1 #include <linux/types.h>
2 #include <linux/init.h>
3 #include <linux/netfilter.h>
4 #include <linux/ip.h>
5 #include <linux/udp.h>
6 #include <linux/if.h>
7
8 #include <linux/netfilter_ipv4/ip_nat.h>
9 #include <linux/netfilter_ipv4/ip_nat_rule.h>
10 #include <linux/netfilter_ipv4/ip_nat_protocol.h>
11
12 static int
udp_in_range(const struct ip_conntrack_tuple * tuple,enum ip_nat_manip_type maniptype,const union ip_conntrack_manip_proto * min,const union ip_conntrack_manip_proto * max)13 udp_in_range(const struct ip_conntrack_tuple *tuple,
14 enum ip_nat_manip_type maniptype,
15 const union ip_conntrack_manip_proto *min,
16 const union ip_conntrack_manip_proto *max)
17 {
18 u_int16_t port;
19
20 if (maniptype == IP_NAT_MANIP_SRC)
21 port = tuple->src.u.udp.port;
22 else
23 port = tuple->dst.u.udp.port;
24
25 return ntohs(port) >= ntohs(min->udp.port)
26 && ntohs(port) <= ntohs(max->udp.port);
27 }
28
29 static int
udp_unique_tuple(struct ip_conntrack_tuple * tuple,const struct ip_nat_range * range,enum ip_nat_manip_type maniptype,const struct ip_conntrack * conntrack)30 udp_unique_tuple(struct ip_conntrack_tuple *tuple,
31 const struct ip_nat_range *range,
32 enum ip_nat_manip_type maniptype,
33 const struct ip_conntrack *conntrack)
34 {
35 static u_int16_t port = 0;
36 u_int16_t *portptr;
37 unsigned int range_size, min, i;
38
39 if (maniptype == IP_NAT_MANIP_SRC)
40 portptr = &tuple->src.u.udp.port;
41 else
42 portptr = &tuple->dst.u.udp.port;
43
44 /* If no range specified... */
45 if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)) {
46 /* If it's dst rewrite, can't change port */
47 if (maniptype == IP_NAT_MANIP_DST)
48 return 0;
49
50 if (ntohs(*portptr) < 1024) {
51 /* Loose convention: >> 512 is credential passing */
52 if (ntohs(*portptr)<512) {
53 min = 1;
54 range_size = 511 - min + 1;
55 } else {
56 min = 600;
57 range_size = 1023 - min + 1;
58 }
59 } else {
60 min = 1024;
61 range_size = 65535 - 1024 + 1;
62 }
63 } else {
64 min = ntohs(range->min.udp.port);
65 range_size = ntohs(range->max.udp.port) - min + 1;
66 }
67
68 for (i = 0; i < range_size; i++, port++) {
69 *portptr = htons(min + port % range_size);
70 if (!ip_nat_used_tuple(tuple, conntrack))
71 return 1;
72 }
73 return 0;
74 }
75
76 static void
udp_manip_pkt(struct iphdr * iph,size_t len,const struct ip_conntrack_manip * manip,enum ip_nat_manip_type maniptype)77 udp_manip_pkt(struct iphdr *iph, size_t len,
78 const struct ip_conntrack_manip *manip,
79 enum ip_nat_manip_type maniptype)
80 {
81 struct udphdr *hdr = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
82 u_int32_t oldip;
83 u_int16_t *portptr;
84
85 if (maniptype == IP_NAT_MANIP_SRC) {
86 /* Get rid of src ip and src pt */
87 oldip = iph->saddr;
88 portptr = &hdr->source;
89 } else {
90 /* Get rid of dst ip and dst pt */
91 oldip = iph->daddr;
92 portptr = &hdr->dest;
93 }
94 if (hdr->check) /* 0 is a special case meaning no checksum */
95 hdr->check = ip_nat_cheat_check(~oldip, manip->ip,
96 ip_nat_cheat_check(*portptr ^ 0xFFFF,
97 manip->u.udp.port,
98 hdr->check));
99 *portptr = manip->u.udp.port;
100 }
101
102 static unsigned int
udp_print(char * buffer,const struct ip_conntrack_tuple * match,const struct ip_conntrack_tuple * mask)103 udp_print(char *buffer,
104 const struct ip_conntrack_tuple *match,
105 const struct ip_conntrack_tuple *mask)
106 {
107 unsigned int len = 0;
108
109 if (mask->src.u.udp.port)
110 len += sprintf(buffer + len, "srcpt=%u ",
111 ntohs(match->src.u.udp.port));
112
113
114 if (mask->dst.u.udp.port)
115 len += sprintf(buffer + len, "dstpt=%u ",
116 ntohs(match->dst.u.udp.port));
117
118 return len;
119 }
120
121 static unsigned int
udp_print_range(char * buffer,const struct ip_nat_range * range)122 udp_print_range(char *buffer, const struct ip_nat_range *range)
123 {
124 if (range->min.udp.port != 0 || range->max.udp.port != 0xFFFF) {
125 if (range->min.udp.port == range->max.udp.port)
126 return sprintf(buffer, "port %u ",
127 ntohs(range->min.udp.port));
128 else
129 return sprintf(buffer, "ports %u-%u ",
130 ntohs(range->min.udp.port),
131 ntohs(range->max.udp.port));
132 }
133 else return 0;
134 }
135
136 struct ip_nat_protocol ip_nat_protocol_udp
137 = { { NULL, NULL }, "UDP", IPPROTO_UDP,
138 udp_manip_pkt,
139 udp_in_range,
140 udp_unique_tuple,
141 udp_print,
142 udp_print_range
143 };
144