Re: [Discuss-gnuradio] UHD: cannot find usrp2.

[Marcus D. Leech]

On 12/17/2010 09:56 PM, Josh Blum wrote:
>
>
> Disabling the firewall entirely seems to fix it. Thats using a
> sledgehammer when you need a chisel. :-)
>
> -josh
>
> _______________________________________________
>
>   
The "most elegant" way to solve this is with a "conntrack" module for
the kernel, a la the conntrack
  module for netbios-ns and snmp.  But in lieu of that, the following
line in /etc/sysconfig/iptables
  (on Fedoren):

-A INPUT -m state --state NEW -m udp -p udp --sport 49152:49153 --dport
1024:65535 -j ACCEPT

Appears  to allow uhd_find_devices to do its thing.

Any protocol that does "discovery" using a UDP broadcast, followed by a
unicast reply will run
  into trouble with iptables, which is why "conntrack" modules were
invented to handle
  specific protocols that use a broadcast "discovery" phase. While there
appears to have been
  discussion of a "generic" conntrack module to cover this case, it
doesn't appear to have been
  worked on.

The problem with the iptables config line above is that it doesn't
*quite* provide the required security
  semantic that would be provided by a conntrack module.  But it will
suffice for now.




-- 
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org