Provide a mechanism for returning the encapsulator as well as the

encapsulated option; this will be needed for modifications to the options
block.

diff --git a/src/include/gpxe/dhcp.h b/src/include/gpxe/dhcp.h
index 26016cf..cc9b94e 100644 (file)
--- a/src/include/gpxe/dhcp.h
+++ b/src/include/gpxe/dhcp.h
@@ -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 ) );

diff --git a/src/net/dhcpopts.c b/src/net/dhcpopts.c
index 35a65da..faa3a50 100644 (file)
--- a/src/net/dhcpopts.c
+++ b/src/net/dhcpopts.c
@@ -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 );
 }
 
 /**