum((u8 *)frag->data, skb_headlen(frag),
  64                                           crc32);
  65         crc32 = sctp_end_cksum(crc32);
  66         hdr->checksum = crc32;
  67
  68         return true;
  69 }
  70
  71 static const struct nf_nat_protocol nf_nat_protocol_sctp = {
  72         .protonum               = IPPROTO_SCTP,
  73         .manip_pkt              = sctp_manip_pkt,
  74         .in_range               = nf_nat_proto_in_range,
  75         .unique_tuple           = sctp_unique_tuple,
  76 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
  77         .nlattr_to_range        = nf_nat_proto_nlattr_to_range,
  78 #endif
  79 };
  80
  81 static int __init nf_nat_proto_sctp_init(void)
  82 {
  83         return nf_nat_protocol_register(&nf_nat_protocol_sctp);
  84 }
  85
  86 static void __exit nf_nat_proto_sctp_exit(void)
  87 {
  88         nf_nat_protocol_unregister(&nf_nat_protocol_sctp);
  89 }
  90
  91 module_init(nf_nat_proto_sctp_init);
  92 module_exit(nf_nat_proto_sctp_exit);
  93
  94 MODULE_LICENSE("GPL");
  95 MODULE_DESCRIPTION("SCTP NAT protocol helper");
  96 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");