Re: Raspberry Pi as bridge

[Edgar Pettijohn <edgar%pettijohn-web.com@localhost>]

On Jan 22, 2019 1:49 PM, Greg Troxel <gdt%lexort.com@localhost> wrote:
>
> Jörn Clausen <joernc%googlemail.com@localhost> writes:
>
> > I am trying to use a Raspberry Pi running
> >
> > NetBSD armv7 8.99.30 NetBSD 8.99.30 (RPI2)
> >
> > as a bridge to extend my WiFi net to some devices. I have two NICs,
> > usmsc0 (internal RJ45) and urtwn0 (WiFi USB). urtwn0 is up and running
> > and works as desired. I have followed the bridge instructions in the
> > NetBSD guides, i.e.
> >
> > $ cat /etc/ifconfig.bridge0
> > create
> > !brconfig $int add urtwn0 add usmsc0 up
>
> That is probably ok, but note that the interfaces each have to be up,
> and generally you would have one configured with an address and one not.
> I have done this on a box with two wired ethernets.  It generally works,
> but there is some wierdness with ND6 in terms of getting replies on the
> secondary (no-addr) interface with the mac addr of the primary
> interface.
>
> You didn't mention what you are doing about urtwn0 and config.   If you
> are using it in hostap mode and using a different ssid, then that sounds
> plausible.  I am unclear on what happens if the same ssid.
>
> > tcpdump on either interface shows that broadcast packages are passed
> > between interfaces, but nothing else. A DHCP request coming in via
> > usmsc0 from a device is visible on urtwn0 but is not passed on to my
> > DHCP server.
>
> Defintely run 'brconfig bridge0' and look at the output.  In particular
> you should see an "address cache" section, showing which mac addrs have
> been learned as on each side.
>
> To support bridging, an interface has to do PROMISC mode in hardware, so
> that incoming packets with not-us unicast mac addresses are received.
> The cache will help in understanding how that is working.
>
> > I have
> >
> > net.inet.ip.forwarding = 1
> >
> > and because it sounded helpful also
> >
> > net.inet.ip.subnetsarelocal = 0
> >
> > but no change.
>
> Your box is not intending to do ip forwarding.  So that's irrelevant,
> and I would undo that setting, not because it's harmful, but because
> it's non-standard and not helpful, and simpler is better.
>
> > Any ideas? Is the Raspi kernel missing something that makes it
> > unusable as a bridge?
>
> If 'brconfig bridge0' looks ok, it has "pseudo-device bridge".
>
>
> Feel free to send me 'ifconfig' and 'brconfig bridge0' offlist (as
> unwrapped text/plain :-).

You may want to look into dhcrelay(8).