trezor-firmware/core/src/trezor/wire/thp/ack_handler.py

from storage.cache_thp import SessionThpCache
from trezor import log

from . import thp_session as THP


def handle_received_ACK(session: SessionThpCache, sync_bit: int) -> None:

    if _ack_is_not_expected(session):
        if __debug__:
            log.debug(__name__, "Received unexpected ACK message")
        return
    if _ack_has_incorrect_sync_bit(session, sync_bit):
        if __debug__:
            log.debug(__name__, "Received ACK message with wrong sync bit")
        return

    # ACK is expected and it has correct sync bit
    if __debug__:
        log.debug(__name__, "Received ACK message with correct sync bit")
    THP.sync_set_can_send_message(session, True)


def _ack_is_not_expected(session: SessionThpCache) -> bool:
    return THP.sync_can_send_message(session)


def _ack_has_incorrect_sync_bit(session: SessionThpCache, sync_bit: int) -> bool:
    return THP.sync_get_send_bit(session) != sync_bit