/*
* 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/dhcp.h>
#include <gpxe/dhcpopts.h>
/** @file
*
* DHCP options
*
*/
/**
* Obtain printable version of a DHCP option tag
*
* @v tag DHCP option tag
* @ret name String representation of the tag
*
*/
static inline char * dhcp_tag_name ( unsigned int tag ) {
static char name[8];
if ( DHCP_IS_ENCAP_OPT ( tag ) ) {
snprintf ( name, sizeof ( name ), "%d.%d",
DHCP_ENCAPSULATOR ( tag ),
DHCP_ENCAPSULATED ( tag ) );
} else {
snprintf ( name, sizeof ( name ), "%d", tag );
}
return name;
}
/**
* Get pointer to DHCP option
*
* @v options DHCP options block
* @v offset Offset within options block
* @ret option DHCP option
*/
static inline __attribute__ (( always_inline )) struct dhcp_option *
dhcp_option ( struct dhcp_options *options, unsigned int offset ) {
return ( ( struct dhcp_option * ) ( options->data + offset ) );
}
/**
* Get offset of a DHCP option
*
* @v options DHCP options block
* @v option DHCP option
* @ret offset Offset within options block
*/
static inline __attribute__ (( always_inline )) int
dhcp_option_offset ( struct dhcp_options *options,
struct dhcp_option *option ) {
return ( ( ( void * ) option ) - options->data );
}
/**
* Calculate length of any DHCP option
*
* @v option DHCP option
* @ret len Length (including tag and length field)
*/
static unsigned int dhcp_option_len ( struct dhcp_option *option ) {
if ( ( option->tag == DHCP_END ) || ( option->tag == DHCP_PAD ) ) {
return 1;
} else {
return ( option->len + DHCP_OPTION_HEADER_LEN );
}
}
/**
* Find DHCP option within DHCP options block, and its encapsulator (if any)
*
* @v options DHCP options block
* @v tag DHCP option tag to search for
* @ret encap_offset Offset of encapsulating DHCP option
* @ret offset Offset of DHCP option, or negative error
*
* Searches for the DHCP option matching the specified tag within the
* DHCP option block. Encapsulated options may be searched for by
* using DHCP_ENCAP_OPT() to construct the tag value.
*
* If the option is encapsulated, and @c encapsulator is non-NULL, it
* will be filled in with the offset of the encapsulating option.
*
* This routine is designed to be paranoid. It does not assume that
* the option data is well-formatted, and so must guard against flaws
* such as options missing a @c DHCP_END terminator, or options whose
* length would take them beyond the end of the data block.
*/
static int find_dhcp_option_with_encap ( struct dhcp_options *options,
unsigned int tag,
int *encap_offset ) {
unsigned int original_tag __attribute__ (( unused )) = tag;
struct dhcp_option *option;
int offset = 0;
ssize_t remaining = options->len;
unsigned int option_len;
/* Sanity check */
if ( tag == DHCP_PAD )
return -ENOENT;
/* Search for option */
while ( remaining ) {
/* Calculate length of this option. Abort processing
* if the length is malformed (i.e. takes us beyond
* the end of the data block).
*/
option = dhcp_option ( options, offset );
option_len = dhcp_option_len ( option );
remaining -= option_len;
if ( remaining < 0 )
break;
/* Check for explicit end marker */
if ( option->tag == DHCP_END )
break;
/* Check for matching tag */
if ( option->tag == tag ) {
DBGC ( options, "DHCPOPT %p found %s (length %d)\n",
options, dhcp_tag_name ( original_tag ),
option_len );
return offset;
}
/* Check for start of matching encapsulation block */
if ( DHCP_IS_ENCAP_OPT ( tag ) &&
( option->tag == DHCP_ENCAPSULATOR ( tag ) ) ) {
if ( encap_offset )
*encap_offset = offset;
/* Continue search within encapsulated option block */
tag = DHCP_ENCAPSULATED ( tag );
remaining = option_len;
offset += DHCP_OPTION_HEADER_LEN;
continue;
}
offset += option_len;
}
return -ENOENT;
}
/**
* Resize a DHCP option
*
* @v options DHCP option block
* @v offset Offset of option to resize
* @v encap_offset Offset of encapsulating offset (or -ve for none)
* @v old_len Old length (including header)
* @v new_len New length (including header)
* @v can_realloc Can reallocate options data if necessary
* @ret rc Return status code
*/
static int resize_dhcp_option ( struct dhcp_options *options,
int offset, int encap_offset,
size_t old_len, size_t new_len,
int can_realloc ) {
struct dhcp_option *encapsulator;
struct dhcp_option *option;
ssize_t delta = ( new_len - old_len );
size_t new_options_len;
size_t new_encapsulator_len;
void *new_data;
void *source;
void *dest;
void *end;
/* Check for sufficient space, and update length fields */
if ( new_len > DHCP_MAX_LEN ) {
DBGC ( options, "DHCPOPT %p overlength option\n", options );
return -ENOSPC;
}
new_options_len = ( options->len + delta );
if ( new_options_len > options->max_len ) {
/* Reallocate options block if allowed to do so. */
if ( can_realloc ) {
new_data = realloc ( options->data, new_options_len );
if ( ! new_data ) {
DBGC ( options, "DHCPOPT %p could not "
"reallocate to %zd bytes\n", options,
new_options_len );
return -ENOMEM;
}
options->data = new_data;
options->max_len = new_options_len;
} else {
DBGC ( options, "DHCPOPT %p out of space\n", options );
return -ENOMEM;
}
}
if ( encap_offset >= 0 ) {
encapsulator = dhcp_option ( options, encap_offset );
new_encapsulator_len = ( encapsulator->len + delta );
if ( new_encapsulator_len > DHCP_MAX_LEN ) {
DBGC ( options, "DHCPOPT %p overlength encapsulator\n",
options );
return -ENOSPC;
}
encapsulator->len = new_encapsulator_len;
}
options->len = new_options_len;
/* Move remainder of option data */
option = dhcp_option ( options, offset );
source = ( ( ( void * ) option ) + old_len );
dest = ( ( ( void * ) option ) + new_len );
end = ( options->data + options->max_len );
memmove ( dest, source, ( end - dest ) );
return 0;
}
/**
* Set value of DHCP option
*
* @v options DHCP option block
* @v tag DHCP option tag
* @v data New value for DHCP option
* @v len Length of value, in bytes
* @v can_realloc Can reallocate options data if necessary
* @ret offset Offset of DHCP option, or negative error
*
* Sets the value of a DHCP option within the options block. The
* option may or may not already exist. Encapsulators will be created
* (and deleted) as necessary.
*
* This call may fail due to insufficient space in the options block.
* If it does fail, and the option existed previously, the option will
* be left with its original value.
*/
static int set_dhcp_option ( struct dhcp_options *options, unsigned int tag,
const void *data, size_t len,
int can_realloc ) {
static const uint8_t empty_encapsulator[] = { DHCP_END };
int offset;
int encap_offset = -1;
int creation_offset = 0;
struct dhcp_option *option;
unsigned int encap_tag = DHCP_ENCAPSULATOR ( tag );
size_t old_len = 0;
size_t new_len = ( len ? ( len + DHCP_OPTION_HEADER_LEN ) : 0 );
int rc;
/* Sanity check */
if ( tag == DHCP_PAD )
return -ENOTTY;
/* Find old instance of this option, if any */
offset = find_dhcp_option_with_encap ( options, tag, &encap_offset );
if ( offset >= 0 ) {
old_len = dhcp_option_len ( dhcp_option ( options, offset ) );
DBGC ( options, "DHCPOPT %p resizing %s from %zd to %zd\n",
options, dhcp_tag_name ( tag ), old_len, new_len );
} else {
DBGC ( options, "DHCPOPT %p creating %s (length %zd)\n",
options, dhcp_tag_name ( tag ), new_len );
}
/* Ensure that encapsulator exists, if required */
if ( encap_tag ) {
if ( encap_offset < 0 )
encap_offset = set_dhcp_option ( options, encap_tag,
empty_encapsulator, 1,
can_realloc );
if ( encap_offset < 0 )
return encap_offset;
creation_offset = ( encap_offset + DHCP_OPTION_HEADER_LEN );
}
/* Create new option if necessary */
if ( offset < 0 )
offset = creation_offset;
/* Resize option to fit new data */
if ( ( rc = resize_dhcp_option ( options, offset, encap_offset,
old_len, new_len,
can_realloc ) ) != 0 )
return rc;
/* Copy new data into option, if applicable */
if ( len ) {
option = dhcp_option ( options, offset );
option->tag = tag;
option->len = len;
memcpy ( &option->data, data, len );
}
/* Delete encapsulator if there's nothing else left in it */
if ( encap_offset >= 0 ) {
option = dhcp_option ( options, encap_offset );
if ( option->len <= 1 )
set_dhcp_option ( options, encap_tag, NULL, 0, 0 );
}
return offset;
}
/**
* Store value of DHCP option setting
*
* @v options DHCP option block
* @v tag Setting tag number
* @v data Setting data, or NULL to clear setting
* @v len Length of setting data
* @ret rc Return status code
*/
int dhcpopt_store ( struct dhcp_options *options, unsigned int tag,
const void *data, size_t len ) {
int offset;
offset = set_dhcp_option ( options, tag, data, len, 0 );
if ( offset < 0 )
return offset;
return 0;
}
/**
* Store value of DHCP option setting, extending options block if necessary
*
* @v options DHCP option block
* @v tag Setting tag number
* @v data Setting data, or NULL to clear setting
* @v len Length of setting data
* @ret rc Return status code
*/
int dhcpopt_extensible_store ( struct dhcp_options *options, unsigned int tag,
const void *data, size_t len ) {
int offset;
offset = set_dhcp_option ( options, tag, data, len, 1 );
if ( offset < 0 )
return offset;
return 0;
}
/**
* Fetch value of DHCP option setting
*
* @v options DHCP option block
* @v tag Setting tag number
* @v data Buffer to fill with setting data
* @v len Length of buffer
* @ret len Length of setting data, or negative error
*/
int dhcpopt_fetch ( struct dhcp_options *options, unsigned int tag,
void *data, size_t len ) {
int offset;
struct dhcp_option *option;
size_t option_len;
offset = find_dhcp_option_with_encap ( options, tag, NULL );
if ( offset < 0 )
return offset;
option = dhcp_option ( options, offset );
option_len = option->len;
if ( len > option_len )
len = option_len;
memcpy ( data, option->data, len );
return option_len;
}
/**
* Recalculate length of DHCP options block
*
* @v options Uninitialised DHCP option block
*
* The "used length" field will be updated based on scanning through
* the block to find the end of the options.
*/
static void dhcpopt_update_len ( struct dhcp_options *options ) {
struct dhcp_option *option;
int offset = 0;
ssize_t remaining = options->max_len;
unsigned int option_len;
/* Find last non-pad option */
options->len = 0;
while ( remaining ) {
option = dhcp_option ( options, offset );
option_len = dhcp_option_len ( option );
remaining -= option_len;
if ( remaining < 0 )
break;
offset += option_len;
if ( option->tag != DHCP_PAD )
options->len = offset;
}
}
/**
* Initialise prepopulated block of DHCP options
*
* @v options Uninitialised DHCP option block
* @v data Memory for DHCP option data
* @v max_len Length of memory for DHCP option data
*
* The memory content must already be filled with valid DHCP options.
* A zeroed block counts as a block of valid DHCP options.
*/
void dhcpopt_init ( struct dhcp_options *options, void *data,
size_t max_len ) {
/* Fill in fields */
options->data = data;
options->max_len = max_len;
/* Update length */
dhcpopt_update_len ( options );
DBGC ( options, "DHCPOPT %p created (data %p len %#zx max_len %#zx)\n",
options, options->data, options->len, options->max_len );
}
