2.4.0 tcp over firewall - no connection

2.4.0 tcp over firewall - no connection

[Eugene Crosser]

I noticed rather strange behavior: stock 2.4.0 with old ISA 3Com
on UP compiled as UP cannot open TCP connection to hosts behind a
firewall.  E.g. it is impossible to go to http://www.etrade.com/ -
connect just never finishes.  2.2.17 on the same hardware works
right.  2.4.0 on SMP over PPP connection works right too.  MTU
is 1500 in both cases.  In both cases, kernel is compiled with
netfilter as modules, but those are not loaded.

I did not investigate further yet, just wanted to bring this to
attention of those whom it may concern...

Eugene
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Re: 2.4.0 tcp over firewall - no connection

[Doug McNaught]

crosser@average.org (Eugene Crosser) writes:

> I noticed rather strange behavior: stock 2.4.0 with old ISA 3Com
> on UP compiled as UP cannot open TCP connection to hosts behind a
> firewall.  E.g. it is impossible to go to http://www.etrade.com/ -
> connect just never finishes.  2.2.17 on the same hardware works
> right.  2.4.0 on SMP over PPP connection works right too.  MTU
> is 1500 in both cases.  In both cases, kernel is compiled with
> netfilter as modules, but those are not loaded.

Known problem, exhaustively discussed on the list, and not related
to your NIC.  Disable ECN (explicit congestion notification), either
in your kernel compile or in /proc/sys/<something>.

-Doug
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Re: 2.4.0 tcp over firewall - no connection

[Eugene Crosser]

In article <m3itnnru8n.fsf@belphigor.mcnaught.org>,
        Doug McNaught <doug@wireboard.com> writes:

>> I noticed rather strange behavior: stock 2.4.0 with old ISA 3Com
>> on UP compiled as UP cannot open TCP connection to hosts behind a
>> firewall.  E.g. it is impossible to go to http://www.etrade.com/ -
>> connect just never finishes.  2.2.17 on the same hardware works
>> right.  2.4.0 on SMP over PPP connection works right too.  MTU
>> is 1500 in both cases.  In both cases, kernel is compiled with
>> netfilter as modules, but those are not loaded.
> 
> Known problem, exhaustively discussed on the list, and not related
> to your NIC.  Disable ECN (explicit congestion notification), either
> in your kernel compile or in /proc/sys/<something>.

This really was ECN, sorry for noise in this list...

Eugene
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