extensions/libipt_helper.c

/* Shared library add-on to iptables to add related packet matching support. */
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>

#include <iptables.h>
#include <linux/netfilter_ipv4/ipt_helper.h>

/* Function which prints out usage message. */
static void
help(void)
{
	printf(
"helper match v%s options:\n"
"[!] --helper value         Match helper value\n"
"\n",
NETFILTER_VERSION);
}

static struct option opts[] = {
	{ "helper", 1, 0, '1' },
	{0}
};

/* Initialize the match. */
static void
init(struct ipt_entry_match *m, unsigned int *nfcache)
{
	/* Can't cache this. */
	*nfcache |= NFC_UNKNOWN;
}

/* 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,
      unsigned int *nfcache,
      struct ipt_entry_match **match)
{
	struct ipt_helper_info *info = (struct ipt_helper_info *)(*match)->data;

	switch (c) {
	case '1':
		if (check_inverse(optarg, &invert))
			optind++;
		strncpy(info->name, optarg, 29);
		if (invert)
			info->invert = 1;
		*flags = 1;
		break;

	default:
		return 0;
	}
	return 1;
}

/* Final check; must have specified --helper. */
static void
final_check(unsigned int flags)
{
	if (!flags)
		exit_error(PARAMETER_PROBLEM,
			   "helper match: You must specify `--helper'");
}

/* Prints out the info. */
static void
print(const struct ipt_ip *ip,
      const struct ipt_entry_match *match,
      int numeric)
{
	struct ipt_helper_info *info = (struct ipt_helper_info *)match->data;

	printf("helper match %s\"%s\" ", info->invert ? "! " : "", info->name);
}

/* Saves the union ipt_info in parsable form to stdout. */
static void
save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
{
	struct ipt_helper_info *info = (struct ipt_helper_info *)match->data;

	printf("%s--helper \"%s\" ",info->invert ? "! " : "", info->name);
}

static
struct iptables_match helper
= { NULL,
    "helper",
    NETFILTER_VERSION,
    IPT_ALIGN(sizeof(struct ipt_helper_info)),
    IPT_ALIGN(sizeof(struct ipt_helper_info)),
    &help,
    &init,
    &parse,
    &final_check,
    &print,
    &save,
    opts
};

void _init(void)
{
	register_match(&helper);
}