nat: fix incorrect session removal case

Add a condition where a TCP session in transitory timeout is kept
instead of being erroneously deleted.

Type: fix
Signed-off-by: Klement Sekera <ksekera@cisco.com>
Change-Id: Ic625c8c88cc8864293ebd57b0321505652af9380

3 files changed, 43 insertions, 10 deletions

diff --git a/src/plugins/nat/in2out_ed.c b/src/plugins/nat/in2out_ed.c
index 5973d36ba19..d9a45dc1398 100644
--- a/src/plugins/nat/in2out_ed.c
+++ b/src/plugins/nat/in2out_ed.c
@@ -586,7 +586,7 @@ static_always_inline int
 nat44_ed_not_translate_output_feature (snat_main_t * sm, ip4_header_t * ip,
 				       u16 src_port, u16 dst_port,
 				       u32 thread_index, u32 rx_sw_if_index,
-				       u32 tx_sw_if_index)
+				       u32 tx_sw_if_index, f64 now)
 {
   clib_bihash_kv_16_8_t kv, value;
   snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
@@ -604,13 +604,12 @@ nat44_ed_not_translate_output_feature (snat_main_t * sm, ip4_header_t * ip,
       s =
 	pool_elt_at_index (tsm->sessions,
 			   ed_value_get_session_index (&value));
-      if (nat44_is_ses_closed (s))
+      if (nat44_is_ses_closed (s)
+	  && (!s->tcp_closed_timestamp || now >= s->tcp_closed_timestamp))
 	{
 	  nat_free_session_data (sm, s, thread_index, 0);
 	  nat_ed_session_delete (sm, s, thread_index, 1);
 	}
-      else
-	s->flags |= SNAT_SESSION_FLAG_OUTPUT_FEATURE;
       return 1;
     }
 
@@ -658,6 +657,7 @@ icmp_match_in2out_ed (snat_main_t * sm, vlib_node_runtime_t * node,
   vlib_main_t *vm = vlib_get_main ();
   snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
   *dont_translate = 0;
+  f64 now = vlib_time_now (vm);
 
   sw_if_index = vnet_buffer (b)->sw_if_index[VLIB_RX];
   rx_fib_index = ip4_fib_table_get_index_for_sw_if_index (sw_if_index);
@@ -679,7 +679,7 @@ icmp_match_in2out_ed (snat_main_t * sm, vlib_node_runtime_t * node,
 	  if (PREDICT_FALSE
 	      (nat44_ed_not_translate_output_feature
 	       (sm, ip, l_port, r_port, thread_index,
-		sw_if_index, vnet_buffer (b)->sw_if_index[VLIB_TX])))
+		sw_if_index, vnet_buffer (b)->sw_if_index[VLIB_TX], now)))
 	    {
 	      *dont_translate = 1;
 	      goto out;
@@ -1311,7 +1311,8 @@ nat44_ed_in2out_slow_path_node_fn_inline (vlib_main_t * vm,
 		  (nat44_ed_not_translate_output_feature
 		   (sm, ip0, vnet_buffer (b0)->ip.reass.l4_src_port,
 		    vnet_buffer (b0)->ip.reass.l4_dst_port, thread_index,
-		    sw_if_index0, vnet_buffer (b0)->sw_if_index[VLIB_TX])))
+		    sw_if_index0, vnet_buffer (b0)->sw_if_index[VLIB_TX],
+		    now)))
 		goto trace0;
 
 	      /*
diff --git a/src/plugins/nat/nat.h b/src/plugins/nat/nat.h
index 710c86fc8d9..a713f7b51cf 100644
--- a/src/plugins/nat/nat.h
+++ b/src/plugins/nat/nat.h
@@ -199,8 +199,7 @@ typedef enum
 #define SNAT_SESSION_FLAG_ENDPOINT_DEPENDENT   16
 #define SNAT_SESSION_FLAG_FWD_BYPASS           32
 #define SNAT_SESSION_FLAG_AFFINITY             64
-#define SNAT_SESSION_FLAG_OUTPUT_FEATURE       128
-#define SNAT_SESSION_FLAG_EXACT_ADDRESS        256
+#define SNAT_SESSION_FLAG_EXACT_ADDRESS        128
 
 /* NAT interface flags */
 #define NAT_INTERFACE_FLAG_IS_INSIDE 1
diff --git a/src/plugins/nat/test/test_nat44.py b/src/plugins/nat/test/test_nat44.py
index de4210fa3ff..c71b706cc34 100644
--- a/src/plugins/nat/test/test_nat44.py
+++ b/src/plugins/nat/test/test_nat44.py
@@ -5726,6 +5726,14 @@ class TestNAT44EndpointDependent(MethodHolder):
 
     def test_tcp_close(self):
         """ Close TCP session from inside network - output feature """
+        old_timeouts = self.vapi.nat_get_timeouts()
+        new_transitory = 2
+        self.vapi.nat_set_timeouts(
+                udp=old_timeouts.udp,
+                tcp_established=old_timeouts.tcp_established,
+                icmp=old_timeouts.icmp,
+                tcp_transitory=new_transitory)
+
         self.vapi.nat44_forwarding_enable_disable(enable=1)
         self.nat44_add_address(self.pg1.local_ip4)
         twice_nat_addr = '10.0.1.3'
@@ -5808,9 +5816,34 @@ class TestNAT44EndpointDependent(MethodHolder):
         self.pg_start()
         self.pg1.get_capture(1)
 
-        sessions = self.vapi.nat44_user_session_dump(self.pg0.remote_ip4,
-                                                     0)
+        # session now in transitory timeout
+        # try SYN packet out->in - should be dropped
+        p = (Ether(src=self.pg1.remote_mac, dst=self.pg1.local_mac) /
+             IP(src=self.pg1.remote_ip4, dst=service_ip) /
+             TCP(sport=33898, dport=80, flags="S"))
+        self.pg1.add_stream(p)
+        self.pg_enable_capture(self.pg_interfaces)
+        self.pg_start()
+
+        self.sleep(new_transitory, "wait for transitory timeout")
+        self.pg0.assert_nothing_captured(0)
+
+        # session should still exist
+        sessions = self.vapi.nat44_user_session_dump(self.pg0.remote_ip4, 0)
+        self.assertEqual(len(sessions) - start_sessnum, 1)
+
+        # send FIN+ACK packet out -> in - will cause session to be wiped
+        # but won't create a new session
+        p = (Ether(src=self.pg1.remote_mac, dst=self.pg1.local_mac) /
+             IP(src=self.pg1.remote_ip4, dst=service_ip) /
+             TCP(sport=33898, dport=80, flags="FA", seq=300, ack=101))
+        self.pg1.add_stream(p)
+        self.pg_enable_capture(self.pg_interfaces)
+        self.pg_start()
+
+        sessions = self.vapi.nat44_user_session_dump(self.pg0.remote_ip4, 0)
         self.assertEqual(len(sessions) - start_sessnum, 0)
+        self.pg0.assert_nothing_captured(0)
 
     def test_tcp_session_close_in(self):
         """ Close TCP session from inside network """