Timeout when performing time sync during client install

We use ntpd now to sync time before fetching a TGT during client
install.  Unfortuantely, ntpd will hang forever if it is unable to
reach the NTP server.

This patch adds the ability for commands run via ipautil.run() to
have an optional timeout.  This capability is used by the NTP sync
code that is run during ipa-client-install.

Ticket: https://fedorahosted.org/freeipa/ticket/4842
Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>

ipa-client/ipaclient/ntpconf.py

@@ -18,6 +18,7 @@
 #
 
 from ipapython import ipautil
+from ipapython.ipa_log_manager import root_logger
 import shutil
 import os
 from ipaplatform.tasks import tasks
@@ -149,7 +150,12 @@ def synconce_ntp(server_fqdn):
 
     tmp_ntp_conf = ipautil.write_tmp_file('server %s' % server_fqdn)
     try:
-        ipautil.run([ntpd, '-qgc', tmp_ntp_conf.name])
+        # The ntpd command will never exit if it is unable to reach the
+        # server, so timeout after 15 seconds.
+        timeout = 15
+        root_logger.info('Attempting to sync time using ntpd.  '
+                         'Will timeout after %d seconds' % timeout)
+        ipautil.run([ntpd, '-qgc', tmp_ntp_conf.name], timeout=timeout)
         return True
     except ipautil.CalledProcessError:
         return False

ipaplatform/base/paths.py

@@ -186,6 +186,7 @@ class BasePathNamespace(object):
     SSLGET = "/usr/bin/sslget"
     SSS_SSH_AUTHORIZEDKEYS = "/usr/bin/sss_ssh_authorizedkeys"
     SSS_SSH_KNOWNHOSTSPROXY = "/usr/bin/sss_ssh_knownhostsproxy"
+    BIN_TIMEOUT = "/usr/bin/timeout"
     UPDATE_CA_TRUST = "/usr/bin/update-ca-trust"
     BIN_WGET = "/usr/bin/wget"
     ZIP = "/usr/bin/zip"

ipapython/ipautil.py

@@ -249,7 +249,7 @@ def shell_quote(string):
 
 def run(args, stdin=None, raiseonerr=True,
         nolog=(), env=None, capture_output=True, skip_output=False, cwd=None,
-        runas=None):
+        runas=None, timeout=None):
     """
     Execute a command and return stdin, stdout and the process return code.
 
@@ -277,6 +277,8 @@ def run(args, stdin=None, raiseonerr=True,
     :param cwd: Current working directory
     :param runas: Name of a user that the command shold be run as. The spawned
         process will have both real and effective UID and GID set.
+    :param timeout: Timeout if the command hasn't returned within the specified
+        number of seconds.
     """
     p_in = None
     p_out = None
@@ -302,6 +304,11 @@ def run(args, stdin=None, raiseonerr=True,
         p_out = subprocess.PIPE
         p_err = subprocess.PIPE
 
+    if timeout:
+        # If a timeout was provided, use the timeout command
+        # to execute the requested command.
+        args[0:0] = [paths.BIN_TIMEOUT, str(timeout)]
+
     arg_string = nolog_replace(' '.join(shell_quote(a) for a in args), nolog)
     root_logger.debug('Starting external process')
     root_logger.debug('args=%s' % arg_string)
@@ -332,6 +339,9 @@ def run(args, stdin=None, raiseonerr=True,
         if skip_output:
             p_out.close()   # pylint: disable=E1103
 
+    if timeout and p.returncode == 124:
+        root_logger.debug('Process did not complete before timeout')
+
     root_logger.debug('Process finished, return code=%s', p.returncode)
 
     # The command and its output may include passwords that we don't want