libipt_REDIRECT.c revision ae06c6dc6d68d11ed15d4c6c47b7b7a709d3c9cb 
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 <net/netfilter/nf_nat.h>
8
9enum {
10	O_TO_PORTS = 0,
11	O_RANDOM,
12	F_TO_PORTS = 1 << O_TO_PORTS,
13	F_RANDOM   = 1 << O_RANDOM,
14};
15
16static 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
25static 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
31static void REDIRECT_init(struct xt_entry_target *t)
32{
33	struct nf_nat_multi_range *mr = (struct nf_nat_multi_range *)t->data;
34
35	/* Actually, it's 0, but it's ignored at the moment. */
36	mr->rangesize = 1;
37}
38
39/* Parses ports */
40static void
41parse_ports(const char *arg, struct nf_nat_multi_range *mr)
42{
43	char *end = "";
44	unsigned int port, maxport;
45
46	mr->range[0].flags |= IP_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
75static void REDIRECT_parse(struct xt_option_call *cb)
76{
77	const struct ipt_entry *entry = cb->xt_entry;
78	struct nf_nat_multi_range *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 |= IP_NAT_RANGE_PROTO_RANDOM;
99		break;
100	case O_RANDOM:
101		if (cb->xflags & F_TO_PORTS)
102			mr->range[0].flags |= IP_NAT_RANGE_PROTO_RANDOM;
103		break;
104	}
105}
106
107static void REDIRECT_print(const void *ip, const struct xt_entry_target *target,
108                           int numeric)
109{
110	const struct nf_nat_multi_range *mr = (const void *)target->data;
111	const struct nf_nat_range *r = &mr->range[0];
112
113	if (r->flags & IP_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 & IP_NAT_RANGE_PROTO_RANDOM)
119			printf(" random");
120	}
121}
122
123static void REDIRECT_save(const void *ip, const struct xt_entry_target *target)
124{
125	const struct nf_nat_multi_range *mr = (const void *)target->data;
126	const struct nf_nat_range *r = &mr->range[0];
127
128	if (r->flags & IP_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 & IP_NAT_RANGE_PROTO_RANDOM)
134			printf(" --random");
135	}
136}
137
138static struct xtables_target redirect_tg_reg = {
139	.name		= "REDIRECT",
140	.version	= XTABLES_VERSION,
141	.family		= NFPROTO_IPV4,
142	.size		= XT_ALIGN(sizeof(struct nf_nat_multi_range)),
143	.userspacesize	= XT_ALIGN(sizeof(struct nf_nat_multi_range)),
144	.help		= REDIRECT_help,
145	.init		= REDIRECT_init,
146 	.x6_parse	= REDIRECT_parse,
147	.print		= REDIRECT_print,
148	.save		= REDIRECT_save,
149	.x6_options	= REDIRECT_opts,
150};
151
152void _init(void)
153{
154	xtables_register_target(&redirect_tg_reg);
155}
156