ltm rule command DATAGRAM dns

iRule(1)		      BIG-IP TMSH Manual		      iRule(1)



DATAGRAM::dns
       Returns DNS header information.

SYNOPSIS
       DATAGRAM::dns (id | qr | opcode | qdcount | ancount | nscount |
       arcount)

DESCRIPTION
       This iRules command returns DNS header information.
	 Note: L4 protocol of the packet must be either TCP or UDP for this
       command
	       to work. Also, the L4 port must be equal to the dns port
       (typically port 53).

       DATAGRAM::dns id

	    * Returns DNS header 16-bit aXXidentificationaXX field as an integer value.

       DATAGRAM::dns qr

	    * Returns DNS header aXXquery/responseaXX as a boolean value.
	      0 indicates a aXXqueryaXX and 1 indicates a aXXresponseaXX.

       DATAGRAM::dns opcode

	    * Returns DNS header aXXopcodeaXX as a string.
	      Values include aXXQueryaXX, aXXIQueryaXX, aXXStatusaXX, aXXNotifyaXX, aXXUpdateaXX and aXXUnassignedaXX.

       DATAGRAM::dns qdcount

	    * Returns DNS header field aXXquestion countaXX as an integer value.

       DATAGRAM::dns ancount

	    * Returns DNS header field aXXanswer countaXX as an integer value.

       DATAGRAM::dns nscount

	    * Returns DNS header field aXXauthority record countaXX as an integer value.

       DATAGRAM::dns qdcount

	    * Returns DNS header field aXXadditional record countaXX as an integer value.

RETURN VALUE
VALID DURING
       FLOW_INIT, CLIENT_DATA

EXAMPLES
	when FLOW_INIT {
	  if { [IP::protocol] == 6 } {
	    log local0. "TCP Payload Length = [DATAGRAM::tcp payload_length] Payload: [DATAGRAM::tcp payload 100]"
	    log local0. "DNS Header fields ID: [DATAGRAM::dns id] QR: [DATAGRAM::dns qr] OPCODE: [DATAGRAM::dns opcode] QDCOUNT: [DATAGRAM::dns qdcount]"
	  }
	  if { [IP::protocol] == 17 } {
	    log local0. "UDP Payload Length = [DATAGRAM::udp payload_length] Payload: [DATAGRAM::udp payload 100]"
	    log local0. "DNS Header fields ID: [DATAGRAM::dns id] QR: [DATAGRAM::dns qr] OPCODE: [DATAGRAM::dns opcode] QDCOUNT: [DATAGRAM::dns qdcount]"
	  }
	}

HINTS
SEE ALSO
CHANGE LOG
       @BIGIP-12.0.0 --First introduced the command.



BIG-IP				  2017-01-31			      iRule(1)