Reduce probability of dying when the system lacks memory

Some servers can only be accessed via their re6st IP. re6st itself uses little
memory so it should not die when it fails to fork.

re6st/tunnel.py

@@ -16,7 +16,7 @@ class MultiGatewayManager(dict):
         if gw:
             cmd = 'ip', '-4', 'route', cmd, '%s/32' % dest, 'via', gw
             logging.trace('%r', cmd)
-            subprocess.call(cmd)
+            subprocess.check_call(cmd)
 
     def add(self, dest, route):
         try:
@@ -150,7 +150,7 @@ class TunnelManager(object):
             action = 'add'
         args = 'ip', 'tuntap', action, 'dev', iface, 'mode', 'tap'
         logging.debug('%r', args)
-        subprocess.call(args)
+        subprocess.check_call(args)
         return iface
 
     def delInterfaces(self):

re6st/utils.py

@@ -147,6 +147,14 @@ exit = exit()
 
 class Popen(subprocess.Popen):
 
+    def __init__(self, *args, **kw):
+      try:
+          super(Popen, self).__init__(*args, **kw)
+      except OSError, e:
+          if e.errno != errno.ENOMEM:
+            raise
+          self.returncode = -1
+
     def stop(self):
         self.terminate()
         t = threading.Timer(5, self.kill)
@@ -230,8 +238,7 @@ def iterRoutes(network, exclude_prefix=None):
                 yield iface, prefix
 
 def decrypt(key_path, data):
-    p = subprocess.Popen(
-        ('openssl', 'rsautl', '-decrypt', '-inkey', key_path),
+    p = Popen(('openssl', 'rsautl', '-decrypt', '-inkey', key_path),
               stdin=subprocess.PIPE, stdout=subprocess.PIPE)
     out, err = p.communicate(data)
     if p.returncode:
@@ -242,7 +249,7 @@ def encrypt(cert, data):
     r, w = os.pipe()
     try:
         threading.Thread(target=os.write, args=(w, cert)).start()
-        p = subprocess.Popen(('openssl', 'rsautl', '-encrypt', '-certin',
+        p = Popen(('openssl', 'rsautl', '-encrypt', '-certin',
                               '-inkey', '/proc/self/fd/%u' % r),
                   stdin=subprocess.PIPE, stdout=subprocess.PIPE)
         out, err = p.communicate(data)

re6stnet

@@ -369,7 +369,11 @@ def main():
                     try:
                         while True:
                             time.sleep(60)
+                            try:
                                 check_no_default_route()
+                            except OSError, e:
+                                if e.errno != errno.ENOMEM:
+                                    raise
                     except:
                         utils.log_exception()
                     finally: