layer2 ipfw fwd
Julian Elischer
julian at freebsd.org
Mon Dec 21 14:40:39 UTC 2015
On 21/12/2015 5:47 PM, bycn82 wrote:
> why fwd based on MAC? Can share more info of your requirement?
you still decide to FWD based on IP address, but you do it while the
packet is still in the layer 2 bridge.
let me give you a concrete example
If I have a bridge between two networks. it is a transparent bridge,
in other words nothing sees the bridge.
However using layer 2 IPFW, I can block packets from side A from
getting to side B.
In addition I can redirect (using ipfw fwd and this patch) packets
that are coming in, from side A to port 80 on side B, to a local proxy
or http filter.
Everything else just flows back and forth across the bridge.
Using IP spoofing/forwarding the proxy filter will create a socket
that pretends to be the side B destination and respond directly, even
though it doesn't have that address. It may in turn open a socket to
the original destination and forward the request, or, maybe it won't,
depending on policy.
But nothing else is aware of its existence. it is as though a segment
of cable started filtering web content.
This is EXACTLY what the cisco/ironport web filter appliance does...
>
>
> On Monday, 21 December 2015, Julian Elischer <julian at freebsd.org
> <mailto:julian at freebsd.org>> wrote:
>
> On 21/12/2015 10:20 AM, Ganbold Tsagaankhuu wrote:
>
> Hi,
>
> Does ipfw support layer2 fwd to support transparent proxying
> on bridge?
>
> Does similar change like
> https://lists.freebsd.org/pipermail/freebsd-ipfw/2003-September/000526.html
> ever get committed?
>
> I don't believe this was applied..
> I did similar when I worked for Ironport/Cisco.
> But it's a trade-off between bloat and usefulness.
>
>
> thanks a lot,
>
> Ganbold
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