Re: No internet connection

[Jason Opperisano <opie@817west.com>]

On Thu, 2004-09-09 at 12:00, Nick Drage wrote:
> > for the sake of the list archives:
> > 
> >   # DHCP server -> client
> >   iptables -A INPUT -p udp --sport 67 --dport 68 -j ACCEPT
> > 
> >   # DHCP client -> server
> >   iptables -A OUTPUT -p udp --sport 68 --dport 67 -j ACCEPT
> 
> Not wishing to be paranoid, buuuuuuuuutttttttt..... couldn't you
> usefully restrict those by source and destination IP?

i dunno.  assuming you know the IP address of the DHCP server in
advance...it could be this:

   iptables -A OUTPUT -p udp -s 0.0.0.0/32 --sport 68 \
     -d 255.255.255.255/32 --dport 67 -j ACCEPT

   iptables -A OUTPUT -p udp --sport 68 \
     -d $DHCP_SRV --dport 67 -j ACCEPT

   iptables -A INPUT -p udp -s $DHCP_SRV --sport 67 \
     --dport 68 -j ACCEPT

with some scripting, you could programatically add in the IP of the FW
to those rules and re-run the iptables script every time the address
changes...

i guess i was trying to show the building blocks of what it takes to
allow a firewall to be a DHCP client...paranoia is left as an exercise
for the reader...  ;-)

-j

-- 
Jason Opperisano <opie@817west.com>