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/* Shared library add-on to iptables to add masquerade support. */
#include <stdbool.h>
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>
#include <xtables.h>
#include <limits.h> /* INT_MAX in ip_tables.h */
#include <linux/netfilter_ipv4/ip_tables.h>
#include <net/netfilter/nf_nat.h>
static void MASQUERADE_help(void)
{
printf(
"MASQUERADE target options:\n"
" --to-ports <port>[-<port>]\n"
" Port (range) to map to.\n"
" --random\n"
" Randomize source port.\n");
}
static const struct option MASQUERADE_opts[] = {
{.name = "to-ports", .has_arg = true, .val = '1'},
{.name = "random", .has_arg = false, .val = '2'},
XT_GETOPT_TABLEEND,
};
static void MASQUERADE_init(struct xt_entry_target *t)
{
struct nf_nat_multi_range *mr = (struct nf_nat_multi_range *)t->data;
/* Actually, it's 0, but it's ignored at the moment. */
mr->rangesize = 1;
}
/* Parses ports */
static void
parse_ports(const char *arg, struct nf_nat_multi_range *mr)
{
char *end;
unsigned int port, maxport;
mr->range[0].flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
if (!xtables_strtoui(arg, &end, &port, 0, UINT16_MAX))
xtables_param_act(XTF_BAD_VALUE, "MASQUERADE", "--to-ports", arg);
switch (*end) {
case '\0':
mr->range[0].min.tcp.port
= mr->range[0].max.tcp.port
= htons(port);
return;
case '-':
if (!xtables_strtoui(end + 1, NULL, &maxport, 0, UINT16_MAX))
break;
if (maxport < port)
break;
mr->range[0].min.tcp.port = htons(port);
mr->range[0].max.tcp.port = htons(maxport);
return;
default:
break;
}
xtables_param_act(XTF_BAD_VALUE, "MASQUERADE", "--to-ports", arg);
}
static int MASQUERADE_parse(int c, char **argv, int invert, unsigned int *flags,
const void *e, struct xt_entry_target **target)
{
const struct ipt_entry *entry = e;
int portok;
struct nf_nat_multi_range *mr
= (struct nf_nat_multi_range *)(*target)->data;
if (entry->ip.proto == IPPROTO_TCP
|| entry->ip.proto == IPPROTO_UDP
|| entry->ip.proto == IPPROTO_SCTP
|| entry->ip.proto == IPPROTO_DCCP
|| entry->ip.proto == IPPROTO_ICMP)
portok = 1;
else
portok = 0;
switch (c) {
case '1':
if (!portok)
xtables_error(PARAMETER_PROBLEM,
"Need TCP, UDP, SCTP or DCCP with port specification");
if (xtables_check_inverse(optarg, &invert, NULL, 0, argv))
xtables_error(PARAMETER_PROBLEM,
"Unexpected `!' after --to-ports");
parse_ports(optarg, mr);
return 1;
case '2':
mr->range[0].flags |= IP_NAT_RANGE_PROTO_RANDOM;
return 1;
}
return 0;
}
static void
MASQUERADE_print(const void *ip, const struct xt_entry_target *target,
int numeric)
{
const struct nf_nat_multi_range *mr = (const void *)target->data;
const struct nf_nat_range *r = &mr->range[0];
if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
printf(" masq ports: ");
printf("%hu", ntohs(r->min.tcp.port));
if (r->max.tcp.port != r->min.tcp.port)
printf("-%hu", ntohs(r->max.tcp.port));
}
if (r->flags & IP_NAT_RANGE_PROTO_RANDOM)
printf(" random");
}
static void
MASQUERADE_save(const void *ip, const struct xt_entry_target *target)
{
const struct nf_nat_multi_range *mr = (const void *)target->data;
const struct nf_nat_range *r = &mr->range[0];
if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
printf(" --to-ports %hu", ntohs(r->min.tcp.port));
if (r->max.tcp.port != r->min.tcp.port)
printf("-%hu", ntohs(r->max.tcp.port));
}
if (r->flags & IP_NAT_RANGE_PROTO_RANDOM)
printf(" --random");
}
static struct xtables_target masquerade_tg_reg = {
.name = "MASQUERADE",
.version = XTABLES_VERSION,
.family = NFPROTO_IPV4,
.size = XT_ALIGN(sizeof(struct nf_nat_multi_range)),
.userspacesize = XT_ALIGN(sizeof(struct nf_nat_multi_range)),
.help = MASQUERADE_help,
.init = MASQUERADE_init,
.parse = MASQUERADE_parse,
.print = MASQUERADE_print,
.save = MASQUERADE_save,
.extra_opts = MASQUERADE_opts,
};
void _init(void)
{
xtables_register_target(&masquerade_tg_reg);
}
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