[ovs-dev] [PATCH v3] ovn-nbctl: Fix the ovn-nbctl test "LBs - daemon" which fails during rpm build

Ben Pfaff blp at ovn.org
Wed Oct 31 22:59:34 UTC 2018


OK, that answers the first question.  What about if no DNS servers are
available; what does the resolver do in that case?

On Wed, Oct 31, 2018 at 03:24:13PM -0700, Yifeng Sun wrote:
> Hi Ben,
> 
> The dns resolving depends on libunbound's ub_resolve, which, from
> Numan's experience as well as my reading on its documentation,
> doesn't support timeout. I agree there is a bug and we should fix it.
> 
> Thanks,
> Yifeng
> 
> On Wed, Oct 31, 2018 at 1:59 PM Ben Pfaff <blp at ovn.org> wrote:
> 
> > On Thu, Oct 25, 2018 at 03:27:41PM +0530, nusiddiq at redhat.com wrote:
> > > From: Numan Siddique <nusiddiq at redhat.com>
> > >
> > > When 'make check' is called by the mock rpm build (which disables
> > networking),
> > > the test "ovn-nbctl: LBs - daemon" fails when it runs the command
> > > "ovn-nbctl lb-add lb0 30.0.0.1a 192.168.10.10:80,192.168.10.20:80".
> > ovn-nbctl
> > > extracts the vip by calling the socket util function
> > 'inet_parse_active()',
> > > and this function blocks when libunbound function ub_resolve() is called
> > > further down. ub_resolve() is a blocking function without timeout and
> > all the
> > > ovs/ovn utilities use this function.
> > >
> > > As reported by Timothy Redaelli, the issue can also be reproduced by
> > running
> > > the below commands
> > >
> > > $ sudo unshare -mn -- sh -c 'ip addr add dev lo 127.0.0.1 && \
> > >   mount --bind /dev/null /etc/resolv.conf && runuser $SUDO_USER'
> > > $ make sandbox SANDBOXFLAGS="--ovn"
> > > $ ovn-nbctl -vsocket_util:off lb-add lb0 30.0.0.1a \
> > >   192.168.10.10:80,192.168.10.20:80
> > >
> > > To address this issue, this patch adds a new function -
> > inet_parse_ip_addr_and_port()
> > > which expects IP:[port] address in the 'target_' argument and disables
> > resolving
> > > the host. This new function is now used in ovn-northd, ovn-nbctl and
> > ovn-trace.
> > > It is fine to use this function as load balancer VIP cannot be a
> > hostname.
> > >
> > > Reported-by: Timothy Redaelli <tredaelli at redhat.com>
> > > Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=1641672
> > > Tested-by: Timothy Redaelli <tredaelli at redhat.com>
> > > Signed-off-by: Numan Siddique <nusiddiq at redhat.com>
> >
> > I have multiple thoughts here.
> >
> > First, if the resolver in OVS never times out, then that seems like a
> > bug in the OVS resolver.  Yifeng, you wrote the DNS code.  Is it true
> > that it never times out?  If so, should we fix that.
> >
> > Second, about the mock RPM build with disabled networking.  Does this
> > environment have a /etc/resolv.conf that specifies a DNS server?  If it
> > does, then that seems like a bug in the build environment.  If it does
> > not, then that seems like a bug in our DNS resolver code, because DNS
> > resolution should immediately fail if no DNS servers are available.
> >
> > Third, again about naming.  If we are going to have two functions that
> > act similarly, with the only difference being that one resolves DNS
> > names and the other does not, then the naming should reflect that
> > clearly.  It still isn't obvious to me with the new names.
> >
> > Thanks,
> >
> > Ben.
> >


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