channel: Implement new escape sequence

tbot/machine/board/uboot.py

@@ -380,9 +380,7 @@ def interactive(self) -> None:
         can interactively run commands.  This method is used by the
         ``interactive_uboot`` testcase.
         """
-        tbot.log.message(
-            f"Entering interactive shell ({tbot.log.c('CTRL+D to exit').bold}) ..."
-        )
+        tbot.log.message(f"Entering interactive shell...")
 
         # It is important to send a space before the newline.  Otherwise U-Boot
         # will reexecute the last command which we definitely do not want here.

tbot/machine/channel/channel.py

@@ -1010,17 +1010,29 @@ def take(self) -> "Channel":
 
     # interactive {{{
     def attach_interactive(
-        self, end_magic: typing.Union[str, bytes, None] = None
+        self, end_magic: typing.Union[str, bytes, None] = None, ctrld_exit: bool = False
     ) -> None:
         """
         Connect tbot's terminal to this channel.
 
         Allows the user to interact directly with whatever this channel is
         connected to.
 
-        :param str, bytes end_magic: String that, when detected, should end the
-            interactive session.  If no ``end_magic`` is given, pressing
-            ``CTRL-D`` will terminate the session.
+        The interactive session can be exited at any point by **pressing**
+        ``CTRL+]`` **three times within 1 second**.
+
+        :param str, bytes end_magic: The ``end_magic`` parameter may be used to
+            define an automatic exit condition (sequence sent from the remote
+            side to trigger the end).
+        :param bool ctrld_exit:  If ``True``, pressing ``CTRL-D`` will also
+            terminate the session immediately.
+
+        .. versionchanged:: UNRELEASED
+
+           - The escape sequence is now "Press ``CTRL-]`` three times within 1
+             second".
+           - The ``ctrld_exit`` parameter was added to restore the old
+             "``CTRL-D`` to exit" behavior.
         """
         end_magic_bytes = (
             end_magic.encode("utf-8") if isinstance(end_magic, str) else end_magic
@@ -1034,8 +1046,14 @@ def attach_interactive(
         old_blacklist = self._write_blacklist
         self._write_blacklist = []
 
+        escape_timestamp = None
         previous: typing.Deque[int] = collections.deque(maxlen=3)
 
+        if not ctrld_exit:
+            tbot.log.message(
+                tbot.log.c("Press CTRL+] three times within 1 second to exit.").bold
+            )
+
         oldtty = termios.tcgetattr(sys.stdin)
         try:
             tty.setraw(sys.stdin.fileno())
@@ -1067,13 +1085,22 @@ def attach_interactive(
                 if sys.stdin in r:
                     data = sys.stdin.buffer.read(4096)
                     previous.extend(data)
-                    if end_magic is None and data == b"\x04":
-                        break
-                    for a, b in itertools.zip_longest(previous, b"\r~."):
-                        if a != b:
-                            break
-                    else:
+
+                    # Old ^D to exit behavior
+                    if ctrld_exit and data == b"\x04":
                         break
+
+                    # Detect whether ^] was pressed 3 times in 1 second
+                    now = time.monotonic()
+                    if escape_timestamp is None and 0x1D in previous:
+                        escape_timestamp = now
+                    elif escape_timestamp is not None:
+                        if now < escape_timestamp + 1:
+                            if previous.count(0x1D) >= 3:
+                                break
+                        else:
+                            escape_timestamp = None
+
                     self.send(data)
 
             sys.stdout.write("\r\n")

tbot/machine/linux/ash.py

@@ -268,6 +268,11 @@ def interactive(self) -> None:
 
         try:
             self.ch.sendline("exit")
-            self.ch.read_until_prompt(timeout=0.5)
+            try:
+                self.ch.read_until_prompt(timeout=0.5)
+            except TimeoutError:
+                # we might still be in the inner shell so let's try exiting again
+                self.ch.sendline("exit")
+                self.ch.read_until_prompt(timeout=0.5)
         except TimeoutError:
             raise Exception("Failed to reacquire shell after interactive session!")

tbot/machine/linux/bash.py

@@ -276,6 +276,11 @@ def interactive(self) -> None:
 
         try:
             self.ch.sendline("exit")
-            self.ch.read_until_prompt(timeout=0.5)
+            try:
+                self.ch.read_until_prompt(timeout=0.5)
+            except TimeoutError:
+                # we might still be in the inner shell so let's try exiting again
+                self.ch.sendline("exit")
+                self.ch.read_until_prompt(timeout=0.5)
         except TimeoutError:
             raise Exception("Failed to reacquire shell after interactive session!")

tbot/machine/shell.py

@@ -108,7 +108,5 @@ def interactive(self) -> None:
         Connect tbot's stdio to this machine's channel.  This will allow
         interactive access to the machine.
         """
-        tbot.log.message(
-            f"Entering interactive shell ({tbot.log.c('CTRL+D to exit').bold}) ..."
-        )
+        tbot.log.message(f"Entering interactive shell...")
         self.ch.attach_interactive()

tbot_contrib/gdb.py

@@ -103,7 +103,7 @@ def interactive(self) -> None:
         tbot.log.message(
             f"Entering interactive GDB shell ({tbot.log.c('CTRL+D to exit').bold}) ..."
         )
-        self.ch.attach_interactive()
+        self.ch.attach_interactive(ctrld_exit=True)
 
         self.ch.sendcontrol("C")
         self.ch.read_until_prompt("(gdb) ")