Problem this snippet solves:

We wanted a way to collect information about the VPN sessions that connect to our F5 systems. The APM reports are useful, however, there are some gaps. We also wanted to bring the information into our Splunk system for analysis. Information collected: time_session_started; client_ip; assigned_ip; vpn_host; user_name; SSL; SSLcipher; session_id; time_session_ended; vpn_run_time; vpn_end_reason.

The reason for saving the TCP/HTTP/SSL information to ACCESS::session variables was to allow them to be used in the ACCESS_SESSION_CLOSED event. Normally, these session variables are lost prior to the activation of this event. I would normally put the HSL::open earlier also, but the variable was removed prior to this event, so I had to open it at this point.

How to use this snippet:

Add this iRule to the virtual server for any APM session. You will need to prepare a pool with a Splunk indexer to receive the log entries. I used a separate TCP port so I could send these logs to separate index.

Code :

when ACCESS_POLICY_COMPLETED {
  set vpn_start_time [clock clicks -milliseconds]
  ACCESS::session data set "session.custom.sesstart" ${vpn_start_time}
  ACCESS::session data set "session.custom.fmtstart" [clock format [clock seconds] -format "%d/%b/%Y:%H:%M:%S -%Z"]
  ACCESS::session data set "session.custom.rmtip" [IP::remote_addr]
  ACCESS::session data set "session.custom.vpnhost" [virtual name]
  ACCESS::session data set "session.custom.sesssl" [SSL::cipher version]
  ACCESS::session data set "session.custom.sessslcipher" [SSL::cipher name]
}


when ACCESS_SESSION_CLOSED {
  set vpn_stop_time [ clock clicks -milliseconds ]
  set vpn_start_tm [ACCESS::session data get "session.custom.sesstart"]  
  set vpn_elapsed [expr ${vpn_stop_time} - ${vpn_start_tm}]
  set vpn_elapsed [expr int([expr ${vpn_elapsed} / 1000 ] ) ]
  set vpn_elapsed_days [expr {int($vpn_elapsed / 8640)}] 
  set vpn_elapsed [expr {$vpn_elapsed - [expr {$vpn_elapsed_days * 8640}]}]  
  set vpn_elapsed_hr  [expr {int([expr {${vpn_elapsed} / 360}])}] 
  set vpn_elapsed [expr {${vpn_elapsed} - [expr {${vpn_elapsed_hr} * 360}]}]  
  set vpn_elapsed_min [expr int([expr {${vpn_elapsed} / 60}])]  
  set vpn_elapsed [expr {${vpn_elapsed} - [expr {${vpn_elapsed_min} * 60}]}]  
  set req_1 "time_session_started=[ACCESS::session data get "session.custom.fmtstart"]"
  set req_2 "client_ip=[ACCESS::session data get "session.custom.rmtip"],assigned_ip=[ACCESS::session data get "session.assigned.clientip"]"
  set req_3 "vpn_host=[ACCESS::session data get "session.custom.vpnhost"]"
  set req_4 "user_name=[ACCESS::session data get "session.logon.last.username"]"  
  set req_5 "SSL=\"[ACCESS::session data get "session.custom.sesssl"]\""
  set req_5a "SSLcipher=\"[ACCESS::session data get "session.custom.sessslcipher"]\""
  set resp_1 "time_session_ended=[clock format [clock seconds] -format "%d/%b/%Y:%H:%M:%S -%Z"]"
  set resp_2 "session_id=[ACCESS::session data get session.user.sessionid]"
  set resp_3 "vpn_run_time=${vpn_elapsed_days} days ${vpn_elapsed_hr}:${vpn_elapsed_min}:${vpn_elapsed}"
  set resp_4 "vpn_end_reason=[ACCESS::session data get "session.end"]"
  set aclog [HSL::open -proto TCP -pool SplunkVPN ]
  HSL::send $aclog "$req_1,$resp_1,$req_4,$req_2,$resp_2,$resp_3,$resp_4,$req_3,$req_5,$req_5a\r\n"
  log local0.info "total: $vpn_elapsed"
}

Tested this on version:

11.6

APM Session Elapsed Time Log