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Date:      Thu, 30 Oct 2008 13:36:58 +1100
From:      Terry Sposato <terry@sucked-in.com>
To:        jackbarnett@gmail.com
Cc:        Polytropon <freebsd@edvax.de>, Freebsd questions <freebsd-questions@freebsd.org>
Subject:   Re: Firewalls in FreeBSD?
Message-ID:  <20081030133658.79084brlqjxwpv6s@webmail.tabmow.info>
In-Reply-To: <49091B32.9060306@gmail.com>
References:  <49090BA3.5090407@gmail.com> <20081030031231.8a5fccb9.freebsd@edvax.de> <49091B32.9060306@gmail.com>

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Quoting Jack Barnett <jackbarnett@gmail.com>:

>
>    yes, that is my setup.
>    hrm... well, I disabled the firewall completely, restarted, but still
>    doesn't work.
>    I have gateway and natd both enabled.  x10 is the "external" interface
>    (the one that is dhcp and connects to the cable modem).
>    I don't want to redirect anything to my windows box.  I just want
>    anything that connects out from my windows box to be able to connect
>    or send data back in.
>    For example, I load up a client (game) and it connects out on XYZ
>    port.  The server will send data back on ABC.
>    The problem, from what I can tell; is that I can get a connection out
>    - but when the server tries to send data back on ABC it is discarded.
>    Polytropon wrote:
>
> If I understood you correctly, your setting is:
>
>         (Modem/Router)---DHCP---(FreeBSD)---("Windows")
>
> I may respond directly on your configuration settings:
>
> On Wed, 29 Oct 2008 20:19:31 -0500, Jack Barnett =20
> [1]<jackbarnett@gmail.com> wro
> te:
>
>
>      gateway_enable=3D"YES"
>      #firewall_enable=3D"YES"
>      #firewall_type=3D"open"
>      firewall_type=3D"simple"
>      #firewall_type=3D"open"
>      firewall_logging=3D"YES"
>
>
> Use instead:
>
>         gateway_enable=3D"YES"
>         natd_enable=3D"YES"
>         natd_interface=3D"xl0"
>
> You may add special redirect directives to NATD's settings, such
> as
>         natd_flags=3D"-redirect_port tcp 192.168.1.2:5900 5900"
>         natd_flags=3D"-redirect_port tcp 192.168.1.5:23 6666"
>
> or
>         natd_flags=3D"-redirect_address 192.168.1.2 141.44.165.58 \
>                 -redirect_address 192.168.1.5 141.44.165.58"
>
> Examples taken from a very old configuration. :-)
>
> Then,
>
>         firewall_enable=3D"YES"
>         firewall_type=3D"/etc/ipfw.conf"
>
> Then, be sure to have nice firewall settings, you can use things
> similar to this, enabling just the services you really need and want,
> it's easy to write your own one or to rewrite this:
>
>         -f flush
>         add divert natd ip      from any to any         via     xl0
>         add allow       tcp     from any to any ftp     in recv xl0
>         add allow       tcp     from any to any ssh     in recv xl0
>         add allow       tcp     from any to any auth    in recv xl0
>         add allow       udp     from any to any ntp     in recv xl0
>         add allow       udp     from any to any ntalk   in recv xl0
>         add deny        udp     from any to any x11     in recv xl0
>         add reset       tcp     from any to any x11     in recv xl0
>         add allow       ipencap from any to any
>         add allow       ip      from any to any
>
> This should work fine. NB to use the correct interface names.
>
> References
>
>    1. mailto:jackbarnett@gmail.com
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>

Jack,

It is most likely caused by your ruleset not being stateful. If =20
packets are going out certain sessions and your firewall isn't then =20
allowing back in you would see the issue you are seeing. I am not sure =20
how this is accomplished via ipfw as I use pf but there would be a =20
tonne of documentation out there on how to make your rules stateful.


Regards,

Terry Sposato
terry@sucked-in.com
Have you been sucked in?
http://www.sucked-in.com

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