source: bootcd/isolinux/syslinux-6.03/gpxe/src/net/fakedhcp.c

/*
 * Copyright (C) 2008 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <gpxe/settings.h>
#include <gpxe/netdevice.h>
#include <gpxe/dhcppkt.h>
#include <gpxe/fakedhcp.h>

/** @file
 *
 * Fake DHCP packets
 *
 */

/**
 * Copy settings to DHCP packet
 *
 * @v dest              Destination DHCP packet
 * @v source            Source settings block
 * @v encapsulator      Encapsulating setting tag number, or zero
 * @ret rc              Return status code
 */
static int copy_encap_settings ( struct dhcp_packet *dest,
                                 struct settings *source,
                                 unsigned int encapsulator ) {
        struct setting setting = { .name = "" };
        unsigned int subtag;
        unsigned int tag;
        int len;
        int check_len;
        int rc;

        for ( subtag = DHCP_MIN_OPTION; subtag <= DHCP_MAX_OPTION; subtag++ ) {
                tag = DHCP_ENCAP_OPT ( encapsulator, subtag );
                switch ( tag ) {
                case DHCP_EB_ENCAP:
                case DHCP_VENDOR_ENCAP:
                        /* Process encapsulated settings */
                        if ( ( rc = copy_encap_settings ( dest, source,
                                                          tag ) ) != 0 )
                                return rc;
                        break;
                default:
                        /* Copy setting, if present */
                        setting.tag = tag;
                        len = fetch_setting_len ( source, &setting );
                        if ( len < 0 )
                                break;
                        {
                                char buf[len];

                                check_len = fetch_setting ( source, &setting,
                                                            buf, sizeof (buf));
                                assert ( check_len == len );
                                if ( ( rc = dhcppkt_store ( dest, tag, buf,
                                                            sizeof(buf) )) !=0)
                                        return rc;
                        }
                        break;
                }
        }

        return 0;
}

/**
 * Copy settings to DHCP packet
 *
 * @v dest              Destination DHCP packet
 * @v source            Source settings block
 * @ret rc              Return status code
 */
static int copy_settings ( struct dhcp_packet *dest,
                           struct settings *source ) {
        return copy_encap_settings ( dest, source, 0 );
}

/**
 * Create fake DHCPDISCOVER packet
 *
 * @v netdev            Network device
 * @v data              Buffer for DHCP packet
 * @v max_len           Size of DHCP packet buffer
 * @ret rc              Return status code
 *
 * Used by external code.
 */
int create_fakedhcpdiscover ( struct net_device *netdev,
                              void *data, size_t max_len ) {
        struct dhcp_packet dhcppkt;
        struct in_addr ciaddr = { 0 };
        int rc;

        if ( ( rc = dhcp_create_request ( &dhcppkt, netdev, DHCPDISCOVER,
                                          ciaddr, data, max_len ) ) != 0 ) {
                DBG ( "Could not create DHCPDISCOVER: %s\n",
                      strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Create fake DHCPACK packet
 *
 * @v netdev            Network device
 * @v data              Buffer for DHCP packet
 * @v max_len           Size of DHCP packet buffer
 * @ret rc              Return status code
 *
 * Used by external code.
 */
int create_fakedhcpack ( struct net_device *netdev,
                         void *data, size_t max_len ) {
        struct dhcp_packet dhcppkt;
        int rc;

        /* Create base DHCPACK packet */
        if ( ( rc = dhcp_create_packet ( &dhcppkt, netdev, DHCPACK, NULL, 0,
                                         data, max_len ) ) != 0 ) {
                DBG ( "Could not create DHCPACK: %s\n", strerror ( rc ) );
                return rc;
        }

        /* Merge in globally-scoped settings, then netdev-specific
         * settings.  Do it in this order so that netdev-specific
         * settings take precedence regardless of stated priorities.
         */
        if ( ( rc = copy_settings ( &dhcppkt, NULL ) ) != 0 ) {
                DBG ( "Could not set DHCPACK global settings: %s\n",
                      strerror ( rc ) );
                return rc;
        }
        if ( ( rc = copy_settings ( &dhcppkt,
                                    netdev_settings ( netdev ) ) ) != 0 ) {
                DBG ( "Could not set DHCPACK netdev settings: %s\n",
                      strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Create fake PXE Boot Server ACK packet
 *
 * @v netdev            Network device
 * @v data              Buffer for DHCP packet
 * @v max_len           Size of DHCP packet buffer
 * @ret rc              Return status code
 *
 * Used by external code.
 */
int create_fakepxebsack ( struct net_device *netdev,
                          void *data, size_t max_len ) {
        struct dhcp_packet dhcppkt;
        struct settings *proxy_settings;
        struct settings *pxebs_settings;
        int rc;

        /* Identify available settings */
        proxy_settings = find_settings ( PROXYDHCP_SETTINGS_NAME );
        pxebs_settings = find_settings ( PXEBS_SETTINGS_NAME );
        if ( ( ! proxy_settings ) && ( ! pxebs_settings ) ) {
                /* No PXE boot server; return the regular DHCPACK */
                return create_fakedhcpack ( netdev, data, max_len );
        }

        /* Create base DHCPACK packet */
        if ( ( rc = dhcp_create_packet ( &dhcppkt, netdev, DHCPACK, NULL, 0,
                                         data, max_len ) ) != 0 ) {
                DBG ( "Could not create PXE BS ACK: %s\n",
                      strerror ( rc ) );
                return rc;
        }

        /* Merge in ProxyDHCP options */
        if ( proxy_settings &&
             ( ( rc = copy_settings ( &dhcppkt, proxy_settings ) ) != 0 ) ) {
                DBG ( "Could not copy ProxyDHCP settings: %s\n",
                      strerror ( rc ) );
                return rc;
        }

        /* Merge in BootServerDHCP options, if present */
        if ( pxebs_settings &&
             ( ( rc = copy_settings ( &dhcppkt, pxebs_settings ) ) != 0 ) ) {
                DBG ( "Could not copy PXE BS settings: %s\n",
                      strerror ( rc ) );
                return rc;
        }

        return 0;
}