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Add priority mechanism

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This commit is contained in:
Michael Brown 2006-06-28 13:48:02 +00:00
parent bd0c8b21ad
commit 291f072b82
2 changed files with 76 additions and 16 deletions
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9
src/include/gpxe/dhcp.h
View File

@ -84,4 +84,13 @@ struct dhcp_option_block {
size_t len;
};
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 );
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 ) );
}
#endif /* _GPXE_DHCP_H */

83
src/net/dhcpopts.c
View File

@ -93,10 +93,6 @@ static inline unsigned int dhcp_option_len ( struct dhcp_option *option ) {
* 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.
*
* Searching for @c DHCP_PAD or @c DHCP_END tags, or using either @c
* DHCP_PAD or @c DHCP_END as the encapsulator when constructing the
* tag via DHCP_ENCAP_OPT() will produce undefined behaviour.
*/
static struct dhcp_option * find_dhcp_option_raw ( unsigned int tag,
void *data, size_t len ) {
@ -104,14 +100,7 @@ static struct dhcp_option * find_dhcp_option_raw ( unsigned int tag,
ssize_t remaining = len;
unsigned int option_len;
assert ( tag != DHCP_PAD );
assert ( tag != DHCP_END );
assert ( DHCP_ENCAPSULATOR ( tag ) != DHCP_END );
while ( remaining ) {
/* Check for explicit end marker */
if ( option->tag == DHCP_END )
break;
/* Calculate length of this option. Abort processing
* if the length is malformed (i.e. takes us beyond
* the end of the data block).
@ -123,6 +112,9 @@ static struct dhcp_option * find_dhcp_option_raw ( unsigned int tag,
/* Check for matching tag */
if ( option->tag == tag )
return option;
/* Check for explicit end marker */
if ( option->tag == DHCP_END )
break;
/* Check for start of matching encapsulation block */
if ( DHCP_ENCAPSULATOR ( tag ) &&
( option->tag == DHCP_ENCAPSULATOR ( tag ) ) ) {
@ -136,6 +128,46 @@ static struct dhcp_option * find_dhcp_option_raw ( unsigned int tag,
return NULL;
}
/**
* Find DHCP option within 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
* 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 );
}
/**
* Find length of used portion of DHCP options block
*
* @v options DHCP options block
* @ret len Length of used portion of data block
*
* This searches for the @c DHCP_END marker within the options block.
* If found, the length of the used portion of the block (i.e. the
* portion containing everything @b before the @c DHCP_END marker, but
* excluding the @c DHCP_END marker itself) is returned.
*
* If no @c DHCP_END marker is present, the length of the whole
* options block is returned.
*/
size_t dhcp_option_block_len ( struct dhcp_option_block *options ) {
void *dhcpend;
if ( ( dhcpend = find_dhcp_option ( DHCP_END, options ) ) ) {
return ( dhcpend - options->data );
} else {
return options->len;
}
}
/**
* Find DHCP option within all registered DHCP options blocks
*
@ -145,14 +177,19 @@ static struct dhcp_option * find_dhcp_option_raw ( unsigned int tag,
* Searches within all registered DHCP option blocks for the specified
* tag. Encapsulated options may be searched for by using
* DHCP_ENCAP_OPT() to construct the tag value.
*
* 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 ( unsigned int tag ) {
struct dhcp_option * find_global_dhcp_option ( unsigned int tag ) {
struct dhcp_option_block *options;
struct dhcp_option *option;
list_for_each_entry ( options, &option_blocks, list ) {
if ( ( option = find_dhcp_option_raw ( tag, options->data,
options->len ) ) )
if ( ( option = find_dhcp_option ( tag, options ) ) )
return option;
}
return NULL;
@ -163,10 +200,24 @@ struct dhcp_option * find_dhcp_option ( unsigned int tag ) {
*
* @v options DHCP option block
*
* Register a block of DHCP options
* Register a block of DHCP options.
*/
void register_dhcp_options ( struct dhcp_option_block *options ) {
list_add ( &options->list, &option_blocks );
struct dhcp_option_block *existing_options;
signed int existing_priority;
signed int priority;
/* Determine priority of new block */
priority = find_dhcp_num_option ( DHCP_EB_PRIORITY, options );
/* Insert after any existing blocks which have a higher priority */
list_for_each_entry ( existing_options, &option_blocks, list ) {
existing_priority = find_dhcp_num_option ( DHCP_EB_PRIORITY,
existing_options );
if ( priority > existing_priority )
break;
}
list_add_tail ( &options->list, &existing_options->list );
}
/**