shim: release fd when error happens in RemotePublisher::connect()

A RawFd won't be automatically released when going out of scope,
so we need to close the just created RawFd when error happens
in RemotePublisher::connect().

Signed-off-by: Liu Jiang <gerry@linux.alibaba.com>

crates/shim/src/publisher.rs

@@ -16,7 +16,6 @@
 
 //! Implements a client to publish events from the shim back to containerd.
 
-use std::os::unix::io::RawFd;
 use std::time::{SystemTime, UNIX_EPOCH};
 
 use containerd_shim_client as client;
@@ -38,18 +37,22 @@ pub struct RemotePublisher {
 
 impl RemotePublisher {
     /// Connect to containerd's TTRPC endpoint.
+    ///
     /// containerd uses `/run/containerd/containerd.sock.ttrpc` by default
     pub fn new(address: impl AsRef<str>) -> Result<RemotePublisher, Error> {
-        let fd = Self::connect(address)?;
-        let client = Client::new(fd);
+        let client = Self::connect(address)?;
 
         Ok(RemotePublisher {
             client: EventsClient::new(client),
         })
     }
 
-    fn connect(address: impl AsRef<str>) -> Result<RawFd, nix::Error> {
+    fn connect(address: impl AsRef<str>) -> Result<Client, nix::Error> {
         use nix::sys::socket::*;
+        use nix::unistd::close;
+
+        let unix_addr = UnixAddr::new(address.as_ref())?;
+        let sock_addr = SockAddr::Unix(unix_addr);
 
         // SOCK_CLOEXEC flag is Linux specific
         #[cfg(target_os = "linux")]
@@ -65,18 +68,23 @@ impl RemotePublisher {
         #[cfg(not(target_os = "linux"))]
         {
             use nix::fcntl::{fcntl, FcntlArg, FdFlag};
-            fcntl(fd, FcntlArg::F_SETFD(FdFlag::FD_CLOEXEC))?;
+            fcntl(fd, FcntlArg::F_SETFD(FdFlag::FD_CLOEXEC)).map_err(|e| {
+                let _ = close(fd);
+                e
+            })?;
         }
 
-        let unix_addr = UnixAddr::new(address.as_ref())?;
-        let sock_addr = SockAddr::Unix(unix_addr);
+        connect(fd, &sock_addr).map_err(|e| {
+            let _ = close(fd);
+            e
+        })?;
 
-        connect(fd, &sock_addr)?;
-
-        Ok(fd)
+        // Client::new() takes ownership of the RawFd.
+        Ok(Client::new(fd))
     }
 
-    /// Publish new event.
+    /// Publish a new event.
+    ///
     /// Event object can be anything that Protobuf able serialize (e.g. implement `Message` trait).
     pub fn publish(
         &self,