1 /* (C) 1999-2001 Paul `Rusty' Russell
2 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
3 *
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.
7 */
8
9 #include <linux/types.h>
10 #include <linux/init.h>
11 #include <linux/netfilter.h>
12 #include <linux/ip.h>
13 #include <linux/udp.h>
14 #include <linux/if.h>
15
16 #include <linux/netfilter_ipv4/ip_nat.h>
17 #include <linux/netfilter_ipv4/ip_nat_core.h>
18 #include <linux/netfilter_ipv4/ip_nat_rule.h>
19 #include <linux/netfilter_ipv4/ip_nat_protocol.h>
20
21 static int
22 udp_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)
26 {
27 u_int16_t port;
28
29 if (maniptype == IP_NAT_MANIP_SRC)
30 port = tuple->src.u.udp.port;
31 else
32 port = tuple->dst.u.udp.port;
33
34 return ntohs(port) >= ntohs(min->udp.port)
35 && ntohs(port) <= ntohs(max->udp.port);
36 }
37
38 static int
39 udp_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)
43 {
44 static u_int16_t port, *portptr;
45 unsigned int range_size, min, i;
46
47 if (maniptype == IP_NAT_MANIP_SRC)
48 portptr = &tuple->src.u.udp.port;
49 else
50 portptr = &tuple->dst.u.udp.port;
51
52 /* If no range specified... */
53 if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)) {
54 /* If it's dst rewrite, can't change port */
55 if (maniptype == IP_NAT_MANIP_DST)
56 return 0;
57
58 if (ntohs(*portptr) < 1024) {
59 /* Loose convention: >> 512 is credential passing */
60 if (ntohs(*portptr)<512) {
61 min = 1;
62 range_size = 511 - min + 1;
63 } else {
64 min = 600;
65 range_size = 1023 - min + 1;
66 }
67 } else {
68 min = 1024;
69 range_size = 65535 - 1024 + 1;
70 }
71 } else {
72 min = ntohs(range->min.udp.port);
73 range_size = ntohs(range->max.udp.port) - min + 1;
74 }
75
76 for (i = 0; i < range_size; i++, port++) {
77 *portptr = htons(min + port % range_size);
78 if (!ip_nat_used_tuple(tuple, conntrack))
79 return 1;
80 }
81 return 0;
82 }
83
84 static int
85 udp_manip_pkt(struct sk_buff **pskb,
86 unsigned int iphdroff,
87 const struct ip_conntrack_tuple *tuple,
88 enum ip_nat_manip_type maniptype)
89 {
90 struct iphdr *iph = (struct iphdr *)((*pskb)->data + iphdroff);
91 struct udphdr *hdr;
92 unsigned int hdroff = iphdroff + iph->ihl*4;
93 u32 oldip, newip;
94 u16 *portptr, newport;
95
96 if (!skb_ip_make_writable(pskb, hdroff + sizeof(*hdr)))
97 return 0;
98
99 iph = (struct iphdr *)((*pskb)->data + iphdroff);
100 hdr = (struct udphdr *)((*pskb)->data + hdroff);
101
102 if (maniptype == IP_NAT_MANIP_SRC) {
103 /* Get rid of src ip and src pt */
104 oldip = iph->saddr;
105 newip = tuple->src.ip;
106 newport = tuple->src.u.udp.port;
107 portptr = &hdr->source;
108 } else {
109 /* Get rid of dst ip and dst pt */
110 oldip = iph->daddr;
111 newip = tuple->dst.ip;
112 newport = tuple->dst.u.udp.port;
113 portptr = &hdr->dest;
114 }
115 if (hdr->check) /* 0 is a special case meaning no checksum */
116 hdr->check = ip_nat_cheat_check(~oldip, newip,
117 ip_nat_cheat_check(*portptr ^ 0xFFFF,
118 newport,
119 hdr->check));
120 *portptr = newport;
121 return 1;
122 }
123
124 static unsigned int
125 udp_print(char *buffer,
126 const struct ip_conntrack_tuple *match,
127 const struct ip_conntrack_tuple *mask)
128 {
129 unsigned int len = 0;
130
131 if (mask->src.u.udp.port)
132 len += sprintf(buffer + len, "srcpt=%u ",
133 ntohs(match->src.u.udp.port));
134
135
136 if (mask->dst.u.udp.port)
137 len += sprintf(buffer + len, "dstpt=%u ",
138 ntohs(match->dst.u.udp.port));
139
140 return len;
141 }
142
143 static unsigned int
144 udp_print_range(char *buffer, const struct ip_nat_range *range)
145 {
146 if (range->min.udp.port != 0 || range->max.udp.port != 0xFFFF) {
147 if (range->min.udp.port == range->max.udp.port)
148 return sprintf(buffer, "port %u ",
149 ntohs(range->min.udp.port));
150 else
151 return sprintf(buffer, "ports %u-%u ",
152 ntohs(range->min.udp.port),
153 ntohs(range->max.udp.port));
154 }
155 else return 0;
156 }
157
158 struct ip_nat_protocol ip_nat_protocol_udp
159 = { "UDP", IPPROTO_UDP,
160 udp_manip_pkt,
161 udp_in_range,
162 udp_unique_tuple,
163 udp_print,
164 udp_print_range
165 };
166
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