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xNBA/src/net/dhcpopts.c

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/*
* 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 <stdint.h>
#include <byteswap.h>
#include <errno.h>
#include <string.h>
#include <malloc.h>
#include <assert.h>
#include <vsprintf.h>
#include <gpxe/list.h>
#include <gpxe/in.h>
#include <gpxe/dhcp.h>
/** @file
*
* DHCP options
*
*/
/** List of registered DHCP option blocks */
static LIST_HEAD ( option_blocks );
/**
* 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;
}
/**
* Obtain value of a numerical DHCP option
*
* @v option DHCP option, or NULL
* @ret value Numerical value of the option, or 0
*
* Parses the numerical value from a DHCP option, if present. It is
* permitted to call dhcp_num_option() with @c option set to NULL; in
* this case 0 will be returned.
*
* The caller does not specify the size of the DHCP option data; this
* is implied by the length field stored within the DHCP option
* itself.
*/
unsigned long dhcp_num_option ( struct dhcp_option *option ) {
unsigned long value = 0;
uint8_t *data;
if ( option ) {
/* This is actually smaller code than using htons()
* etc., and will also cope well with malformed
* options (such as zero-length options).
*/
for ( data = option->data.bytes ;
data < ( option->data.bytes + option->len ) ; data++ )
value = ( ( value << 8 ) | *data );
}
return value;
}
/**
* Obtain value of an IPv4-address DHCP option
*
* @v option DHCP option, or NULL
* @v inp IPv4 address to fill in
*
* Parses the IPv4 address value from a DHCP option, if present. It
* is permitted to call dhcp_ipv4_option() with @c option set to NULL;
* in this case the address will be set to 0.0.0.0.
*/
void dhcp_ipv4_option ( struct dhcp_option *option, struct in_addr *inp ) {
if ( option )
*inp = option->data.in;
}
/**
* Print DHCP string option value into buffer
*
* @v buf Buffer into which to write the string
* @v size Size of buffer
* @v option DHCP option, or NULL
* @ret len Length of formatted string
*
* DHCP option strings are stored without a NUL terminator. This
* function provides a convenient way to extract these DHCP strings
* into standard C strings. It is permitted to call dhcp_snprintf()
* with @c option set to NULL; in this case the buffer will be filled
* with an empty string.
*
* The usual snprintf() semantics apply with regard to buffer size,
* return value when the buffer is too small, etc.
*/
int dhcp_snprintf ( char *buf, size_t size, struct dhcp_option *option ) {
size_t len;
char *content = "";
if ( option ) {
/* Shrink buffer size so that it is only just large
* enough to contain the option data. snprintf() will
* take care of everything else (inserting the NUL etc.)
*/
len = ( option->len + 1 );
if ( len < size )
size = len;
content = option->data.string;
}
return snprintf ( buf, size, "%s", content );
}
/**
* Calculate length of a normal DHCP option
*
* @v option DHCP option
* @ret len Length (including tag and length field)
*
* @c option may not be a @c DHCP_PAD or @c DHCP_END option.
*/
static inline unsigned int dhcp_option_len ( struct dhcp_option *option ) {
assert ( option->tag != DHCP_PAD );
assert ( option->tag != DHCP_END );
return ( option->len + DHCP_OPTION_HEADER_LEN );
}
/**
* Calculate length of any DHCP option
*
* @v option DHCP option
* @ret len Length (including tag and length field)
*/
static inline unsigned int dhcp_any_option_len ( struct dhcp_option *option ) {
if ( ( option->tag == DHCP_END ) || ( option->tag == DHCP_PAD ) ) {
return 1;
} else {
return dhcp_option_len ( option );
}
}
/**
* 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 encapsulator Encapsulating DHCP option
* @ret option DHCP option, or NULL if not found
*
* 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 a pointer to 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 struct dhcp_option *
find_dhcp_option_with_encap ( struct dhcp_option_block *options,
unsigned int tag,
struct dhcp_option **encapsulator ) {
unsigned int original_tag __attribute__ (( unused )) = tag;
struct dhcp_option *option = options->data;
ssize_t remaining = options->len;
unsigned int option_len;
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_len = dhcp_any_option_len ( option );
remaining -= option_len;
if ( remaining < 0 )
break;
/* Check for matching tag */
if ( option->tag == tag ) {
DBG ( "Found DHCP option %s (length %d) in block %p\n",
dhcp_tag_name ( original_tag ), option->len,
options );
return option;
}
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/* Check for explicit end marker */
if ( option->tag == DHCP_END )
break;
/* Check for start of matching encapsulation block */
if ( DHCP_IS_ENCAP_OPT ( tag ) &&
( option->tag == DHCP_ENCAPSULATOR ( tag ) ) ) {
if ( encapsulator )
*encapsulator = option;
/* Continue search within encapsulated option block */
tag = DHCP_ENCAPSULATED ( tag );
remaining = option->len;
option = ( void * ) &option->data;
continue;
}
option = ( ( ( void * ) option ) + option_len );
}
return NULL;
}
/**
* Find DHCP option within DHCP options block
*
* @v options DHCP options block, or NULL
* @v tag DHCP option tag to search for
* @ret option DHCP option, or NULL if not found
*
* 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.
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*
* If @c options is NULL, all registered option blocks will be
* searched. Where multiple option blocks contain the same DHCP
* option, the option from the highest-priority block will be
* returned. (Priority of an options block is determined by the value
* of the @c DHCP_EB_PRIORITY option within the block, if present; the
* default priority is zero).
*/
struct dhcp_option * find_dhcp_option ( struct dhcp_option_block *options,
unsigned int tag ) {
struct dhcp_option *option;
if ( options ) {
return find_dhcp_option_with_encap ( options, tag, NULL );
} else {
list_for_each_entry ( options, &option_blocks, list ) {
if ( ( option = find_dhcp_option ( options, tag ) ) )
return option;
}
return NULL;
}
}
/**
* Register DHCP option block
*
* @v options DHCP option block
*
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* Register a block of DHCP options.
*/
void register_dhcp_options ( struct dhcp_option_block *options ) {
struct dhcp_option_block *existing;
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/* Determine priority of new block */
options->priority = find_dhcp_num_option ( options, DHCP_EB_PRIORITY );
DBG ( "Registering DHCP options block %p with priority %d\n",
options, options->priority );
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/* Insert after any existing blocks which have a higher priority */
list_for_each_entry ( existing, &option_blocks, list ) {
if ( options->priority > existing->priority )
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break;
}
list_add_tail ( &options->list, &existing->list );
}
/**
* Unregister DHCP option block
*
* @v options DHCP option block
*/
void unregister_dhcp_options ( struct dhcp_option_block *options ) {
list_del ( &options->list );
}
/**
* Initialise empty 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
*
* Populates the DHCP option data with a single @c DHCP_END option and
* fills in the fields of the @c dhcp_option_block structure.
*/
void init_dhcp_options ( struct dhcp_option_block *options,
void *data, size_t max_len ) {
struct dhcp_option *option;
options->data = data;
options->max_len = max_len;
option = options->data;
option->tag = DHCP_END;
options->len = 1;
DBG ( "DHCP options block %p initialised (data %p max_len %#zx)\n",
options, options->data, options->max_len );
}
/**
* Allocate space for a block of DHCP options
*
* @v max_len Maximum length of option block
* @ret options DHCP option block, or NULL
*
* Creates a new DHCP option block and populates it with an empty
* options list. This call does not register the options block.
*/
struct dhcp_option_block * alloc_dhcp_options ( size_t max_len ) {
struct dhcp_option_block *options;
options = malloc ( sizeof ( *options ) + max_len );
if ( options ) {
init_dhcp_options ( options,
( (void *) options + sizeof ( *options ) ),
max_len );
}
return options;
}
/**
* Free DHCP options block
*
* @v options DHCP option block
*/
void free_dhcp_options ( struct dhcp_option_block *options ) {
free ( options );
}
/**
* Resize a DHCP option
*
* @v options DHCP option block
* @v option DHCP option to resize
* @v encapsulator Encapsulating option (or NULL)
* @v old_len Old length (including header)
* @v new_len New length (including header)
* @ret rc Return status code
*/
static int resize_dhcp_option ( struct dhcp_option_block *options,
struct dhcp_option *option,
struct dhcp_option *encapsulator,
size_t old_len, size_t new_len ) {
void *source = ( ( ( void * ) option ) + old_len );
void *dest = ( ( ( void * ) option ) + new_len );
void *end = ( options->data + options->max_len );
ssize_t delta = ( new_len - old_len );
size_t new_options_len;
size_t new_encapsulator_len;
/* Check for sufficient space, and update length fields */
if ( new_len > DHCP_MAX_LEN )
return -ENOMEM;
new_options_len = ( options->len + delta );
if ( new_options_len > options->max_len )
return -ENOMEM;
if ( encapsulator ) {
new_encapsulator_len = ( encapsulator->len + delta );
if ( new_encapsulator_len > DHCP_MAX_LEN )
return -ENOMEM;
encapsulator->len = new_encapsulator_len;
}
options->len = new_options_len;
/* Move remainder of option data */
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
* @ret option DHCP option, or NULL
*
* 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.
*/
struct dhcp_option * set_dhcp_option ( struct dhcp_option_block *options,
unsigned int tag,
const void *data, size_t len ) {
static const uint8_t empty_encapsulator[] = { DHCP_END };
struct dhcp_option *option;
void *insertion_point = options->data;
struct dhcp_option *encapsulator = NULL;
unsigned int encap_tag = DHCP_ENCAPSULATOR ( tag );
size_t old_len = 0;
size_t new_len = ( len ? ( len + DHCP_OPTION_HEADER_LEN ) : 0 );
/* Find old instance of this option, if any */
option = find_dhcp_option_with_encap ( options, tag, &encapsulator );
if ( option ) {
old_len = dhcp_option_len ( option );
DBG ( "Resizing DHCP option %s from length %d to %d in block "
"%p\n", dhcp_tag_name (tag), option->len, len, options );
} else {
old_len = 0;
DBG ( "Creating DHCP option %s (length %d) in block %p\n",
dhcp_tag_name ( tag ), len, options );
}
/* Ensure that encapsulator exists, if required */
if ( DHCP_IS_ENCAP_OPT ( tag ) ) {
if ( ! encapsulator )
encapsulator = set_dhcp_option ( options, encap_tag,
empty_encapsulator,
sizeof ( empty_encapsulator) );
if ( ! encapsulator )
return NULL;
insertion_point = &encapsulator->data;
}
/* Create new option if necessary */
if ( ! option )
option = insertion_point;
/* Resize option to fit new data */
if ( resize_dhcp_option ( options, option, encapsulator,
old_len, new_len ) != 0 )
return NULL;
/* Copy new data into option, if applicable */
if ( len ) {
option->tag = tag;
option->len = len;
memcpy ( &option->data, data, len );
}
/* Delete encapsulator if there's nothing else left in it */
if ( encapsulator && ( encapsulator->len <= 1 ) )
set_dhcp_option ( options, encap_tag, NULL, 0 );
return option;
}
/**
* Find DHCP option within all registered DHCP options blocks
*
* @v tag DHCP option tag to search for
* @ret option DHCP option, or NULL if not found
*
* This function exists merely as a notational shorthand for
* find_dhcp_option() with @c options set to NULL.
*/
struct dhcp_option * find_global_dhcp_option ( unsigned int tag ) {
return find_dhcp_option ( NULL, tag );
}
/**
* Find DHCP numerical option, and return its value
*
* @v options DHCP options block
* @v tag DHCP option tag to search for
* @ret value Numerical value of the option, or 0 if not found
*
* This function exists merely as a notational shorthand for a call to
* find_dhcp_option() followed by a call to dhcp_num_option(). It is
* not possible to distinguish between the cases "option not found"
* and "option has a value of zero" using this function; if this
* matters to you then issue the two constituent calls directly and
* check that find_dhcp_option() returns a non-NULL value.
*/
unsigned long find_dhcp_num_option ( struct dhcp_option_block *options,
unsigned int tag ) {
return dhcp_num_option ( find_dhcp_option ( options, tag ) );
}
/**
* Find DHCP numerical option, and return its value
*
* @v tag DHCP option tag to search for
* @ret value Numerical value of the option, or 0 if not found
*
* This function exists merely as a notational shorthand for a call to
* find_global_dhcp_option() followed by a call to dhcp_num_option().
* It is not possible to distinguish between the cases "option not
* found" and "option has a value of zero" using this function; if
* this matters to you then issue the two constituent calls directly
* and check that find_global_dhcp_option() returns a non-NULL value.
*/
unsigned long find_global_dhcp_num_option ( unsigned int tag ) {
return dhcp_num_option ( find_global_dhcp_option ( tag ) );
}
/**
* Find DHCP IPv4-address option, and return its value
*
* @v options DHCP options block
* @v tag DHCP option tag to search for
* @v inp IPv4 address to fill in
* @ret value Numerical value of the option, or 0 if not found
*
* This function exists merely as a notational shorthand for a call to
* find_dhcp_option() followed by a call to dhcp_ipv4_option(). It is
* not possible to distinguish between the cases "option not found"
* and "option has a value of 0.0.0.0" using this function; if this
* matters to you then issue the two constituent calls directly and
* check that find_dhcp_option() returns a non-NULL value.
*/
void find_dhcp_ipv4_option ( struct dhcp_option_block *options,
unsigned int tag, struct in_addr *inp ) {
dhcp_ipv4_option ( find_dhcp_option ( options, tag ), inp );
}
/**
* Find DHCP IPv4-address option, and return its value
*
* @v options DHCP options block
* @v tag DHCP option tag to search for
* @v inp IPv4 address to fill in
* @ret value Numerical value of the option, or 0 if not found
*
* This function exists merely as a notational shorthand for a call to
* find_dhcp_option() followed by a call to dhcp_ipv4_option(). It is
* not possible to distinguish between the cases "option not found"
* and "option has a value of 0.0.0.0" using this function; if this
* matters to you then issue the two constituent calls directly and
* check that find_dhcp_option() returns a non-NULL value.
*/
void find_global_dhcp_ipv4_option ( unsigned int tag, struct in_addr *inp ) {
dhcp_ipv4_option ( find_global_dhcp_option ( tag ), inp );
}
/**
* Delete DHCP option
*
* @v options DHCP options block
* @v tag DHCP option tag
*
* This function exists merely as a notational shorthand for a call to
* set_dhcp_option() with @c len set to zero.
*/
void delete_dhcp_option ( struct dhcp_option_block *options,
unsigned int tag ) {
set_dhcp_option ( options, tag, NULL, 0 );
}