NAT44: recycle old sessions for forwarding bypass (VPP-1240)

Change-Id: I7e6b0e7e91cc032b1685f35de5d84363a85158a5
Signed-off-by: Matus Fabian <matfabia@cisco.com>

4 files changed, 98 insertions, 17 deletions

diff --git a/src/plugins/nat/in2out.c b/src/plugins/nat/in2out.c
index 996c626d46c..7d9d6c3e6c1 100755
--- a/src/plugins/nat/in2out.c
+++ b/src/plugins/nat/in2out.c
@@ -490,11 +490,14 @@ icmp_get_ed_key(ip4_header_t *ip0, nat_ed_ses_key_t *p_key0)
 }
 
 static inline int
-nat_not_translate_output_feature_fwd (snat_main_t * sm, ip4_header_t * ip)
+nat_not_translate_output_feature_fwd (snat_main_t * sm, ip4_header_t * ip,
+                                      u32 thread_index)
 {
   nat_ed_ses_key_t key;
   clib_bihash_kv_16_8_t kv, value;
   udp_header_t *udp;
+  snat_session_t *s = 0;
+  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
 
   if (!sm->forwarding_enabled)
     return 0;
@@ -525,7 +528,19 @@ nat_not_translate_output_feature_fwd (snat_main_t * sm, ip4_header_t * ip)
   kv.key[1] = key.as_u64[1];
 
   if (!clib_bihash_search_16_8 (&sm->in2out_ed, &kv, &value))
-    return value.value == ~0ULL;
+    {
+      s = pool_elt_at_index (sm->per_thread_data[thread_index].sessions, value.value);
+      if (is_fwd_bypass_session (s))
+        {
+          /* Per-user LRU list maintenance */
+          clib_dlist_remove (tsm->list_pool, s->per_user_index);
+          clib_dlist_addtail (tsm->list_pool, s->per_user_list_head_index,
+                              s->per_user_index);
+          return 1;
+        }
+      else
+        return 0;
+    }
 
   return 0;
 }
@@ -1348,9 +1363,9 @@ snat_in2out_lb (snat_main_t *sm,
 
   if (!clib_bihash_search_16_8 (&sm->in2out_ed, &s_kv, &s_value))
     {
-      if (s_value.value == ~0ULL)
-        return 0;
       s = pool_elt_at_index (tsm->sessions, s_value.value);
+      if (is_fwd_bypass_session (s))
+        return 0;
     }
   else
     {
@@ -1588,7 +1603,7 @@ snat_in2out_node_fn_inline (vlib_main_t * vm,
             {
               if (is_output_feature)
                 {
-                  if (PREDICT_FALSE(nat_not_translate_output_feature_fwd(sm, ip0)))
+                  if (PREDICT_FALSE(nat_not_translate_output_feature_fwd(sm, ip0, thread_index)))
                     goto trace00;
                 }
 
@@ -1780,7 +1795,7 @@ snat_in2out_node_fn_inline (vlib_main_t * vm,
             {
               if (is_output_feature)
                 {
-                  if (PREDICT_FALSE(nat_not_translate_output_feature_fwd(sm, ip1)))
+                  if (PREDICT_FALSE(nat_not_translate_output_feature_fwd(sm, ip1, thread_index)))
                     goto trace01;
                 }
 
@@ -2008,7 +2023,7 @@ snat_in2out_node_fn_inline (vlib_main_t * vm,
             {
                if (is_output_feature)
                 {
-                  if (PREDICT_FALSE(nat_not_translate_output_feature_fwd(sm, ip0)))
+                  if (PREDICT_FALSE(nat_not_translate_output_feature_fwd(sm, ip0, thread_index)))
                     goto trace0;
                 }
 
diff --git a/src/plugins/nat/nat.c b/src/plugins/nat/nat.c
index 764bc1db6bb..51fbb1336e1 100755
--- a/src/plugins/nat/nat.c
+++ b/src/plugins/nat/nat.c
@@ -152,6 +152,21 @@ nat_free_session_data (snat_main_t * sm, snat_session_t * s, u32 thread_index)
   snat_main_per_thread_data_t *tsm =
     vec_elt_at_index (sm->per_thread_data, thread_index);
 
+  if (is_fwd_bypass_session (s))
+    {
+      ed_key.l_addr = s->in2out.addr;
+      ed_key.r_addr = s->ext_host_addr;
+      ed_key.l_port = s->in2out.port;
+      ed_key.r_port = s->ext_host_port;
+      ed_key.proto = snat_proto_to_ip_proto (s->in2out.protocol);
+      ed_key.fib_index = 0;
+      ed_kv.key[0] = ed_key.as_u64[0];
+      ed_kv.key[1] = ed_key.as_u64[1];
+      if (clib_bihash_add_del_16_8 (&sm->in2out_ed, &ed_kv, 0))
+        clib_warning ("in2out_ed key del failed");
+      return;
+    }
+
   /* Endpoint dependent session lookup tables */
   if (is_ed_session (s))
     {
diff --git a/src/plugins/nat/nat.h b/src/plugins/nat/nat.h
index fb4ed98f837..8d7d1738fb3 100644
--- a/src/plugins/nat/nat.h
+++ b/src/plugins/nat/nat.h
@@ -129,6 +129,7 @@ typedef enum {
 #define SNAT_SESSION_FLAG_UNKNOWN_PROTO  2
 #define SNAT_SESSION_FLAG_LOAD_BALANCING 4
 #define SNAT_SESSION_FLAG_TWICE_NAT      8
+#define SNAT_SESSION_FLAG_FWD_BYPASS     16
 
 #define NAT_INTERFACE_FLAG_IS_INSIDE 1
 #define NAT_INTERFACE_FLAG_IS_OUTSIDE 2
@@ -463,6 +464,12 @@ typedef struct {
 */
 #define is_lb_session(s) (s->flags & SNAT_SESSION_FLAG_LOAD_BALANCING)
 
+/** \brief Check if NAT session is forwarding bypass.
+    @param s NAT session
+    @return 1 if NAT session is load-balancing
+*/
+#define is_fwd_bypass_session(s) (s->flags & SNAT_SESSION_FLAG_FWD_BYPASS)
+
 /** \brief Check if NAT session is endpoint dependent.
     @param s NAT session
     @return 1 if NAT session is endpoint dependent
diff --git a/src/plugins/nat/out2in.c b/src/plugins/nat/out2in.c
index 553883d1144..637a07341e0 100755
--- a/src/plugins/nat/out2in.c
+++ b/src/plugins/nat/out2in.c
@@ -333,11 +333,15 @@ next_src_nat (snat_main_t * sm, ip4_header_t * ip, u32 proto, u16 src_port,
 }
 
 static void
-create_bypass_for_fwd(snat_main_t * sm, ip4_header_t * ip)
+create_bypass_for_fwd(snat_main_t * sm, ip4_header_t * ip, u32 rx_fib_index,
+                      u32 thread_index)
 {
   nat_ed_ses_key_t key;
-  clib_bihash_kv_16_8_t kv;
+  clib_bihash_kv_16_8_t kv, value;
   udp_header_t *udp;
+  snat_user_t *u;
+  snat_session_t *s = 0;
+  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
 
   if (ip->protocol == IP_PROTOCOL_ICMP)
     {
@@ -363,10 +367,50 @@ create_bypass_for_fwd(snat_main_t * sm, ip4_header_t * ip)
   key.fib_index = 0;
   kv.key[0] = key.as_u64[0];
   kv.key[1] = key.as_u64[1];
-  kv.value = ~0ULL;
 
-  if (clib_bihash_add_del_16_8 (&sm->in2out_ed, &kv, 1))
-    clib_warning ("in2out_ed key add failed");
+  if (!clib_bihash_search_16_8 (&sm->in2out_ed, &kv, &value))
+    {
+      s = pool_elt_at_index (tsm->sessions, value.value);
+    }
+  else
+    {
+      if (PREDICT_FALSE (maximum_sessions_exceeded(sm, thread_index)))
+        return;
+
+      u = nat_user_get_or_create (sm, &ip->dst_address, sm->inside_fib_index, thread_index);
+      if (!u)
+        {
+          clib_warning ("create NAT user failed");
+          return;
+        }
+
+      s = nat_session_alloc_or_recycle (sm, u, thread_index);
+      if (!s)
+        {
+          clib_warning ("create NAT session failed");
+          return;
+        }
+
+      s->ext_host_addr = key.r_addr;
+      s->ext_host_port = key.r_port;
+      s->flags |= SNAT_SESSION_FLAG_FWD_BYPASS;
+      s->outside_address_index = ~0;
+      s->out2in.addr = key.l_addr;
+      s->out2in.port = key.l_port;
+      s->out2in.protocol = ip_proto_to_snat_proto (key.proto);
+      s->out2in.fib_index = 0;
+      s->in2out = s->out2in;
+      user_session_increment (sm, u, 0);
+
+      kv.value = s - tsm->sessions;
+      if (clib_bihash_add_del_16_8 (&sm->in2out_ed, &kv, 1))
+        clib_warning ("in2out_ed key add failed");
+    }
+
+  /* Per-user LRU list maintenance */
+  clib_dlist_remove (tsm->list_pool, s->per_user_index);
+  clib_dlist_addtail (tsm->list_pool, s->per_user_list_head_index,
+                      s->per_user_index);
 }
 
 /**
@@ -446,7 +490,7 @@ u32 icmp_match_out2in_slow(snat_main_t *sm, vlib_node_runtime_t *node,
                   next0 = SNAT_OUT2IN_NEXT_IN2OUT;
                   goto out;
                 }
-              create_bypass_for_fwd(sm, ip0);
+              create_bypass_for_fwd(sm, ip0, rx_fib_index0, thread_index);
               goto out;
             }
         }
@@ -1193,7 +1237,7 @@ snat_out2in_node_fn (vlib_main_t * vm,
                           next0 = SNAT_OUT2IN_NEXT_IN2OUT;
                           goto trace0;
                         }
-                      create_bypass_for_fwd(sm, ip0);
+                      create_bypass_for_fwd(sm, ip0, rx_fib_index0, thread_index);
                       goto trace0;
                     }
                 }
@@ -1371,7 +1415,7 @@ snat_out2in_node_fn (vlib_main_t * vm,
                           next1 = SNAT_OUT2IN_NEXT_IN2OUT;
                           goto trace1;
                         }
-                      create_bypass_for_fwd(sm, ip1);
+                      create_bypass_for_fwd(sm, ip1, rx_fib_index1, thread_index);
                       goto trace1;
                     }
                 }
@@ -1585,7 +1629,7 @@ snat_out2in_node_fn (vlib_main_t * vm,
                           next0 = SNAT_OUT2IN_NEXT_IN2OUT;
                           goto trace00;
                         }
-                      create_bypass_for_fwd(sm, ip0);
+                      create_bypass_for_fwd(sm, ip0, rx_fib_index0, thread_index);
                       goto trace00;
                     }
                 }
@@ -1841,7 +1885,7 @@ nat44_out2in_reass_node_fn (vlib_main_t * vm,
                               next0 = SNAT_OUT2IN_NEXT_IN2OUT;
                               goto trace0;
                             }
-                          create_bypass_for_fwd(sm, ip0);
+                          create_bypass_for_fwd(sm, ip0, rx_fib_index0, thread_index);
                           goto trace0;
                         }
                     }