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# 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
import inspect
import logging
import re
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
# In case cros_host is being ran via SSP on an older Moblab version with an
# older chromite version.
from chromite.lib import metrics
except ImportError:
metrics = utils.metrics_mock
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
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.
def _initialize(self, hostname, *args, **dargs):
Construct a SSHHost object
hostname: network hostname or address of remote machine
super(SSHHost, self)._initialize(hostname=hostname, *args, **dargs)
def ssh_command(self, connect_timeout=30, options='', alive_interval=300):
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.
options = "%s %s" % (options, self.master_ssh_option)
base_cmd = self.make_ssh_command(user=self.user, port=self.port,
return "%s %s" % (base_cmd, self.hostname)
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.
stack_frames = inspect.stack()
stack = ''
# The last 2 frames on the stack are boring. Print 5-2=3 stack frames.
count = min(5, len(stack_frames))
if count >= 3:
stack = inspect.getframeinfo(stack_frames[2][0]).function
for frame in stack_frames[3:count]:
function_name = inspect.getframeinfo(frame[0]).function
stack = '%s|%s' % (function_name, stack)
del stack_frames
# If "logger" executable exists on the DUT use it to respew |command|.
# Then regardless of "logger" run |command| as usual.
command = ('if type "logger" > /dev/null 2>&1; then'
' logger -tag "autotest" "server[stack::%s] -> ssh_run(%s)";'
'fi; '
'%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()."""
ssh_cmd = self.ssh_command(connect_timeout, options)
if not env.strip():
env = ""
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): - 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}
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}
# 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 return None on timeouts
# (and only on timeouts).
original_ignore_timeout = ignore_timeout
ignore_timeout = True
ssh_failure_retry_count = 2
ssh_failure_retry_count = 0
ssh_call_count = 0
while True:
# Increment call count first, in case throws an
# exception.
ssh_call_count += 1
result =, timeout, True, stdout, stderr,
verbose=False, stdin=stdin,
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'^ssh: .*: Name or service not known',
failure_name = 'dns_failure'
failure_name = 'error_255'
elif result.exit_status > 0:
failure_name = 'nonzero_status'
# 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
if ssh_failure_retry_count == 2:
logging.debug('retrying ssh command after %s',
ssh_failure_retry_count -= 1
elif ssh_failure_retry_count == 1:
# After two failures, restart the master connection
# before the final try.
logging.debug('retry 2: restarting master connection')
# Last retry: reinstate timeout behavior.
ignore_timeout = original_ignore_timeout
ssh_failure_retry_count -= 1
# No retry conditions occurred. Exit the loop.
# 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'^ssh: connect to host .* port .*: '
r'Connection timed out\r$', result.stderr):
counters_inc('run', 'final_timeout')
raise error.AutoservSSHTimeout("ssh timed out", 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')
raise error.AutoservRunError("command execution error", result)
counters_inc('run', failure_name)
return result
def run(self, command, timeout=3600, 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.
@param timeout: command execution timeout
@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
if verbose:
logging.debug("Running (ssh) '%s'", command)
command = self._verbose_logger_command(command)
# Start a master SSH connection if necessary.
env = " ".join("=".join(pair) for pair in self.env.iteritems())
return self._run(command, timeout, ignore_status,
stdout_tee, stderr_tee, connect_timeout, env,
options, stdin, args, ignore_timeout,
except error.CmdError, 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 ``
@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 >/dev/null 2>&1 & echo -n $!'
return % 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, 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,
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)
if the command was successul, raises an exception
- 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 =, timeout, ignore_status=True,
# 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)
raise error.AutoservRunError(
'%s failed, found error pattern: "%s"' % (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 not ignore_status and result.exit_status > 0:
raise error.AutoservRunError("command execution error", result)
def setup_ssh_key(self):
"""Setup SSH Key"""
logging.debug('Performing SSH key setup on %s:%d as %s.',
self.hostname, self.port, self.user)
host = pxssh.pxssh()
host.login(self.hostname, self.user, self.password,
public_key = utils.get_public_key()
host.sendline('mkdir -p ~/.ssh')
host.sendline('chmod 700 ~/.ssh')
host.sendline("echo '%s' >> ~/.ssh/authorized_keys; " %
host.sendline('chmod 600 ~/.ssh/authorized_keys')
logging.debug('SSH key setup complete.')
logging.debug('SSH key setup has failed.')
def setup_ssh(self):
"""Setup SSH"""
if self.password:
except error.AutoservSshPingHostError: