[exim] SMTP connections from *.client.comcast.net

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Author: Martin Nicholas
Date:  
To: exim-users
Subject: [exim] SMTP connections from *.client.comcast.net
I have a problem using 4.34 under Debian-stable(2.4.27-0).
Connections from Comcast DSL lines are never terminated.
The connection HELOs (including the usual lies in
some cases) ok but the Helo ACL never runs, or at least nothing is written to
the log which should (in my system) always be the case. Nothing more is
heard. These child processes then hang around forever; neither stopping the
daemon nor waiting for the keepalive timeout, kills them.
I've kludged a solution by using embedded perl to look for these rogue
processes, but
this is a worrying problem (d0s attacks and the like). A log entry is made:
"SMTP connection from c-67-172-15-53.client.comcast.net [67.172.15.53] closed
after SIGTERM"
after the deed is done. I currently count them out after 16m.

Has anyone else seen this or just me? I guess this is a networking problem. It
has only occurred recently. Comcast don't get any special treatment from my
setup.

The evidence:
root@gu:~# ps  -H -u Debian-exim
  PID TTY          TIME CMD
 6892 ?        00:00:03 exim4
 7048 ?        01:37:17   exim4
 7162 ?        01:19:23   exim4
 7269 ?        00:59:50   exim4
 7280 ?        00:59:22   exim4
 7315 ?        00:56:04   exim4
 7688 ?        00:30:33   exim4
 8165 ?        00:19:20   exim4
 8167 ?        00:19:18   exim4
 8434 ?        00:14:12   exim4
root@gu:~# exiwhat
 6892 daemon: -q57m, listening for SMTP on [69.10.158.63]:25
 7048 handling incoming connection from (c-24-3-211-71.client.comcast.net) 
[24.3.211.71]
 7162 handling incoming connection from (c-24-13-11-242.client.comcast.net) 
[24.13.11.242]
 7269 handling incoming connection from (c-24-14-24-6.client.comcast.net) 
[24.14.24.6]
 7280 handling incoming connection from (c-24-3-123-67.client.comcast.net) 
[24.3.123.67]
 7315 handling incoming connection from (c-24-14-71-213.client.comcast.net) 
[24.14.71.213]
 7688 handling incoming connection from (c-67-165-118-111.client.comcast.net) 
[67.165.118.111]
 8165 handling incoming connection from (c-24-13-229-207.client.comcast.net) 
[24.13.229.207]
 8167 handling incoming connection from (c-24-13-229-207.client.comcast.net) 
[24.13.229.207]
 8434 handling incoming connection from (c-67-169-179-253.client.comcast.net) 
[67.169.179.253]
root@gu:~#


--
Regards,

Martin Nicholas.

E-mail: mgn@???