Real signal delivery on Linux (observed via x86_64-musl workspace
testing) can interrupt blocking and nonblocking recv/recvmsg calls
with EINTR. Several production and test receive paths treated that as
a fatal error rather than a transient interruption:
- Client::open's blocking receive loop and Client::recv_once/
recv_available's blocking receive returned ClientError::Socket on
Interrupted instead of retrying within their existing timeout
budget.
- AsyncClient::poll_open and poll_recv's nonblocking recvmsg path
(Linux ancillary) failed the same way instead of retrying through
the existing readiness/work-budget machinery.
- The server's ancillary receive loop could terminate the listener on
an interrupted nonblocking recvmsg.
- The client's MSG_ERRQUEUE TX-timestamp drain turned an interrupted
read of optional metadata into a fatal ClientError::Socket.
- Fake-server test helpers panicked or misclassified EINTR as a
timeout instead of retrying it.
Interrupted is now retried transparently everywhere a receive can
observe it, while preserving each path's existing timing contract:
- Blocking Open reuses its already-absolute per-attempt deadline, so
interruptions resume within the same attempt without retransmitting
or extending the deadline.
- recv_once/recv_available compute one absolute deadline per logical
receive (when a timeout is configured) so repeated interruptions
cannot extend it past the configured timeout, and restore the
socket's configured read timeout afterward so a later call in the
same recv_available budget is unaffected.
- AsyncClient's poll_open already bounds its retry loop with
OPEN_POLL_WORK_BUDGET; poll_recv gains an equivalent
RECV_POLL_WORK_BUDGET, since unlike WouldBlock, Interrupted does not
clear Tokio's readiness state, so an unbounded retry loop was
otherwise possible under sustained signal delivery.
- The server's receive loop retries Interrupted the same way it
already retries WouldBlock, yielding to the runtime after a bounded
number of consecutive interruptions for the same reason.
- The error-queue drain treats an interrupted read as no record
obtained this drain (deferring to the next natural drain point)
rather than a socket error, matching its existing EWOULDBLOCK
handling.
Deterministic regression tests use a small test-only injection hook
(mirroring existing send-injection test hooks) rather than real signal
timing, covering: Open completing despite interruptions with no
retransmit, Open's deadline not extending under repeated
interruptions, recv_once classifying a reply normally despite
interruptions, recv_once's timeout not extending under repeated
interruptions, and the AsyncClient equivalents for open and recv.
No protocol, session, or timeout-classification behavior changes; no
new dependencies; send-side EINTR handling is unchanged and out of
scope.
Moves the client userspace probe sent_at measurement to immediately
after a successful UDP send, improving raw RTT and the userspace
upstream-OWD fallback by excluding the socket send-call interval and
the small amount of local work preceding it.
All fallible probe-commit preflight (timeout deadline checked_add,
capacity/collision checks) still runs before the send, from a private
pre-send anchor (SessionMachine::finalize_probe_commit). The public
sent_at is now supplied afterward to an infallible
SessionMachine::commit_probe_sent, so DurationOverflow still guarantees
nothing was transmitted and a WouldBlock try_send still commits
nothing.
The operational probe timeout deadline stays anchored to the pre-send
timestamp on purpose, not to the new post-send sent_at, preserving
existing timeout/loss timing. Linux kernel TX_SOFTWARE plausibility
keeps its own pre-send wall-clock lower bound
(PendingProbe::tx_not_before_wall) instead of the post-send sent_at,
since a legitimate TX_SOFTWARE timestamp can be generated while the
send syscall is still in flight and would otherwise be wrongly
rejected.
Also flags (without touching production code) that irtt-stats'
ReplySample::from_reply_parts feeds the public sent_at directly into
IpdvSample.client_send_mono/client_send_wall_ns, so the upstream/send
IPDV component naturally shifts along with the sent_at semantics
change; per scope this is reported rather than compensated for.
Upstream one-way delay now prefers the correlated Linux TX_SOFTWARE wall
timestamp retained by PendingProbe when it is locally plausible (sent_at
<= kernel_tx <= received_at, all on the client's own wall clock), falling
back to the userspace sent_at.wall sample otherwise. RTT, downstream OWD,
IPDV, and timeout/scheduling semantics are unchanged.
Advance delayed managed schedules to the latest due cadence slot and then directly to the first future deadline. Apply the same absolute-cadence behavior to the single runner and group burst/staggered pacing, while leaving the manual Client send API caller-paced.
Bound receive waits by the next send deadline so 10 ms intervals are not hidden behind the managed socket timeout. Add deterministic delayed-slot, finite-end, burst, staggered, and receive-bound regressions.
Allow one-way delay samples to represent negative values caused by wall-clock skew between client and server. Update CLI output and statistics collection to correctly handle and report these signed durations.
Hide internal fields to improve type safety and provide helper methods for unit conversions and negative value checks. Fix several feature-gated test compilation issues.
Simplify RttSample by merging signed and unsigned fields into a single SignedDuration for adjusted and effective RTT. This ensures accurate reporting and statistics when server processing time exceeds raw RTT.
Split the monolithic `probes_replies.rs` file into logical submodules and expose internal packet processing methods to improve test maintainability and coverage of boundary conditions.
Nils Andreas Svee