Add pre-start script to fail fast when app and system domains overlap

Signed-off-by: Eric Saxby <esaxby@pivotal.io>

jobs/cloud_controller_ng/spec

@@ -29,6 +29,8 @@ templates:
   dea_ca.crt.erb: config/certs/dea_ca.crt
   dea_client.crt.erb: config/certs/dea_client.crt
   dea_client.key.erb: config/certs/dea_client.key
+  pre-start.sh.erb: bin/pre-start
+  check_for_domain_overlap.sh: bin/check_for_domain_overlap.sh
 
 packages:
   - capi_utils

jobs/cloud_controller_ng/templates/check_for_domain_overlap.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+
+
+function check_for_domain_overlap {
+  system_domain=$1
+  shift
+  app_domains=($@)
+
+  for app_domain in "${app_domains[@]}"; do
+    if [[ $app_domain == *$system_domain ]]; then
+      echo "Invalid configuration: app_domains contains the value ${app_domain} which is a sub-domain of the system_domain, ${system_domain}."
+      return 1
+    fi
+  done
+}
+

jobs/cloud_controller_ng/templates/pre-start.sh.erb

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+
+SCRIPT_DIR="$(dirname "${BASH_SOURCE[0]}")"
+source "${SCRIPT_DIR}/check_for_domain_overlap.sh"
+
+app_domains=(<%= p('app_domains').join(' ') %>)
+system_domain=<%= p('system_domain') %>
+
+check_for_domain_overlap $system_domain ${app_domains[@]}
+exit $?