/*-
 * Copyright (c) 2018 Andrey V. Elsukov <ae@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/mbuf.h>

static int linkhdr;

static void
update_values(void)
{

	max_hdr = max_linkhdr + max_protohdr;
	max_datalen = MHLEN - max_hdr;
	if (max_datalen < 1)
		panic("%s: max_datalen < 1", __func__);
}

static int
modevent(module_t mod, int type, void *unused)
{

	switch (type) {
	case MOD_LOAD:
		linkhdr = max_linkhdr;
		/*
		 * Ethernet header -> 14-18 bytes
		 * IPv4 header -> 20+ bytes
		 * IPv6 header -> 40 bytes
		 * GRE header -> 4+ bytes
		 * 18 + 40 + 4 = 62
		 */
		max_linkhdr = 62;
		update_values();
		break;
	case MOD_UNLOAD:
		max_linkhdr = linkhdr;
		update_values();
		break;
	default:
		return (EOPNOTSUPP);
	}
	return (0);
}

static moduledata_t mod = {
	"linkhdrmod",
	modevent,
	0
};

DECLARE_MODULE(linkhdrmod, mod, SI_SUB_KLD, SI_ORDER_ANY);
MODULE_VERSION(linkhdrmod, 1);