1 /* (C) 1999-2001 Paul `Rusty' Russell
2 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
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.
9 #include <linux/types.h>
10 #include <linux/init.h>
11 #include <linux/netfilter.h>
13 #include <linux/tcp.h>
15 #include <linux/netfilter/nfnetlink_conntrack.h>
16 #include <linux/netfilter_ipv4/ip_nat.h>
17 #include <linux/netfilter_ipv4/ip_nat_rule.h>
18 #include <linux/netfilter_ipv4/ip_nat_protocol.h>
19 #include <linux/netfilter_ipv4/ip_nat_core.h>
22 tcp_in_range(const struct ip_conntrack_tuple *tuple,
23 enum ip_nat_manip_type maniptype,
24 const union ip_conntrack_manip_proto *min,
25 const union ip_conntrack_manip_proto *max)
29 if (maniptype == IP_NAT_MANIP_SRC)
30 port = tuple->src.u.tcp.port;
32 port = tuple->dst.u.tcp.port;
34 return ntohs(port) >= ntohs(min->tcp.port)
35 && ntohs(port) <= ntohs(max->tcp.port);
39 tcp_unique_tuple(struct ip_conntrack_tuple *tuple,
40 const struct ip_nat_range *range,
41 enum ip_nat_manip_type maniptype,
42 const struct ip_conntrack *conntrack)
44 static u_int16_t port;
46 unsigned int range_size, min, i;
48 if (maniptype == IP_NAT_MANIP_SRC)
49 portptr = &tuple->src.u.tcp.port;
51 portptr = &tuple->dst.u.tcp.port;
53 /* If no range specified... */
54 if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)) {
55 /* If it's dst rewrite, can't change port */
56 if (maniptype == IP_NAT_MANIP_DST)
59 /* Map privileged onto privileged. */
60 if (ntohs(*portptr) < 1024) {
61 /* Loose convention: >> 512 is credential passing */
62 if (ntohs(*portptr)<512) {
64 range_size = 511 - min + 1;
67 range_size = 1023 - min + 1;
71 range_size = 65535 - 1024 + 1;
74 min = ntohs(range->min.tcp.port);
75 range_size = ntohs(range->max.tcp.port) - min + 1;
78 for (i = 0; i < range_size; i++, port++) {
79 *portptr = htons(min + port % range_size);
80 if (!ip_nat_used_tuple(tuple, conntrack)) {
88 tcp_manip_pkt(struct sk_buff **pskb,
89 unsigned int iphdroff,
90 const struct ip_conntrack_tuple *tuple,
91 enum ip_nat_manip_type maniptype)
93 struct iphdr *iph = (struct iphdr *)((*pskb)->data + iphdroff);
95 unsigned int hdroff = iphdroff + iph->ihl*4;
97 u16 *portptr, newport, oldport;
98 int hdrsize = 8; /* TCP connection tracking guarantees this much */
100 /* this could be a inner header returned in icmp packet; in such
101 cases we cannot update the checksum field since it is outside of
102 the 8 bytes of transport layer headers we are guaranteed */
103 if ((*pskb)->len >= hdroff + sizeof(struct tcphdr))
104 hdrsize = sizeof(struct tcphdr);
106 if (!skb_make_writable(pskb, hdroff + hdrsize))
109 iph = (struct iphdr *)((*pskb)->data + iphdroff);
110 hdr = (struct tcphdr *)((*pskb)->data + hdroff);
112 if (maniptype == IP_NAT_MANIP_SRC) {
113 /* Get rid of src ip and src pt */
115 newip = tuple->src.ip;
116 newport = tuple->src.u.tcp.port;
117 portptr = &hdr->source;
119 /* Get rid of dst ip and dst pt */
121 newip = tuple->dst.ip;
122 newport = tuple->dst.u.tcp.port;
123 portptr = &hdr->dest;
129 if (hdrsize < sizeof(*hdr))
133 if ((*pskb)->proto_csum_blank)
134 hdr->check = ip_nat_cheat_check(oldip, ~newip, hdr->check);
137 hdr->check = ip_nat_cheat_check(~oldip, newip,
138 ip_nat_cheat_check(oldport ^ 0xFFFF,
144 struct ip_nat_protocol ip_nat_protocol_tcp = {
146 .protonum = IPPROTO_TCP,
148 .manip_pkt = tcp_manip_pkt,
149 .in_range = tcp_in_range,
150 .unique_tuple = tcp_unique_tuple,
151 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
152 defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
153 .range_to_nfattr = ip_nat_port_range_to_nfattr,
154 .nfattr_to_range = ip_nat_port_nfattr_to_range,