net/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/sctp.h>
  12 #include <linux/module.h>
  13 #include <net/sctp/checksum.h>
  14
  15 #include <net/netfilter/nf_nat_l4proto.h>
  16
  17 static u_int16_t nf_sctp_port_rover;
  18
  19 static void
  20 sctp_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
  30 static bool
  31 sctp_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         __be32 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         crc32 = sctp_end_cksum(crc32);
  59         hdr->checksum = crc32;
  60
  61         return true;
  62 }
  63
  64 static const struct nf_nat_l4proto nf_nat_l4proto_sctp = {
  65         .l4proto                = IPPROTO_SCTP,
  66         .manip_pkt              = sctp_manip_pkt,
  67         .in_range               = nf_nat_l4proto_in_range,
  68         .unique_tuple           = sctp_unique_tuple,
  69 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
  70         .nlattr_to_range        = nf_nat_l4proto_nlattr_to_range,
  71 #endif
  72 };
  73
  74 static int __init nf_nat_proto_sctp_init(void)
  75 {
  76         int err;
  77
  78         err = nf_nat_l4proto_register(NFPROTO_IPV4, &nf_nat_l4proto_sctp);
  79         if (err < 0)
  80                 goto err1;
  81         err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_sctp);
  82         if (err < 0)
  83                 goto err2;
  84         return 0;
  85
  86 err2:
  87         nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_sctp);
  88 err1:
  89         return err;
  90 }
  91
  92 static void __exit nf_nat_proto_sctp_exit(void)
  93 {
  94         nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_sctp);
  95         nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_sctp);
  96 }
  97
  98 module_init(nf_nat_proto_sctp_init);
  99 module_exit(nf_nat_proto_sctp_exit);
 100
 101 MODULE_LICENSE("GPL");
 102 MODULE_DESCRIPTION("SCTP NAT protocol helper");
 103 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");