94 lines
2.7 KiB
C
94 lines
2.7 KiB
C
/* (C) 1999-2001 Paul `Rusty' Russell
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* (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/types.h>
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#include <linux/init.h>
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#include <linux/ip.h>
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#include <linux/tcp.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter/nfnetlink_conntrack.h>
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#include <net/netfilter/nf_nat.h>
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#include <net/netfilter/nf_nat_rule.h>
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#include <net/netfilter/nf_nat_protocol.h>
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#include <net/netfilter/nf_nat_core.h>
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static u_int16_t tcp_port_rover;
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static bool
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tcp_unique_tuple(struct nf_conntrack_tuple *tuple,
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const struct nf_nat_range *range,
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enum nf_nat_manip_type maniptype,
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const struct nf_conn *ct)
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{
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return nf_nat_proto_unique_tuple(tuple, range, maniptype, ct,
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&tcp_port_rover);
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}
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static bool
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tcp_manip_pkt(struct sk_buff *skb,
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unsigned int iphdroff,
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const struct nf_conntrack_tuple *tuple,
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enum nf_nat_manip_type maniptype)
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{
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const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
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struct tcphdr *hdr;
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unsigned int hdroff = iphdroff + iph->ihl*4;
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__be32 oldip, newip;
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__be16 *portptr, newport, oldport;
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int hdrsize = 8; /* TCP connection tracking guarantees this much */
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/* this could be a inner header returned in icmp packet; in such
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cases we cannot update the checksum field since it is outside of
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the 8 bytes of transport layer headers we are guaranteed */
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if (skb->len >= hdroff + sizeof(struct tcphdr))
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hdrsize = sizeof(struct tcphdr);
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if (!skb_make_writable(skb, hdroff + hdrsize))
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return false;
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iph = (struct iphdr *)(skb->data + iphdroff);
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hdr = (struct tcphdr *)(skb->data + hdroff);
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if (maniptype == IP_NAT_MANIP_SRC) {
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/* Get rid of src ip and src pt */
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oldip = iph->saddr;
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newip = tuple->src.u3.ip;
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newport = tuple->src.u.tcp.port;
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portptr = &hdr->source;
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} else {
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/* Get rid of dst ip and dst pt */
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oldip = iph->daddr;
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newip = tuple->dst.u3.ip;
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newport = tuple->dst.u.tcp.port;
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portptr = &hdr->dest;
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}
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oldport = *portptr;
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*portptr = newport;
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if (hdrsize < sizeof(*hdr))
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return true;
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inet_proto_csum_replace4(&hdr->check, skb, oldip, newip, 1);
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inet_proto_csum_replace2(&hdr->check, skb, oldport, newport, 0);
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return true;
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}
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const struct nf_nat_protocol nf_nat_protocol_tcp = {
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.protonum = IPPROTO_TCP,
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.me = THIS_MODULE,
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.manip_pkt = tcp_manip_pkt,
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.in_range = nf_nat_proto_in_range,
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.unique_tuple = tcp_unique_tuple,
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#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
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.range_to_nlattr = nf_nat_proto_range_to_nlattr,
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.nlattr_to_range = nf_nat_proto_nlattr_to_range,
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#endif
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};
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