Added TcpFastOpenConnect sockopt

changelog/2247.added.md

@@ -0,0 +1 @@
+Added `TcpFastOpenConnect` sockopt to support `TCP_FASTOPEN_CONNECT` available on linux.

src/sys/socket/sockopt.rs

@@ -600,6 +600,26 @@ sockopt_impl!(
     libc::TCP_USER_TIMEOUT,
     u32
 );
+#[cfg(linux_android)]
+#[cfg(feature = "net")]
+sockopt_impl!(
+    #[cfg_attr(docsrs, doc(cfg(feature = "net")))]
+    /// Enables TCP Fast Open (RFC 7413) on a connecting socket. If a fast open
+    /// cookie is not available (first attempt to connect), `connect` syscall
+    /// will behave as usual, except for internally trying to solicit a cookie
+    /// from remote peer. When cookie is available, the next `connect` syscall
+    /// will immediately succeed without actually establishing TCP connection.
+    /// The connection establishment will be defered till the next `write` or
+    /// `sendmsg` syscalls on the socket, allowing TCP prtocol to establish
+    /// connection and send data in the same packets. Note: calling `read` right
+    /// after `connect` without `write` on the socket will cause the blocking
+    /// socket to be blocked forever.
+    TcpFastOpenConnect,
+    Both,
+    libc::IPPROTO_TCP,
+    libc::TCP_FASTOPEN_CONNECT,
+    bool
+);
 sockopt_impl!(
     /// Sets or gets the maximum socket receive buffer in bytes.
     RcvBuf,

test/sys/test_sockopt.rs

@@ -576,3 +576,27 @@ fn test_ip_bind_address_no_port() {
         "getting IP_BIND_ADDRESS_NO_PORT on an inet stream socket should succeed",
     ));
 }
+
+#[test]
+#[cfg(linux_android)]
+fn test_tcp_fast_open_connect() {
+    let fd = socket(
+        AddressFamily::Inet,
+        SockType::Stream,
+        SockFlag::empty(),
+        SockProtocol::Tcp,
+    )
+    .unwrap();
+    setsockopt(&fd, sockopt::TcpFastOpenConnect, &true).expect(
+        "setting TCP_FASTOPEN_CONNECT on an inet stream socket should succeed",
+    );
+    assert!(getsockopt(&fd, sockopt::TcpFastOpenConnect).expect(
+        "getting TCP_FASTOPEN_CONNECT on an inet stream socket should succeed",
+    ));
+    setsockopt(&fd, sockopt::TcpFastOpenConnect, &false).expect(
+        "unsetting TCP_FASTOPEN_CONNECT on an inet stream socket should succeed",
+    );
+    assert!(!getsockopt(&fd, sockopt::TcpFastOpenConnect).expect(
+        "getting TCP_FASTOPEN_CONNECT on an inet stream socket should succeed",
+    ));
+}