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>
11 #include <linux/random.h>
13 #include <linux/tcp.h>
15 #include <linux/netfilter.h>
16 #include <linux/netfilter/nfnetlink_conntrack.h>
17 #include <net/netfilter/nf_nat.h>
18 #include <net/netfilter/nf_nat_rule.h>
19 #include <net/netfilter/nf_nat_protocol.h>
20 #include <net/netfilter/nf_nat_core.h>
23 tcp_in_range(const struct nf_conntrack_tuple
*tuple
,
24 enum nf_nat_manip_type maniptype
,
25 const union nf_conntrack_man_proto
*min
,
26 const union nf_conntrack_man_proto
*max
)
30 if (maniptype
== IP_NAT_MANIP_SRC
)
31 port
= tuple
->src
.u
.tcp
.port
;
33 port
= tuple
->dst
.u
.tcp
.port
;
35 return ntohs(port
) >= ntohs(min
->tcp
.port
) &&
36 ntohs(port
) <= ntohs(max
->tcp
.port
);
40 tcp_unique_tuple(struct nf_conntrack_tuple
*tuple
,
41 const struct nf_nat_range
*range
,
42 enum nf_nat_manip_type maniptype
,
43 const struct nf_conn
*ct
)
45 static u_int16_t port
;
47 unsigned int range_size
, min
, i
;
49 if (maniptype
== IP_NAT_MANIP_SRC
)
50 portptr
= &tuple
->src
.u
.tcp
.port
;
52 portptr
= &tuple
->dst
.u
.tcp
.port
;
54 /* If no range specified... */
55 if (!(range
->flags
& IP_NAT_RANGE_PROTO_SPECIFIED
)) {
56 /* If it's dst rewrite, can't change port */
57 if (maniptype
== IP_NAT_MANIP_DST
)
60 /* Map privileged onto privileged. */
61 if (ntohs(*portptr
) < 1024) {
62 /* Loose convention: >> 512 is credential passing */
63 if (ntohs(*portptr
)<512) {
65 range_size
= 511 - min
+ 1;
68 range_size
= 1023 - min
+ 1;
72 range_size
= 65535 - 1024 + 1;
75 min
= ntohs(range
->min
.tcp
.port
);
76 range_size
= ntohs(range
->max
.tcp
.port
) - min
+ 1;
79 if (range
->flags
& IP_NAT_RANGE_PROTO_RANDOM
)
82 for (i
= 0; i
< range_size
; i
++, port
++) {
83 *portptr
= htons(min
+ port
% range_size
);
84 if (!nf_nat_used_tuple(tuple
, ct
))
91 tcp_manip_pkt(struct sk_buff
**pskb
,
92 unsigned int iphdroff
,
93 const struct nf_conntrack_tuple
*tuple
,
94 enum nf_nat_manip_type maniptype
)
96 struct iphdr
*iph
= (struct iphdr
*)((*pskb
)->data
+ iphdroff
);
98 unsigned int hdroff
= iphdroff
+ iph
->ihl
*4;
100 __be16
*portptr
, newport
, oldport
;
101 int hdrsize
= 8; /* TCP connection tracking guarantees this much */
103 /* this could be a inner header returned in icmp packet; in such
104 cases we cannot update the checksum field since it is outside of
105 the 8 bytes of transport layer headers we are guaranteed */
106 if ((*pskb
)->len
>= hdroff
+ sizeof(struct tcphdr
))
107 hdrsize
= sizeof(struct tcphdr
);
109 if (!skb_make_writable(pskb
, hdroff
+ hdrsize
))
112 iph
= (struct iphdr
*)((*pskb
)->data
+ iphdroff
);
113 hdr
= (struct tcphdr
*)((*pskb
)->data
+ hdroff
);
115 if (maniptype
== IP_NAT_MANIP_SRC
) {
116 /* Get rid of src ip and src pt */
118 newip
= tuple
->src
.u3
.ip
;
119 newport
= tuple
->src
.u
.tcp
.port
;
120 portptr
= &hdr
->source
;
122 /* Get rid of dst ip and dst pt */
124 newip
= tuple
->dst
.u3
.ip
;
125 newport
= tuple
->dst
.u
.tcp
.port
;
126 portptr
= &hdr
->dest
;
132 if (hdrsize
< sizeof(*hdr
))
135 nf_proto_csum_replace4(&hdr
->check
, *pskb
, oldip
, newip
, 1);
136 nf_proto_csum_replace2(&hdr
->check
, *pskb
, oldport
, newport
, 0);
140 struct nf_nat_protocol nf_nat_protocol_tcp
= {
142 .protonum
= IPPROTO_TCP
,
144 .manip_pkt
= tcp_manip_pkt
,
145 .in_range
= tcp_in_range
,
146 .unique_tuple
= tcp_unique_tuple
,
147 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
148 .range_to_nfattr
= nf_nat_port_range_to_nfattr
,
149 .nfattr_to_range
= nf_nat_port_nfattr_to_range
,