Add concept of DHCP option applicators.

src/include/gpxe/dhcp.h

 #include <gpxe/list.h>
 #include <gpxe/in.h>
 #include <gpxe/refcnt.h>
+#include <gpxe/tables.h>
 
 struct net_device;
 struct job_interface;
 	struct dhcp_option_block options;
 };
 
+/** A DHCP option applicator */
+struct dhcp_option_applicator {
+	/** DHCP option tag */
+	unsigned int tag;
+	/** Applicator
+	 *
+	 * @v tag	DHCP option tag
+	 * @v option	DHCP option
+	 * @ret rc	Return status code
+	 */
+	int ( * apply ) ( unsigned int tag, struct dhcp_option *option );
+};
+
+/** Declare a DHCP option applicator */
+#define __dhcp_applicator \
+	__table ( struct dhcp_option_applicator, dhcp_appicators, 01 )
+
 /**
  * Get reference to DHCP options block
  *
 					   struct in_addr *inp );
 extern void delete_dhcp_option ( struct dhcp_option_block *options,
 				 unsigned int tag );
+extern int apply_dhcp_options ( struct dhcp_option_block *options );
 
 extern struct dhcp_option_block dhcp_request_options;
 extern int create_dhcp_packet ( struct net_device *netdev, uint8_t msgtype,

src/net/dhcpopts.c

 #include <assert.h>
 #include <gpxe/list.h>
 #include <gpxe/in.h>
+#include <gpxe/uri.h>
 #include <gpxe/dhcp.h>
 
 /** @file
 /** List of registered DHCP option blocks */
 static LIST_HEAD ( option_blocks );
 
+/** Registered DHCP option applicators */
+static struct dhcp_option_applicator dhcp_option_applicators[0]
+	__table_start ( struct dhcp_option_applicator, dhcp_applicators );
+static struct dhcp_option_applicator dhcp_option_applicators_end[0]
+	__table_end ( struct dhcp_option_applicator, dhcp_applicators );
+
 /**
  * Obtain printable version of a DHCP option tag
  *
 			  unsigned int tag ) {
 	set_dhcp_option ( options, tag, NULL, 0 );
 }
+
+/**
+ * Apply DHCP options
+ *
+ * @v options		DHCP options block, or NULL
+ * @ret rc		Return status code
+ */
+int apply_dhcp_options ( struct dhcp_option_block *options ) {
+	struct dhcp_option_applicator *applicator;
+	struct dhcp_option *option;
+	struct in_addr tftp_server;
+	struct uri *uri;
+	char uri_string[32];
+	unsigned int tag;
+	int rc;
+
+	/* Set current working URI based on TFTP server */
+	find_dhcp_ipv4_option ( options, DHCP_EB_SIADDR, &tftp_server );
+	snprintf ( uri_string, sizeof ( uri_string ),
+		   "tftp://%s/", inet_ntoa ( tftp_server ) );
+	uri = parse_uri ( uri_string );
+	if ( ! uri )
+		return -ENOMEM;
+	churi ( uri );
+	uri_put ( uri );
+
+	/* Call all registered DHCP option applicators */
+	for ( applicator = dhcp_option_applicators ;
+	      applicator < dhcp_option_applicators_end ; applicator++ ) {
+		tag = applicator->tag;
+		option = find_dhcp_option ( options, tag );
+		if ( ! option )
+			continue;
+		if ( ( rc = applicator->apply ( tag, option ) ) != 0 ) {
+			DBG ( "Could not apply DHCP option %s: %s\n",
+			      dhcp_tag_name ( tag ), strerror ( rc ) );
+			return rc;
+		}
+	}
+
+	return 0;
+}

src/net/udp/dhcp.c

 #include <gpxe/retry.h>
 #include <gpxe/tcpip.h>
 #include <gpxe/ip.h>
-#include <gpxe/uri.h>
 #include <gpxe/dhcp.h>
 
 /** @file
  *
  */
 
-/* Avoid dragging in dns.o */
-struct sockaddr_tcpip nameserver;
-
-/* Avoid dragging in syslog.o */
-struct in_addr syslogserver;
-
 /**
  * Configure network device from DHCP options
  *
 	struct in_addr address = { 0 };
 	struct in_addr netmask = { 0 };
 	struct in_addr gateway = { INADDR_NONE };
-	struct sockaddr_in *sin_nameserver;
-	struct in_addr tftp_server;
-	struct uri *uri;
-	char uri_string[32];
 	int rc;
 
 	/* Clear any existing routing table entry */
 		return rc;
 	}
 
-	/* Retrieve other DHCP options that we care about */
-	sin_nameserver = ( struct sockaddr_in * ) &nameserver;
-	sin_nameserver->sin_family = AF_INET;
-	find_dhcp_ipv4_option ( options, DHCP_DNS_SERVERS,
-				&sin_nameserver->sin_addr );
-	find_dhcp_ipv4_option ( options, DHCP_LOG_SERVERS,
-				&syslogserver );
-
-	/* Set current working URI based on TFTP server */
-	find_dhcp_ipv4_option ( options, DHCP_EB_SIADDR, &tftp_server );
-	snprintf ( uri_string, sizeof ( uri_string ),
-		   "tftp://%s/", inet_ntoa ( tftp_server ) );
-	uri = parse_uri ( uri_string );
-	if ( ! uri )
-		return -ENOMEM;
-	churi ( uri );
-	uri_put ( uri );
+	/* Apply other DHCP options */
+	if ( ( rc = apply_dhcp_options ( options ) ) != 0 ) {
+		DBG ( "Could not apply %s DHCP result options: %s\n",
+		      netdev->name, strerror ( rc ) );
+		return rc;
+	}
 
 	return 0;
 }

src/net/udp/dns.c

 #include <gpxe/resolv.h>
 #include <gpxe/retry.h>
 #include <gpxe/tcpip.h>
+#include <gpxe/dhcp.h>
 #include <gpxe/dns.h>
 
 /** @file
 	.name = "DNS",
 	.resolv = dns_resolv,
 };
+
+/**
+ * Apply DHCP nameserver option
+ *
+ * @v tag		DHCP option tag
+ * @v option		DHCP option
+ */
+static int apply_dhcp_nameserver ( unsigned int tag __unused,
+				   struct dhcp_option *option ) {
+	struct sockaddr_in *sin_nameserver;
+
+	sin_nameserver = ( struct sockaddr_in * ) &nameserver;
+	sin_nameserver->sin_family = AF_INET;
+	dhcp_ipv4_option ( option, &sin_nameserver->sin_addr );
+	return 0;
+}
+
+/** DHCP nameserver applicator */
+struct dhcp_option_applicator dhcp_nameserver_applicator __dhcp_applicator = {
+	.tag = DHCP_DNS_SERVERS,
+	.apply = apply_dhcp_nameserver,
+};