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From: Andrew Schulman <andrex AT alumni DOT utexas DOT net>
Subject:  Re: Cygwin and firewalls
Date:  Sat, 18 Jun 2005 14:51:19 -0400
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>> Why is this a Cygwin question?  A firewall is a firewall.  Network
>> applications, both Cygwin and non-Cygwin, have to deal with it.  I don't
>> know what a Cygwin-hostile firewall would look like.
> 
> Cygwin uses sockets to implement many of its functions, such as IPC.
> Some overzealous firewalls install themselves deeply into the winsock
> stack (I believe it's called 'layered service provider' API) and install
> hooks throughout.  This can cause things to break if the firewall
> implementation is not done properly and without bugs, or causes the
> semantics of socket operations to change.  See for example, the threads
> about crappy VPN clients causing cygwin programs to hang, or the
> Zonealarm firewall causing the X11 server to hang at startup.  Sadly the
> archives are littered with examples of poorly written firewall-type
> software that causes things to break, so it's not such a stupid
> question.

OK, thanks.  Learn something new every day.



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