pmtu.sh from net in ubuntu_kernel_selftests failed on F-PPC

[Po-Hsu Lin]

Issue found on modoc / baltar with Focal 5.4.0-34.38

TEST: ipv6: cleanup of cached exceptions - nexthop objects [FAIL]

 # selftests: net: pmtu.sh
 # TEST: ipv4: PMTU exceptions [ OK ]
 # TEST: ipv4: PMTU exceptions - nexthop objects [ OK ]
 # TEST: ipv6: PMTU exceptions [ OK ]
 # TEST: ipv6: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv4 over vxlan4: PMTU exceptions [ OK ]
 # TEST: IPv4 over vxlan4: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv6 over vxlan4: PMTU exceptions [ OK ]
 # TEST: IPv6 over vxlan4: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv4 over vxlan6: PMTU exceptions [ OK ]
 # TEST: IPv4 over vxlan6: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv6 over vxlan6: PMTU exceptions [ OK ]
 # TEST: IPv6 over vxlan6: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv4 over geneve4: PMTU exceptions [ OK ]
 # TEST: IPv4 over geneve4: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv6 over geneve4: PMTU exceptions [ OK ]
 # TEST: IPv6 over geneve4: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv4 over geneve6: PMTU exceptions [ OK ]
 # TEST: IPv4 over geneve6: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv6 over geneve6: PMTU exceptions [ OK ]
 # TEST: IPv6 over geneve6: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv4 over fou4: PMTU exceptions [ OK ]
 # TEST: IPv4 over fou4: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv6 over fou4: PMTU exceptions [ OK ]
 # TEST: IPv6 over fou4: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv4 over fou6: PMTU exceptions [ OK ]
 # TEST: IPv4 over fou6: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv6 over fou6: PMTU exceptions [ OK ]
 # TEST: IPv6 over fou6: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv4 over gue4: PMTU exceptions [ OK ]
 # TEST: IPv4 over gue4: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv6 over gue4: PMTU exceptions [ OK ]
 # TEST: IPv6 over gue4: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv4 over gue6: PMTU exceptions [ OK ]
 # TEST: IPv4 over gue6: PMTU exceptions - nexthop objects [ OK ]
 # TEST: IPv6 over gue6: PMTU exceptions [ OK ]
 # TEST: IPv6 over gue6: PMTU exceptions - nexthop objects [ OK ]
 # TEST: vti6: PMTU exceptions [ OK ]
 # TEST: vti4: PMTU exceptions [ OK ]
 # TEST: vti4: default MTU assignment [ OK ]
 # TEST: vti6: default MTU assignment [ OK ]
 # TEST: vti4: MTU setting on link creation [ OK ]
 # TEST: vti6: MTU setting on link creation [ OK ]
 # TEST: vti6: MTU changes on link changes [ OK ]
 # TEST: ipv4: cleanup of cached exceptions [ OK ]
 # TEST: ipv4: cleanup of cached exceptions - nexthop objects [ OK ]
 # TEST: ipv6: cleanup of cached exceptions [ OK ]
 # TEST: ipv6: cleanup of cached exceptions - nexthop objects [FAIL]
 # can't delete veth device in a timely manner, PMTU dst likely leaked
 # TEST: ipv4: list and flush cached exceptions [ OK ]
 # TEST: ipv4: list and flush cached exceptions - nexthop objects [ OK ]
 # TEST: ipv6: list and flush cached exceptions [ OK ]
 # TEST: ipv6: list and flush cached exceptions - nexthop objects [ OK ]
 not ok 16 selftests: net: pmtu.sh # exit=1

This issue does not exist in 5.4.0-33.37 on node baltar
 # TEST: ipv6: cleanup of cached exceptions - nexthop objects [ OK ]

[Po-Hsu Lin (cypressyew)]

Verified with 5.4.0-33 on node "baltar", this issue does not exist. And it can be reproduced with 5.4.0-34