# Lint as: python2, python3 # # Copyright 2007 Google Inc. Released under the GPL v2 """ This module defines the SSHHost class. Implementation details: You should import the "hosts" package instead of importing each type of host. SSHHost: a remote machine with a ssh access """ from __future__ import absolute_import from __future__ import division from __future__ import print_function import inspect import logging import re import time import common from autotest_lib.client.common_lib import error from autotest_lib.client.common_lib import pxssh from autotest_lib.server import utils from autotest_lib.server.hosts import abstract_ssh import six # In case cros_host is being ran via SSP on an older Moblab version with an # older chromite version. try: from chromite.lib import metrics except ImportError: metrics = utils.metrics_mock def THIS_IS_SLOW(func): """Mark the given function as slow, when looking at calls to it""" func.__name__ = '%s__SLOW__' % func.__name__ return func class SSHHost(abstract_ssh.AbstractSSHHost): """ This class represents a remote machine controlled through an ssh session on which you can run programs. It is not the machine autoserv is running on. The machine must be configured for password-less login, for example through public key authentication. It includes support for controlling the machine through a serial console on which you can run programs. If such a serial console is set up on the machine then capabilities such as hard reset and boot strap monitoring are available. If the machine does not have a serial console available then ordinary SSH-based commands will still be available, but attempts to use extensions such as console logging or hard reset will fail silently. Implementation details: This is a leaf class in an abstract class hierarchy, it must implement the unimplemented methods in parent classes. """ RUN_TIMEOUT = 3600 def _initialize(self, hostname, *args, **dargs): """ Construct a SSHHost object Args: hostname: network hostname or address of remote machine """ super(SSHHost, self)._initialize(hostname=hostname, *args, **dargs) self._default_run_timeout = self.RUN_TIMEOUT self.setup_ssh() def ssh_command(self, connect_timeout=30, options='', alive_interval=300, alive_count_max=3, connection_attempts=1): """ Construct an ssh command with proper args for this host. @param connect_timeout: connection timeout (in seconds) @param options: SSH options @param alive_interval: SSH Alive interval. @param alive_count_max: SSH AliveCountMax. @param connection_attempts: SSH ConnectionAttempts """ options = " ".join([options, self._master_ssh.ssh_option]) base_cmd = self.make_ssh_command(user=self.user, port=self.port, opts=options, hosts_file=self.known_hosts_file, connect_timeout=connect_timeout, alive_interval=alive_interval, alive_count_max=alive_count_max, connection_attempts=connection_attempts) return "%s %s" % (base_cmd, self.hostname) def _get_server_stack_state(self, lowest_frames=0, highest_frames=None): """ Get the server stack frame status. @param lowest_frames: the lowest frames to start printing. @param highest_frames: the highest frames to print. (None means no restriction) """ stack_frames = inspect.stack() stack = '' for frame in stack_frames[lowest_frames:highest_frames]: function_name = inspect.getframeinfo(frame[0]).function stack = '%s|%s' % (function_name, stack) del stack_frames return stack[:-1] # Delete the last '|' character def _verbose_logger_command(self, command): """ Prepend the command for the client with information about the ssh command to be executed and the server stack state. @param command: the ssh command to be executed. """ # The last few frames on the stack are not useful, so skip them. stack = self._get_server_stack_state(lowest_frames=3, highest_frames=6) # If logger executable exists on the DUT, use it to report the command. # Then regardless of logger, run the command as usual. command = ('test -x /usr/bin/logger && /usr/bin/logger' ' -t autotest "from [%s] ssh_run: %s"; %s' % (stack, utils.sh_escape(command), command)) return command def _run(self, command, timeout, ignore_status, stdout, stderr, connect_timeout, env, options, stdin, args, ignore_timeout, ssh_failure_retry_ok): """Helper function for run().""" if connect_timeout > timeout: # timeout passed from run() may be smaller than 1, because we # subtract the elapsed time from the original timeout supplied. connect_timeout = max(int(timeout), 1) original_cmd = command ssh_cmd = self.ssh_command(connect_timeout, options) if not env.strip(): env = "" else: env = "export %s;" % env for arg in args: command += ' "%s"' % utils.sh_escape(arg) full_cmd = '%s "%s %s"' % (ssh_cmd, env, utils.sh_escape(command)) # TODO(jrbarnette): crbug.com/484726 - When we're in an SSP # container, sometimes shortly after reboot we will see DNS # resolution errors on ssh commands; the problem never # occurs more than once in a row. This especially affects # the autoupdate_Rollback test, but other cases have been # affected, too. # # We work around it by detecting the first DNS resolution error # and retrying exactly one time. dns_error_retry_count = 1 def counters_inc(counter_name, failure_name): """Helper function to increment metrics counters. @param counter_name: string indicating which counter to use @param failure_name: string indentifying an error, or 'success' """ if counter_name == 'call': # ssh_counter records the outcome of each ssh invocation # inside _run(), including exceptions. ssh_counter = metrics.Counter('chromeos/autotest/ssh/calls') fields = {'error' : failure_name or 'success', 'attempt' : ssh_call_count} ssh_counter.increment(fields=fields) if counter_name == 'run': # run_counter records each call to _run() with its result # and how many tries were made. Calls are recorded when # _run() exits (including exiting with an exception) run_counter = metrics.Counter('chromeos/autotest/ssh/runs') fields = {'error' : failure_name or 'success', 'attempt' : ssh_call_count} run_counter.increment(fields=fields) # If ssh_failure_retry_ok is True, retry twice on timeouts and generic # error 255: if a simple retry doesn't work, kill the ssh master # connection and try again. (Note that either error could come from # the command running in the DUT, in which case the retry may be # useless but, in theory, also harmless.) if ssh_failure_retry_ok: # Ignore ssh command timeout, even though it could be a timeout due # to the command executing in the remote host. Note that passing # ignore_timeout = True makes utils.run() return None on timeouts # (and only on timeouts). original_ignore_timeout = ignore_timeout ignore_timeout = True ssh_failure_retry_count = 2 else: ssh_failure_retry_count = 0 ssh_call_count = 0 while True: try: # Increment call count first, in case utils.run() throws an # exception. ssh_call_count += 1 result = utils.run(full_cmd, timeout, True, stdout, stderr, verbose=False, stdin=stdin, stderr_is_expected=ignore_status, ignore_timeout=ignore_timeout) except Exception as e: # No retries on exception. counters_inc('call', 'exception') counters_inc('run', 'exception') raise e failure_name = None if result: if result.exit_status == 255: if re.search(r'^ssh: .*: Name or service not known', result.stderr): failure_name = 'dns_failure' else: failure_name = 'error_255' elif result.exit_status > 0: failure_name = 'nonzero_status' else: # result == None failure_name = 'timeout' # Record the outcome of the ssh invocation. counters_inc('call', failure_name) if failure_name: # There was a failure: decide whether to retry. if failure_name == 'dns_failure': if dns_error_retry_count > 0: logging.debug('retrying ssh because of DNS failure') dns_error_retry_count -= 1 continue else: if ssh_failure_retry_count == 2: logging.debug('retrying ssh command after %s', failure_name) ssh_failure_retry_count -= 1 continue elif ssh_failure_retry_count == 1: # After two failures, restart the master connection # before the final try. logging.debug('retry 2: restarting master connection') self.restart_master_ssh() # Last retry: reinstate timeout behavior. ignore_timeout = original_ignore_timeout ssh_failure_retry_count -= 1 continue # No retry conditions occurred. Exit the loop. break # The outcomes of ssh invocations have been recorded. Now record # the outcome of this function. if ignore_timeout and not result: counters_inc('run', 'ignored_timeout') return None # The error messages will show up in band (indistinguishable # from stuff sent through the SSH connection), so we have the # remote computer echo the message "Connected." before running # any command. Since the following 2 errors have to do with # connecting, it's safe to do these checks. if result.exit_status == 255: if re.search(r'^ssh: connect to host .* port .*: ' r'Connection timed out\r$', result.stderr): counters_inc('run', 'final_timeout') raise error.AutoservSSHTimeout( "ssh timed out: %r" % original_cmd.strip(), result) if "Permission denied." in result.stderr: msg = "ssh permission denied" counters_inc('run', 'final_eperm') raise error.AutoservSshPermissionDeniedError(msg, result) if not ignore_status and result.exit_status > 0: counters_inc('run', 'final_run_error') msg = result.stderr.strip() if not msg: msg = result.stdout.strip() if msg: msg = msg.splitlines()[-1] raise error.AutoservRunError("command execution error (%d): %r" % (result.exit_status, msg), result) counters_inc('run', failure_name) return result def set_default_run_timeout(self, timeout): """Set the default timeout for run.""" if timeout < 0: raise error.TestError('Invalid timeout %d', timeout) self._default_run_timeout = timeout @THIS_IS_SLOW def run(self, command, timeout=None, ignore_status=False, stdout_tee=utils.TEE_TO_LOGS, stderr_tee=utils.TEE_TO_LOGS, connect_timeout=30, options='', stdin=None, verbose=True, args=(), ignore_timeout=False, ssh_failure_retry_ok=False): """ Run a command on the remote host. @note: This RPC call has an overhead of minimum 40ms and up to 400ms on servers (crbug.com/734887). Each time a call is added for every job, a server core dies in the lab. @see: common_lib.hosts.host.run() @param timeout: command execution timeout in seconds. Default is _default_run_timeout (1 hour). @param connect_timeout: ssh connection timeout (in seconds) @param options: string with additional ssh command options @param verbose: log the commands @param ignore_timeout: bool True if SSH command timeouts should be ignored. Will return None on command timeout. @param ssh_failure_retry_ok: True if the command may be retried on probable ssh failure (error 255 or timeout). When true, the command may be executed up to three times, the second time after restarting the ssh master connection. Use only for commands that are idempotent, because when a "probable ssh failure" occurs, we cannot tell if the command executed or not. @raises AutoservRunError: if the command failed @raises AutoservSSHTimeout: ssh connection has timed out """ # For example if the command is a list, we need to convert it to a # string first. if not isinstance(command, six.string_types): command = ' '.join(command) if timeout is None: timeout = self._default_run_timeout start_time = time.time() with metrics.SecondsTimer('chromeos/autotest/ssh/master_ssh_time', scale=0.001): if verbose: stack = self._get_server_stack_state(lowest_frames=1, highest_frames=7) logging.debug("Running (ssh) '%s' from '%s'", command, stack) command = self._verbose_logger_command(command) self.start_master_ssh(min( timeout, self.DEFAULT_START_MASTER_SSH_TIMEOUT_S, )) env = " ".join("=".join(pair) for pair in six.iteritems(self.env)) elapsed = time.time() - start_time try: return self._run(command, timeout - elapsed, ignore_status, stdout_tee, stderr_tee, connect_timeout, env, options, stdin, args, ignore_timeout, ssh_failure_retry_ok) except error.CmdError as cmderr: # We get a CmdError here only if there is timeout of that # command. Catch that and stuff it into AutoservRunError and # raise it. timeout_message = str('Timeout encountered: %s' % cmderr.args[0]) raise error.AutoservRunError(timeout_message, cmderr.args[1]) def run_background(self, command, verbose=True): """Start a command on the host in the background. The command is started on the host in the background, and this method call returns immediately without waiting for the command's completion. The PID of the process on the host is returned as a string. The command may redirect its stdin, stdout, or stderr as necessary. Without redirection, all input and output will use /dev/null. @param command The command to run in the background @param verbose As for `self.run()` @return Returns the PID of the remote background process as a string. """ # Redirection here isn't merely hygienic; it's a functional # requirement. sshd won't terminate until stdin, stdout, # and stderr are all closed. # # The subshell is needed to do the right thing in case the # passed in command has its own I/O redirections. cmd_fmt = '( %s ) /dev/null 2>&1 & echo -n $!' return self.run(cmd_fmt % command, verbose=verbose).stdout def run_short(self, command, **kwargs): """ Calls the run() command with a short default timeout. Takes the same arguments as does run(), with the exception of the timeout argument which here is fixed at 60 seconds. It returns the result of run. @param command: the command line string """ return self.run(command, timeout=60, **kwargs) def run_grep(self, command, timeout=30, ignore_status=False, stdout_ok_regexp=None, stdout_err_regexp=None, stderr_ok_regexp=None, stderr_err_regexp=None, connect_timeout=30): """ Run a command on the remote host and look for regexp in stdout or stderr to determine if the command was successul or not. @param command: the command line string @param timeout: time limit in seconds before attempting to kill the running process. The run() function will take a few seconds longer than 'timeout' to complete if it has to kill the process. @param ignore_status: do not raise an exception, no matter what the exit code of the command is. @param stdout_ok_regexp: regexp that should be in stdout if the command was successul. @param stdout_err_regexp: regexp that should be in stdout if the command failed. @param stderr_ok_regexp: regexp that should be in stderr if the command was successul. @param stderr_err_regexp: regexp that should be in stderr if the command failed. @param connect_timeout: connection timeout (in seconds) Returns: if the command was successul, raises an exception otherwise. Raises: AutoservRunError: - the exit code of the command execution was not 0. - If stderr_err_regexp is found in stderr, - If stdout_err_regexp is found in stdout, - If stderr_ok_regexp is not found in stderr. - If stdout_ok_regexp is not found in stdout, """ # We ignore the status, because we will handle it at the end. result = self.run(command, timeout, ignore_status=True, connect_timeout=connect_timeout) # Look for the patterns, in order for (regexp, stream) in ((stderr_err_regexp, result.stderr), (stdout_err_regexp, result.stdout)): if regexp and stream: err_re = re.compile (regexp) if err_re.search(stream): raise error.AutoservRunError( '%r failed, found error pattern: %r' % (command, regexp), result) for (regexp, stream) in ((stderr_ok_regexp, result.stderr), (stdout_ok_regexp, result.stdout)): if regexp and stream: ok_re = re.compile (regexp) if ok_re.search(stream): if ok_re.search(stream): return if not ignore_status and result.exit_status > 0: msg = result.stderr.strip() if not msg: msg = result.stdout.strip() if msg: msg = msg.splitlines()[-1] raise error.AutoservRunError("command execution error (%d): %r" % (result.exit_status, msg), result) def setup_ssh_key(self): """Setup SSH Key""" logging.debug('Performing SSH key setup on %s as %s.', self.host_port, self.user) try: host = pxssh.pxssh() host.login(self.hostname, self.user, self.password, port=self.port) public_key = utils.get_public_key() host.sendline('mkdir -p ~/.ssh') host.prompt() host.sendline('chmod 700 ~/.ssh') host.prompt() host.sendline("echo '%s' >> ~/.ssh/authorized_keys; " % public_key) host.prompt() host.sendline('chmod 600 ~/.ssh/authorized_keys') host.prompt() host.logout() logging.debug('SSH key setup complete.') except: logging.debug('SSH key setup has failed.') try: host.logout() except: pass def setup_ssh(self): """Setup SSH""" if self.password: try: self.ssh_ping() except error.AutoservSshPingHostError: self.setup_ssh_key()