/* MPLS forwarding table updates using netlink over GNU/Linux system.
 * Copyright (C) 2016  Cumulus Networks, Inc.
 *
 * This file is part of Quagga.
 *
 * Quagga is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * Quagga is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <zebra.h>
#include "zebra/rt.h"
#include "zebra/rt_netlink.h"
#include "zebra/zebra_mpls.h"

/*
 * Install Label Forwarding entry into the kernel.
 */
int kernel_add_lsp(zebra_lsp_t *lsp)
{
	int ret;

	if (!lsp || !lsp->best_nhlfe) // unexpected
		return -1;

	UNSET_FLAG(lsp->flags, LSP_FLAG_CHANGED);
	ret = netlink_mpls_multipath(RTM_NEWROUTE, lsp);
	if (!ret)
		SET_FLAG(lsp->flags, LSP_FLAG_INSTALLED);
	else
		clear_nhlfe_installed(lsp);

	return ret;
}

/*
 * Update Label Forwarding entry in the kernel. This means that the Label
 * forwarding entry is already installed and needs an update - either a new
 * path is to be added, an installed path has changed (e.g., outgoing label)
 * or an installed path (but not all paths) has to be removed.
 * TODO: Performs a DEL followed by ADD now, need to change to REPLACE. Note
 * that REPLACE was originally implemented for IPv4 nexthops but removed as
 * it was not functioning when moving from swap to PHP as that was signaled
 * through the metric field (before kernel-MPLS). This shouldn't be an issue
 * any longer, so REPLACE can be reintroduced.
 */
int kernel_upd_lsp(zebra_lsp_t *lsp)
{
	int ret;

	if (!lsp || !lsp->best_nhlfe) // unexpected
		return -1;

	UNSET_FLAG(lsp->flags, LSP_FLAG_CHANGED);

	/* First issue a DEL and clear the installed flag. */
	netlink_mpls_multipath(RTM_DELROUTE, lsp);
	UNSET_FLAG(lsp->flags, LSP_FLAG_INSTALLED);

	/* Then issue an ADD. */
	ret = netlink_mpls_multipath(RTM_NEWROUTE, lsp);
	if (!ret)
		SET_FLAG(lsp->flags, LSP_FLAG_INSTALLED);
	else
		clear_nhlfe_installed(lsp);

	return ret;
}

/*
 * Delete Label Forwarding entry from the kernel.
 */
int kernel_del_lsp(zebra_lsp_t *lsp)
{
	if (!lsp) // unexpected
		return -1;

	if (CHECK_FLAG(lsp->flags, LSP_FLAG_INSTALLED)) {
		netlink_mpls_multipath(RTM_DELROUTE, lsp);
		UNSET_FLAG(lsp->flags, LSP_FLAG_INSTALLED);
	}

	return 0;
}

int mpls_kernel_init(void)
{
	struct stat st;

	/*
	 * Check if the MPLS module is loaded in the kernel.
	 */
	if (stat("/proc/sys/net/mpls", &st) != 0)
		return -1;

	return 0;
};