Ryan HuberandClaude Opus 5.5 21075ba32e udp/darwin: batch receives and connected-socket sends with recvmsg_x/sendmsg_x ...

internal/msgx is the one copy of xnu's private batched socket calls: the
msghdr_x layout, Send/Recv through the raw syscall (EINTR retried) and
Unsupported for the errnos a kernel or sandbox refuses them with.

Every socket the listener owns reads with recvmsg_x: the listener and each
connected socket run their own reader goroutine, and hand whole batches to
ListenOut over a channel. ListenOut runs the EncReader over a batch and
flushes once, so the reader stays single-threaded without a lock that
readers contend on, and the next recvmsg_x overlaps the decrypt of the last
batch. Batch buffers (64 x MTU) come from a per-listener free list that
keeps up to 11; a reader takes one only while its socket is readable, so
idle connected sockets hold none. A batch with a header intact msghdr_x
entries can't produce, or ENOSYS/EPERM/EOPNOTSUPP, switches every reader to
one datagram per read for good.

Connected sockets send runs with sendmsg_x, which xnu batches through the
stack on a connected socket. EAGAIN/ENOBUFS keep #1901's single-datagram
stall handling; a refused sendmsg_x retries the datagram with write and
turns sendmsg_x off once that goes through.

The connected-socket knobs lose their NEBULA_CONNSOCK* environment
overrides and keep #1901's defaults.

Based on Caleb Jasik's #1895 (recvmsg_x) and #1897 (sendmsg_x), and Jack
Doan's internal/msgx shape from #1898.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

2026-09-30 11:11:48 +00:00

..

msgx

udp/darwin: batch receives and connected-socket sends with recvmsg_x/sendmsg_x

2026-09-30 11:11:48 +00:00