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