On Linux, best-effort upgrade the socket's SO_TIMESTAMPING flags to
TX_SOFTWARE | OPT_ID | OPT_TSONLY after a successful Open and before the
first Echo probe. Promote the #103 error-queue foundation to production:
MSG_ERRQUEUE is drained opportunistically with a fixed per-call budget at
several natural choke points (after a probe send, before processing a
reply, before evaluating timeouts), and each automatic OPT_ID timestamp is
correlated directly with wire_seq — safe because Linux rolls back its
speculative sk_tskey increment on every send failure, wire_seq and the
kernel counter start together at every Open, and a socket can never be
reopened for a second session. The observed kernel TX wall timestamp is
retained on PendingProbe (surviving pending -> timed-out retention) as
dormant metadata only; RTT, OWD, and IPDV are unchanged and continue to use
the userspace send timestamp exclusively. Capability failure is fully
non-fatal and RX timestamping is unaffected either way. Non-Linux and
non-ancillary builds are unchanged.
It was an attempt at handling integer wraparound more cleanly keeping in mind that we have a continuous mode,
and so we can more easily reach seq > u32::MAX
However after running the numbers, if we run with a interval of 10ms, it's still gonna take ~497 days before we hit integer overflow, so for now it doesn't seem worth to have this extra logic to handle something that'll in 99.9% of cases be purely an edge case
Keeping in mind autorate usage, in sqm-autorate-rust each send loop is 500 ms by default, and the sleep is then 500 ms / 5 reflectors, so our interval is 100 ms. that means it'll take 4970 days or ~13.6 years to reach the limit. Not worth dealing with IMO
Nils Andreas Svee