Add more robust ssh ping to be run on reboot for updates.

remote_access.sh

 # Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Library for setting up remote access and running remote commands.
 
 DEFAULT_PRIVATE_KEY="${GCLIENT_ROOT}/src/scripts/mod_for_test_scripts/\
 ssh_keys/testing_rsa"
 
 DEFINE_string remote "" "remote hostname/IP of running Chromium OS instance"
@@ skipping 16 matching lines @@
             UserKnownHostsFile=$TMP_KNOWN_HOSTS" --no-R \
     --files-from=$1 root@${FLAGS_remote}:/ $2
 }
 
 function remote_sh() {
   REMOTE_OUT=$(ssh -p ${FLAGS_ssh_port} -o StrictHostKeyChecking=no -o \
     UserKnownHostsFile=$TMP_KNOWN_HOSTS root@$FLAGS_remote "$@")
   return ${PIPESTATUS[0]}
 }
 
+# Checks to see if pid $1 is running.
+function is_pid_running() {
+  ps -p ${1} 2>&1 > /dev/null
+}
+
+# Wait function given an additional timeout argument.
+# $1 - pid to wait on.
+# $2 - timeout to wait for.
+function wait_with_timeout() {
+  local pid=$1
+  local timeout=$2
+  local -r TIMEOUT_INC=1
+  local current_timeout=0
+  while is_pid_running ${pid} && [ ${current_timeout} -lt ${timeout} ]; do
+    sleep ${TIMEOUT_INC}
+    current_timeout=$((current_timeout + TIMEOUT_INC))
+  done
+  is_pid_running ${pid}
+}
+
+# Robust ping that will monitor ssh and not hang even if ssh hangs.
+function ping_ssh() {
+  remote_sh "true" &
+  local pid=$!
+  wait_with_timeout ${pid} 5
+  ! kill -9 ${pid} 2> /dev/null
+}
+
 function remote_sh_allow_changed_host_key() {
   rm -f $TMP_KNOWN_HOSTS
+  ping_ssh
   remote_sh "$@"
 }
 
 function set_up_remote_access() {
   if [ -z "$SSH_AGENT_PID" ]; then
     eval $(ssh-agent)
     OWN_SSH_AGENT=1
   else
     OWN_SSH_AGENT=0
   fi
@@ skipping 57 matching lines @@
 
 function remote_access_init() {
   TMP_PRIVATE_KEY=$TMP/private_key
   TMP_KNOWN_HOSTS=$TMP/known_hosts
   if [ -z "$FLAGS_remote" ]; then
     echo "Please specify --remote=<IP-or-hostname> of the Chromium OS instance"
     exit 1
   fi
   set_up_remote_access
 }