#include <stdio.h>

#include <xtables.h>

#include <linux/netfilter/xt_tcpmss.h>

enum {

	O_TCPMSS = 0,

};

static void tcpmss_help(void)

{

	printf(

"tcpmss match options:\n"

"[!] --mss value[:value]	Match TCP MSS range.\n"

"				(only valid for TCP SYN or SYN/ACK packets)\n");

}

static const struct xt_option_entry tcpmss_opts[] = {

	{.name = "mss", .id = O_TCPMSS, .type = XTTYPE_UINT16RC,

	 .flags = XTOPT_MAND | XTOPT_INVERT},

	XTOPT_TABLEEND,

};

static void tcpmss_parse(struct xt_option_call *cb)

{

	struct xt_tcpmss_match_info *mssinfo = cb->data;

	xtables_option_parse(cb);

	mssinfo->mss_min = cb->val.u16_range[0];

	mssinfo->mss_max = mssinfo->mss_min;

	if (cb->nvals == 2) {

		mssinfo->mss_max = cb->val.u16_range[1];

		if (mssinfo->mss_max < mssinfo->mss_min)

			xtables_error(PARAMETER_PROBLEM,

				      "tcpmss: invalid range given");

	}

	if (cb->invert)

		mssinfo->invert = 1;

}

static void

tcpmss_print(const void *ip, const struct xt_entry_match *match, int numeric)

{

	const struct xt_tcpmss_match_info *info = (void *)match->data;

	printf(" tcpmss match %s", info->invert ? "!" : "");

	if (info->mss_min == info->mss_max)

		printf("%u", info->mss_min);

	else

		printf("%u:%u", info->mss_min, info->mss_max);

}

static void tcpmss_save(const void *ip, const struct xt_entry_match *match)

{

	const struct xt_tcpmss_match_info *info = (void *)match->data;

	printf("%s --mss ", info->invert ? " !" : "");

	if (info->mss_min == info->mss_max)

		printf("%u", info->mss_min);

	else

		printf("%u:%u", info->mss_min, info->mss_max);

}

static struct xtables_match tcpmss_match = {

	.family		= NFPROTO_UNSPEC,

	.name		= "tcpmss",

	.version	= XTABLES_VERSION,

	.size		= XT_ALIGN(sizeof(struct xt_tcpmss_match_info)),

	.userspacesize	= XT_ALIGN(sizeof(struct xt_tcpmss_match_info)),

	.help		= tcpmss_help,

	.print		= tcpmss_print,

	.save		= tcpmss_save,

	.x6_parse	= tcpmss_parse,

	.x6_options	= tcpmss_opts,

};

void _init(void)

{

	xtables_register_match(&tcpmss_match);

}