net/netfilter/nf_nat_proto_dccp.c

   1 /*
   2  * DCCP NAT protocol helper
   3  *
   4  * Copyright (c) 2005, 2006, 2008 Patrick McHardy <kaber@trash.net>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  */
  11
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/init.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/dccp.h>
  17
  18 #include <net/netfilter/nf_conntrack.h>
  19 #include <net/netfilter/nf_nat.h>
  20 #include <net/netfilter/nf_nat_l3proto.h>
  21 #include <net/netfilter/nf_nat_l4proto.h>
  22
  23 static u_int16_t dccp_port_rover;
  24
  25 static void
  26 dccp_unique_tuple(const struct nf_nat_l3proto *l3proto,
  27                   struct nf_conntrack_tuple *tuple,
  28                   const struct nf_nat_range *range,
  29                   enum nf_nat_manip_type maniptype,
  30                   const struct nf_conn *ct)
  31 {
  32         nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,
  33                                     &dccp_port_rover);
  34 }
  35
  36 static bool
  37 dccp_manip_pkt(struct sk_buff *skb,
  38                const struct nf_nat_l3proto *l3proto,
  39                unsigned int iphdroff, unsigned int hdroff,
  40                const struct nf_conntrack_tuple *tuple,
  41                enum nf_nat_manip_type maniptype)
  42 {
  43         struct dccp_hdr *hdr;
  44         __be16 *portptr, oldport, newport;
  45         int hdrsize = 8; /* DCCP connection tracking guarantees this much */
  46
  47         if (skb->len >= hdroff + sizeof(struct dccp_hdr))
  48                 hdrsize = sizeof(struct dccp_hdr);
  49
  50         if (!skb_make_writable(skb, hdroff + hdrsize))
  51                 return false;
  52
  53         hdr = (struct dccp_hdr *)(skb->data + hdroff);
  54
  55         if (maniptype == NF_NAT_MANIP_SRC) {
  56                 newport = tuple->src.u.dccp.port;
  57                 portptr = &hdr->dccph_sport;
  58         } else {
  59                 newport = tuple->dst.u.dccp.port;
  60                 portptr = &hdr->dccph_dport;
  61         }
  62
  63         oldport = *portptr;
  64         *portptr = newport;
  65
  66         if (hdrsize < sizeof(*hdr))
  67                 return true;
  68
  69         l3proto->csum_update(skb, iphdroff, &hdr->dccph_checksum,
  70                              tuple, maniptype);
  71         inet_proto_csum_replace2(&hdr->dccph_checksum, skb, oldport, newport,
  72                                  0);
  73         return true;
  74 }
  75
  76 static const struct nf_nat_l4proto nf_nat_l4proto_dccp = {
  77         .l4proto                = IPPROTO_DCCP,
  78         .manip_pkt              = dccp_manip_pkt,
  79         .in_range               = nf_nat_l4proto_in_range,
  80         .unique_tuple           = dccp_unique_tuple,
  81 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
  82         .nlattr_to_range        = nf_nat_l4proto_nlattr_to_range,
  83 #endif
  84 };
  85
  86 static int __init nf_nat_proto_dccp_init(void)
  87 {
  88         int err;
  89
  90         err = nf_nat_l4proto_register(NFPROTO_IPV4, &nf_nat_l4proto_dccp);
  91         if (err < 0)
  92                 goto err1;
  93         err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_dccp);
  94         if (err < 0)
  95                 goto err2;
  96         return 0;
  97
  98 err2:
  99         nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_dccp);
 100 err1:
 101         return err;
 102 }
 103
 104 static void __exit nf_nat_proto_dccp_fini(void)
 105 {
 106         nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_dccp);
 107         nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_dccp);
 108
 109 }
 110
 111 module_init(nf_nat_proto_dccp_init);
 112 module_exit(nf_nat_proto_dccp_fini);
 113
 114 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
 115 MODULE_DESCRIPTION("DCCP NAT protocol helper");
 116 MODULE_LICENSE("GPL");