[LTP] [PATCH] netns: Fix duplicate address detection (dad)

[Dan Rue]

On Wed, Nov 22, 2017 at 03:40:10PM +0300, Alexey Kodanev wrote:
> On 11/22/2017 12:36 AM, Dan Rue wrote:
> > Symptoms (+ command, error):
> >     netns_comm_ip_ipv6_ioctl:
> >         + ip netns exec tst_net_ns1 ping6 -q -c2 -I veth1 fd00::2
> >         connect: Cannot assign requested address
> >
> >     netns_comm_ip_ipv6_netlink:
> >         + ip netns exec tst_net_ns0 ping6 -q -c2 -I veth0 fd00::3
> >         connect: Cannot assign requested address
> >
> >     netns_comm_ns_exec_ipv6_ioctl:
> >         + ns_exec 6689 net ping6 -q -c2 -I veth0 fd00::3
> >         connect: Cannot assign requested address
> >
> >     netns_comm_ns_exec_ipv6_netlin:
> >         + ns_exec 6891 net ping6 -q -c2 -I veth0 fd00::3
> >         connect: Cannot assign requested address
> >
> > The error is coming from ping6, which is trying to get an IP address for
> > veth0 (due to -I veth0), but cannot, because the interface is not
> > immediately available due to dad. The existing code to disable dad is
> > disables it for the virtual interfaces, but it needs to be disabled for
> > all interfaces in the network namespace to be effective.
> 
> 
> Looks like Linux 4.14 specific and it's fixed with the following patch:
> 094009531612 ("ipv6: set all.accept_dad to 0 by default")
> 
> I'm not sure if we need to change the test-case if we want to catch
> similar bug with backward compatibility...

Good find! I'm happy withdrawing this patch.

> 
> Thanks,
> Alexey
> 
> > Also, changed it to use sysctl -w because I think it is a little cleaner
> > to read and understand.
> >
> > Lastly, dropped setting accept_ra. It does not seem to be necessary to
> > disable.
> >
> > Signed-off-by: Dan Rue <dan.rue@linaro.org>
> > ---
> >  testcases/kernel/containers/netns/netns_helper.sh | 10 ++++------
> >  1 file changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/testcases/kernel/containers/netns/netns_helper.sh b/testcases/kernel/containers/netns/netns_helper.sh
> > index a95cdf206..95add0544 100755
> > --- a/testcases/kernel/containers/netns/netns_helper.sh
> > +++ b/testcases/kernel/containers/netns/netns_helper.sh
> > @@ -256,12 +256,10 @@ netns_set_ip()
> >  	# there is no other host with the same address, the address is
> >  	# considered to be "tentative" (attempts to bind() to the address fail
> >  	# with EADDRNOTAVAIL) which may cause problems for tests using ipv6.
> > -	echo 0 | $NS_EXEC $NS_HANDLE0 $NS_TYPE \
> > -		tee /proc/sys/net/ipv6/conf/veth0/accept_dad \
> > -		/proc/sys/net/ipv6/conf/veth0/accept_ra >/dev/null
> > -	echo 0 | $NS_EXEC $NS_HANDLE1 $NS_TYPE \
> > -		tee /proc/sys/net/ipv6/conf/veth1/accept_dad \
> > -		/proc/sys/net/ipv6/conf/veth1/accept_ra >/dev/null
> > +	$NS_EXEC $NS_HANDLE0 $NS_TYPE sysctl -w net.ipv6.conf.all.accept_dad=0
> > +	$NS_EXEC $NS_HANDLE0 $NS_TYPE sysctl -w net.ipv6.conf.veth0.accept_dad=0
> > +	$NS_EXEC $NS_HANDLE1 $NS_TYPE sysctl -w net.ipv6.conf.all.accept_dad=0
> > +	$NS_EXEC $NS_HANDLE1 $NS_TYPE sysctl -w net.ipv6.conf.veth1.accept_dad=0