On 9/28/20 5:33 PM, Krzysztof Klimonda wrote:
> Hi,
> 

Hi Krzysztof,

> We're still doing some scale tests of OpenStack ussuri with ml2/ovn driver. 
> We've deployed 140 virtualized compute nodes, and started creating routers 
> that share single external network between them. Additionally, each router is 
> connected to a private network.
> Previously[1] we hit a problem of too many logical flows being generated per 
> router connected to the same "external" network - this put too much stress on 
> ovn-controller and ovs-vswitchd on compute nodes, and we've applied a 
> patch[2] to limit a number of logical flows created per router.
> After we dealt with that we've done more testing and created 200 routers 
> connected to single external network. After that we've noticed the following 
> logs in ovs-vswitchd.log:
> 
> ---8<---8<---8<---
> 2020-09-28T11:10:18.938Z|18401|ofproto_dpif_xlate(handler9)|WARN|over 4096 
> resubmit actions on bridge br-int while processing 
> icmp6,in_port=1,vlan_tci=0x0000,dl_src=fa:16:3e:9b:77:c3,dl_dst=33:33:00:00:00:02,ipv6_src=fe80::f816:3eff:fe9b:77c3,ipv6_dst=ff02::2,ipv6_label=0x2564e,nw_tos=0,nw_ecn=0,nw_ttl=255,icmp_type=133,icmp_code=0
> ---8<---8<---8<---
> 
> That starts happening after I create ~178 routers connected to the same 
> external network.
> 
> IPv6 RS ICMP packets are coming from the external network - that's due to the 
> fact that all virtual compute nodes have IPv6 address on their interface used 
> for the external network and are trying to discover a gateway. That's by 
> accident, and we can remove IPv6 address from that interface, however I'm 
> worried that it would just hide some bigger issue with flows generated by OVN.
> 

Is this an IPv4 cluster; are there IPv6 addresses configured on the
logical router ports connected to the external network?

If there are IPv6 addresses, do the logical router ports connected to
the external network have
Logical_Router_Port.ipv6_ra_configs.address_mode set?

If not, we could try to enhance the broadcast domain limiting code in
OVN [3] to also limit sending router solicitations only to router ports
with address_mode configured.

Regards,
Dumitru

[3]
https://github.com/ovn-org/ovn/blob/20a20439219493f27eb222617f045ba54c95ebfc/northd/ovn-northd.c#L6424

> software stack:
> 
> ovn: 20.06.2
> ovs: 2.13.1
> neutron: 16.1.0
> 
> [1] 
> http://lists.openstack.org/pipermail/openstack-discuss/2020-September/017370.html
> [2] https://review.opendev.org/#/c/752678/
> 

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