Description of problem:

While setting mixed IPv6 and IPv4 members in the same pool HTTP request hangs on reaching (SYN send without response) IPv6 member and then falls back to IPv4 member.


Version-Release number of selected component (if applicable): 
devstack master + master OVN/OVS


How reproducible:
Setup Load_Balancer with 2 members. One will be IPv4, second one IPv6.
Add both to the same Load_Balancer. Create a FIP that points on loadbalancer VIP. Try to reach FIP. Some of requests hangs and falls back to call IPv4 member.

I've already checked if IPv6 member responds at all - yes it works from different host withing the same network.


This scenario is covered by:
octavia_tempest_plugin.tests.scenario.v2.test_traffic_ops.TrafficOperationsScenarioTest.test_mixed_ipv4_ipv6_members_traffic


Created Load_Balancer:
stack@ovn-octavia-gate:~/devstack$ ovn-nbctl list load_balancer
_uuid               : 27fbcb55-ab47-404f-8b83-f41b7238bcd0
external_ids        : {enabled=True, "listener_a82a9c06-8ab1-44b0-9210-275f734b86f0"="80:pool_16a881a1-a4f1-4789-9329-40ecd9d649c1", lr_ref="neutron-2e7f04f8-fc52-4dc5-aacf-1b027f47b559", ls_refs="{\"neutron-32e5bf63-aff8-4a9e-aeb9-84482bb0017a\": 1, \"neutron-61255b5b-d513-43d5-9ea4-064960e01049\": 1, \"neutron-9e7a6391-e47a-4b89-9739-d4d8fcf02de6\": 1}", "neutron:vip"="10.1.1.6", "neutron:vip_fip"="172.24.4.249", "neutron:vip_port_id"="5ccc504c-f4bc-4f0e-8ef3-cbaf59c90d04", "pool_16a881a1-a4f1-4789-9329-40ecd9d649c1"="member_9e16bc68-a49a-4d32-96e7-c974104b2090_10.2.1.104:80,member_4b3878a8-8c4a-40af-8512-baf34f9d7b9e_fd77:1457:4cf0:26a8::3d0:80"}
name                : "e6aaf4f3-fdcc-4325-a9f4-6fe3a03c7bc9"
protocol            : tcp
vips                : {"10.1.1.6:80"="10.2.1.104:80,fd77:1457:4cf0:26a8::3d0:80", "172.24.4.249:80"="10.2.1.104:80,fd77:1457:4cf0:26a8::3d0:80"}
stack@ovn-octavia-gate:~/devstack$ 



Actual results:
IPv6 member is not reachable via LB.

Expected results:
IPv6 member responds.


Additional info: