fixed DHCPv6 relay decoding

dhcp_protect.c

 				offset += 2; // msg-type, hop-count
 		}
 
-		while(offset+1<pktlen) {
-			uint8_t code = (uint8_t)pkt[offset];
-			uint8_t len  = (uint8_t)pkt[offset+1];
+		while(offset+4<=pktlen) {
+			uint16_t code = ntohs((uint16_t)pkt[offset]);
+			uint16_t len  = ntohs((uint16_t)pkt[offset+2]);
 
-			offset+=2;
+			offset+=4;
+
+			if ( code == 9 ) // relay message
+				continue;
 
 			if ( code == 1 ) { // Client identifier / DUID
 				// make sure there's enough space