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

2 files changed, 145 insertions, 14 deletions

diff --git a/src/plugins/nat/nat44/ed_inlines.h b/src/plugins/nat/nat44/ed_inlines.h
new file mode 100644
index 00000000000..37212f36bf5
--- /dev/null
+++ b/src/plugins/nat/nat44/ed_inlines.h
@@ -0,0 +1,144 @@
+/*
+ * simple nat plugin
+ *
+ * Copyright (c) 2020 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __included_ed_inlines_h__
+#define __included_ed_inlines_h__
+
+#include <float.h>
+#include <vppinfra/clib.h>
+#include <nat/nat.h>
+#include <nat/nat_inlines.h>
+
+static_always_inline int
+nat_ed_lru_insert (snat_main_per_thread_data_t * tsm,
+		   snat_session_t * s, f64 now, u8 proto)
+{
+  dlist_elt_t *lru_list_elt;
+  pool_get (tsm->lru_pool, lru_list_elt);
+  s->lru_index = lru_list_elt - tsm->lru_pool;
+  switch (proto)
+    {
+    case IP_PROTOCOL_UDP:
+      s->lru_head_index = tsm->udp_lru_head_index;
+      break;
+    case IP_PROTOCOL_TCP:
+      s->lru_head_index = tsm->tcp_trans_lru_head_index;
+      break;
+    case IP_PROTOCOL_ICMP:
+      s->lru_head_index = tsm->icmp_lru_head_index;
+      break;
+    default:
+      s->lru_head_index = tsm->unk_proto_lru_head_index;
+      break;
+    }
+  clib_dlist_addtail (tsm->lru_pool, s->lru_head_index, s->lru_index);
+  lru_list_elt->value = s - tsm->sessions;
+  s->last_lru_update = now;
+  return 1;
+}
+
+always_inline void
+nat_ed_session_delete (snat_main_t * sm, snat_session_t * ses,
+		       u32 thread_index, int 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 (lru_delete)
+    {
+      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));
+
+}
+
+static_always_inline int
+nat_lru_free_one_with_head (snat_main_t * sm, int thread_index,
+			    f64 now, u32 head_index)
+{
+  snat_session_t *s = NULL;
+  dlist_elt_t *oldest_elt;
+  f64 sess_timeout_time;
+  u32 oldest_index;
+  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
+  oldest_index = clib_dlist_remove_head (tsm->lru_pool, head_index);
+  if (~0 != oldest_index)
+    {
+      oldest_elt = pool_elt_at_index (tsm->lru_pool, oldest_index);
+      s = pool_elt_at_index (tsm->sessions, oldest_elt->value);
+
+      sess_timeout_time =
+	s->last_heard + (f64) nat44_session_get_timeout (sm, s);
+      if (now >= sess_timeout_time
+	  || (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, 0);
+	  return 1;
+	}
+      else
+	{
+	  clib_dlist_addhead (tsm->lru_pool, head_index, oldest_index);
+	}
+    }
+  return 0;
+}
+
+static_always_inline int
+nat_lru_free_one (snat_main_t * sm, int thread_index, f64 now)
+{
+  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
+  int rc = 0;
+#define _(p)                                                       \
+  if ((rc = nat_lru_free_one_with_head (sm, thread_index, now,     \
+                                        tsm->p##_lru_head_index))) \
+    {                                                              \
+      return rc;                                                   \
+    }
+  _(tcp_trans);
+  _(udp);
+  _(unk_proto);
+  _(icmp);
+  _(tcp_estab);
+#undef _
+  return 0;
+}
+
+static_always_inline snat_session_t *
+nat_ed_session_alloc (snat_main_t * sm, u32 thread_index, f64 now, u8 proto)
+{
+  snat_session_t *s;
+  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
+
+  nat_lru_free_one (sm, thread_index, now);
+
+  pool_get (tsm->sessions, s);
+  clib_memset (s, 0, sizeof (*s));
+
+  nat_ed_lru_insert (tsm, s, now, proto);
+
+  s->ha_last_refreshed = now;
+  vlib_set_simple_counter (&sm->total_sessions, thread_index, 0,
+			   pool_elts (tsm->sessions));
+  return s;
+}
+
+#endif
diff --git a/src/plugins/nat/nat44/inlines.h b/src/plugins/nat/nat44/inlines.h
index a5118ea2fa6..62121dfb0db 100644
--- a/src/plugins/nat/nat44/inlines.h
+++ b/src/plugins/nat/nat44/inlines.h
@@ -59,25 +59,12 @@ nat44_session_reuse_old (snat_main_t * sm, snat_user_t * u,
   s->ext_host_port = 0;
   s->ext_host_nat_addr.as_u32 = 0;
   s->ext_host_nat_port = 0;
-  s->tcp_close_timestamp = 0;
+  s->tcp_closed_timestamp = 0;
   s->ha_last_refreshed = now;
   return s;
 }
 
 static_always_inline void
-nat44_global_lru_insert (snat_main_per_thread_data_t * tsm,
-			 snat_session_t * s, f64 now)
-{
-  dlist_elt_t *lru_list_elt;
-  pool_get (tsm->global_lru_pool, lru_list_elt);
-  s->global_lru_index = lru_list_elt - tsm->global_lru_pool;
-  clib_dlist_addtail (tsm->global_lru_pool, tsm->global_lru_head_index,
-		      s->global_lru_index);
-  lru_list_elt->value = s - tsm->sessions;
-  s->last_lru_update = now;
-}
-
-static_always_inline void
 nat44_sessions_clear ()
 {
   snat_main_t *sm = &snat_main;