Provide a mechanism for returning the encapsulator as well as the
encapsulated option; this will be needed for modifications to the options block.
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@ -88,6 +88,20 @@ extern unsigned long dhcp_num_option ( struct dhcp_option *option );
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extern struct dhcp_option * find_dhcp_option ( unsigned int tag,
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extern struct dhcp_option * find_dhcp_option ( unsigned int tag,
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struct dhcp_option_block *options );
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struct dhcp_option_block *options );
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/**
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* Find DHCP numerical option, and return its value
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*
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* @v tag DHCP option tag to search for
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* @v options DHCP options block
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* @ret value Numerical value of the option, or 0 if not found
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*
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* This function exists merely as a notational shorthand for a call to
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* find_dhcp_option() followed by a call to dhcp_num_option(). It is
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* not possible to distinguish between the cases "option not found"
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* and "option has a value of zero" using this function; if this
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* matters to you then issue the two constituent calls directly and
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* check that find_dhcp_option() returns a non-NULL value.
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*/
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static inline unsigned long
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static inline unsigned long
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find_dhcp_num_option ( unsigned int tag, struct dhcp_option_block *options ) {
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find_dhcp_num_option ( unsigned int tag, struct dhcp_option_block *options ) {
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return dhcp_num_option ( find_dhcp_option ( tag, options ) );
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return dhcp_num_option ( find_dhcp_option ( tag, options ) );
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@ -78,26 +78,32 @@ static inline unsigned int dhcp_option_len ( struct dhcp_option *option ) {
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}
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}
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/**
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/**
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* Find DHCP option within block of raw data
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* Find DHCP option within DHCP options block, and its encapsulator (if any)
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*
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*
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* @v tag DHCP option tag to search for
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* @v tag DHCP option tag to search for
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* @v data Data block
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* @v options DHCP options block
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* @v len Length of data block
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* @ret encapsulator Encapsulating option (if applicable, may be NULL)
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* @ret option DHCP option, or NULL if not found
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* @ret option DHCP option, or NULL if not found
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*
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*
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* Searches for the DHCP option matching the specified tag within the
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* Searches for the DHCP option matching the specified tag within the
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* block of data. Encapsulated options may be searched for by using
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* block of data. Encapsulated options may be searched for by using
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* DHCP_ENCAP_OPT() to construct the tag value.
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* DHCP_ENCAP_OPT() to construct the tag value. If the option is an
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* encapsulated option, and @c encapsulator is non-NULL, it will be
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* filled in with a pointer to the encapsulating option, if present.
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* Note that the encapsulating option may be present even if the
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* encapsulated option is absent, in which case @c encapsulator will
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* be set but the function will return NULL.
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*
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*
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* This routine is designed to be paranoid. It does not assume that
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* This routine is designed to be paranoid. It does not assume that
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* the option data is well-formatted, and so must guard against flaws
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* the option data is well-formatted, and so must guard against flaws
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* such as options missing a @c DHCP_END terminator, or options whose
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* such as options missing a @c DHCP_END terminator, or options whose
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* length would take them beyond the end of the data block.
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* length would take them beyond the end of the data block.
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*/
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*/
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static struct dhcp_option * find_dhcp_option_raw ( unsigned int tag,
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static struct dhcp_option *
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void *data, size_t len ) {
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find_dhcp_option_encap ( unsigned int tag, struct dhcp_option_block *options,
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struct dhcp_option *option = data;
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struct dhcp_option **encapsulator ) {
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ssize_t remaining = len;
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struct dhcp_option *option = options->data;
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ssize_t remaining = options->len;
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unsigned int option_len;
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unsigned int option_len;
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while ( remaining ) {
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while ( remaining ) {
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@ -118,10 +124,12 @@ static struct dhcp_option * find_dhcp_option_raw ( unsigned int tag,
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/* Check for start of matching encapsulation block */
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/* Check for start of matching encapsulation block */
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if ( DHCP_ENCAPSULATOR ( tag ) &&
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if ( DHCP_ENCAPSULATOR ( tag ) &&
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( option->tag == DHCP_ENCAPSULATOR ( tag ) ) ) {
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( option->tag == DHCP_ENCAPSULATOR ( tag ) ) ) {
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/* Search within encapsulated option block */
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/* Continue search within encapsulated option block */
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return find_dhcp_option_raw ( DHCP_ENCAPSULATED( tag ),
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if ( encapsulator )
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&option->data,
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*encapsulator = option;
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option->len );
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remaining = option->len;
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option = ( void * ) &option->data;
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continue;
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}
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}
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option = ( ( ( void * ) option ) + option_len );
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option = ( ( ( void * ) option ) + option_len );
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}
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}
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@ -129,19 +137,19 @@ static struct dhcp_option * find_dhcp_option_raw ( unsigned int tag,
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}
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}
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/**
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/**
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* Find DHCP option within options block
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* Find DHCP option within DHCP options block
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*
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*
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* @v tag DHCP option tag to search for
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* @v tag DHCP option tag to search for
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* @v options DHCP options block
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* @v options DHCP options block
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* @ret option DHCP option, or NULL if not found
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* @ret option DHCP option, or NULL if not found
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*
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*
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* Searches for the DHCP option matching the specified tag within the
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* Searches for the DHCP option matching the specified tag within the
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* options block. Encapsulated options may be searched for by using
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* block of data. Encapsulated options may be searched for by using
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* DHCP_ENCAP_OPT() to construct the tag value.
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* DHCP_ENCAP_OPT() to construct the tag value.
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*/
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*/
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struct dhcp_option * find_dhcp_option ( unsigned int tag,
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struct dhcp_option * find_dhcp_option ( unsigned int tag,
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struct dhcp_option_block *options ) {
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struct dhcp_option_block *options ) {
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return find_dhcp_option_raw ( tag, options->data, options->len );
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return find_dhcp_option_encap ( tag, options, NULL );
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}
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}
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/**
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/**
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