LXR linux/net/ipv4/netfilter/nf_nat_proto

   1/* (C) 1999-2001 Paul `Rusty' Russell
   2 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   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/tcp.h>
  13
  14#include <linux/netfilter.h>
  15#include <linux/netfilter/nfnetlink_conntrack.h>
  16#include <net/netfilter/nf_nat.h>
  17#include <net/netfilter/nf_nat_rule.h>
  18#include <net/netfilter/nf_nat_protocol.h>
  19#include <net/netfilter/nf_nat_core.h>
  20
  21static u_int16_t tcp_port_rover;
  22
  23static bool
  24tcp_unique_tuple(struct nf_conntrack_tuple *tuple,
  25                 const struct nf_nat_range *range,
  26                 enum nf_nat_manip_type maniptype,
  27                 const struct nf_conn *ct)
  28{
  29        return nf_nat_proto_unique_tuple(tuple, range, maniptype, ct,
  30                                         &tcp_port_rover);
  31}
  32
  33static bool
  34tcp_manip_pkt(struct sk_buff *skb,
  35              unsigned int iphdroff,
  36              const struct nf_conntrack_tuple *tuple,
  37              enum nf_nat_manip_type maniptype)
  38{
  39        const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
  40        struct tcphdr *hdr;
  41        unsigned int hdroff = iphdroff + iph->ihl*4;
  42        __be32 oldip, newip;
  43        __be16 *portptr, newport, oldport;
  44        int hdrsize = 8; /* TCP connection tracking guarantees this much */
  45
  46        /* this could be a inner header returned in icmp packet; in such
  47           cases we cannot update the checksum field since it is outside of
  48           the 8 bytes of transport layer headers we are guaranteed */
  49        if (skb->len >= hdroff + sizeof(struct tcphdr))
  50                hdrsize = sizeof(struct tcphdr);
  51
  52        if (!skb_make_writable(skb, hdroff + hdrsize))
  53                return false;
  54
  55        iph = (struct iphdr *)(skb->data + iphdroff);
  56        hdr = (struct tcphdr *)(skb->data + hdroff);
  57
  58        if (maniptype == IP_NAT_MANIP_SRC) {
  59                /* Get rid of src ip and src pt */
  60                oldip = iph->saddr;
  61                newip = tuple->src.u3.ip;
  62                newport = tuple->src.u.tcp.port;
  63                portptr = &hdr->source;
  64        } else {
  65                /* Get rid of dst ip and dst pt */
  66                oldip = iph->daddr;
  67                newip = tuple->dst.u3.ip;
  68                newport = tuple->dst.u.tcp.port;
  69                portptr = &hdr->dest;
  70        }
  71
  72        oldport = *portptr;
  73        *portptr = newport;
  74
  75        if (hdrsize < sizeof(*hdr))
  76                return true;
  77
  78        inet_proto_csum_replace4(&hdr->check, skb, oldip, newip, 1);
  79        inet_proto_csum_replace2(&hdr->check, skb, oldport, newport, 0);
  80        return true;
  81}
  82
  83const struct nf_nat_protocol nf_nat_protocol_tcp = {
  84        .protonum               = IPPROTO_TCP,
  85        .me                     = THIS_MODULE,
  86        .manip_pkt              = tcp_manip_pkt,
  87        .in_range               = nf_nat_proto_in_range,
  88        .unique_tuple           = tcp_unique_tuple,
  89#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
  90        .range_to_nlattr        = nf_nat_proto_range_to_nlattr,
  91        .nlattr_to_range        = nf_nat_proto_nlattr_to_range,
  92#endif
  93};
  94