Continuing problems in a bridged VNET setup

[Marko Zec]

Perhaps you could ditch if_bridge(4) and epair(4), and try ng_eiface(4)
with ng_bridge(4) instead?  Works rock-solid 24/7 here on 11.2 / 11.3.

Marko

On Fri, 20 Dec 2019 11:19:24 +0100
"Patrick M. Hausen" <hausen at punkt.de> wrote:

> Hi all,
> 
> we still experience occasional network outages in production,
> yet have not been able to find the root cause.
> 
> We run around 50 servers with VNET jails. some of them with
> a handful, the busiest ones with 50 or more jails each.
> 
> Every now and then the jails are not reachable over the net,
> anymore. The server itself is up and running, all jails are
> up and running, one can ssh to the server but none of the
> jails can communicate over the network.
> 
> There seems to be no pattern to the time of occurrance except
> that more jails on one system make it "more likely".
> Also having more than one bridge, e.g. for private networks
> between jails seems to increase the probability.
> When a server shows the problem it tends to get into the state
> rather frequently, a couple of hours inbetween. Then again
> most servers run for weeks without exhibiting the problem.
> That's what makes it so hard to reproduce. The last couple of
> days one system was failing regularly until we reduced the number
> of jails from around 80 to around 50. Now it seems stable again.
> 
> I have a test system with lots of jails that I work with gatling
> that did not show a single failure so far :-(
> 
> 
> Setup:
> 
> All jails are iocage jails with VNET interfaces. They are
> connected to at least one bridge that starts with the
> physical external interface as a member and gets jails'
> epair interfaces added as they start up. All jails are managed
> by iocage.
> 
> ifconfig_igb0="-rxcsum -rxcsum6 -txcsum -txcsum6 -vlanhwtag
> -vlanhwtso up" cloned_interfaces="bridge0"
> ifconfig_bridge0_name="inet0"
> ifconfig_inet0="addm igb0 up"
> ifconfig_inet0_ipv6="inet6 <host-address>/64 auto_linklocal"
> 
> $ iocage get interfaces vpro0087
> vnet0:inet0
> 
> $ ifconfig inet0
> inet0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0
> mtu 1500 ether 90:1b:0e:63:ef:51
> 	inet6 fe80::921b:eff:fe63:ef51%inet0 prefixlen 64 scopeid 0x4
> 	inet6 <host-address> prefixlen 64
> 	nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
> 	groups: bridge
> 	id 00:00:00:00:00:00 priority 32768 hellotime 2 fwddelay 15
> 	maxage 20 holdcnt 6 proto rstp maxaddr 2000 timeout 1200
> 	root id 00:00:00:00:00:00 priority 32768 ifcost 0 port 0
> 	member: vnet0.4 flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
> 	        ifmaxaddr 0 port 7 priority 128 path cost 2000
> 	member: vnet0.1 flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
> 	        ifmaxaddr 0 port 6 priority 128 path cost 2000
> 	member: igb0 flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
> 	        ifmaxaddr 0 port 1 priority 128 path cost 2000000
> 
> 
> What we tried:
> 
> At first we suspected the bridge to become "wedged" somehow. This was
> corroborated by talking to various people at devsummits and EuroBSDCon
> with Kristof Provost specifically suggesting that if_bridge was
> still under giant lock and there might be a problem here that the
> lock is not released under some race condition and then the entire
> bridge subsystem would be stalled. That sounds plausible given the
> random occurrance.
> 
> But I think we can rule out that one, because:
> 
> - ifconfig up/down does not help
> - the host is still communicating fine over the same bridge interface
> - tearing down the bridge, kldunload (!) of if_bridge.ko followed by
>   a new kldload and reconstructing the members with `ifconfig addm`
>   does not help, either
> - only a host reboot restores function
> 
> Finally I created a not iocage managed jail on the problem host.
> Please ignore the `iocage` in the path, I used it to populate the
> root directory. But it is not started by iocage at boot time and
> the manual config is this:
> 
> testjail {
>         host.hostname = "testjail";   # hostname
>         path = "/iocage/jails/testjail/root";     # root directory
>         exec.clean;
>         exec.system_user = "root";
>         exec.jail_user = "root";
>         vnet; 
> 	vnet.interface = "epair999b";
>         exec.prestart += "ifconfig epair999 create; ifconfig
> epair999a inet6 2A00:B580:8000:8000::1/64 auto_linklocal";
> exec.poststop += "sleep 2; ifconfig epair999a destroy; sleep 2"; 
>         # Standard stuff
>         exec.start += "/bin/sh /etc/rc";
>         exec.stop = "/bin/sh /etc/rc.shutdown";
>         exec.consolelog = "/var/log/jail_testjail_console.log";
>         mount.devfs;          #mount devfs
>         allow.raw_sockets;    #allow ping-pong
>         devfs_ruleset="4";    #devfs ruleset for this jail
> }
> 
> $ cat /iocage/jails/testjail/root/etc/rc.conf
> hostname="testjail"
> 
> ifconfig_epair999b_ipv6="inet6 2A00:B580:8000:8000::2/64
> auto_linklocal"
> 
> When I do `service jail onestart testjail` I can then ping6 the jail
> from the host and the host from the jail. As you can see the
> if_bridge is not involved in this traffic.
> 
> When the host is in the wedged state and I start this testjail the
> same way, no communication across the epair interface is possible.
> 
> To me this seems to indicate that not the bridge but all epair
> interfaces stop working at the very same time.
> 
> 
> OS is RELENG_11_3, hardware and specifically network adapters vary,
> we have igb, ix, ixl, bnxt ...
> 
> 
> Does anyone have a suggestion what diagnostic measures could help to
> pinpoint the culprit? The random occurrance and the fact that the
> problem seems to prefer the production environment only makes this a
> real pain ...
> 
> 
> Thanks and kind regards,
> Patrick