client: bind socket to abstract name before connect

it seems that the server can't sendto() an unbound peer

src/bin/luac.rs

@@ -4,11 +4,12 @@ use std::{
     os::unix::net::{
 	UnixDatagram,
 	SocketAncillary,
-	AncillaryData
+	SocketAddr
     },
     env,
     io::IoSlice
 };
+use std::os::linux::net::SocketAddrExt;
 
 fn main() {
     let mut payload = "".to_string();
@@ -22,7 +23,11 @@ fn main() {
     let Ok(sock_path) = env::var("LUAD_SOCKET_PATH") else {
 	panic!("need to set LUAD_SOCKET_PATH env var");
     };
-    let sock = UnixDatagram::unbound().expect("socket");
+    let pid = std::process::id();
+
+    let addr = SocketAddr::from_abstract_name(pid.to_le_bytes()).expect("addr");
+    let sock = UnixDatagram::bind_addr(&addr).expect("bind");
+
     sock.connect(sock_path).expect("connect");
     let fds = [0, 1, 2];
     let mut ancillary_buffer = [0; 128];