Re: [Exim] silently dropping connections on high bandwidth l…

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Autore: Philip Hazel
Data:  
To: Andreas M. Kirchwitz
CC: exim-users
Oggetto: Re: [Exim] silently dropping connections on high bandwidth load
On 13 Aug 2003, Andreas M. Kirchwitz wrote:

> I'm connected with ISDN (64 kbit/s), and if the utilization of the
> line is very high, Exim sometimes silently drops incoming connections
> upon connect. No entry to the logfile (mainlog) is made, no SMTP
> response code is given. I don't even get the typical log entry
> "SMTP connection from [1.2.3.4]:4711 (TCP/IP connection count = 1)".


That almost suggests that Exim didn't even receive the connection.
Writing that log message happens pretty early on.

> If Exim drops the connection, it usually happens within the first
> about 5 seconds after the connection has been initiated from the
> outside world (Internet).


I think the first thing to try to find out is whether it is Exim, or
your OS, that is dropping the connection (3-way TCP handshake not
completing in time?). But I don't know how to do this. Maybe tcpdump
could help.

> However, once the SMTP connection has been established, Exim won't
> drop the connection (even on high bandwidth load).


Again, that suggests Exim isn't actually getting the connection in the
problem cases.


--
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.
Get the Exim 4 book:    http://www.uit.co.uk/exim-book