Re: [libvirt] [PATCH] util: set error if DAD is not finished

On 10/29/2015 08:32 AM, Maxim Perevedentsev wrote: > On 10/29/2015 12:47 PM, Luyao Huang wrote: >> If DAD not finished in 5 seconds, user will get an >> unknown error like this: >> >> # virsh net-start ipv6 >> error: Failed to start network ipv6 >> error: An error occurred, but the cause is unknown >> >> Call virReportError to set an error. >> >> Signed-off-by: Luyao Huang <lhuang(a)redhat.com&gt; >> --- >> I found the DAD will take 7 seconds >> on my machine, and i cannot create a network which >> use ipv6 now :( . Can we offer a way allow user to change this >> timeout ? maybe add a configuration file option in >> libvirtd.conf. > > Could you please send the related records of your sysctl -a? > Max DAD timeout should be > rand() % net.ipv6.conf.default.router_solicitation_delay + > net.ipv6.conf.default.dad_transmits * > net.ipv6.neigh.default.retrans_time_ms > I wonder whether my calculations were faulty or it is your specific > configuration. > On my system, these are set to 1, 1, and 1000, and I've found that DAD takes something between 5.7 and 6.8 seconds to complete (it was at the lower end with a single IP address, and at the high end with 70 IP addresses (or also with 20 IPs, so I don't think it's going to get substantially higher). (Too bad I didn't do this *before* I pushed, rather than relying on a successful build and reports of proper operation on your system :-/) Based on that, I think it makes sense to push a patch that sets the timeout to 20 seconds (and push Luyao's patch ragardless). Since the timeout is meant to catch an "infinite" wait, I think 20 seconds is okay; I don't want to add yet another tunable parameter unless we really need to.