mirror of
https://github.com/trezor/trezor-firmware.git
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refactor(core/wire): simplify the message handling loop
This commit is contained in:
matejcik
matejcik
parent
b387970468
commit
dd655422f1
@ -37,7 +37,7 @@ reads the message's header. When the message type is known the first handler is
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import protobuf
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from storage.cache import InvalidSessionError
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from trezor import log, loop, messages, ui, utils, workflow
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from trezor import log, loop, messages, utils, workflow
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from trezor.messages import FailureType
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from trezor.messages.Failure import Failure
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from trezor.wire import codec_v1
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@ -283,6 +283,108 @@ class UnexpectedMessageError(Exception):
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self.msg = msg
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async def _handle_single_message(
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ctx: Context, msg: codec_v1.Message, use_workflow: bool
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) -> codec_v1.Message | None:
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"""Handle a message that was loaded from USB by the caller.
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Find the appropriate handler, run it and write its result on the wire. In case
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a problem is encountered at any point, write the appropriate error on the wire.
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If the workflow finished normally or with an error, the return value is None.
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If an unexpected message had arrived on the wire while the workflow was processing,
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the workflow is shut down with an `UnexpectedMessageError`. This is not considered
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an "error condition" to return over the wire -- instead the message is processed
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as if starting a new workflow.
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In such case, the `UnexpectedMessageError` is caught and the message is returned
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to the caller. It will then be processed in the next iteration of the message loop.
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"""
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if __debug__:
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try:
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msg_type = messages.get_type(msg.type).__name__
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except KeyError:
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msg_type = "%d - unknown message type" % msg.type
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log.debug(
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__name__,
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"%s:%x receive: <%s>",
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ctx.iface.iface_num(),
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ctx.sid,
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msg_type,
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)
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res_msg: protobuf.MessageType | None = None
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# We need to find a handler for this message type. Should not raise.
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handler = find_handler(ctx.iface, msg.type)
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if handler is None:
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# If no handler is found, we can skip decoding and directly
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# respond with failure.
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await ctx.write(unexpected_message())
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return None
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# Here we make sure we always respond with a Failure response
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# in case of any errors.
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try:
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# Find a protobuf.MessageType subclass that describes this
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# message. Raises if the type is not found.
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req_type = messages.get_type(msg.type)
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# Try to decode the message according to schema from
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# `req_type`. Raises if the message is malformed.
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req_msg = _wrap_protobuf_load(msg.data, req_type)
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# Create the handler task.
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task = handler(ctx, req_msg)
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# Run the workflow task. Workflow can do more on-the-wire
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# communication inside, but it should eventually return a
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# response message, or raise an exception (a rather common
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# thing to do). Exceptions are handled in the code below.
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if use_workflow:
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# Spawn a workflow around the task. This ensures that concurrent
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# workflows are shut down.
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res_msg = await workflow.spawn(task)
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else:
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# For debug messages, ignore workflow processing and just await
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# results of the handler.
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res_msg = await task
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except UnexpectedMessageError as exc:
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# Workflow was trying to read a message from the wire, and
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# something unexpected came in. See Context.read() for
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# example, which expects some particular message and raises
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# UnexpectedMessageError if another one comes in.
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# In order not to lose the message, we return it to the caller.
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# TODO:
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# We might handle only the few common cases here, like
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# Initialize and Cancel.
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return exc.msg
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except BaseException as exc:
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# Either:
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# - the message had a type that has a registered handler, but does not have
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# a protobuf class
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# - the message was not valid protobuf
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# - workflow raised some kind of an exception while running
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# - something canceled the workflow from the outside
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if __debug__:
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if isinstance(exc, ActionCancelled):
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log.debug(__name__, "cancelled: {}".format(exc.message))
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elif isinstance(exc, loop.TaskClosed):
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log.debug(__name__, "cancelled: loop task was closed")
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else:
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log.exception(__name__, exc)
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res_msg = failure(exc)
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if res_msg is not None:
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# perform the write outside the big try-except block, so that usb write
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# problem bubbles up
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await ctx.write(res_msg)
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return None
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async def handle_session(
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iface: WireInterface, session_id: int, is_debug_session: bool = False
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) -> None:
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@ -292,158 +394,47 @@ async def handle_session(
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ctx_buffer = WIRE_BUFFER
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ctx = Context(iface, session_id, ctx_buffer)
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next_msg: codec_v1.Message | None = None
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res_msg: protobuf.MessageType | None = None
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req_type = None
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req_msg = None
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if __debug__ and is_debug_session:
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import apps.debug
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apps.debug.DEBUG_CONTEXT = ctx
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# Take a mark of modules that are imported at this point, so we can
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# roll back and un-import any others.
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modules = utils.unimport_begin()
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while True:
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try:
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if next_msg is None:
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# We are not currently reading a message, so let's wait for one.
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# If the decoding fails, exception is raised and we try again
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# (with the same `Reader` instance, it's OK). Even in case of
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# de-synchronized wire communication, report with a message
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# header is eventually received, after a couple of tries.
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# If the previous run did not keep an unprocessed message for us,
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# wait for a new one coming from the wire.
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msg = await ctx.read_from_wire()
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if __debug__:
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try:
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msg_type = messages.get_type(msg.type).__name__
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except KeyError:
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msg_type = "%d - unknown message type" % msg.type
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log.debug(
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__name__,
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"%s:%x receive: <%s>",
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iface.iface_num(),
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session_id,
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msg_type,
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)
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else:
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# We have a reader left over from earlier. We should process
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# this message instead of waiting for new one.
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# Process the message from previous run.
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msg = next_msg
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next_msg = None
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# Now we are in a middle of reading a message and we need to decide
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# what to do with it, based on its type from the message header.
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# From this point on, we should take care to read it in full and
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# send a response.
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try:
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next_msg = await _handle_single_message(
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ctx, msg, use_workflow=not is_debug_session
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)
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finally:
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if not __debug__ or not is_debug_session:
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# Unload modules imported by the workflow. Should not raise.
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# This is not done for the debug session because the snapshot taken
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# in a debug session would clear modules which are in use by the
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# workflow running on wire.
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utils.unimport_end(modules)
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# Take a mark of modules that are imported at this point, so we can
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# roll back and un-import any others. Should not raise.
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if is_debug_session:
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modules = utils.unimport_begin()
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# We need to find a handler for this message type. Should not
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# raise.
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handler = find_handler(iface, msg.type)
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if handler is None:
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# If no handler is found, we can skip decoding and directly
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# respond with failure. Should not raise.
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res_msg = unexpected_message()
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else:
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# We found a valid handler for this message type.
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# Workflow task, declared for the finally block
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wf_task: HandlerTask | None = None
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# Here we make sure we always respond with a Failure response
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# in case of any errors.
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try:
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# Find a protobuf.MessageType subclass that describes this
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# message. Raises if the type is not found.
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req_type = messages.get_type(msg.type)
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# Try to decode the message according to schema from
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# `req_type`. Raises if the message is malformed.
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req_msg = _wrap_protobuf_load(msg.data, req_type)
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# At this point, message reports are all processed and
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# correctly parsed into `req_msg`.
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# Create the workflow task.
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wf_task = handler(ctx, req_msg)
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# Run the workflow task. Workflow can do more on-the-wire
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# communication inside, but it should eventually return a
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# response message, or raise an exception (a rather common
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# thing to do). Exceptions are handled in the code below.
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if not is_debug_session:
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res_msg = await workflow.spawn(wf_task)
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else:
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res_msg = await wf_task
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except UnexpectedMessageError as exc:
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# Workflow was trying to read a message from the wire, and
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# something unexpected came in. See Context.read() for
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# example, which expects some particular message and raises
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# UnexpectedMessageError if another one comes in.
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# In order not to lose the message, we pass on the reader
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# to get picked up by the workflow logic in the beginning of
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# the cycle, which processes it in the usual manner.
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# TODO:
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# We might handle only the few common cases here, like
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# Initialize and Cancel.
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next_msg = exc.msg
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res_msg = None
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except Exception as exc:
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# Either:
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# - the first workflow message had a type that has a
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# registered handler, but does not have a protobuf class
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# - the first workflow message was not a valid protobuf
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# - workflow raised some kind of an exception while running
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# - something canceled the workflow from the outside
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if __debug__:
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if isinstance(exc, ActionCancelled):
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log.debug(__name__, "cancelled: {}".format(exc.message))
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elif isinstance(exc, loop.TaskClosed):
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log.debug(__name__, "cancelled: loop task was closed")
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else:
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log.exception(__name__, exc)
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res_msg = failure(exc)
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finally:
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# If we ran a workflow task, and a default workflow is on, make sure
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# we do not race against the layout that is inside.
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# TODO: this is very hacky and complects wire with the ui
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if wf_task is not None and workflow.default_task is not None:
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await ui.wait_until_layout_is_running()
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if res_msg is not None:
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# Either the workflow returned a response, or we created one.
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# Write it on the wire. Possibly, the incoming message haven't
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# been read in full. We ignore this case here and let the rest
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# of the reports get processed while waiting for the message
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# header.
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# TODO: if the write fails, we do not unimport the loaded modules
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await ctx.write(res_msg)
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# Cleanup, so garbage collection triggered after un-importing can
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# pick up the trash.
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req_type = None
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req_msg = None
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res_msg = None
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handler = None
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wf_task = None
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# Unload modules imported by the workflow. Should not raise.
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utils.unimport_end(modules)
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if not is_debug_session and next_msg is None: # and msg_type != 0:
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loop.clear()
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return
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if next_msg is None:
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# Shut down the loop if there is no next message waiting.
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# Let the session be restarted from `main`.
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loop.clear()
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return
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except Exception as exc:
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# The session handling should never exit, just log and continue.
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# Log and try again. The session handler can only exit explicitly via
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# loop.clear() above.
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if __debug__:
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log.exception(__name__, exc)
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