1 /* (C) 1999-2001 Paul `Rusty' Russell
2 * (C) 2002-2006 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>
12 #include <linux/tcp.h>
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>
22 tcp_in_range(const struct nf_conntrack_tuple
*tuple
,
23 enum nf_nat_manip_type maniptype
,
24 const union nf_conntrack_man_proto
*min
,
25 const union nf_conntrack_man_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 nf_conntrack_tuple
*tuple
,
40 const struct nf_nat_range
*range
,
41 enum nf_nat_manip_type maniptype
,
42 const struct nf_conn
*ct
)
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 (!nf_nat_used_tuple(tuple
, ct
))
87 tcp_manip_pkt(struct sk_buff
**pskb
,
88 unsigned int iphdroff
,
89 const struct nf_conntrack_tuple
*tuple
,
90 enum nf_nat_manip_type maniptype
)
92 struct iphdr
*iph
= (struct iphdr
*)((*pskb
)->data
+ iphdroff
);
94 unsigned int hdroff
= iphdroff
+ iph
->ihl
*4;
96 __be16
*portptr
, newport
, oldport
;
97 int hdrsize
= 8; /* TCP connection tracking guarantees this much */
99 /* this could be a inner header returned in icmp packet; in such
100 cases we cannot update the checksum field since it is outside of
101 the 8 bytes of transport layer headers we are guaranteed */
102 if ((*pskb
)->len
>= hdroff
+ sizeof(struct tcphdr
))
103 hdrsize
= sizeof(struct tcphdr
);
105 if (!skb_make_writable(pskb
, hdroff
+ hdrsize
))
108 iph
= (struct iphdr
*)((*pskb
)->data
+ iphdroff
);
109 hdr
= (struct tcphdr
*)((*pskb
)->data
+ hdroff
);
111 if (maniptype
== IP_NAT_MANIP_SRC
) {
112 /* Get rid of src ip and src pt */
114 newip
= tuple
->src
.u3
.ip
;
115 newport
= tuple
->src
.u
.tcp
.port
;
116 portptr
= &hdr
->source
;
118 /* Get rid of dst ip and dst pt */
120 newip
= tuple
->dst
.u3
.ip
;
121 newport
= tuple
->dst
.u
.tcp
.port
;
122 portptr
= &hdr
->dest
;
128 if (hdrsize
< sizeof(*hdr
))
131 nf_proto_csum_replace4(&hdr
->check
, *pskb
, oldip
, newip
, 1);
132 nf_proto_csum_replace2(&hdr
->check
, *pskb
, oldport
, newport
, 0);
136 struct nf_nat_protocol nf_nat_protocol_tcp
= {
138 .protonum
= IPPROTO_TCP
,
140 .manip_pkt
= tcp_manip_pkt
,
141 .in_range
= tcp_in_range
,
142 .unique_tuple
= tcp_unique_tuple
,
143 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
144 defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
145 .range_to_nfattr
= nf_nat_port_range_to_nfattr
,
146 .nfattr_to_range
= nf_nat_port_nfattr_to_range
,