Change algorithm of TCP relaying

network/sockopts.go

@@ -0,0 +1,71 @@
+package network
+
+import (
+	"fmt"
+	"net"
+
+	"golang.org/x/sys/unix"
+)
+
+// SetClientSocketOptions tunes a TCP socket that represents a connection to
+// end user (not Telegram service or fronting domain).
+func SetClientSocketOptions(conn net.Conn, bufferSize int) error {
+	tcpConn := conn.(*net.TCPConn) // nolint: forcetypeassert
+
+	if err := tcpConn.SetNoDelay(false); err != nil {
+		return fmt.Errorf("cannot disable TCP_NO_DELAY: %w", err)
+	}
+
+	return setCommonSocketOptions(tcpConn, bufferSize)
+}
+
+// SetServerSocketOptions tunes a TCP socket that represents a connection to
+// remote server like Telegram or fronting domain (but not end user).
+func SetServerSocketOptions(conn net.Conn, bufferSize int) error {
+	tcpConn := conn.(*net.TCPConn) // nolint: forcetypeassert
+
+	if err := tcpConn.SetNoDelay(true); err != nil {
+		return fmt.Errorf("cannot enable TCP_NO_DELAY: %w", err)
+	}
+
+	return setCommonSocketOptions(tcpConn, bufferSize)
+}
+
+func setCommonSocketOptions(conn *net.TCPConn, bufferSize int) error {
+	if err := conn.SetReadBuffer(bufferSize); err != nil {
+		return fmt.Errorf("cannot set read buffer size: %w", err)
+	}
+
+	if err := conn.SetWriteBuffer(bufferSize); err != nil {
+		return fmt.Errorf("cannot set write buffer size: %w", err)
+	}
+
+	if err := conn.SetKeepAlive(false); err != nil {
+		return fmt.Errorf("cannot disable TCP keepalive probes: %w", err)
+	}
+
+	if err := conn.SetLinger(tcpLingerTimeout); err != nil {
+		return fmt.Errorf("cannot set TCP linger timeout: %w", err)
+	}
+
+	rawConn, err := conn.SyscallConn()
+	if err != nil {
+		return fmt.Errorf("cannot get underlying raw connection")
+	}
+
+	rawConn.Control(func(fd uintptr) { // nolint: errcheck
+		err = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_REUSEADDR, 1)
+		if err != nil {
+			err = fmt.Errorf("cannot set SO_REUSEADDR: %w", err)
+
+			return
+		}
+
+		err = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_REUSEPORT, 1)
+		if err != nil {
+			err = fmt.Errorf("cannot set SO_REUSEPORT: %w", err)
+		}
+	})
+
+	return nil
+}