ipsec: GCM, Anti-replay and ESN fixess

Type: fix

Several Fixes:
 1 - Anti-replay did not work with GCM becuase it overwrote the sequence
number in the ESP header. To fix i added the seq num to the per-packet
data so it is preserved
 2 - The high sequence number was not byte swapped during ESP encrypt.
 3 - openssl engine was the only one to return FAIL_DECRYPT for bad GCM
the others return BAD_HMAC. removed the former
 4 - improved tracing to show the low and high seq numbers
 5 - documented the anti-replay window checks
 6 - fixed scapy patch for ESN support for GCM
 7 - tests for anti-reply (w/ and w/o ESN) for each crypto algo

Change-Id: Id65d96b6d1d4dd821b2ab557e87468fff6d70e5b
Signed-off-by: Neale Ranns <nranns@cisco.com>

test/test_ipsec_esp.py

@@ -486,6 +486,14 @@ class TestIpsecEspAll(ConfigIpsecESP,
                     #
                     self.unconfig_network()
 
+                    #
+                    # reconfigure the network and SA to run the
+                    # anti replay tests
+                    #
+                    self.config_network(self.params.values())
+                    self.verify_tra_anti_replay()
+                    self.unconfig_network()
+
 
 if __name__ == '__main__':
     unittest.main(testRunner=VppTestRunner)