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/skbuff.h>
  14 #include <linux/dccp.h>
  15
  16 #include <net/netfilter/nf_conntrack.h>
  17 #include <net/netfilter/nf_nat.h>
  18 #include <net/netfilter/nf_nat_l3proto.h>
  19 #include <net/netfilter/nf_nat_l4proto.h>
  20
  21 static u_int16_t dccp_port_rover;
  22
  23 static void
  24 dccp_unique_tuple(const struct nf_nat_l3proto *l3proto,
  25                   struct nf_conntrack_tuple *tuple,
  26                   const struct nf_nat_range *range,
  27                   enum nf_nat_manip_type maniptype,
  28                   const struct nf_conn *ct)
  29 {
  30         nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,
  31                                     &dccp_port_rover);
  32 }
  33
  34 static bool
  35 dccp_manip_pkt(struct sk_buff *skb,
  36                const struct nf_nat_l3proto *l3proto,
  37                unsigned int iphdroff, unsigned int hdroff,
  38                const struct nf_conntrack_tuple *tuple,
  39                enum nf_nat_manip_type maniptype)
  40 {
  41         struct dccp_hdr *hdr;
  42         __be16 *portptr, oldport, newport;
  43         int hdrsize = 8; /* DCCP connection tracking guarantees this much */
  44
  45         if (skb->len >= hdroff + sizeof(struct dccp_hdr))
  46                 hdrsize = sizeof(struct dccp_hdr);
  47
  48         if (!skb_make_writable(skb, hdroff + hdrsize))
  49                 return false;
  50
  51         hdr = (struct dccp_hdr *)(skb->data + hdroff);
  52
  53         if (maniptype == NF_NAT_MANIP_SRC) {
  54                 newport = tuple->src.u.dccp.port;
  55                 portptr = &hdr->dccph_sport;
  56         } else {
  57                 newport = tuple->dst.u.dccp.port;
  58                 portptr = &hdr->dccph_dport;
  59         }
  60
  61         oldport = *portptr;
  62         *portptr = newport;
  63
  64         if (hdrsize < sizeof(*hdr))
  65                 return true;
  66
  67         l3proto->csum_update(skb, iphdroff, &hdr->dccph_checksum,
  68                              tuple, maniptype);
  69         inet_proto_csum_replace2(&hdr->dccph_checksum, skb, oldport, newport,
  70                                  false);
  71         return true;
  72 }
  73
  74 const struct nf_nat_l4proto nf_nat_l4proto_dccp = {
  75         .l4proto                = IPPROTO_DCCP,
  76         .manip_pkt              = dccp_manip_pkt,
  77         .in_range               = nf_nat_l4proto_in_range,
  78         .unique_tuple           = dccp_unique_tuple,
  79 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
  80         .nlattr_to_range        = nf_nat_l4proto_nlattr_to_range,
  81 #endif
  82 };