[dhcpv6] Add DHCPv6 "filename" setting

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/dhcpv6.h

 /** DHCPv6 domain search list option */
 #define DHCPV6_DOMAIN_LIST 24
 
+/** DHCPv6 bootfile URI option */
+#define DHCPV6_BOOTFILE_URL 59
+
+/** DHCPv6 bootfile parameters option */
+#define DHCPV6_BOOTFILE_PARAM 60
+
 /** DHCPv6 syslog server option
  *
  * This option code has not yet been assigned by IANA.  Please update

src/net/udp/dhcpv6.c

 /** Options to be requested */
 static uint16_t dhcpv6_requested_options[] = {
 	htons ( DHCPV6_DNS_SERVERS ), htons ( DHCPV6_DOMAIN_LIST ),
+	htons ( DHCPV6_BOOTFILE_URL ), htons ( DHCPV6_BOOTFILE_PARAM ),
 };
 
 /**
 	ref_put ( &dhcpv6->refcnt );
 	return rc;
 }
+
+/** Boot filename setting */
+const struct setting filename6_setting __setting ( SETTING_BOOT, filename ) = {
+	.name = "filename",
+	.description = "Boot filename",
+	.tag = DHCPV6_BOOTFILE_URL,
+	.type = &setting_type_string,
+	.scope = &ipv6_scope,
+};