[SR-Users] strange conditional "if ($au!=$tU)" with previous exit

[PICCORO McKAY Lenz]

i have this in asterisk integration how to, and i noted the "exit"
before the "if($au!=$tU)" .. i dont understan the conditional and the
exit there!

please can someon xplain me that!?

# authenticate the REGISTER requests (uncomment to enable auth)
#!ifdef WITH_ASTERISK
   if (!www_authorize("$td", "sipusers"))
#!else
   if (!www_authorize("$td", "subscriber"))
#!endif
   {
      www_challenge("$td", "0");
      exit;
   }
   if ($au!=$tU)
   {
   sl_send_reply("403","Forbidden auth ID");
   exit;
   }

i investigate at the kamailio cgf documentation and there's no clear
topic related!

http://www.kamailio.org/wiki/cookbooks/5.2.x/pseudovariables#tu_-_to_uri

Lenz McKAY Gerardo (PICCORO)
http://qgqlochekone.blogspot.com