Author: Nathan Ollerenshaw Date: To: Kjetil Torgrim Homme CC: exim-users Subject: Re: [exim] broken ESMTP hosts
On Oct 26, 2004, at 12:44 AM, Kjetil Torgrim Homme wrote:
> On man, 2004-10-25 at 18:49 +0900, Nathan Ollerenshaw wrote:
>> This gets stranger;
>>
>> After testing from Windows, Solaris, Linux 2.4 kernel, it seems that
>> this is a bug with the 2.6.x kernel!
>
> probably not a bug, but rather it uses TCP options or window sizing
> which the remote firewall takes a dislike to. I'd whip out a network
> sniffer to see exactly what the difference is.
You're absolutely right.
Doing some more constrained googles indeed turned up a little gem; by
default the linux kernel 2.6.8 and below uses a
net.ipv4.tcp_default_win_scale set to 7, which breaks when talking to
OpenBSD hosts. Its more likely a bug with OpenBSD from what I've read
of people's postings on the matter.
linux 2.6.9 has this set to 0 by default, so thats why the problem is
'fixed'.
