On 5 Apr 2000, Rhett R. Rodewald wrote:
> DNS lookups (from QNX) appear to be sent on succesive ports, starting at
> 5001 or so. (i.e. the next DNS lookup will be sent on port 5002, 5003,
> 5004... etc.)
>
> 1) I don't understand why DNS lookups aren't sent on port 53.
DNS lookups get sent *to* port 53, not necessarily (and not usually)
*from* port 53.
> 2) I don't know why QNX keeps incrementing which port it uses.
This is normal practice to distinguish different "connections" (although
that term is used lossely with UDP). It's not strictly necessary with
DNS, since DNS also have an internal request ID, but DNS typically works
"just like everything else" in that regard.
> 3) MiamiTCPDump shows sends but no responses on the ethernet side:
>
> MiamiTCPDump: listening on eth0
> HAL_9000.5004 > ns3.dns.rcn.net.domain: 1+ A? www.qnx.com. (29)
> HAL_9000.5004 > ns3.dns.rcn.net.domain: 1+ A? www.qnx.com. (29)
> HAL_9000.5004 > ns3.dns.rcn.net.domain: 1+ A? www.qnx.com. (29)
>
>
> 4) MiamiTCPDump shows an "unreachable" error when trying to route the
> reply from the DNS server:
This is the normal firewall problem. With TCP one can recognize an
incoming packet as a "response" without knowledge of the application
protocol. But this isn't true of UDP, thereby causing trouble, although
if NAT understood DNS specifially it could get around that.
> 5) Is there anyway to configure the MiamiDx Firewall to allow this to work
> properly, without completely disabling the Firewall?
That depends on the port numbers.
Fred Wright
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