fixed DHCPv6 relay message decoding

dhcp_protect.c

@@ -302,8 +302,10 @@ void dp_dhcpv6_check(dp_conf *conf, unsigned char *pkt, int pktlen, int offset,
 
 			offset+=4;
 
-			if ( code == 9 ) // relay message
+			if ( code == 9 ) { // relay message
+				offset += 4;
 				continue;
+			}
 
 			if ( code == 1 ) { // Client identifier / DUID
 				// make sure there's enough space