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Provide a mechanism for returning the encapsulator as well as the

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encapsulated option; this will be needed for modifications to the options
block.
This commit is contained in:
Michael Brown 2006-06-28 18:59:54 +00:00
parent c9ea710930
commit 51d62d1a3c
2 changed files with 37 additions and 15 deletions
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14
src/include/gpxe/dhcp.h
View File

@ -88,6 +88,20 @@ extern unsigned long dhcp_num_option ( struct dhcp_option *option );
extern struct dhcp_option * find_dhcp_option ( unsigned int tag,
struct dhcp_option_block *options );
/**
* Find DHCP numerical option, and return its value
*
* @v tag DHCP option tag to search for
* @v options DHCP options block
* @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.
*/
static inline unsigned long
find_dhcp_num_option ( unsigned int tag, struct dhcp_option_block *options ) {
return dhcp_num_option ( find_dhcp_option ( tag, options ) );

38
src/net/dhcpopts.c
View File

@ -78,26 +78,32 @@ static inline unsigned int dhcp_option_len ( struct dhcp_option *option ) {
}
/**
* Find DHCP option within block of raw data
* Find DHCP option within DHCP options block, and its encapsulator (if any)
*
* @v tag DHCP option tag to search for
* @v data Data block
* @v len Length of data block
* @v options DHCP options block
* @ret encapsulator Encapsulating option (if applicable, may be NULL)
* @ret option DHCP option, or NULL if not found
*
* Searches for the DHCP option matching the specified tag within the
* block of data. Encapsulated options may be searched for by using
* DHCP_ENCAP_OPT() to construct the tag value.
* DHCP_ENCAP_OPT() to construct the tag value. If the option is an
* encapsulated option, and @c encapsulator is non-NULL, it will be
* filled in with a pointer to the encapsulating option, if present.
* Note that the encapsulating option may be present even if the
* encapsulated option is absent, in which case @c encapsulator will
* be set but the function will return NULL.
*
* 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_raw ( unsigned int tag,
void *data, size_t len ) {
struct dhcp_option *option = data;
ssize_t remaining = len;
static struct dhcp_option *
find_dhcp_option_encap ( unsigned int tag, struct dhcp_option_block *options,
struct dhcp_option **encapsulator ) {
struct dhcp_option *option = options->data;
ssize_t remaining = options->len;
unsigned int option_len;
while ( remaining ) {
@ -118,10 +124,12 @@ static struct dhcp_option * find_dhcp_option_raw ( unsigned int tag,
/* Check for start of matching encapsulation block */
if ( DHCP_ENCAPSULATOR ( tag ) &&
( option->tag == DHCP_ENCAPSULATOR ( tag ) ) ) {
/* Search within encapsulated option block */
return find_dhcp_option_raw ( DHCP_ENCAPSULATED( tag ),
&option->data,
option->len );
/* Continue search within encapsulated option block */
if ( encapsulator )
*encapsulator = option;
remaining = option->len;
option = ( void * ) &option->data;
continue;
}
option = ( ( ( void * ) option ) + option_len );
}
@ -129,19 +137,19 @@ static struct dhcp_option * find_dhcp_option_raw ( unsigned int tag,
}
/**
* Find DHCP option within options block
* Find DHCP option within DHCP options block
*
* @v tag DHCP option tag to search for
* @v options DHCP options block
* @ret option DHCP option, or NULL if not found
*
* Searches for the DHCP option matching the specified tag within the
* options block. Encapsulated options may be searched for by using
* block of data. Encapsulated options may be searched for by using
* DHCP_ENCAP_OPT() to construct the tag value.
*/
struct dhcp_option * find_dhcp_option ( unsigned int tag,
struct dhcp_option_block *options ) {
return find_dhcp_option_raw ( tag, options->data, options->len );
return find_dhcp_option_encap ( tag, options, NULL );
}
/**