On Thu, 28 Aug 2025 23:49:18 +0200 Florian Westphal wrote:

But all logs I saw show same scenario:
1. Failing tests have pmtu discovery off (i.e., ip fragmentation)
2. The test file is much larger than first-pass default (2M Byte)
3. peers have much larger MTUs compared to the 'network'.

These errors are very reproducible when re-running the test with
the same commandline arguments.

The timeout became much more prominent with
1d2fbaad7cd8 ("tcp: stronger sk_rcvbuf checks"): reassembled packets
typically have a skb->truesize more than double the skb length.

As that commit is intentional and pmtud-off with
large-tcp-packets-as-fragments is not normal adjust the test to use a
smaller file for the pmtu-off subtests.

While at it, add more information to pass/fail messages and
also run the dscp alteration subtest with pmtu discovery enabled.

Thank you for fixing!