backporting security fix of issue 9129 (smtpd module vulnerable to DoS attacks in case of connection bashing)
diff --git a/Lib/smtpd.py b/Lib/smtpd.py
index c3bd6a5..94bd8e6 100755
--- a/Lib/smtpd.py
+++ b/Lib/smtpd.py
@@ -121,7 +121,15 @@
         self.__rcpttos = []
         self.__data = ''
         self.__fqdn = socket.getfqdn()
-        self.__peer = conn.getpeername()
+        try:
+            self.__peer = conn.getpeername()
+        except socket.error as err:
+            # a race condition  may occur if the other end is closing
+            # before we can get the peername
+            self.close()
+            if err.args[0] != errno.ENOTCONN:
+                raise
+            return
         print >> DEBUGSTREAM, 'Peer:', repr(self.__peer)
         self.push('220 %s %s' % (self.__fqdn, __version__))
         self.set_terminator('\r\n')
@@ -291,7 +299,20 @@
                 localaddr, remoteaddr)
 
     def handle_accept(self):
-        conn, addr = self.accept()
+        try:
+            conn, addr = self.accept()
+        except TypeError:
+            # sometimes accept() might return None
+            return
+        except socket.error as err:
+            # ECONNABORTED might be thrown
+            if err.args[0] != errno.ECONNABORTED:
+                raise
+            return
+        else:
+            # sometimes addr == None instead of (ip, port)
+            if addr == None:
+                return
         print >> DEBUGSTREAM, 'Incoming connection from %s' % repr(addr)
         channel = SMTPChannel(self, conn, addr)