fib_tests.sh in ubuntu_kernel_selftests failed with IPv4 mangling tests Connection check - server side

Issue spotted on:
  * F-gke-5.15 5.15.0-1029.34~20.04.1 on instance e2-highcpu-8
  * J-oracle 5.15.0-1032.38 in instance VM.Standard.E3.Flex-4c.8m

Test failed with:
  # TEST: Connection check - server side [FAIL]

It seems to be flaky, with F-gke-5.15 this has passed with e2-highcpu-8 on 3rd attempt.

Test log:
  Running 'make run_tests -C net TEST_PROGS=fib_tests.sh TEST_GEN_PROGS='' TEST_CUSTOM_PROGS='''
  make: Entering directory '/home/ubuntu/autotest/client/tmp/ubuntu_kernel_selftests/src/linux/tools/testing/selftests/net'
  make --no-builtin-rules ARCH=x86 -C ../../../.. headers_install
  make[1]: Entering directory '/home/ubuntu/autotest/client/tmp/ubuntu_kernel_selftests/src/linux'
    INSTALL ./usr/include
  make[1]: Leaving directory '/home/ubuntu/autotest/client/tmp/ubuntu_kernel_selftests/src/linux'
  TAP version 13
  1..1
  # selftests: net: fib_tests.sh
  #
  # Single path route test
  # Start point
  # TEST: IPv4 fibmatch [ OK ]
  # TEST: IPv6 fibmatch [ OK ]
  # Nexthop device deleted
  # TEST: IPv4 fibmatch - no route [ OK ]
  # TEST: IPv6 fibmatch - no route [ OK ]
  #
  # Multipath route test
  # Start point
  # TEST: IPv4 fibmatch [ OK ]
  # TEST: IPv6 fibmatch [ OK ]
  # One nexthop device deleted
  # TEST: IPv4 - multipath route removed on delete [ OK ]
  # TEST: IPv6 - multipath down to single path [ OK ]
  # Second nexthop device deleted
  # TEST: IPv6 - no route [ OK ]
  #
  # Single path, admin down
  # Start point
  # TEST: IPv4 fibmatch [ OK ]
  # TEST: IPv6 fibmatch [ OK ]
  # Route deleted on down
  # TEST: IPv4 fibmatch [ OK ]
  # TEST: IPv6 fibmatch [ OK ]
  #
  # Admin down multipath
  # Verify start point
  # TEST: IPv4 fibmatch [ OK ]
  # TEST: IPv6 fibmatch [ OK ]
  # One device down, one up
  # TEST: IPv4 fibmatch on down device [ OK ]
  # TEST: IPv6 fibmatch on down device [ OK ]
  # TEST: IPv4 fibmatch on up device [ OK ]
  # TEST: IPv6 fibmatch on up device [ OK ]
  # TEST: IPv4 flags on down device [ OK ]
  # TEST: IPv6 flags on down device [ OK ]
  # TEST: IPv4 flags on up device [ OK ]
  # TEST: IPv6 flags on up device [ OK ]
  # Other device down and up
  # TEST: IPv4 fibmatch on down device [ OK ]
  # TEST: IPv6 fibmatch on down device [ OK ]
  # TEST: IPv4 fibmatch on up device [ OK ]
  # TEST: IPv6 fibmatch on up device [ OK ]
  # TEST: IPv4 flags on down device [ OK ]
  # TEST: IPv6 flags on down device [ OK ]
  # TEST: IPv4 flags on up device [ OK ]
  # TEST: IPv6 flags on up device [ OK ]
  # Both devices down
  # TEST: IPv4 fibmatch [ OK ]
  # TEST: IPv6 fibmatch [ OK ]
  #
  # Local carrier tests - single path
  # Start point
  # TEST: IPv4 fibmatch [ OK ]
  # TEST: IPv6 fibmatch [ OK ]
  # TEST: IPv4 - no linkdown flag [ OK ]
  # TEST: IPv6 - no linkdown flag [ OK ]
  # Carrier off on nexthop
  # TEST: IPv4 fibmatch [ OK ]
  # TEST: IPv6 fibmatch [ OK ]
  # TEST: IPv4 - linkdown flag set [ OK ]
  # TEST: IPv6 - linkdown flag set [ OK ]
  # Route to local address with carrier down
  # TEST: IPv4 fibmatch [ OK ]
  # TEST: IPv6 fibmatch [ OK ]
  # TEST: IPv4 linkdown flag set [ OK ]
  # TEST: IPv6 linkdown flag set [ OK ]
  #
  # Single path route carrier test
  # Start point
  # TEST: IPv4 fibmatch [ OK ]
  # TEST: IPv6 fibmatch [ OK ]
  # TEST: IPv4 no linkdown flag [ OK ]
  # TEST: IPv6 no linkdown flag [ OK ]
  # Carrier down
  # TEST: IPv4 fibmatch [ OK ]
  # TEST: IPv6 fibmatch [ OK ]
  # TEST: IPv4 linkdown flag set [ OK ]
  # TEST: IPv6 linkdown flag set [ OK ]
  # Second address added with carrier down
  # TEST: IPv4 fibmatch [ OK ]
  # TEST: IPv6 fibmatch [ OK ]
  # TEST: IPv4 linkdown flag set [ OK ]
  # TEST: IPv6 linkdown flag set [ OK ]
  #
  # IPv4 nexthop tests
  # <<< write me >>>
  #
  # IPv6 nexthop tests
  # TEST: Directly connected nexthop, unicast address [ OK ]
  # TEST: Directly connected nexthop, unicast address with device [ OK ]
  # TEST: Gateway is linklocal address [ OK ]
  # TEST: Gateway is linklocal address, no device [ OK ]
  # TEST: Gateway can not be local unicast address [ OK ]
  # TEST: Gateway can not be local unicast address, with device [ OK ]
  # TEST: Gateway can not be a local linklocal address [ OK ]
  # TEST: Gateway can be local address in a VRF [ OK ]
  # TEST: Gateway can be local address in a VRF, with device [ OK ]
  # TEST: Gateway can be local linklocal address in a VRF [ OK ]
  # TEST: Redirect to VRF lookup [ OK ]
  # TEST: VRF route, gateway can be local address in default VRF [ OK ]
  # TEST: VRF route, gateway can not be a local address [ OK ]
  # TEST: VRF route, gateway can not be a local addr with device [ OK ]
  #
  # FIB rule with suppress_prefixlength
  # TEST: FIB rule suppress test [ OK ]
  #
  # IPv6 route add / append tests
  # TEST: Attempt to add duplicate route - gw [ OK ]
  # TEST: Attempt to add duplicate route - dev only [ OK ]
  # TEST: Attempt to add duplicate route - reject route [ OK ]
  # TEST: Append nexthop to existing route - gw [ OK ]
  # TEST: Add multipath route [ OK ]
  # TEST: Attempt to add duplicate multipath route [ OK ]
  # TEST: Route add with different metrics [ OK ]
  # TEST: Route delete with metric [ OK ]
  #
  # IPv6 route replace tests
  # TEST: Single path with single path [ OK ]
  # TEST: Single path with multipath [ OK ]
  # TEST: Single path with single path via multipath attribute [ OK ]
  # TEST: Invalid nexthop [ OK ]
  # TEST: Single path - replace of non-existent route [ OK ]
  # TEST: Multipath with multipath [ OK ]
  # TEST: Multipath with single path [ OK ]
  # TEST: Multipath with single path via multipath attribute [ OK ]
  # TEST: Multipath with dev-only [ OK ]
  # TEST: Multipath - invalid first nexthop [ OK ]
  # TEST: Multipath - invalid second nexthop [ OK ]
  # TEST: Multipath - replace of non-existent route [ OK ]
  #
  # IPv4 route add / append tests
  # TEST: Attempt to add duplicate route - gw [ OK ]
  # TEST: Attempt to add duplicate route - dev only [ OK ]
  # TEST: Attempt to add duplicate route - reject route [ OK ]
  # TEST: Add new nexthop for existing prefix [ OK ]
  # TEST: Append nexthop to existing route - gw [ OK ]
  # TEST: Append nexthop to existing route - dev only [ OK ]
  # TEST: Append nexthop to existing route - reject route [ OK ]
  # TEST: Append nexthop to existing reject route - gw [ OK ]
  # TEST: Append nexthop to existing reject route - dev only [ OK ]
  # TEST: add multipath route [ OK ]
  # TEST: Attempt to add duplicate multipath route [ OK ]
  # TEST: Route add with different metrics [ OK ]
  # TEST: Route delete with metric [ OK ]
  #
  # IPv4 route replace tests
  # TEST: Single path with single path [ OK ]
  # TEST: Single path with multipath [ OK ]
  # TEST: Single path with reject route [ OK ]
  # TEST: Single path with single path via multipath attribute [ OK ]
  # TEST: Invalid nexthop [ OK ]
  # TEST: Single path - replace of non-existent route [ OK ]
  # TEST: Multipath with multipath [ OK ]
  # TEST: Multipath with single path [ OK ]
  # TEST: Multipath with single path via multipath attribute [ OK ]
  # TEST: Multipath with reject route [ OK ]
  # TEST: Multipath - invalid first nexthop [ OK ]
  # TEST: Multipath - invalid second nexthop [ OK ]
  # TEST: Multipath - replace of non-existent route [ OK ]
  # TEST: Cached route removed from VRF port device [ OK ]
  #
  # IPv6 prefix route tests
  # TEST: Default metric [ OK ]
  # TEST: User specified metric on first device [ OK ]
  # TEST: User specified metric on second device [ OK ]
  # TEST: Delete of address on first device [ OK ]
  # TEST: Modify metric of address [ OK ]
  # TEST: Prefix route removed on link down [ OK ]
  # TEST: Prefix route with metric on link up [ OK ]
  # TEST: Set metric with peer route on local side [ OK ]
  # TEST: Set metric with peer route on peer side [ OK ]
  # TEST: Modify metric and peer address on local side [ OK ]
  # TEST: Modify metric and peer address on peer side [ OK ]
  #
  # IPv4 prefix route tests
  # TEST: Default metric [ OK ]
  # TEST: User specified metric on first device [ OK ]
  # TEST: User specified metric on second device [ OK ]
  # TEST: Delete of address on first device [ OK ]
  # TEST: Modify metric of address [ OK ]
  # TEST: Prefix route removed on link down [ OK ]
  # TEST: Prefix route with metric on link up [ OK ]
  # TEST: Modify metric of .0/24 address [ OK ]
  # TEST: Set metric of address with peer route [ OK ]
  # TEST: Modify metric and peer address for peer route [ OK ]
  #
  # IPv6 routes with metrics
  # TEST: Single path route with mtu metric [ OK ]
  # TEST: Multipath route via 2 single routes with mtu metric on first [ OK ]
  # TEST: Multipath route via 2 single routes with mtu metric on 2nd [ OK ]
  # TEST: MTU of second leg [ OK ]
  # TEST: Multipath route with mtu metric [ OK ]
  # TEST: Using route with mtu metric [ OK ]
  # TEST: Invalid metric (fails metric_convert) [ OK ]
  #
  # IPv4 route add / append tests
  # TEST: Single path route with mtu metric [ OK ]
  # TEST: Multipath route with mtu metric [ OK ]
  # TEST: Using route with mtu metric [ OK ]
  # TEST: Invalid metric (fails metric_convert) [ OK ]
  #
  # IPv4 route with IPv6 gateway tests
  # TEST: Single path route with IPv6 gateway [ OK ]
  # TEST: Single path route with IPv6 gateway - ping [ OK ]
  # TEST: Single path route delete [ OK ]
  # TEST: Multipath route add - v6 nexthop then v4 [ OK ]
  # TEST: Multipath route delete - nexthops in wrong order [ OK ]
  # TEST: Multipath route delete exact match [ OK ]
  # TEST: Multipath route add - v4 nexthop then v6 [ OK ]
  # TEST: Multipath route delete - nexthops in wrong order [ OK ]
  # TEST: Multipath route delete exact match [ OK ]
  #
  # IPv4 rp_filter tests
  # TEST: rp_filter passes local packets [ OK ]
  # TEST: rp_filter passes loopback packets [ OK ]
  #
  # IPv4 delete address route tests
  # Regular FIB info
  # TEST: Route removed from VRF when source address deleted [ OK ]
  # TEST: Route in default VRF not removed [ OK ]
  # TEST: Route removed in default VRF when source address deleted [ OK ]
  # TEST: Route in VRF is not removed by address delete [ OK ]
  # Identical FIB info with different table ID
  # TEST: Route removed from VRF when source address deleted [ OK ]
  # TEST: Route in default VRF not removed [ OK ]
  # TEST: Route removed in default VRF when source address deleted [ OK ]
  # TEST: Route in VRF is not removed by address delete [ OK ]
  # Table ID 0
  # TEST: Route removed in default VRF when source address deleted [ OK ]
  #
  # IPv4 mangling tests
  # TEST: Connection with correct parameters [ OK ]
  # TEST: Connection with incorrect parameters [ OK ]
  # TEST: Connection with correct parameters - mangling [ OK ]
  # TEST: Connection with correct parameters - no mangling [ OK ]
  # TEST: Connection check - server side [FAIL]
  #
  # IPv6 mangling tests
  # TEST: Connection with correct parameters [ OK ]
  # TEST: Connection with incorrect parameters [ OK ]
  # TEST: Connection with correct parameters - mangling [ OK ]
  # TEST: Connection with correct parameters - no mangling [ OK ]
  # TEST: Connection check - server side [ OK ]
  #
  # Tests passed: 180
  # Tests failed: 1
  not ok 1 selftests: net: fib_tests.sh # exit=1