src/antlion/controllers/sl4a_lib/rpc_connection.py

#!/usr/bin/env python3
#
# Copyright 2022 The Fuchsia Authors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import json
import socket
import threading

from antlion import logger
from antlion.controllers.sl4a_lib import rpc_client

# The Session UID when a UID has not been received yet.
UNKNOWN_UID = -1


class Sl4aConnectionCommand(object):
    """Commands that can be invoked on the sl4a client.

    INIT: Initializes a new sessions in sl4a.
    CONTINUE: Creates a connection.
    """
    INIT = 'initiate'
    CONTINUE = 'continue'


class RpcConnection(object):
    """A single RPC Connection thread.

    Attributes:
        _client_socket: The socket this connection uses.
        _socket_file: The file created over the _client_socket.
        _ticket_counter: The counter storing the current ticket number.
        _ticket_lock: A lock on the ticket counter to prevent ticket collisions.
        adb: A reference to the AdbProxy of the AndroidDevice. Used for logging.
        log: The logger for this RPC Client.
        ports: The Sl4aPorts object that stores the ports this connection uses.
        uid: The SL4A session ID.
    """

    def __init__(self, adb, ports, client_socket, socket_fd, uid=UNKNOWN_UID):
        self._client_socket = client_socket
        self._socket_file = socket_fd
        self._ticket_counter = 0
        self._ticket_lock = threading.Lock()
        self.adb = adb
        self.uid = uid

        def _log_formatter(message):
            """Defines the formatting used in the logger."""
            return '[SL4A Client|%s|%s|%s] %s' % (self.adb.serial,
                                                  self.ports.client_port,
                                                  self.uid, message)

        self.log = logger.create_logger(_log_formatter)

        self.ports = ports
        self.set_timeout(rpc_client.SOCKET_TIMEOUT)

    def open(self):
        if self.uid != UNKNOWN_UID:
            start_command = Sl4aConnectionCommand.CONTINUE
        else:
            start_command = Sl4aConnectionCommand.INIT

        self._initiate_handshake(start_command)

    def _initiate_handshake(self, start_command):
        """Establishes a connection with the SL4A server.

        Args:
            start_command: The command to send. See Sl4aConnectionCommand.
        """
        try:
            resp = self._cmd(start_command)
        except socket.timeout as e:
            self.log.error('Failed to open socket connection: %s', e)
            raise
        if not resp:
            raise rpc_client.Sl4aProtocolError(
                rpc_client.Sl4aProtocolError.NO_RESPONSE_FROM_HANDSHAKE)
        result = json.loads(str(resp, encoding='utf8'))
        if result['status']:
            self.uid = result['uid']
        else:
            self.log.warning(
                'UID not received for connection %s.' % self.ports)
            self.uid = UNKNOWN_UID
        self.log.debug('Created connection over: %s.' % self.ports)

    def _cmd(self, command):
        """Sends an session protocol command to SL4A to establish communication.

        Args:
            command: The name of the command to execute.

        Returns:
            The line that was written back.
        """
        self.send_request(json.dumps({'cmd': command, 'uid': self.uid}))
        return self.get_response()

    def get_new_ticket(self):
        """Returns a ticket for a new request."""
        with self._ticket_lock:
            self._ticket_counter += 1
            ticket = self._ticket_counter
        return ticket

    def set_timeout(self, timeout):
        """Sets the socket's wait for response timeout."""
        self._client_socket.settimeout(timeout)

    def send_request(self, request):
        """Sends a request over the connection."""
        self._socket_file.write(request.encode('utf8') + b'\n')
        self._socket_file.flush()
        self.log.debug('Sent: ' + request)

    def get_response(self):
        """Returns the first response sent back to the client."""
        data = self._socket_file.readline()
        self.log.debug('Received: ' + data.decode('utf8', errors='replace'))
        return data

    def close(self):
        """Closes the connection gracefully."""
        self._client_socket.close()
        self.adb.remove_tcp_forward(self.ports.forwarded_port)