unixgram: Make fd non-blocking

src/devices/src/virtio/net/unixgram.rs

@@ -19,11 +19,40 @@ pub struct Unixgram {
 impl Unixgram {
     /// Create the backend with a pre-established connection to the userspace network proxy.
     pub fn new(fd: RawFd) -> Self {
+        // Ensure the socket is in non-blocking mode.
+        match fcntl(fd, FcntlArg::F_GETFL) {
+            Ok(flags) => match OFlag::from_bits(flags) {
+                Some(flags) => {
+                    if let Err(e) = fcntl(fd, FcntlArg::F_SETFL(flags | OFlag::O_NONBLOCK)) {
+                        warn!("error switching to non-blocking: id={fd}, err={e}");
+                    }
+                }
+                None => error!("invalid fd flags id={fd}"),
+            },
+            Err(e) => error!("couldn't obtain fd flags id={fd}, err={e}"),
+        };
+
+        #[cfg(target_os = "macos")]
+        {
+            // nix doesn't provide an abstraction for SO_NOSIGPIPE, fall back to libc.
+            let option_value: libc::c_int = 1;
+            unsafe {
+                libc::setsockopt(
+                    fd,
+                    libc::SOL_SOCKET,
+                    libc::SO_NOSIGPIPE,
+                    &option_value as *const _ as *const libc::c_void,
+                    std::mem::size_of_val(&option_value) as libc::socklen_t,
+                )
+            };
+        }
+
         Self { fd }
     }
 
     /// Create the backend opening a connection to the userspace network proxy.
     pub fn open(path: PathBuf, send_vfkit_magic: bool) -> Result<Self, ConnectError> {
+        // We cannot create a non-blocking socket on macOS here. This is done later in new().
         let fd = socket(
             AddressFamily::Unix,
             SockType::Datagram,
@@ -47,34 +76,6 @@ impl Unixgram {
             send(fd, &VFKIT_MAGIC, MsgFlags::empty()).map_err(ConnectError::SendingMagic)?;
         }
 
-        // macOS forces us to do this here instead of just using SockFlag::SOCK_NONBLOCK above.
-        match fcntl(fd, FcntlArg::F_GETFL) {
-            Ok(flags) => match OFlag::from_bits(flags) {
-                Some(flags) => {
-                    if let Err(e) = fcntl(fd, FcntlArg::F_SETFL(flags | OFlag::O_NONBLOCK)) {
-                        warn!("error switching to non-blocking: id={fd}, err={e}");
-                    }
-                }
-                None => error!("invalid fd flags id={fd}"),
-            },
-            Err(e) => error!("couldn't obtain fd flags id={fd}, err={e}"),
-        };
-
-        #[cfg(target_os = "macos")]
-        {
-            // nix doesn't provide an abstraction for SO_NOSIGPIPE, fall back to libc.
-            let option_value: libc::c_int = 1;
-            unsafe {
-                libc::setsockopt(
-                    fd,
-                    libc::SOL_SOCKET,
-                    libc::SO_NOSIGPIPE,
-                    &option_value as *const _ as *const libc::c_void,
-                    std::mem::size_of_val(&option_value) as libc::socklen_t,
-                )
-            };
-        }
-
         if let Err(e) = setsockopt(fd, sockopt::SndBuf, &(7 * 1024 * 1024)) {
             log::warn!("Failed to increase SO_SNDBUF (performance may be decreased): {e}");
         }