Prosody would let the stream opening timeout if it receives it in more
than one TCP packet, which seems like a bug.
The behaviour was highly non-deterministic, a release build would almost
always (but not always) succeed to connect to a localhost Prosody, a
debug build would almost always (but not always) fail, and
RUST_LOG=trace would make any build fail to connect, as would strace.
My theory is that successful runs rely on the kernel merging all five
TCP packets in a single one, and any tracing would add sufficient delay
in-between to let it send every packet on its own.
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