howto enable udp for bind8
Kevin Darcy
kcd at daimlerchrysler.com
Tue Nov 21 03:24:19 UTC 2000
Nico Lembrechts wrote:
> Hi,
> I am setting up a name server on my openbsd 2.7 box. For my internal
> network it already works fine. Now i set up a slave server somwhere else
> and tried to do a zone transfer. with this the problems started. After a
> lot of digging i find out that the when i do a nslookup on the slave
> server, set the server to my master and try to look up a domain, this is
> done over udp. a netstat on my master server tells me that port 53 only
> listens for tcp connections. A have read trough all the documentation
> bud can't find howto setup the server to listen for udp connections
> also.
Well, UDP is a connectionless protocol, so technically there is no such
thing as listen()'ing on a UDP port. Instead, the nameserver bind()'s a
datagram socket to port 53 and then select()'s on that socket to see if
anything has arrived. When you do a netstat -an | grep \.53 you should see
something like:
127.0.0.1.53 Idle
129.9.209.47.53 Idle
127.0.0.1.53 *.* 0 0 0 0 LISTEN
129.9.209.47.53 *.* 0 0 0 0 LISTEN
The "Idle" entries are UDP sockets which don't happen to be transferring
any data currently. named is in a sense "listen"ing on UDP port 53, but
it's technically not a listen() and therefore netstat doesn't show a
"LISTEN" state for the sockets.
> I suppose that the zone transfers are also done over udp ?
No, actually they are done over TCP. I think you're barking up the wrong
tree. Your zone transfer problems are probably caused by something
unrelated to the UDP protocol. Look at your logs. Oftentimes a syntax error
in the master file will cause it to answer non-authoritatively for the
zone, which in turn inhibits zone transfers.
- Kevin
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