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/random.h>
12 #include <linux/netfilter.h>
14 #include <linux/udp.h>
17 #include <linux/netfilter_ipv4/ip_nat.h>
18 #include <linux/netfilter_ipv4/ip_nat_core.h>
19 #include <linux/netfilter_ipv4/ip_nat_rule.h>
20 #include <linux/netfilter_ipv4/ip_nat_protocol.h>
23 udp_in_range(const struct ip_conntrack_tuple *tuple,
24 enum ip_nat_manip_type maniptype,
25 const union ip_conntrack_manip_proto *min,
26 const union ip_conntrack_manip_proto *max)
30 if (maniptype == IP_NAT_MANIP_SRC)
31 port = tuple->src.u.udp.port;
33 port = tuple->dst.u.udp.port;
35 return ntohs(port) >= ntohs(min->udp.port)
36 && ntohs(port) <= ntohs(max->udp.port);
40 udp_unique_tuple(struct ip_conntrack_tuple *tuple,
41 const struct ip_nat_range *range,
42 enum ip_nat_manip_type maniptype,
43 const struct ip_conntrack *conntrack)
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.udp.port;
52 portptr = &tuple->dst.u.udp.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 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.udp.port);
75 range_size = ntohs(range->max.udp.port) - min + 1;
78 /* Start from random port to avoid prediction */
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 (!ip_nat_used_tuple(tuple, conntrack))
91 udp_manip_pkt(struct sk_buff **pskb,
92 unsigned int iphdroff,
93 const struct ip_conntrack_tuple *tuple,
94 enum ip_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;
102 if (!skb_make_writable(pskb, hdroff + sizeof(*hdr)))
105 iph = (struct iphdr *)((*pskb)->data + iphdroff);
106 hdr = (struct udphdr *)((*pskb)->data + hdroff);
108 if (maniptype == IP_NAT_MANIP_SRC) {
109 /* Get rid of src ip and src pt */
111 newip = tuple->src.ip;
112 newport = tuple->src.u.udp.port;
113 portptr = &hdr->source;
115 /* Get rid of dst ip and dst pt */
117 newip = tuple->dst.ip;
118 newport = tuple->dst.u.udp.port;
119 portptr = &hdr->dest;
122 if (hdr->check || (*pskb)->ip_summed == CHECKSUM_PARTIAL) {
123 nf_proto_csum_replace4(&hdr->check, *pskb, oldip, newip, 1);
124 nf_proto_csum_replace2(&hdr->check, *pskb, *portptr, newport, 0);
126 hdr->check = CSUM_MANGLED_0;
132 struct ip_nat_protocol ip_nat_protocol_udp = {
134 .protonum = IPPROTO_UDP,
136 .manip_pkt = udp_manip_pkt,
137 .in_range = udp_in_range,
138 .unique_tuple = udp_unique_tuple,
139 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
140 defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
141 .range_to_nfattr = ip_nat_port_range_to_nfattr,
142 .nfattr_to_range = ip_nat_port_nfattr_to_range,