cachedhcp.c

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/*
 * 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/vlan.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;
        /** VLAN tag (if applicable) */
        unsigned int vlan;
};

/** 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 %s does not match %s\n",
                               cache->name, ll_protocol->ntoa ( chaddr ),
                               netdev->name );
                        return 0;
                }

                /* Do nothing unless cached packet's VLAN tag matches
                 * this network device.
                 */
                if ( vlan_tag ( netdev ) != cache->vlan ) {
                        DBGC ( colour, "CACHEDHCP %s VLAN %d does not match "
                               "%s\n", cache->name, cache->vlan,
                               netdev->name );
                        return 0;
                }

                /* Use network device's settings block */
                settings = netdev_settings ( netdev );
                DBGC ( colour, "CACHEDHCP %s is for %s\n",
                       cache->name, netdev->name );
        }

        /* 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 vlan              VLAN tag, if any
 * @v data              DHCPACK packet buffer
 * @v max_len           Maximum possible length
 * @ret rc              Return status code
 */
int cachedhcp_record ( struct cached_dhcp_packet *cache, unsigned int vlan,
                       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;
        cache->vlan = vlan;

        return 0;
}

/**
 * Cached DHCP packet startup function
 *
 */
static void cachedhcp_startup ( void ) {

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

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

        /* Report unclaimed DHCPACK, if any.  Do not free yet, since
         * it may still be claimed by a dynamically created device
         * such as a VLAN device.
         */
        if ( cached_dhcpack.dhcppkt ) {
                DBGC ( colour, "CACHEDHCP %s unclaimed\n",
                       cached_dhcpack.name );
        }
}

/**
 * Cached DHCP packet shutdown function
 *
 * @v booting           System is shutting down for OS boot
 */
static void cachedhcp_shutdown ( int booting __unused ) {

        /* Free cached DHCPACK, if any */
        if ( cached_dhcpack.dhcppkt ) {
                DBGC ( colour, "CACHEDHCP %s never claimed\n",
                       cached_dhcpack.name );
        }
        cachedhcp_free ( &cached_dhcpack );
}

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

/**
 * 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,
};