[Pidgin] #17255: SASL login on IRC fails on esper.net

[Pidgin]

#17255: SASL login on IRC fails on esper.net
---------------------+---------------------------
 Reporter:  ali1234  |      Owner:  elb
     Type:  defect   |     Status:  new
Milestone:           |  Component:  IRC
  Version:  2.12.0   |   Keywords:  SASL IRC PING
---------------------+---------------------------
 To reproduce:

 1. Connect to irc.esper.net and register with nickserv. (optional, since
 pidgin never even attempts to authenticate.)
 2. In account screen, enter nickserv password in password field and enable
 SASL authentication.
 3. Re-connect to esper.net.

 Result: Pidgin never attempts SASL authentication, connection hangs
 immediately on connecting. Debug log contains no useful information.

 Note that SASL works correctly on Freenode. Also note that Hexchat SASL
 works correctly on esper.net.

 Here is a log of the TCP communications, made with wireshark, when
 connecting to Freenode:


 {{{
 CAP REQ :sasl
 USER ali1234 * chat.freenode.net :Alistair Buxton
 NICK ali1234
 :weber.freenode.net NOTICE * :*** Looking up your hostname...
 :weber.freenode.net NOTICE * :*** Checking Ident
 :weber.freenode.net NOTICE * :*** Couldn't look up your hostname
 :weber.freenode.net NOTICE * :*** No Ident response
 :weber.freenode.net CAP * ACK :sasl
 AUTHENTICATE DIGEST-MD5
 ... etc
 }}}


 Here is a log when connecting to esper.net:


 {{{
 CAP REQ :sasl
 USER ajb * irc.esper.net :purple
 NICK ajb
 :catastrophe.esper.net NOTICE * :*** Looking up your hostname...
 :catastrophe.esper.net NOTICE * :*** Checking Ident
 :catastrophe.esper.net NOTICE * :*** Couldn't look up your hostname
 :catastrophe.esper.net NOTICE * :*** No Ident response
 :catastrophe.esper.net CAP * ACK :sasl
 PING :FFFFFFFFFACB15BA
 PONG :FFFFFFFFFACB15BA
 ERROR :Closing Link: xx.xx.xx.xx (Connection timed out)
 QUIT :Leaving.
 }}}


 It appears as if the PING from the server causes pidgin to get distracted
 and forget that it is supposed to be logging in. Instead it just does
 nothing until the connection times out.

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Ticket URL: <https://developer.pidgin.im/ticket/17255>
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