Added dhcp_ipv4_option() and friends.

Added test code to configure the interface for IPv4 after DHCP.

src/include/gpxe/dhcp.h

 		uint8_t byte;
 		uint16_t word;
 		uint32_t dword;
+		struct in_addr in;
 		uint8_t bytes[0];
 	} data;
 } __attribute__ (( packed ));
 };
 
 extern unsigned long dhcp_num_option ( struct dhcp_option *option );
+extern void dhcp_ipv4_option ( struct dhcp_option *option,
+			       struct in_addr *inp );
 extern struct dhcp_option *
 find_dhcp_option ( struct dhcp_option_block *options, unsigned int tag );
 extern void register_dhcp_options ( struct dhcp_option_block *options );
 extern unsigned long find_dhcp_num_option ( struct dhcp_option_block *options,
 					    unsigned int tag );
 extern unsigned long find_global_dhcp_num_option ( unsigned int tag );
+extern void find_dhcp_ipv4_option ( struct dhcp_option_block *options,
+				    unsigned int tag, struct in_addr *inp );
+extern void find_global_dhcp_ipv4_option ( unsigned int tag,
+					   struct in_addr *inp );
 extern void delete_dhcp_option ( struct dhcp_option_block *options,
 				 unsigned int tag );
 

src/net/dhcpopts.c

 #include <assert.h>
 #include <vsprintf.h>
 #include <gpxe/list.h>
+#include <gpxe/in.h>
 #include <gpxe/dhcp.h>
 
 /** @file
 	return value;
 }
 
+/**
+ * Obtain value of an IPv4-address DHCP option
+ *
+ * @v option		DHCP option, or NULL
+ * @v inp		IPv4 address to fill in
+ *
+ * Parses the IPv4 address value from a DHCP option, if present.  It
+ * is permitted to call dhcp_ipv4_option() with @c option set to NULL;
+ * in this case the address will be set to 0.0.0.0.
+ */
+void dhcp_ipv4_option ( struct dhcp_option *option, struct in_addr *inp ) {
+	if ( option )
+		*inp = option->data.in;
+}
+
 /**
  * Calculate length of a normal DHCP option
  *
 	return dhcp_num_option ( find_global_dhcp_option ( tag ) );
 }
 
+/**
+ * Find DHCP IPv4-address option, and return its value
+ *
+ * @v options		DHCP options block
+ * @v tag		DHCP option tag to search for
+ * @v inp		IPv4 address to fill in
+ * @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_ipv4_option().  It is
+ * not possible to distinguish between the cases "option not found"
+ * and "option has a value of 0.0.0.0" 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.
+ */
+void find_dhcp_ipv4_option ( struct dhcp_option_block *options,
+			     unsigned int tag, struct in_addr *inp ) {
+	dhcp_ipv4_option ( find_dhcp_option ( options, tag ), inp );
+}
+
+/**
+ * Find DHCP IPv4-address option, and return its value
+ *
+ * @v options		DHCP options block
+ * @v tag		DHCP option tag to search for
+ * @v inp		IPv4 address to fill in
+ * @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_ipv4_option().  It is
+ * not possible to distinguish between the cases "option not found"
+ * and "option has a value of 0.0.0.0" 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.
+ */
+void find_global_dhcp_ipv4_option ( unsigned int tag, struct in_addr *inp ) {
+	dhcp_ipv4_option ( find_global_dhcp_option ( tag ), inp );
+}
+
 /**
  * Delete DHCP option
  *

src/tests/dhcptest.c

 #include <string.h>
+#include <vsprintf.h>
+#include <byteswap.h>
+#include <gpxe/ip.h>
 #include <gpxe/dhcp.h>
 
 int test_dhcp ( struct net_device *netdev ) {
 	struct dhcp_session dhcp;
+	struct in_addr address = { htonl ( 0 ) };
+	struct in_addr netmask = { htonl ( 0 ) };
+	struct in_addr gateway = { INADDR_NONE };
+	int rc;
 
+	/* Bring IP interface up with address 0.0.0.0 */
+	if ( ( rc = add_ipv4_address ( netdev, address, netmask,
+				       gateway ) ) != 0 )
+		goto out_no_del_ipv4;
+
+	/* Issue DHCP request */
 	memset ( &dhcp, 0, sizeof ( dhcp ) );
 	dhcp.netdev = netdev;
-	return async_wait ( start_dhcp ( &dhcp ) );
+	if ( ( rc = async_wait ( start_dhcp ( &dhcp ) ) ) != 0 )
+		goto out_no_options;
+
+	/* Retrieve IP address configuration */
+	find_dhcp_ipv4_option ( dhcp.options, DHCP_EB_YIADDR, &address );
+	find_dhcp_ipv4_option ( dhcp.options, DHCP_SUBNET_MASK, &netmask );
+	find_dhcp_ipv4_option ( dhcp.options, DHCP_ROUTERS, &gateway );
+
+	/* Remove old IP address configuration */
+	del_ipv4_address ( netdev );
+
+	/* Set up new IP address configuration */
+	if ( ( rc = add_ipv4_address ( netdev, address, netmask,
+				       gateway ) ) != 0 )
+		goto out_no_del_ipv4;
+
+	printf ( "IP %s", inet_ntoa ( address ) );
+	printf ( " netmask %s", inet_ntoa ( netmask ) );
+	printf ( " gateway %s\n", inet_ntoa ( gateway ) );
+
+	/* Free DHCP options */
+	free_dhcp_options ( dhcp.options );
+ out_no_options:
+	/* Take down IP interface */
+	del_ipv4_address ( netdev );
+ out_no_del_ipv4:
+	return rc;
 }