nat: fix LRU blocked by inactive session

This fixes a situation where long-lived inactive session blocks LRU
list. Solution is to have multiple LRU lists based on session type.
This helps because session timeout is same for all sessions of same
type.

Type: fix

Signed-off-by: Klement Sekera <ksekera@cisco.com>
Change-Id: I5e54b2aab73b23911d6518d42e8c3f166c69a38c

1 files changed, 42 insertions, 31 deletions

diff --git a/src/plugins/nat/nat_inlines.h b/src/plugins/nat/nat_inlines.h
index e5ac421a6f9..d37cb10b6fd 100644
--- a/src/plugins/nat/nat_inlines.h
+++ b/src/plugins/nat/nat_inlines.h
@@ -261,8 +261,11 @@ nat44_delete_session (snat_main_t * sm, snat_session_t * ses,
 
   clib_dlist_remove (tsm->list_pool, ses->per_user_index);
   pool_put_index (tsm->list_pool, ses->per_user_index);
-  clib_dlist_remove (tsm->global_lru_pool, ses->global_lru_index);
-  pool_put_index (tsm->global_lru_pool, ses->global_lru_index);
+  if (sm->endpoint_dependent)
+    {
+      clib_dlist_remove (tsm->lru_pool, ses->lru_index);
+      pool_put_index (tsm->lru_pool, ses->lru_index);
+    }
   pool_put (tsm->sessions, ses);
   vlib_set_simple_counter (&sm->total_sessions, thread_index, 0,
 			   pool_elts (tsm->sessions));
@@ -280,25 +283,6 @@ nat44_delete_session (snat_main_t * sm, snat_session_t * ses,
     }
 }
 
-always_inline void
-nat44_ed_delete_session (snat_main_t * sm, snat_session_t * ses,
-			 u32 thread_index, int global_lru_delete
-			 /* delete from global LRU list */ )
-{
-  snat_main_per_thread_data_t *tsm = vec_elt_at_index (sm->per_thread_data,
-						       thread_index);
-
-  if (global_lru_delete)
-    {
-      clib_dlist_remove (tsm->global_lru_pool, ses->global_lru_index);
-    }
-  pool_put_index (tsm->global_lru_pool, ses->global_lru_index);
-  pool_put (tsm->sessions, ses);
-  vlib_set_simple_counter (&sm->total_sessions, thread_index, 0,
-			   pool_elts (tsm->sessions));
-
-}
-
 /** \brief Set TCP session state.
     @return 1 if session was closed, otherwise 0
 */
@@ -307,6 +291,7 @@ nat44_set_tcp_session_state_i2o (snat_main_t * sm, f64 now,
 				 snat_session_t * ses, vlib_buffer_t * b,
 				 u32 thread_index)
 {
+  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
   u8 tcp_flags = vnet_buffer (b)->ip.reass.icmp_type_or_tcp_flags;
   u32 tcp_ack_number = vnet_buffer (b)->ip.reass.tcp_ack_number;
   u32 tcp_seq_number = vnet_buffer (b)->ip.reass.tcp_seq_number;
@@ -331,10 +316,23 @@ nat44_set_tcp_session_state_i2o (snat_main_t * sm, f64 now,
 	  ses->state |= NAT44_SES_O2I_FIN_ACK;
 	  if (nat44_is_ses_closed (ses))
 	    {			// if session is now closed, save the timestamp
-	      ses->tcp_close_timestamp = now + sm->tcp_transitory_timeout;
+	      ses->tcp_closed_timestamp = now + sm->tcp_transitory_timeout;
+	      ses->last_lru_update = now;
 	    }
 	}
     }
+
+  // move the session to proper LRU
+  if (ses->state)
+    {
+      ses->lru_head_index = tsm->tcp_trans_lru_head_index;
+    }
+  else
+    {
+      ses->lru_head_index = tsm->tcp_estab_lru_head_index;
+    }
+  clib_dlist_remove (tsm->lru_pool, ses->lru_index);
+  clib_dlist_addtail (tsm->lru_pool, ses->lru_head_index, ses->lru_index);
   return 0;
 }
 
@@ -344,6 +342,7 @@ nat44_set_tcp_session_state_o2i (snat_main_t * sm, f64 now,
 				 u32 tcp_ack_number, u32 tcp_seq_number,
 				 u32 thread_index)
 {
+  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
   if ((ses->state == 0) && (tcp_flags & TCP_FLAG_RST))
     ses->state = NAT44_SES_RST;
   if ((ses->state == NAT44_SES_RST) && !(tcp_flags & TCP_FLAG_RST))
@@ -364,9 +363,21 @@ nat44_set_tcp_session_state_o2i (snat_main_t * sm, f64 now,
 	ses->state |= NAT44_SES_I2O_FIN_ACK;
       if (nat44_is_ses_closed (ses))
 	{			// if session is now closed, save the timestamp
-	  ses->tcp_close_timestamp = now + sm->tcp_transitory_timeout;
+	  ses->tcp_closed_timestamp = now + sm->tcp_transitory_timeout;
+	  ses->last_lru_update = now;
 	}
     }
+  // move the session to proper LRU
+  if (ses->state)
+    {
+      ses->lru_head_index = tsm->tcp_trans_lru_head_index;
+    }
+  else
+    {
+      ses->lru_head_index = tsm->tcp_estab_lru_head_index;
+    }
+  clib_dlist_remove (tsm->lru_pool, ses->lru_index);
+  clib_dlist_addtail (tsm->lru_pool, ses->lru_head_index, ses->lru_index);
   return 0;
 }
 
@@ -411,7 +422,7 @@ always_inline void
 nat44_session_update_lru (snat_main_t * sm, snat_session_t * s,
 			  u32 thread_index)
 {
-  /* don't update too often - timeout is in a magnitude of seconds anyway */
+  /* don't update too often - timeout is in magnitude of seconds anyway */
   if (s->last_heard > s->last_lru_update + 1)
     {
       if (!sm->endpoint_dependent)
@@ -421,13 +432,13 @@ nat44_session_update_lru (snat_main_t * sm, snat_session_t * s,
 	  clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
 			      s->per_user_list_head_index, s->per_user_index);
 	}
-
-      clib_dlist_remove (sm->per_thread_data[thread_index].global_lru_pool,
-			 s->global_lru_index);
-      clib_dlist_addtail (sm->per_thread_data[thread_index].global_lru_pool,
-			  sm->
-			  per_thread_data[thread_index].global_lru_head_index,
-			  s->global_lru_index);
+      else
+	{
+	  clib_dlist_remove (sm->per_thread_data[thread_index].lru_pool,
+			     s->lru_index);
+	  clib_dlist_addtail (sm->per_thread_data[thread_index].lru_pool,
+			      s->lru_head_index, s->lru_index);
+	}
       s->last_lru_update = s->last_heard;
     }
 }