A partial success left the remaining entries' iovecs, sockaddrs, and
cmsgs fully intact, then threw them away and replanned the remainder
from bufs -- doubling the packing work exactly when the socket is
congested. Give sendFn a start offset so the drain resumes the same
prepared array at the first unsent entry, and skip a kernel-rejected
entry in place the same way. Only the GSO-disable path still replans,
since its entries change shape; it now rewinds precisely to the failed
run instead of the whole chunk, so entries already sent are never
duplicated.
New scripted tests pin the two paths that didn't exist before: a mid-
chunk rejected entry (drop it, resume the rest, start offsets advance)
and a mid-chunk EIO (GSO off, replay only the failed run, no dup of
already-sent packets).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014ugV2edVqoz3tBvq9J6yWp
Behavior untouched; each marker records a known gap and the intended
fix so the next visit doesn't rediscover it: transient zero-sent
sendmmsg errors drop a whole run; the non-vnet Poll queue lacks the
post-wake drain loop; recvmmsg controllen resets touch every entry;
cached handshake packets flush one syscall each; the routines clamp in
activate() would blackhole surplus REUSEPORT sockets if it ever became
reachable; darwin WriteBatch burst-drops on EWOULDBLOCK.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014ugV2edVqoz3tBvq9J6yWp
The rewind (resume after the kernel accepts fewer entries than
submitted) was the hairiest untested logic in the write path; a bug
there silently duplicates or loses packets under backpressure. Give
batchWriter an injectable sendFn and drive WriteBatch through scripted
partial-acceptance sequences over a mixed GSO-run/plain batch, decoding
what "reached the wire" straight from the prepared iovecs rather than
the entryEnd bookkeeping under test. Also pins the zero-progress abort
and the EIO runtime GSO-disable replay.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
JackDoan