Cygwin and firewalls

[Brian Dessent]

Andrew Schulman wrote:

> 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.

Brian

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