/* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/types.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/tcp.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nfnetlink_conntrack.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_l3proto.h>
#include <net/netfilter/nf_nat_l4proto.h>
#include <net/netfilter/nf_nat_core.h>
static u16 tcp_port_rover;
static void
tcp_unique_tuple(const struct nf_nat_l3proto *l3proto,
struct nf_conntrack_tuple *tuple,
const struct nf_nat_range *range,
enum nf_nat_manip_type maniptype,
const struct nf_conn *ct)
{
nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,
&tcp_port_rover);
}
static bool
tcp_manip_pkt(struct sk_buff *skb,
const struct nf_nat_l3proto *l3proto,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
struct tcphdr *hdr;
__be16 *portptr, newport, oldport;
int hdrsize = 8; /* TCP connection tracking guarantees this much */
/* this could be a inner header returned in icmp packet; in such
cases we cannot update the checksum field since it is outside of
the 8 bytes of transport layer headers we are guaranteed */
if (skb->len >= hdroff + sizeof(struct tcphdr))
hdrsize = sizeof(struct tcphdr);
if (!skb_make_writable(skb, hdroff + hdrsize))
return false;
hdr = (struct tcphdr *)(skb->data + hdroff);
if (maniptype == NF_NAT_MANIP_SRC) {
/* Get rid of src port */
newport = tuple->src.u.tcp.port;
portptr = &hdr->source;
} else {
/* Get rid of dst port */
newport = tuple->dst.u.tcp.port;
portptr = &hdr->dest;
}
oldport = *portptr;
*portptr = newport;
if (hdrsize < sizeof(*hdr))
return true;
l3proto->csum_update(skb, iphdroff, &hdr->check, tuple, maniptype);
inet_proto_csum_replace2(&hdr->check, skb, oldport, newport, 0);
return true;
}
const struct nf_nat_l4proto nf_nat_l4proto_tcp = {
.l4proto = IPPROTO_TCP,
.manip_pkt = tcp_manip_pkt,
.in_range = nf_nat_l4proto_in_range,
.unique_tuple = tcp_unique_tuple,
#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
.nlattr_to_range = nf_nat_l4proto_nlattr_to_range,
#endif
};
