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/* Shared library add-on to iptables to add static NAT support.
Author: Svenning Soerensen <svenning@post5.tele.dk>
*/
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>
#include <iptables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ip_nat_rule.h>
#define MODULENAME "NETMAP"
static struct option opts[] = {
{ "to", 1, 0, '1' },
{ 0 }
};
/* Function which prints out usage message. */
static void
help(void)
{
printf(MODULENAME" v%s options:\n"
" --%s address[/mask]\n"
" Network address to map to.\n\n",
NETFILTER_VERSION, opts[0].name);
}
static u_int32_t
bits2netmask(int bits)
{
u_int32_t netmask, bm;
if (bits >= 32 || bits < 0)
return(~0);
for (netmask = 0, bm = 0x80000000; bits; bits--, bm >>= 1)
netmask |= bm;
return htonl(netmask);
}
static int
netmask2bits(u_int32_t netmask)
{
u_int32_t bm;
int bits;
netmask = ntohl(netmask);
for (bits = 0, bm = 0x80000000; netmask & bm; netmask <<= 1)
bits++;
if (netmask)
return -1; /* holes in netmask */
return bits;
}
/* Initialize the target. */
static void
init(struct ipt_entry_target *t, unsigned int *nfcache)
{
struct ip_nat_multi_range *mr = (struct ip_nat_multi_range *)t->data;
/* Actually, it's 0, but it's ignored at the moment. */
mr->rangesize = 1;
/* Can't cache this */
*nfcache |= NFC_UNKNOWN;
}
/* Parses network address */
static void
parse_to(char *arg, struct ip_nat_range *range)
{
char *slash;
struct in_addr *ip;
u_int32_t netmask;
unsigned int bits;
range->flags |= IP_NAT_RANGE_MAP_IPS;
slash = strchr(arg, '/');
if (slash)
*slash = '\0';
ip = dotted_to_addr(arg);
if (!ip)
exit_error(PARAMETER_PROBLEM, "Bad IP address `%s'\n",
arg);
range->min_ip = ip->s_addr;
if (slash) {
if (strchr(slash+1, '.')) {
ip = dotted_to_addr(slash+1);
if (!ip)
exit_error(PARAMETER_PROBLEM, "Bad netmask `%s'\n",
slash+1);
netmask = ip->s_addr;
}
else {
if (string_to_number(slash+1, 0, 32, &bits) == -1)
exit_error(PARAMETER_PROBLEM, "Bad netmask `%s'\n",
slash+1);
netmask = bits2netmask(bits);
}
/* Don't allow /0 (/1 is probably insane, too) */
if (netmask == 0)
exit_error(PARAMETER_PROBLEM, "Netmask needed\n");
}
else
netmask = ~0;
if (range->min_ip & ~netmask) {
if (slash)
*slash = '/';
exit_error(PARAMETER_PROBLEM, "Bad network address `%s'\n",
arg);
}
range->max_ip = range->min_ip | ~netmask;
}
/* Function which parses command options; returns true if it
ate an option */
static int
parse(int c, char **argv, int invert, unsigned int *flags,
const struct ipt_entry *entry,
struct ipt_entry_target **target)
{
struct ip_nat_multi_range *mr
= (struct ip_nat_multi_range *)(*target)->data;
switch (c) {
case '1':
if (check_inverse(optarg, &invert, NULL, 0))
exit_error(PARAMETER_PROBLEM,
"Unexpected `!' after --%s", opts[0].name);
parse_to(optarg, &mr->range[0]);
*flags = 1;
return 1;
default:
return 0;
}
}
/* Final check; need --to */
static void final_check(unsigned int flags)
{
if (!flags)
exit_error(PARAMETER_PROBLEM,
MODULENAME" needs --%s", opts[0].name);
}
/* Prints out the targinfo. */
static void
print(const struct ipt_ip *ip,
const struct ipt_entry_target *target,
int numeric)
{
struct ip_nat_multi_range *mr
= (struct ip_nat_multi_range *)target->data;
struct ip_nat_range *r = &mr->range[0];
struct in_addr a;
int bits;
a.s_addr = r->min_ip;
printf("%s", addr_to_dotted(&a));
a.s_addr = ~(r->min_ip ^ r->max_ip);
bits = netmask2bits(a.s_addr);
if (bits < 0)
printf("/%s", addr_to_dotted(&a));
else
printf("/%d", bits);
}
/* Saves the targinfo in parsable form to stdout. */
static void
save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
{
printf("--%s ", opts[0].name);
print(ip, target, 0);
}
static
struct iptables_target target_module
= { NULL,
MODULENAME,
NETFILTER_VERSION,
IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
&help,
&init,
&parse,
&final_check,
&print,
&save,
opts
};
void _init(void)
{
register_target(&target_module);
}
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