1 #include <stdio.h>
2 #include <string.h>
3 #include <stdlib.h>
4 #include <xtables.h>
5 #include <limits.h> /* INT_MAX in ip_tables.h */
6 #include <linux/netfilter_ipv4/ip_tables.h>
7 #include <linux/netfilter/nf_nat.h>
8
9 enum {
10 O_TO_PORTS = 0,
11 O_RANDOM,
12 F_TO_PORTS = 1 << O_TO_PORTS,
13 F_RANDOM = 1 << O_RANDOM,
14 };
15
REDIRECT_help(void)16 static void REDIRECT_help(void)
17 {
18 printf(
19 "REDIRECT target options:\n"
20 " --to-ports <port>[-<port>]\n"
21 " Port (range) to map to.\n"
22 " [--random]\n");
23 }
24
25 static const struct xt_option_entry REDIRECT_opts[] = {
26 {.name = "to-ports", .id = O_TO_PORTS, .type = XTTYPE_STRING},
27 {.name = "random", .id = O_RANDOM, .type = XTTYPE_NONE},
28 XTOPT_TABLEEND,
29 };
30
REDIRECT_init(struct xt_entry_target * t)31 static void REDIRECT_init(struct xt_entry_target *t)
32 {
33 struct nf_nat_ipv4_multi_range_compat *mr = (struct nf_nat_ipv4_multi_range_compat *)t->data;
34
35 /* Actually, it's 0, but it's ignored at the moment. */
36 mr->rangesize = 1;
37 }
38
39 /* Parses ports */
40 static void
parse_ports(const char * arg,struct nf_nat_ipv4_multi_range_compat * mr)41 parse_ports(const char *arg, struct nf_nat_ipv4_multi_range_compat *mr)
42 {
43 char *end = "";
44 unsigned int port, maxport;
45
46 mr->range[0].flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
47
48 if (!xtables_strtoui(arg, &end, &port, 0, UINT16_MAX) &&
49 (port = xtables_service_to_port(arg, NULL)) == (unsigned)-1)
50 xtables_param_act(XTF_BAD_VALUE, "REDIRECT", "--to-ports", arg);
51
52 switch (*end) {
53 case '\0':
54 mr->range[0].min.tcp.port
55 = mr->range[0].max.tcp.port
56 = htons(port);
57 return;
58 case '-':
59 if (!xtables_strtoui(end + 1, NULL, &maxport, 0, UINT16_MAX) &&
60 (maxport = xtables_service_to_port(end + 1, NULL)) == (unsigned)-1)
61 break;
62
63 if (maxport < port)
64 break;
65
66 mr->range[0].min.tcp.port = htons(port);
67 mr->range[0].max.tcp.port = htons(maxport);
68 return;
69 default:
70 break;
71 }
72 xtables_param_act(XTF_BAD_VALUE, "REDIRECT", "--to-ports", arg);
73 }
74
REDIRECT_parse(struct xt_option_call * cb)75 static void REDIRECT_parse(struct xt_option_call *cb)
76 {
77 const struct ipt_entry *entry = cb->xt_entry;
78 struct nf_nat_ipv4_multi_range_compat *mr = (void *)(*cb->target)->data;
79 int portok;
80
81 if (entry->ip.proto == IPPROTO_TCP
82 || entry->ip.proto == IPPROTO_UDP
83 || entry->ip.proto == IPPROTO_SCTP
84 || entry->ip.proto == IPPROTO_DCCP
85 || entry->ip.proto == IPPROTO_ICMP)
86 portok = 1;
87 else
88 portok = 0;
89
90 xtables_option_parse(cb);
91 switch (cb->entry->id) {
92 case O_TO_PORTS:
93 if (!portok)
94 xtables_error(PARAMETER_PROBLEM,
95 "Need TCP, UDP, SCTP or DCCP with port specification");
96 parse_ports(cb->arg, mr);
97 if (cb->xflags & F_RANDOM)
98 mr->range[0].flags |= NF_NAT_RANGE_PROTO_RANDOM;
99 break;
100 case O_RANDOM:
101 if (cb->xflags & F_TO_PORTS)
102 mr->range[0].flags |= NF_NAT_RANGE_PROTO_RANDOM;
103 break;
104 }
105 }
106
REDIRECT_print(const void * ip,const struct xt_entry_target * target,int numeric)107 static void REDIRECT_print(const void *ip, const struct xt_entry_target *target,
108 int numeric)
109 {
110 const struct nf_nat_ipv4_multi_range_compat *mr = (const void *)target->data;
111 const struct nf_nat_ipv4_range *r = &mr->range[0];
112
113 if (r->flags & NF_NAT_RANGE_PROTO_SPECIFIED) {
114 printf(" redir ports ");
115 printf("%hu", ntohs(r->min.tcp.port));
116 if (r->max.tcp.port != r->min.tcp.port)
117 printf("-%hu", ntohs(r->max.tcp.port));
118 if (mr->range[0].flags & NF_NAT_RANGE_PROTO_RANDOM)
119 printf(" random");
120 }
121 }
122
REDIRECT_save(const void * ip,const struct xt_entry_target * target)123 static void REDIRECT_save(const void *ip, const struct xt_entry_target *target)
124 {
125 const struct nf_nat_ipv4_multi_range_compat *mr = (const void *)target->data;
126 const struct nf_nat_ipv4_range *r = &mr->range[0];
127
128 if (r->flags & NF_NAT_RANGE_PROTO_SPECIFIED) {
129 printf(" --to-ports ");
130 printf("%hu", ntohs(r->min.tcp.port));
131 if (r->max.tcp.port != r->min.tcp.port)
132 printf("-%hu", ntohs(r->max.tcp.port));
133 if (mr->range[0].flags & NF_NAT_RANGE_PROTO_RANDOM)
134 printf(" --random");
135 }
136 }
137
REDIRECT_xlate(struct xt_xlate * xl,const struct xt_xlate_tg_params * params)138 static int REDIRECT_xlate(struct xt_xlate *xl,
139 const struct xt_xlate_tg_params *params)
140 {
141 const struct nf_nat_ipv4_multi_range_compat *mr =
142 (const void *)params->target->data;
143 const struct nf_nat_ipv4_range *r = &mr->range[0];
144
145 if (r->flags & NF_NAT_RANGE_PROTO_SPECIFIED) {
146 xt_xlate_add(xl, "redirect to :%hu", ntohs(r->min.tcp.port));
147 if (r->max.tcp.port != r->min.tcp.port)
148 xt_xlate_add(xl, "-%hu ", ntohs(r->max.tcp.port));
149 if (mr->range[0].flags & NF_NAT_RANGE_PROTO_RANDOM)
150 xt_xlate_add(xl, " random ");
151 }
152
153 return 1;
154 }
155
156 static struct xtables_target redirect_tg_reg = {
157 .name = "REDIRECT",
158 .version = XTABLES_VERSION,
159 .family = NFPROTO_IPV4,
160 .size = XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat)),
161 .userspacesize = XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat)),
162 .help = REDIRECT_help,
163 .init = REDIRECT_init,
164 .x6_parse = REDIRECT_parse,
165 .print = REDIRECT_print,
166 .save = REDIRECT_save,
167 .x6_options = REDIRECT_opts,
168 .xlate = REDIRECT_xlate,
169 };
170
_init(void)171 void _init(void)
172 {
173 xtables_register_target(&redirect_tg_reg);
174 }
175