ltm rule command UDP payload

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



UDP::payload
       Returns the content or length of the current UDP payload.

SYNOPSIS
       UDP::payload (LENGTH | (OFFSET LENGTH))?

       UDP::payload length

       UDP::payload replace OFFSET LENGTH UDP_PAYLOAD

DESCRIPTION
       Returns the content or length of the current UDP payload.  Notice that,
       unlike TCP, there is no need to trigger a collect, and there is no
       corresponding release. Moreover, this command is valid not only in
       CLIENT_DATA and SERVER_DATA, but may be invoked within CLIENT_ACCEPTED.
       In that case, it will evaluate to the data contained in the segment
       that triggered the CLIENT_ACCEPTED event - though not necessarily every
       segment in a UDP stream (see CLIENT_ACCEPTED event description for more
       details).

       Syntax

       UDP::payload [] []

	    * Returns the content of the current UDP payload. If  is
	      specified, and more than  bytes are available, only the first
	       bytes of collected data are returned.

       UDP::payload replace   

	    * Replaces  bytes of the collected payload data starting at
	       with the given .

       UDP::payload length

	    * Returns the length, in bytes, of the current UDP payload.

RETURN VALUE
VALID DURING
       CLIENT_ACCEPTED, CLIENT_CLOSED, CLIENT_DATA, SERVER_CLOSED,
       SERVER_CONNECTED, SERVER_DATA, STREAM_MATCHED

EXAMPLES
	when CLIENT_DATA {
	  # empty payload entirely so there is no packet to send to the server
	  UDP::payload replace 0 [UDP::payload length] ""

	  # craft a string to hold our	packet data, 0x01 0x00 0x00 0x00 0x02 0x00 0x000x00 0x03 0x00 0x00 0x00
	  set packetdata [binary format i1i1i1 1 2 3 ]

	  # then fill payload with our own data from arbitrary length string called packetdata to send to the server
	  # this actually inserts it at the start of the packet, but because we emptiedthe packet above it becomes the new packet
	  UDP::payload replace 0 0 $packetdata

	  # Unlike TCP, UDP has no "collect" or "release"
	}

	   In at least BIG-IP 9.3.0 you can't use UDP::payload replace 0 0
	   $packetdata after emptying the payload entirely
	   A workaround is to insert your data at the start of the packet, then
	   empty the old data from the end

	when CLIENT_DATA {
	  # remember how big the incoming packet was
	  set oldlength [UDP::payload length]

	  # craft a string to hold our	packet data, 0x01 0x00 0x00 0x00 0x02 0x00 0x000x00 0x03 0x00 0x00 0x00
	  set packetdata [binary format i1i1i1 1 2 3 ]

	  # then fill payload with our own data from arbitrary length string called packetdata to send to the server
	  # this actually inserts it at the start of the packet, but because we emptiedthe packet above it becomes the new packet
	  UDP::payload replace 0 0 $packetdata

	  # now empty the old packet off the end
	  UDP::payload replace [string length $packetdata] [expr [UDP::payload length] - [string length $packetdata]] ""
	}

HINTS
SEE ALSO
CHANGE LOG
       @BIGIP-9.0.0 --First introduced the command.



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