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Ryan HuberandClaude Opus 5.5
21075ba32e
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>