AF_UNIX pairs as FreeBSD 11 makes them: SOCK_STREAM, SOCK_DGRAM and
SOCK_SEQPACKET with protocol 0, SOCK_NONBLOCK applied to both ends and
SOCK_CLOEXEC accepted, EAFNOSUPPORT for an unknown family, EOPNOTSUPP
for AF_INET and AF_INET6, EPROTONOSUPPORT for type 0 or a protocol,
EPROTOTYPE for another type, EFAULT for a null output, and nothing
written on failure. The ends are guest sockets, so send, recv,
shutdown, fcntl, poll and close work on them; getsockname and
getpeername report the unnamed AF_UNIX address, recvfrom and recvmsg
no address for a stream and the unnamed one for a datagram. On Linux
the pair is the host's socketpair; on Windows a loopback TCP connection
or two connected UDP sockets, and SOCK_SEQPACKET throws. The remaining
differences from the console are recorded in TechnicalDebt.
OpenSSL's QUIC notifier in 15 catalog titles creates such a pair.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>