/*
* Copyright (C) 2006 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.
*/
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <byteswap.h>
#include <gpxe/netdevice.h>
#include <gpxe/dhcp.h>
/** @file
*
* Dynamic Host Configuration Protocol
*
*/
/** DHCP operation types
*
* This table maps from DHCP message types (i.e. values of the @c
* DHCP_MESSAGE_TYPE option) to values of the "op" field within a DHCP
* packet.
*/
static const uint8_t dhcp_op[] = {
[DHCPDISCOVER] = BOOTP_REQUEST,
[DHCPOFFER] = BOOTP_REPLY,
[DHCPREQUEST] = BOOTP_REQUEST,
[DHCPDECLINE] = BOOTP_REQUEST,
[DHCPACK] = BOOTP_REPLY,
[DHCPNAK] = BOOTP_REPLY,
[DHCPRELEASE] = BOOTP_REQUEST,
[DHCPINFORM] = BOOTP_REQUEST,
};
/**
* Set option within DHCP packet
*
* @v dhcppkt DHCP packet
* @v tag DHCP option tag
* @v data New value for DHCP option
* @v len Length of value, in bytes
* @ret rc Return status code
*
* Sets the option within the first available options block within the
* DHCP packet. Option blocks are tried in the order specified by @c
* dhcp_option_block_fill_order.
*
* The magic options @c DHCP_EB_YIADDR and @c DHCP_EB_SIADDR are
* intercepted and inserted into the appropriate fixed fields within
* the DHCP packet. The option @c DHCP_OPTION_OVERLOAD is silently
* ignored, since our DHCP packet assembly method relies on always
* having option overloading in use.
*/
static int set_dhcp_packet_option ( struct dhcp_packet *dhcppkt,
unsigned int tag, const void *data,
size_t len ) {
struct dhcphdr *dhcphdr = dhcppkt->dhcphdr;
struct dhcp_option_block *options;
struct dhcp_option *option = NULL;
/* Special-case the magic options */
switch ( tag ) {
case DHCP_OPTION_OVERLOAD:
/* Hard-coded in packets we create; always ignore */
return 0;
case DHCP_EB_YIADDR:
memcpy ( &dhcphdr->yiaddr, data, sizeof ( dhcphdr->yiaddr ) );
return 0;
case DHCP_EB_SIADDR:
memcpy ( &dhcphdr->siaddr, data, sizeof ( dhcphdr->siaddr ) );
return 0;
default:
/* Continue processing as normal */
break;
}
/* Set option in first available options block */
for ( options = dhcppkt->options ;
options < &dhcppkt->options[NUM_OPT_BLOCKS] ; options++ ) {
option = set_dhcp_option ( options, tag, data, len );
if ( option )
break;
}
/* Update DHCP packet length */
dhcppkt->len = ( offsetof ( typeof ( *dhcppkt->dhcphdr ), options )
+ dhcppkt->options[OPTS_MAIN].len );
return ( option ? 0 : -ENOSPC );
}
/**
* Set options within DHCP packet
*
* @v dhcppkt DHCP packet
* @v options DHCP option block, or NULL
* @v encapsulator Encapsulating option, or zero
* @ret rc Return status code
*
* Copies options with the specified encapsulator from DHCP options
* blocks into a DHCP packet. Most options are copied verbatim.
* Recognised encapsulated options fields are handled as such.
*
* @c options may specify a single options block, or be left as NULL
* in order to copy options from all registered options blocks.
*/
static int set_dhcp_packet_encap_options ( struct dhcp_packet *dhcppkt,
struct dhcp_option_block *options,
unsigned int encapsulator ) {
unsigned int subtag;
unsigned int tag;
struct dhcp_option *option;
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 options field */
if ( ( rc = set_dhcp_packet_encap_options ( dhcppkt,
options,
tag )) !=0)
return rc;
break;
default:
/* Copy option to reassembled packet */
option = find_dhcp_option ( options, tag );
if ( ! option )
break;
if ( ( rc = set_dhcp_packet_option ( dhcppkt, tag,
&option->data,
option->len)) !=0)
return rc;
break;
};
}
return 0;
}
/**
* Set options within DHCP packet
*
* @v dhcppkt DHCP packet
* @v options DHCP option block, or NULL
* @ret rc Return status code
*
* Copies options from DHCP options blocks into a DHCP packet. Most
* options are copied verbatim. Recognised encapsulated options
* fields are handled as such.
*
* @c options may specify a single options block, or be left as NULL
* in order to copy options from all registered options blocks.
*/
static int set_dhcp_packet_options ( struct dhcp_packet *dhcppkt,
struct dhcp_option_block *options ) {
return set_dhcp_packet_encap_options ( dhcppkt, options, 0 );
}
/**
* Create a DHCP packet
*
* @v dhcp DHCP session
* @v msgtype DHCP message type
* @v data Buffer for DHCP packet
* @v max_len Size of DHCP packet buffer
* @v dhcppkt DHCP packet structure to fill in
* @ret rc Return status code
*
* Creates a DHCP packet in the specified buffer, and fills out a @c
* dhcp_packet structure that can be passed to
* set_dhcp_packet_option() or set_dhcp_packet_options().
*/
int create_dhcp_packet ( struct dhcp_session *dhcp, uint8_t msgtype,
void *data, size_t max_len,
struct dhcp_packet *dhcppkt ) {
struct dhcphdr *dhcphdr = data;
static const uint8_t overloading = ( DHCP_OPTION_OVERLOAD_FILE |
DHCP_OPTION_OVERLOAD_SNAME );
/* Initialise DHCP packet structure */
dhcppkt->dhcphdr = dhcphdr;
dhcppkt->max_len = max_len;
init_dhcp_options ( &dhcppkt->options[OPTS_MAIN], dhcphdr->options,
( max_len -
offsetof ( typeof ( *dhcphdr ), options ) ) );
init_dhcp_options ( &dhcppkt->options[OPTS_FILE], dhcphdr->file,
sizeof ( dhcphdr->file ) );
init_dhcp_options ( &dhcppkt->options[OPTS_SNAME], dhcphdr->sname,
sizeof ( dhcphdr->sname ) );
/* Initialise DHCP packet content */
memset ( dhcphdr, 0, max_len );
dhcphdr->xid = dhcp->xid;
dhcphdr->magic = htonl ( DHCP_MAGIC_COOKIE );
dhcphdr->htype = ntohs ( dhcp->netdev->ll_protocol->ll_proto );
dhcphdr->hlen = dhcp->netdev->ll_protocol->ll_addr_len;
memcpy ( dhcphdr->chaddr, dhcp->netdev->ll_addr, dhcphdr->hlen );
dhcphdr->op = dhcp_op[msgtype];
/* Set DHCP_OPTION_OVERLOAD option within the main options block */
if ( ! set_dhcp_option ( &dhcppkt->options[OPTS_MAIN],
DHCP_OPTION_OVERLOAD, &overloading,
sizeof ( overloading ) ) )
return -ENOSPC;
/* Set DHCP_MESSAGE_TYPE option */
if ( ! set_dhcp_packet_option ( dhcppkt, DHCP_MESSAGE_TYPE,
&msgtype, sizeof ( msgtype ) ) )
return -ENOSPC;
return 0;
}
/**
* Calculate used length of a field containing DHCP options
*
* @v data Field containing DHCP options
* @v max_len Field length
* @ret len Used length (excluding the @c DHCP_END tag)
*/
static size_t dhcp_field_len ( const void *data, size_t max_len ) {
struct dhcp_option_block options;
struct dhcp_option *end;
options.data = ( ( void * ) data );
options.len = max_len;
end = find_dhcp_option ( &options, DHCP_END );
return ( end ? ( ( ( void * ) end ) - data ) : 0 );
}
/**
* Merge field containing DHCP options or string into DHCP options block
*
* @v options DHCP option block
* @v data Field containing DHCP options
* @v max_len Field length
* @v tag DHCP option tag, or 0
*
* If @c tag is non-zero, the field will be treated as a
* NUL-terminated string representing the value of the specified DHCP
* option. If @c tag is zero, the field will be treated as a block of
* DHCP options, and simply appended to the existing options in the
* option block.
*
* The caller must ensure that there is enough space in the options
* block to perform the merge.
*/
static void merge_dhcp_field ( struct dhcp_option_block *options,
const void *data, size_t max_len,
unsigned int tag ) {
size_t len;
void *dest;
struct dhcp_option *end;
if ( tag ) {
set_dhcp_option ( options, tag, data, strlen ( data ) );
} else {
len = dhcp_field_len ( data, max_len );
dest = ( options->data + options->len - 1 );
memcpy ( dest, data, len );
options->len += len;
end = ( dest + len );
end->tag = DHCP_END;
}
}
/**
* Parse DHCP packet and construct DHCP options block
*
* @v data DHCP packet
* @v len Length of DHCP packet
* @ret options DHCP options block, or NULL
*
* Parses a received DHCP packet and canonicalises its contents into a
* single DHCP options block. The "file" and "sname" fields are
* converted into the corresponding DHCP options (@c
* DHCP_BOOTFILE_NAME and @c DHCP_TFTP_SERVER_NAME respectively). If
* these fields are used for option overloading, their options are
* merged in to the options block.
*
* The values of the "yiaddr" and "siaddr" fields will be stored
* within the options block as the magic options @c DHCP_EB_YIADDR and
* @c DHCP_EB_SIADDR.
*
* Note that this call allocates new memory for the constructed DHCP
* options block; it is the responsibility of the caller to eventually
* free this memory.
*/
struct dhcp_option_block * dhcp_parse ( const void *data, size_t len ) {
const struct dhcphdr *dhcphdr = data;
struct dhcp_option_block *options;
size_t options_len;
unsigned int overloading;
/* Sanity check */
if ( len < sizeof ( *dhcphdr ) )
return NULL;
/* Calculate size of resulting concatenated option block:
*
* The "options" field : length of the field minus the DHCP_END tag.
*
* The "file" field : maximum length of the field minus the
* NUL terminator, plus a 2-byte DHCP header or, if used for
* option overloading, the length of the field minus the
* DHCP_END tag.
*
* The "sname" field : as for the "file" field.
*
* 15 bytes for an encapsulated options field to contain the
* value of the "yiaddr" and "siaddr" fields
*
* 1 byte for a final terminating DHCP_END tag.
*/
options_len = ( ( len - offsetof ( typeof ( *dhcphdr ), options ) ) - 1
+ ( sizeof ( dhcphdr->file ) + 1 )
+ ( sizeof ( dhcphdr->sname ) + 1 )
+ 15 /* yiaddr and siaddr */
+ 1 /* DHCP_END tag */ );
/* Allocate empty options block of required size */
options = alloc_dhcp_options ( options_len );
if ( ! options ) {
DBG ( "DHCP could not allocate %d-byte option block\n",
options_len );
return NULL;
}
/* Merge in "options" field, if this is a DHCP packet */
if ( dhcphdr->magic == htonl ( DHCP_MAGIC_COOKIE ) ) {
merge_dhcp_field ( options, dhcphdr->options,
( len -
offsetof ( typeof (*dhcphdr), options ) ),
0 /* Always contains options */ );
}
/* Identify overloaded fields */
overloading = find_dhcp_num_option ( options, DHCP_OPTION_OVERLOAD );
/* Merge in "file" and "sname" fields */
merge_dhcp_field ( options, dhcphdr->file, sizeof ( dhcphdr->file ),
( ( overloading & DHCP_OPTION_OVERLOAD_FILE ) ?
DHCP_BOOTFILE_NAME : 0 ) );
merge_dhcp_field ( options, dhcphdr->sname, sizeof ( dhcphdr->sname ),
( ( overloading & DHCP_OPTION_OVERLOAD_SNAME ) ?
DHCP_TFTP_SERVER_NAME : 0 ) );
/* Set magic options for "yiaddr" and "siaddr", if present */
if ( dhcphdr->yiaddr.s_addr ) {
set_dhcp_option ( options, DHCP_EB_YIADDR,
&dhcphdr->yiaddr, sizeof (dhcphdr->yiaddr) );
}
if ( dhcphdr->siaddr.s_addr ) {
set_dhcp_option ( options, DHCP_EB_SIADDR,
&dhcphdr->siaddr, sizeof (dhcphdr->siaddr) );
}
assert ( options->len <= options->max_len );
return options;
}
