/*
 * Copyright (C) 2013 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program 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 of the
 * License, or any later version.
 *
 * This program 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; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdint.h>
#include <stdlib.h>
#include <errno.h>
#include <ipxe/dhcppkt.h>
#include <ipxe/init.h>
#include <ipxe/netdevice.h>
#include <ipxe/cachedhcp.h>

/** @file
 *
 * Cached DHCP packet
 *
 */

/** A cached DHCP packet */
struct cached_dhcp_packet {
	/** Settings block name */
	const char *name;
	/** DHCP packet (if any) */
	struct dhcp_packet *dhcppkt;
};

/** Cached DHCPACK */
struct cached_dhcp_packet cached_dhcpack = {
	.name = DHCP_SETTINGS_NAME,
};

/** Cached ProxyDHCPOFFER */
struct cached_dhcp_packet cached_proxydhcp = {
	.name = PROXYDHCP_SETTINGS_NAME,
};

/** Cached PXEBSACK */
struct cached_dhcp_packet cached_pxebs = {
	.name = PXEBS_SETTINGS_NAME,
};

/** List of cached DHCP packets */
static struct cached_dhcp_packet *cached_packets[] = {
	&cached_dhcpack,
	&cached_proxydhcp,
	&cached_pxebs,
};

/** Colour for debug messages */
#define colour &cached_dhcpack

/**
 * Free cached DHCP packet
 *
 * @v cache		Cached DHCP packet
 */
static void cachedhcp_free ( struct cached_dhcp_packet *cache ) {

	dhcppkt_put ( cache->dhcppkt );
	cache->dhcppkt = NULL;
}

/**
 * Apply cached DHCP packet settings
 *
 * @v cache		Cached DHCP packet
 * @v netdev		Network device, or NULL
 * @ret rc		Return status code
 */
static int cachedhcp_apply ( struct cached_dhcp_packet *cache,
			     struct net_device *netdev ) {
	struct settings *settings = NULL;
	struct ll_protocol *ll_protocol;
	const uint8_t *chaddr;
	uint8_t *hw_addr;
	uint8_t *ll_addr;
	size_t ll_addr_len;
	int rc;

	/* Do nothing if cache is empty */
	if ( ! cache->dhcppkt )
		return 0;
	chaddr = cache->dhcppkt->dhcphdr->chaddr;

	/* Handle association with network device, if specified */
	if ( netdev ) {
		hw_addr = netdev->hw_addr;
		ll_addr = netdev->ll_addr;
		ll_protocol = netdev->ll_protocol;
		ll_addr_len = ll_protocol->ll_addr_len;

		/* If cached packet's MAC address matches the network
		 * device's permanent MAC address, then assume that
		 * the permanent MAC address ought to be the network
		 * device's current link-layer address.
		 *
		 * This situation can arise when the PXE ROM does not
		 * understand the system-specific mechanism for
		 * overriding the MAC address, and so uses the
		 * permanent MAC address instead.  We choose to match
		 * this behaviour in order to minimise surprise.
		 */
		if ( memcmp ( hw_addr, chaddr, ll_addr_len ) == 0 ) {
			if ( memcmp ( hw_addr, ll_addr, ll_addr_len ) != 0 ) {
				DBGC ( colour, "CACHEDHCP %s resetting %s MAC "
				       "%s ", cache->name, netdev->name,
				       ll_protocol->ntoa ( ll_addr ) );
				DBGC ( colour, "-> %s\n",
				       ll_protocol->ntoa ( hw_addr ) );
			}
			memcpy ( ll_addr, hw_addr, ll_addr_len );
		}

		/* Do nothing unless cached packet's MAC address
		 * matches this network device.
		 */
		if ( memcmp ( ll_addr, chaddr, ll_addr_len ) != 0 ) {
			DBGC ( colour, "CACHEDHCP %s does not match %s\n",
			       cache->name, netdev->name );
			return 0;
		}
		DBGC ( colour, "CACHEDHCP %s is for %s\n",
		       cache->name, netdev->name );

		/* Use network device's settings block */
		settings = netdev_settings ( netdev );
	}

	/* Register settings */
	if ( ( rc = register_settings ( &cache->dhcppkt->settings, settings,
					cache->name ) ) != 0 ) {
		DBGC ( colour, "CACHEDHCP %s could not register settings: %s\n",
		       cache->name, strerror ( rc ) );
		return rc;
	}

	/* Free cached DHCP packet */
	cachedhcp_free ( cache );

	return 0;
}

/**
 * Record cached DHCP packet
 *
 * @v cache		Cached DHCP packet
 * @v data		DHCPACK packet buffer
 * @v max_len		Maximum possible length
 * @ret rc		Return status code
 */
int cachedhcp_record ( struct cached_dhcp_packet *cache, userptr_t data,
		       size_t max_len ) {
	struct dhcp_packet *dhcppkt;
	struct dhcp_packet *tmp;
	struct dhcphdr *dhcphdr;
	unsigned int i;
	size_t len;

	/* Free any existing cached packet */
	cachedhcp_free ( cache );

	/* Allocate and populate DHCP packet */
	dhcppkt = zalloc ( sizeof ( *dhcppkt ) + max_len );
	if ( ! dhcppkt ) {
		DBGC ( colour, "CACHEDHCP %s could not allocate copy\n",
		       cache->name );
		return -ENOMEM;
	}
	dhcphdr = ( ( ( void * ) dhcppkt ) + sizeof ( *dhcppkt ) );
	copy_from_user ( dhcphdr, data, 0, max_len );
	dhcppkt_init ( dhcppkt, dhcphdr, max_len );

	/* Shrink packet to required length.  If reallocation fails,
	 * just continue to use the original packet and waste the
	 * unused space.
	 */
	len = dhcppkt_len ( dhcppkt );
	assert ( len <= max_len );
	tmp = realloc ( dhcppkt, ( sizeof ( *dhcppkt ) + len ) );
	if ( tmp )
		dhcppkt = tmp;

	/* Reinitialise packet at new address */
	dhcphdr = ( ( ( void * ) dhcppkt ) + sizeof ( *dhcppkt ) );
	dhcppkt_init ( dhcppkt, dhcphdr, len );

	/* Discard duplicate packets, since some PXE stacks (including
	 * iPXE itself) will report the DHCPACK packet as the PXEBSACK
	 * if no separate PXEBSACK exists.
	 */
	for ( i = 0 ; i < ( sizeof ( cached_packets ) /
			    sizeof ( cached_packets[0] ) ) ; i++ ) {
		tmp = cached_packets[i]->dhcppkt;
		if ( tmp && ( dhcppkt_len ( tmp ) == len ) &&
		     ( memcmp ( tmp->dhcphdr, dhcppkt->dhcphdr, len ) == 0 ) ) {
			DBGC ( colour, "CACHEDHCP %s duplicates %s\n",
			       cache->name, cached_packets[i]->name );
			dhcppkt_put ( dhcppkt );
			return -EEXIST;
		}
	}

	/* Store as cached packet */
	DBGC ( colour, "CACHEDHCP %s at %#08lx+%#zx/%#zx\n", cache->name,
	       user_to_phys ( data, 0 ), len, max_len );
	cache->dhcppkt = dhcppkt;

	return 0;
}

/**
 * Cached DHCPACK startup function
 *
 */
static void cachedhcp_startup ( void ) {

	/* Apply cached ProxyDHCPOFFER, if any */
	cachedhcp_apply ( &cached_proxydhcp, NULL );

	/* Apply cached PXEBSACK, if any */
	cachedhcp_apply ( &cached_pxebs, NULL );

	/* Free any remaining cached packets */
	if ( cached_dhcpack.dhcppkt ) {
		DBGC ( colour, "CACHEDHCP %s unclaimed\n",
		       cached_dhcpack.name );
	}
	cachedhcp_free ( &cached_dhcpack );
	cachedhcp_free ( &cached_proxydhcp );
	cachedhcp_free ( &cached_pxebs );
}

/** Cached DHCPACK startup function */
struct startup_fn cachedhcp_startup_fn __startup_fn ( STARTUP_LATE ) = {
	.name = "cachedhcp",
	.startup = cachedhcp_startup,
};

/**
 * Apply cached DHCPACK to network device, if applicable
 *
 * @v netdev		Network device
 * @ret rc		Return status code
 */
static int cachedhcp_probe ( struct net_device *netdev ) {

	/* Apply cached DHCPACK to network device, if applicable */
	return cachedhcp_apply ( &cached_dhcpack, netdev );
}

/** Cached DHCP packet network device driver */
struct net_driver cachedhcp_driver __net_driver = {
	.name = "cachedhcp",
	.probe = cachedhcp_probe,
};