/* Shared library add-on to iptables to add TCPMSS target support.

 *

 * Copyright (c) 2000 Marc Boucher

*/

#include "config.h"

#include <stdio.h>

#include <xtables.h>

#include <netinet/ip.h>

#include <linux/netfilter/xt_TCPMSS.h>

enum {

	O_SET_MSS = 0,

	O_CLAMP_MSS,

};

struct mssinfo {

	struct xt_entry_target t;

	struct xt_tcpmss_info mss;

};

static void __TCPMSS_help(int hdrsize)

{

	printf(

"TCPMSS target mutually-exclusive options:\n"

"  --set-mss value               explicitly set MSS option to specified value\n"

"  --clamp-mss-to-pmtu           automatically clamp MSS value to (path_MTU - %d)\n",

hdrsize);

}

static void TCPMSS_help(void)

{

	__TCPMSS_help(sizeof(struct iphdr));

}

static void TCPMSS_help6(void)

{

	__TCPMSS_help(SIZEOF_STRUCT_IP6_HDR);

}

static const struct xt_option_entry TCPMSS4_opts[] = {

	{.name = "set-mss", .id = O_SET_MSS, .type = XTTYPE_UINT16,

	 .min = 0, .max = UINT16_MAX - sizeof(struct iphdr),

	 .flags = XTOPT_PUT, XTOPT_POINTER(struct xt_tcpmss_info, mss)},

	{.name = "clamp-mss-to-pmtu", .id = O_CLAMP_MSS, .type = XTTYPE_NONE},

	XTOPT_TABLEEND,

};

static const struct xt_option_entry TCPMSS6_opts[] = {

	{.name = "set-mss", .id = O_SET_MSS, .type = XTTYPE_UINT16,

	 .min = 0, .max = UINT16_MAX - SIZEOF_STRUCT_IP6_HDR,

	 .flags = XTOPT_PUT, XTOPT_POINTER(struct xt_tcpmss_info, mss)},

	{.name = "clamp-mss-to-pmtu", .id = O_CLAMP_MSS, .type = XTTYPE_NONE},

	XTOPT_TABLEEND,

};

static void TCPMSS_parse(struct xt_option_call *cb)

{

	struct xt_tcpmss_info *mssinfo = cb->data;

	xtables_option_parse(cb);

	if (cb->entry->id == O_CLAMP_MSS)

		mssinfo->mss = XT_TCPMSS_CLAMP_PMTU;

}

static void TCPMSS_check(struct xt_fcheck_call *cb)

{

	if (cb->xflags == 0)

		xtables_error(PARAMETER_PROBLEM,

		           "TCPMSS target: At least one parameter is required");

}

static void TCPMSS_print(const void *ip, const struct xt_entry_target *target,

                         int numeric)

{

	const struct xt_tcpmss_info *mssinfo =

		(const struct xt_tcpmss_info *)target->data;

	if(mssinfo->mss == XT_TCPMSS_CLAMP_PMTU)

		printf(" TCPMSS clamp to PMTU");

	else

		printf(" TCPMSS set %u", mssinfo->mss);

}

static void TCPMSS_save(const void *ip, const struct xt_entry_target *target)

{

	const struct xt_tcpmss_info *mssinfo =

		(const struct xt_tcpmss_info *)target->data;

	if(mssinfo->mss == XT_TCPMSS_CLAMP_PMTU)

		printf(" --clamp-mss-to-pmtu");

	else

		printf(" --set-mss %u", mssinfo->mss);

}

static int TCPMSS_xlate(struct xt_xlate *xl,

			const struct xt_xlate_tg_params *params)

{

	const struct xt_tcpmss_info *mssinfo =

		(const struct xt_tcpmss_info *)params->target->data;

	if (mssinfo->mss == XT_TCPMSS_CLAMP_PMTU)

		xt_xlate_add(xl, "tcp option maxseg size set rt mtu");

	else

		xt_xlate_add(xl, "tcp option maxseg size set %d", mssinfo->mss);

	return 1;

}

static struct xtables_target tcpmss_tg_reg[] = {

	{

		.family        = NFPROTO_IPV4,

		.name          = "TCPMSS",

		.version       = XTABLES_VERSION,

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

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

		.help          = TCPMSS_help,

		.print         = TCPMSS_print,

		.save          = TCPMSS_save,

		.x6_parse      = TCPMSS_parse,

		.x6_fcheck     = TCPMSS_check,

		.x6_options    = TCPMSS4_opts,

		.xlate         = TCPMSS_xlate,

	},

	{

		.family        = NFPROTO_IPV6,

		.name          = "TCPMSS",

		.version       = XTABLES_VERSION,

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

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

		.help          = TCPMSS_help6,

		.print         = TCPMSS_print,

		.save          = TCPMSS_save,

		.x6_parse      = TCPMSS_parse,

		.x6_fcheck     = TCPMSS_check,

		.x6_options    = TCPMSS6_opts,

	},

};

void _init(void)

{

	xtables_register_targets(tcpmss_tg_reg, ARRAY_SIZE(tcpmss_tg_reg));

}