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changewait1's avatar
changewait1
Icon for Altostratus rankAltostratus
May 20, 2025

About DNS irule TCL error

Hi everyone,

I'm encountering a TCL error when using an iRule on my BIG-IP DNS (GSLB) system. The error appears as follows:

 err tmm9[13024]: 01220001:3: TCL error: /Common/IRULE_LOGGING_RESPONSE <DNS_RESPONSE> - Packet alloc for section failure. invoked from within "DNS::answer"

iRule

when DNS_RESPONSE { set timestamp [clock format [clock seconds] -format "%Y-%m-%d %H:%M:%S"] # log local0. "Client IP : [IP::client_addr] / F5 answer : [DNS::answer]" set kt_hsl [HSL::open -publisher /Common/kt_publisher] HSL::send $kt_hsl "$timestamp DNS RESPONSE / Client IP : [IP::client_addr] / F5 answer : [DNS::answer]" 

My questions:
What causes the "Packet alloc for section failure" error when calling DNS::answer?
Is there a way to safely call DNS::answer only when the response is valid?
if the iRule is indeed causing this error, how should I modify it to avoid the issue?

Any insights, workarounds, or documentation references would be greatly appreciated.

Thanks in advance!

irule

3 Replies

  • Injeyan_Kostas's avatar
    Injeyan_Kostas
    Icon for Cumulonimbus rankCumulonimbus
    May 20, 2025

    You should use catch function

    try something like this

    when DNS_RESPONSE 
{ 
	set timestamp [clock format [clock seconds] -format "%Y-%m-%d %H:%M:%S"] 
	# log local0. "Client IP : [IP::client_addr] / F5 answer : [DNS::answer]" 
	set kt_hsl [HSL::open -publisher /Common/kt_publisher] 
	
	if {[catch {HSL::send $kt_hsl "$timestamp DNS RESPONSE / Client IP : [IP::client_addr] / F5 answer : [DNS::answer]"}]} 
	{
        log local0. "ERROR: DNS RESPONSE FAILED"
    }
}

     

    • changewait1's avatar
      changewait1
      Icon for Altostratus rankAltostratus
      May 21, 2025

      Thanks for your help.
      Than, is the log issue caused by the failure of HSL::send due to a DNS RESPONSE failure?
      If so, is it possible to identify the cause of the DNS RESPONSE failure through logs?

      • Injeyan_Kostas's avatar
        Injeyan_Kostas
        Icon for Cumulonimbus rankCumulonimbus
        May 21, 2025

        The problem was that [DNS::answer] was't include a valid or parseable answer

        You may collect the payload to check what is wrong