SchemeSocket trait gains handle_sendmsg(file, payload, flags) with
default EOPNOTSUPP. SocketScheme::call_inner now dispatches
SocketCall::SendMsg (previously commented out).
UDP handle_sendmsg parses the sendmsg buffer format:
[name_len: usize][payload_len: usize][msg_controllen: usize]
[address: bytes][payload: bytes]
Extracts the destination IP:port from the address, sends via
smoltcp's send_slice. Enables sendto() on unconnected UDP sockets.
Unconnected UDP write_buf now returns EDESTADDRREQ instead of
EADDRNOTAVAIL — clearer error for unconnected writes without
sendto.
TCP and ICMP use the default EOPNOTSUPP implementation (they
are connection-oriented or use write_buf).
All 31 tests pass.
Red Bear OS
96f241a40b