libipt_REDIRECT.c revision c0bba1a8033ce15d1eec80da94c8f249a967568e 
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	 .flags = XTOPT_MAND},
28	{.name = "random", .id = O_RANDOM, .type = XTTYPE_NONE},
29	XTOPT_TABLEEND,
30};
31
32static void REDIRECT_init(struct xt_entry_target *t)
33{
34	struct nf_nat_multi_range *mr = (struct nf_nat_multi_range *)t->data;
35
36	/* Actually, it's 0, but it's ignored at the moment. */
37	mr->rangesize = 1;
38}
39
40/* Parses ports */
41static void
42parse_ports(const char *arg, struct nf_nat_multi_range *mr)
43{
44	char *end = "";
45	unsigned int port, maxport;
46
47	mr->range[0].flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
48
49	if (!xtables_strtoui(arg, &end, &port, 0, UINT16_MAX) &&
50	    (port = xtables_service_to_port(arg, NULL)) == (unsigned)-1)
51		xtables_param_act(XTF_BAD_VALUE, "REDIRECT", "--to-ports", arg);
52
53	switch (*end) {
54	case '\0':
55		mr->range[0].min.tcp.port
56			= mr->range[0].max.tcp.port
57			= htons(port);
58		return;
59	case '-':
60		if (!xtables_strtoui(end + 1, NULL, &maxport, 0, UINT16_MAX) &&
61		    (maxport = xtables_service_to_port(end + 1, NULL)) == (unsigned)-1)
62			break;
63
64		if (maxport < port)
65			break;
66
67		mr->range[0].min.tcp.port = htons(port);
68		mr->range[0].max.tcp.port = htons(maxport);
69		return;
70	default:
71		break;
72	}
73	xtables_param_act(XTF_BAD_VALUE, "REDIRECT", "--to-ports", arg);
74}
75
76static void REDIRECT_parse(struct xt_option_call *cb)
77{
78	const struct ipt_entry *entry = cb->xt_entry;
79	struct nf_nat_multi_range *mr = (void *)(*cb->target)->data;
80	int portok;
81
82	if (entry->ip.proto == IPPROTO_TCP
83	    || entry->ip.proto == IPPROTO_UDP
84	    || entry->ip.proto == IPPROTO_SCTP
85	    || entry->ip.proto == IPPROTO_DCCP
86	    || entry->ip.proto == IPPROTO_ICMP)
87		portok = 1;
88	else
89		portok = 0;
90
91	xtables_option_parse(cb);
92	switch (cb->entry->id) {
93	case O_TO_PORTS:
94		if (!portok)
95			xtables_error(PARAMETER_PROBLEM,
96				   "Need TCP, UDP, SCTP or DCCP with port specification");
97		parse_ports(cb->arg, mr);
98		if (cb->xflags & F_RANDOM)
99			mr->range[0].flags |= IP_NAT_RANGE_PROTO_RANDOM;
100		break;
101	case O_RANDOM:
102		if (cb->xflags & F_TO_PORTS)
103			mr->range[0].flags |= IP_NAT_RANGE_PROTO_RANDOM;
104		break;
105	}
106}
107
108static void REDIRECT_print(const void *ip, const struct xt_entry_target *target,
109                           int numeric)
110{
111	const struct nf_nat_multi_range *mr = (const void *)target->data;
112	const struct nf_nat_range *r = &mr->range[0];
113
114	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
115		printf(" redir ports ");
116		printf("%hu", ntohs(r->min.tcp.port));
117		if (r->max.tcp.port != r->min.tcp.port)
118			printf("-%hu", ntohs(r->max.tcp.port));
119		if (mr->range[0].flags & IP_NAT_RANGE_PROTO_RANDOM)
120			printf(" random");
121	}
122}
123
124static void REDIRECT_save(const void *ip, const struct xt_entry_target *target)
125{
126	const struct nf_nat_multi_range *mr = (const void *)target->data;
127	const struct nf_nat_range *r = &mr->range[0];
128
129	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
130		printf(" --to-ports ");
131		printf("%hu", ntohs(r->min.tcp.port));
132		if (r->max.tcp.port != r->min.tcp.port)
133			printf("-%hu", ntohs(r->max.tcp.port));
134		if (mr->range[0].flags & IP_NAT_RANGE_PROTO_RANDOM)
135			printf(" --random");
136	}
137}
138
139static struct xtables_target redirect_tg_reg = {
140	.name		= "REDIRECT",
141	.version	= XTABLES_VERSION,
142	.family		= NFPROTO_IPV4,
143	.size		= XT_ALIGN(sizeof(struct nf_nat_multi_range)),
144	.userspacesize	= XT_ALIGN(sizeof(struct nf_nat_multi_range)),
145	.help		= REDIRECT_help,
146	.init		= REDIRECT_init,
147 	.x6_parse	= REDIRECT_parse,
148	.print		= REDIRECT_print,
149	.save		= REDIRECT_save,
150	.x6_options	= REDIRECT_opts,
151};
152
153void _init(void)
154{
155	xtables_register_target(&redirect_tg_reg);
156}
157