Logging failed proxy attempts

[paul.moser at bt.com]

I'd like to log failed proxied authentication attempts (missing responses) and some information to identify which remote server did not respond.

I've successfully configured a linelog module and Post-Proxy-Type Fail-Authentication section to log a message when no response is received but am struggling to find any way of including in the log message information that will identify (eg. IP address/port or home server name) the remote server that failed to respond.

I've found the Home-Server-Name attribute in the internal dictionary but when I try to use it in the format string in the linelog module it just expands to an empty string which ever attribute list I reference.

eg :
format = "Missing response for %{User-Name}  to %{realm} vs:'%{Virtual-Server}' home server:'%{control:Home-Server-Name}''"

results in a log line of:
Missing response for 'my_realm/username' to 'my_realm' vs:'my-realm-server-auth' hsn:''

Is there some attributes/means of including some information identifying the remote server  in the log message?

Thanks,

Paul