[avahi] problem with nss_mdns4 doing long timesouts looking up
lathiat at bur.st
Fri Mar 23 18:32:46 PDT 2007
On Fri, Mar 23, 2007 at 04:08:49PM -0400, Norman Ramsey wrote:
> > On Sat, 10.03.07 12:20, Norman Ramsey (nr at eecs.harvard.edu) wrote:
> > > With a recent update, it now takes me 10 or 15 seconds to do any opeation
> > > involving ssh. Using strace, I believe I've tracked the problem
> > > to avahi's lair. Here's a fragment of an strace: the NSS opens
> > > libness_mdns4, which connects to an avahi-daemon socket and asks it to
> > > resolve a dotted-decimal address. It takes 5 seconds to time out
> > > (i.e., it takes 5 seconds for the read() to complete). For reasons I
> > > don't understand, ssh does this lookup *twice* to make a connection.
> > > Result: every little remote cvs operation comes with a 10-second
> > > delay. This is driving me crazy; can anyone think of a workaround?
> > If nsswitch.conf is configured correctly (and yours appears to be),
> > this timeout should only happen if no DNS reverse name is configured
> > for that IP address, and neither a mDNS reverse name.
> Very odd. There is a DNS server built into my firewall and this is
> probably causing the problem.
> > There are several way to work around this:
> > 1) Remove the final "mdns4" from the nsswitch.conf line. This will
> > disable reverse mDNS lookups for all IP addresses outside the
> > 169.254.0.0/16 range.
> If I remove mdns4, will the earlier mdns4_minimal be sufficient to
> identify hosts in the .local domain on the same LAN segment?
Yes mdns4_minimal only attempts to resolve .local hostnames and reverse
DNS in the 169.254.0.0 range
> > The current default behaviour does its best to avoid this timeout, by
> > putting the DNS lookups first, but you're still bitten because your
> > DNS doesn't include proper mappings for this IP address.
> Yes. I blame Bill Gates (the firewall is made by Microsoft).
> Thanks so much for the workarounds!
> avahi mailing list
> avahi at lists.freedesktop.org
More information about the avahi