If fast-reboot-dump gives an error, don't continue with fast-reboot (sonic-net#515)

* If fast-reboot-dump gives an error, don't continue with fast-reboot

Author: pavel-shirshov

scripts/fast-reboot

@@ -24,6 +24,7 @@ EXIT_FILE_SYSTEM_FULL=3
 EXIT_NEXT_IMAGE_NOT_EXISTS=4
 EXIT_ORCHAGENT_SHUTDOWN=10
 EXIT_SYNCD_SHUTDOWN=11
+EXIT_FAST_REBOOT_DUMP_FAILURE=12
 
 function error()
 {
@@ -251,6 +252,14 @@ function reboot_pre_check()
     fi
 }
 
+function unload_kernel()
+{
+    # Unload the previously loaded kernel if any loaded
+    if [[ "$(cat /sys/kernel/kexec_loaded)" -eq 1 ]]; then
+        /sbin/kexec -u
+    fi
+}
+
 # main starts here
 parseOptions $@
 
@@ -292,11 +301,7 @@ case "$REBOOT_TYPE" in
         ;;
 esac
 
-# Unload the previously loaded kernel if any loaded
-if [[ "$(cat /sys/kernel/kexec_loaded)" -eq 1 ]]
-then
-    /sbin/kexec -u
-fi
+unload_kernel
 
 setup_reboot_variables
 
@@ -336,7 +341,13 @@ if [[ "$REBOOT_TYPE" = "fast-reboot" ]]; then
     # Dump the ARP and FDB tables to files also as default routes for both IPv4 and IPv6
     # into /host/fast-reboot
     mkdir -p /host/fast-reboot
-    /usr/bin/fast-reboot-dump.py -t /host/fast-reboot
+    FAST_REBOOT_DUMP_RC=0
+    /usr/bin/fast-reboot-dump.py -t /host/fast-reboot || FAST_REBOOT_DUMP_RC=$?
+    if [[ FAST_REBOOT_DUMP_RC -ne 0 ]]; then
+        error "Failed to run fast-reboot-dump.py. Exit code: $FAST_REBOOT_DUMP_RC"
+        unload_kernel
+        exit "${EXIT_FAST_REBOOT_DUMP_FAILURE}"
+    fi
 fi
 
 init_warm_reboot_states

scripts/fast-reboot-dump.py

@@ -9,6 +9,8 @@
 from fcntl import ioctl
 import binascii
 import argparse
+import syslog
+import traceback
 
 
 ARP_CHUNK = binascii.unhexlify('08060001080006040001') # defines a part of the packet for ARP Request
@@ -267,14 +269,27 @@ def main():
     root_dir = args.target
     if not os.path.isdir(root_dir):
         print "Target directory '%s' not found" % root_dir
-        sys.exit(1)
+        return 3
     all_available_macs, map_mac_ip_per_vlan = generate_fdb_entries(root_dir + '/fdb.json')
     arp_entries = generate_arp_entries(root_dir + '/arp.json', all_available_macs)
     generate_default_route_entries(root_dir + '/default_routes.json')
     garp_send(arp_entries, map_mac_ip_per_vlan)
-
-    return
-
+    return 0
 
 if __name__ == '__main__':
-    main()
+    res = 0
+    try:
+        syslog.openlog('fast-reboot-dump')
+        res = main()
+    except KeyboardInterrupt:
+        syslog.syslog(syslog.LOG_NOTICE, "SIGINT received. Quitting")
+        res = 1
+    except Exception as e:
+        syslog.syslog(syslog.LOG_ERR, "Got an exception %s: Traceback: %s" % (str(e), traceback.format_exc()))
+        res = 2
+    finally:
+        syslog.closelog()
+    try:
+        sys.exit(res)
+    except SystemExit:
+        os._exit(res)