avoid-v4-udp-ports ineffective? (BIND 9.8.1-P1)

[Mark Andrews]

In message <4B588336-2DE9-45BD-87EC-98C04B83C660 at columbia.edu>, David Coulthart writes:
> On Nov 17, 2011, at 6:28 PM, Mark Andrews wrote:
> > In message <201111171600.pAHG0uCW011627 at scramble.Princeton.EDU>, Irwin =
> Tillman writes:
> >> It appears that named is trying to use ports I've mentioned in =
> avoid-v4-udp-ports.
> >>=20
> >> Platform: BIND 9.8.1-P1 on Solaris 10 / SPARC
> >>=20
> >> On some of the ports which BIND might otherwise choose to use,=20
> >> I have other daemons running and/or the OS treats the ports
> >> as privileged.  To keep named from trying to use those ports, I have
> >> in named.conf:
> >>=20
> >> options {
> >>    ...
> >>    # there is no use-v4-udp-ports statement.
> >>    avoid-v4-udp-ports { 1812; 1813; 2049; 4045; };
> >>    # I don't speak v6.
> >> };
> >>=20
> >> When I upgraded from BIND 9.7.3-P3 to 9.8.1-P1, I began seeing in the =
> log:
> >>=20
> >> named[9185]: dispatch: warning: dispatch 42d950: open_socket(::#2049) =
> -> permission denied: continuing
> >> named[9185]: dispatch: warning: dispatch 42d950: open_socket(::#4045) =
> -> permission denied: continuing
> >>=20
> >> ...which suggests to me that BIND is trying to use ports I specified =
> in avoid-v4-udp-ports.
> >>=20
> >>=20
> >> Checking get_dispsocket() in ./lib/dns/dispatch.c, I see that a =
> difference
> >> between 9.7.3-P3 and 9.8.1-P1 is that 9.8.1-P1 logs a warning when an =
> attempt
> >> to open the socket returns ISC_R_NOPERM (perhaps the result of bind() =
> returning EACCESS ?),
> >> while 9.7.3-P3 didn't log the warning.  The warning is new.
> >> When confronted with the error, both versions proceed to pick another =
> port to try again.=20
> >> So I don't know if the older version was also trying to use these =
> ports and encountering
> >> the same error.
> >>=20
> >> I imagine Solaris might return EACCESS because:
> >>=20
> >> % ndd /dev/udp udp_extra_priv_ports
> >> 2049=20
> >> 4045=20
> >>=20
> >>=20
> >> I don't understand why named would try to use these ports in the =
> first
> >> place as they appear in avoid-v4-udp-ports.
> >=20
> > 	The "::" in the log message is the IPv6 equivalent of 0.0.0.0 in =
> IPv4.
> > 	You machine *is* dual stacked even if it only has IPv6 on =
> loopback.
> 
> I noticed this same log message on our Solaris 9 servers and I don't see =
> IPv6 enabled on any of our interfaces, including loopback:
> 
> $ /sbin/ifconfig -a inet6
> $ /sbin/ifconfig -a inet=20
> lo0: flags=3D1000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4> mtu 8232 index =
> 1
> 	inet 127.0.0.1 netmask ff000000=20
> bge0: flags=3D1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 =
> index 2
> 	inet 128.59.59.92 netmask ffffff00 broadcast 128.59.59.255
> bge0:10: flags=3D1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 =
> index 2
> 	inet 128.59.59.70 netmask ffffff00 broadcast 128.59.59.255
> 
> It's not a big deal for me as it doesn't happen very often (& can be =
> easily avoided by setting a matching avoid-v6-udp-ports), but it did =
> surprise me.
> 
> Thanks Irwin for the tip on ndd.  I had to avoid those exact same ports =
> & I couldn't find a process bound to port 2049 causing it.

A bound port gives a different error code when you attempt to bind
to it a second time and havn't set the right socket options.  We
expect that error code.  We also expect EPERM but log it.

-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org