Add a safety back off, so we don't spam device with indefinite reboot loop.

dbus_service/dbus-service

@@ -2,7 +2,9 @@
 
 import argparse
 import re
+import os
 import sys
+import time
 import dbus
 import dbus.mainloop.glib
 import dbus.service
@@ -156,6 +158,28 @@ class Device(dbus.service.Object):
         logging.debug('RunCmd')
         return hexlify(tls.app(unhexlify(cmd))).decode()
 
+backoff_file='/usr/share/python-validity/backoff'
+
+# I don't know how to tell systemd to backoff in case of multiple instance of the same template service, help!
+def backoff():
+    if os.path.isfile(backoff_file):
+        with open(backoff_file, 'r') as f:
+            lines = list(map(float, f.readlines()))
+    else:
+        lines=[]
+
+    while len(lines) > 0 and lines[0] + 60 < time.time():
+        lines=lines[1:]
+
+    lines += [time.time()]
+
+    with open(backoff_file, 'w') as f:
+        for l in lines:
+            f.write('%f\n' % l)
+
+    if len(lines) > 10:
+        raise Exception('Refusing to start more than 10 times per minute')
+
 if __name__ == '__main__':
     parser = argparse.ArgumentParser('Open fprintd DBus service')
     parser.add_argument('--debug', help='Enable tracing', action='store_true')
@@ -167,6 +191,8 @@ if __name__ == '__main__':
         usb.trace_enabled = True
         tls.trace_enabled = True
 
+    backoff()
+
     try:
         if args.devpath is None:
             init.open()