Some help with broadcasts through a Linux system

[Jasper van der Neut]

Richard Sharpe wrote:
> 
> Hi,
> 
> I am having problems getting broadcasts through a Linux system.
> 
> Here is the config:
> 
>      172.30.0.0/24               16.153.112.0/24
>      ----------------[Linux Box]------------------
> 
> I have it set up with ip_forward=1.
> 
> However, when I ping 16.153.112.255 from 172.30.0.120, 172.30.0.1 responds,
> and I see nothing on the 16.153.112.0/24 subnet.
> 
> The linux box is running a 2.0.36 kernel.
> 
> It seems that Linux feels that it should not have to forward the broadcast
> datagrams.

Which is the correct behaviour.

> Does anyone have any clues?

If you want to forward your netbios datagram broadcasts you have to do
more than just forwarding because the data contains ip-addresses too.

I've solved this problem by writing a patch for Samba which 'glues' 
the subnets of my linux firewall together. You can find the code
at http://malt-whisky.student.utwente.nl/nbfw/ . The code is not
up-to-date with the latest Samba because I'm abroad, but that's an
exercise for the reader ;)


Jasper