Add the unix socket support for sendto system call

src/libos/src/net/syscalls.rs

@@ -278,12 +278,14 @@ pub fn do_sendto(
     addr_len: libc::socklen_t,
 ) -> Result<isize> {
     debug!(
-        "sendto: fd: {}, base: {:?}, len: {}, addr: {:?}, addr_len: {}",
-        fd, base, len, addr, addr_len
+        "sendto: fd: {}, base: {:?}, len: {}, flags: {} addr: {:?}, addr_len: {}",
+        fd, base, len, flags, addr, addr_len
     );
-    let file_ref = current!().file(fd as FileDesc)?;
-    let socket = file_ref.as_socket()?;
+    from_user::check_array(base as *const u8, len)?;
 
+    let file_ref = current!().file(fd as FileDesc)?;
+    if let Ok(socket) = file_ref.as_socket() {
+        // TODO: check addr and addr_len according to connection mode
         let ret = try_libc!(libc::ocall::sendto(
             socket.fd(),
             base,
@@ -293,6 +295,20 @@ pub fn do_sendto(
             addr_len
         ));
         Ok(ret as isize)
+    } else if let Ok(unix) = file_ref.as_unix_socket() {
+        if !addr.is_null() || addr_len != 0 {
+            return_errno!(EISCONN, "Only connection-mode socket is supported");
+        }
+
+        if !unix.is_connected() {
+            return_errno!(ENOTCONN, "the socket has not been connected yet");
+        }
+
+        let data = unsafe { std::slice::from_raw_parts(base as *const u8, len) };
+        unix.write(data).map(|u| u as isize)
+    } else {
+        return_errno!(EBADF, "unsupported file type");
+    }
 }
 
 pub fn do_recvfrom(

src/libos/src/net/unix_socket.rs

@@ -150,6 +150,14 @@ impl UnixSocketFile {
             }
         }
     }
+
+    pub fn is_connected(&self) -> bool {
+        if let Status::Connected(_) = self.inner.lock().unwrap().status {
+            true
+        } else {
+            false
+        }
+    }
 }
 
 impl Debug for UnixSocketFile {

test/unix_socket/main.c

@@ -101,9 +101,15 @@ int verify_connection(int src_sock, int dest_sock) {
     char buf[1024];
     int i;
     for (i = 0; i < 100; i++) {
+        if (i % 2 == 0) {
             if (write(src_sock, ECHO_MSG, sizeof(ECHO_MSG)) < 0) {
                 THROW_ERROR("writing server message");
             }
+        } else {
+            if (sendto(src_sock, ECHO_MSG, sizeof(ECHO_MSG), 0, NULL, 0) < 0) {
+                THROW_ERROR("sendto server message");
+            }
+        }
 
         if (read(dest_sock, buf, 1024) < 0) {
             THROW_ERROR("reading server message");