Stabilize MTU validation after PMTU cache updates#3692
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Flush the probe's IPv4/IPv6 route cache between under-MTU and PTB checks so cached path MTU does not turn the next oversized ping into a local "message too long" failure instead of a fresh Frag Needed / Packet Too Big from the DUT. Co-authored-by: Cursor <cursoragent@cursor.com>
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Summary
tests/integration/initial/04-mtu.yml.wait: ping_longon the IPv6 under-MTU check for the same path.Why
After an oversized DF ping, Linux/cEOS learns and caches the path MTU. The next oversized ping then fails locally with "message too long" instead of eliciting a fresh ICMP unreachable from the DUT, so the PTB validation becomes flaky or fails even when the DUT is correct. Flushing the cache forces a new discovery attempt and keeps the test asserting DUT behavior.
Test plan
tests/integration/initial/04-mtu.ymlagainst a DUT that previously showed intermittent PTB failuresv4_1400_ptb/v6_1400_ptbstill match Frag Needed / Packet Too Big (not local message-too-long)Made with Cursor