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Re: [Discuss-gnuradio] UHD: cannot find usrp2.
From: |
Marcus D. Leech |
Subject: |
Re: [Discuss-gnuradio] UHD: cannot find usrp2. |
Date: |
Sat, 18 Dec 2010 01:13:45 -0500 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.15) Gecko/20101027 Fedora/3.0.10-1.fc12 Thunderbird/3.0.10 |
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