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