nat: fix dst nat thread issues

Make sure packet lands on the right thread for dst nat case.

Type: fix
Signed-off-by: Klement Sekera <ksekera@cisco.com>
Change-Id: I0ec4e4c2bb3fa80ff73fac588c36d36420ba68fa

4 files changed, 129 insertions, 123 deletions

diff --git a/src/plugins/nat/nat44-ed/nat44_ed.c b/src/plugins/nat/nat44-ed/nat44_ed.c
index c5c2a61f8d5..007296e065f 100644
--- a/src/plugins/nat/nat44-ed/nat44_ed.c
+++ b/src/plugins/nat/nat44-ed/nat44_ed.c
@@ -74,7 +74,6 @@ static_always_inline void nat_validate_interface_counters (snat_main_t *sm,
     }                                                                         \
   while (0)
 
-/* *INDENT-OFF* */
 /* Hook up input features */
 VNET_FEATURE_INIT (nat_pre_in2out, static) = {
   .arc_name = "ip4-unicast",
@@ -172,7 +171,6 @@ VLIB_PLUGIN_REGISTER () = {
     .version = VPP_BUILD_VER,
     .description = "Network Address Translation (NAT)",
 };
-/* *INDENT-ON* */
 
 static void nat44_ed_db_init (u32 translations, u32 translation_buckets);
 
@@ -330,7 +328,6 @@ snat_add_address (snat_main_t * sm, ip4_address_t * addr, u32 vrf_id,
   vlib_thread_main_t *tm = vlib_get_thread_main ();
 
   /* Check if address already exists */
-  /* *INDENT-OFF* */
   vec_foreach (ap, twice_nat ? sm->twice_nat_addresses : sm->addresses)
     {
       if (ap->addr.as_u32 == addr->as_u32)
@@ -339,7 +336,6 @@ snat_add_address (snat_main_t * sm, ip4_address_t * addr, u32 vrf_id,
           return VNET_API_ERROR_VALUE_EXIST;
         }
     }
-  /* *INDENT-ON* */
 
   if (twice_nat)
     vec_add2 (sm->twice_nat_addresses, ap, 1);
@@ -354,7 +350,6 @@ snat_add_address (snat_main_t * sm, ip4_address_t * addr, u32 vrf_id,
   else
     ap->fib_index = ~0;
 
-  /* *INDENT-OFF* */
   #define _(N, i, n, s) \
     clib_memset(ap->busy_##n##_port_refcounts, 0, sizeof(ap->busy_##n##_port_refcounts));\
     ap->busy_##n##_ports = 0; \
@@ -362,13 +357,11 @@ snat_add_address (snat_main_t * sm, ip4_address_t * addr, u32 vrf_id,
     vec_validate_init_empty (ap->busy_##n##_ports_per_thread, tm->n_vlib_mains - 1, 0);
     foreach_nat_protocol
   #undef _
-  /* *INDENT-ON* */
 
   if (twice_nat)
     return 0;
 
   /* Add external address to FIB */
-  /* *INDENT-OFF* */
   pool_foreach (i, sm->interfaces)
    {
      if (nat_interface_is_inside (i))
@@ -385,7 +378,6 @@ snat_add_address (snat_main_t * sm, ip4_address_t * addr, u32 vrf_id,
      snat_add_del_addr_to_fib (addr, 32, i->sw_if_index, 1);
      break;
   }
-  /* *INDENT-ON* */
 
   return 0;
 }
@@ -394,7 +386,6 @@ static int
 is_snat_address_used_in_static_mapping (snat_main_t * sm, ip4_address_t addr)
 {
   snat_static_mapping_t *m;
-  /* *INDENT-OFF* */
   pool_foreach (m, sm->static_mappings)
    {
       if (is_addr_only_static_mapping (m) ||
@@ -404,7 +395,6 @@ is_snat_address_used_in_static_mapping (snat_main_t * sm, ip4_address_t addr)
       if (m->external_addr.as_u32 == addr.as_u32)
         return 1;
   }
-  /* *INDENT-ON* */
 
   return 0;
 }
@@ -460,7 +450,6 @@ nat_ed_static_mapping_del_sessions (snat_main_t * sm,
 {
   snat_session_t *s;
   u32 *indexes_to_free = NULL;
-  /* *INDENT-OFF* */
   pool_foreach (s, tsm->sessions) {
     if (s->in2out.fib_index != fib_index ||
         s->in2out.addr.as_u32 != l_addr.as_u32)
@@ -485,7 +474,6 @@ nat_ed_static_mapping_del_sessions (snat_main_t * sm,
     if (!addr_only)
       break;
   }
-  /* *INDENT-ON* */
   u32 *ses_index;
   vec_foreach (ses_index, indexes_to_free)
   {
@@ -595,13 +583,11 @@ snat_add_static_mapping (ip4_address_t l_addr, ip4_address_t e_addr,
 	{
 	  if (is_identity_static_mapping (m))
 	    {
-              /* *INDENT-OFF* */
               pool_foreach (local, m->locals)
                {
                 if (local->vrf_id == vrf_id)
                   return VNET_API_ERROR_VALUE_EXIST;
               }
-              /* *INDENT-ON* */
 	      pool_get (m->locals, local);
 	      local->vrf_id = vrf_id;
 	      local->fib_index =
@@ -770,13 +756,11 @@ snat_add_static_mapping (ip4_address_t l_addr, ip4_address_t e_addr,
 	  if (vrf_id == ~0)
 	    vrf_id = sm->inside_vrf_id;
 
-          /* *INDENT-OFF* */
           pool_foreach (local, m->locals)
            {
 	    if (local->vrf_id == vrf_id)
               find = local - m->locals;
 	  }
-          /* *INDENT-ON* */
 	  if (find == ~0)
 	    return VNET_API_ERROR_NO_SUCH_ENTRY;
 
@@ -851,7 +835,6 @@ snat_add_static_mapping (ip4_address_t l_addr, ip4_address_t e_addr,
     return 0;
 
   /* Add/delete external address to FIB */
-  /* *INDENT-OFF* */
   pool_foreach (interface, sm->interfaces)
    {
      if (nat_interface_is_inside (interface))
@@ -868,7 +851,6 @@ snat_add_static_mapping (ip4_address_t l_addr, ip4_address_t e_addr,
      snat_add_del_addr_to_fib (&e_addr, 32, interface->sw_if_index, is_add);
      break;
   }
-  /* *INDENT-ON* */
 
   return 0;
 }
@@ -996,12 +978,10 @@ nat44_add_del_lb_static_mapping (ip4_address_t e_addr, u16 e_port,
       /* Assign workers */
       if (sm->num_workers > 1)
 	{
-          /* *INDENT-OFF* */
           clib_bitmap_foreach (i, bitmap)
              {
                vec_add1(m->workers, i);
             }
-          /* *INDENT-ON* */
 	}
     }
   else
@@ -1048,7 +1028,6 @@ nat44_add_del_lb_static_mapping (ip4_address_t e_addr, u16 e_port,
 	  return VNET_API_ERROR_UNSPECIFIED;
 	}
 
-      /* *INDENT-OFF* */
       pool_foreach (local, m->locals)
       {
           fib_table_unlock (local->fib_index, FIB_PROTOCOL_IP4,
@@ -1091,7 +1070,6 @@ nat44_add_del_lb_static_mapping (ip4_address_t e_addr, u16 e_port,
 	      nat_ed_session_delete (sm, s, tsm - sm->per_thread_data, 1);
 	    }
       }
-      /* *INDENT-ON* */
       if (m->affinity)
 	nat_affinity_flush_service (m->affinity_per_service_list_head_index);
       pool_free (m->locals);
@@ -1130,7 +1108,6 @@ nat44_lb_static_mapping_add_del_local (ip4_address_t e_addr, u16 e_port,
   if (!is_lb_static_mapping (m))
     return VNET_API_ERROR_INVALID_VALUE;
 
-  /* *INDENT-OFF* */
   pool_foreach (local, m->locals)
    {
     if ((local->addr.as_u32 == l_addr.as_u32) && (local->port == l_port) &&
@@ -1140,7 +1117,6 @@ nat44_lb_static_mapping_add_del_local (ip4_address_t e_addr, u16 e_port,
         break;
       }
   }
-  /* *INDENT-ON* */
 
   if (is_add)
     {
@@ -1196,7 +1172,6 @@ nat44_lb_static_mapping_add_del_local (ip4_address_t e_addr, u16 e_port,
 	tsm = vec_elt_at_index (sm->per_thread_data, sm->num_workers);
 
       /* Delete sessions */
-      /* *INDENT-OFF* */
       pool_foreach (s, tsm->sessions) {
         if (!(is_lb_session (s)))
           continue;
@@ -1208,14 +1183,12 @@ nat44_lb_static_mapping_add_del_local (ip4_address_t e_addr, u16 e_port,
         nat_free_session_data (sm, s, tsm - sm->per_thread_data, 0);
         nat_ed_session_delete (sm, s, tsm - sm->per_thread_data, 1);
       }
-      /* *INDENT-ON* */
 
       pool_put (m->locals, match_local);
     }
 
   vec_free (m->workers);
 
-  /* *INDENT-OFF* */
   pool_foreach (local, m->locals)
    {
     vec_add1 (locals, local - m->locals);
@@ -1227,7 +1200,6 @@ nat44_lb_static_mapping_add_del_local (ip4_address_t e_addr, u16 e_port,
 	  bitmap, sm->worker_in2out_cb (0, &ip, local->fib_index, 0), 1);
       }
   }
-  /* *INDENT-ON* */
 
   ASSERT (vec_len (locals) > 1);
 
@@ -1243,9 +1215,7 @@ nat44_lb_static_mapping_add_del_local (ip4_address_t e_addr, u16 e_port,
   /* Assign workers */
   if (sm->num_workers > 1)
     {
-      /* *INDENT-OFF* */
       clib_bitmap_foreach (i, bitmap)  { vec_add1(m->workers, i); }
-      /* *INDENT-ON* */
     }
 
   return 0;
@@ -1283,7 +1253,6 @@ snat_del_address (snat_main_t * sm, ip4_address_t addr, u8 delete_sm,
   if (delete_sm)
     {
       ip4_address_t pool_addr = { 0 };
-      /* *INDENT-OFF* */
       pool_foreach (m, sm->static_mappings)
        {
           if (m->external_addr.as_u32 == addr.as_u32)
@@ -1298,7 +1267,6 @@ snat_del_address (snat_main_t * sm, ip4_address_t addr, u8 delete_sm,
                                             is_identity_static_mapping(m),
                                             pool_addr, 0);
       }
-      /* *INDENT-ON* */
     }
   else
     {
@@ -1376,7 +1344,6 @@ expire_per_vrf_sessions (u32 fib_index)
   snat_main_per_thread_data_t *tsm;
   snat_main_t *sm = &snat_main;
 
-  /* *INDENT-OFF* */
   vec_foreach (tsm, sm->per_thread_data)
     {
       vec_foreach (per_vrf_sessions, tsm->per_vrf_sessions_vec)
@@ -1388,7 +1355,6 @@ expire_per_vrf_sessions (u32 fib_index)
             }
         }
     }
-  /* *INDENT-ON* */
 }
 
 void
@@ -1446,7 +1412,6 @@ snat_interface_add_del (u32 sw_if_index, u8 is_inside, int is_del)
       return VNET_API_ERROR_UNSUPPORTED;
     }
 
-  /* *INDENT-OFF* */
   pool_foreach (i, sm->output_feature_interfaces)
    {
     if (i->sw_if_index == sw_if_index)
@@ -1455,7 +1420,6 @@ snat_interface_add_del (u32 sw_if_index, u8 is_inside, int is_del)
         return VNET_API_ERROR_VALUE_EXIST;
       }
   }
-  /* *INDENT-ON* */
 
   if (sm->static_mapping_only && !(sm->static_mapping_connection_tracking))
     feature_name = is_inside ? "nat44-in2out-fast" : "nat44-out2in-fast";
@@ -1483,7 +1447,6 @@ snat_interface_add_del (u32 sw_if_index, u8 is_inside, int is_del)
 
   if (!is_inside)
     {
-      /* *INDENT-OFF* */
       vec_foreach (outside_fib, sm->outside_fibs)
         {
           if (outside_fib->fib_index == fib_index)
@@ -1499,7 +1462,6 @@ snat_interface_add_del (u32 sw_if_index, u8 is_inside, int is_del)
               goto feature_set;
             }
         }
-      /* *INDENT-ON* */
       if (!is_del)
 	{
 	  vec_add2 (sm->outside_fibs, outside_fib, 1);
@@ -1509,7 +1471,6 @@ snat_interface_add_del (u32 sw_if_index, u8 is_inside, int is_del)
     }
 
 feature_set:
-  /* *INDENT-OFF* */
   pool_foreach (i, sm->interfaces)
    {
     if (i->sw_if_index == sw_if_index)
@@ -1587,7 +1548,6 @@ feature_set:
 	goto fib;
       }
   }
-  /* *INDENT-ON* */
 
   if (is_del)
     {
@@ -1618,7 +1578,6 @@ set_flags:
 
   /* Add/delete external addresses to FIB */
 fib:
-  /* *INDENT-OFF* */
   vec_foreach (ap, sm->addresses)
     snat_add_del_addr_to_fib(&ap->addr, 32, sw_if_index, !is_del);
 
@@ -1629,7 +1588,6 @@ fib:
 
     snat_add_del_addr_to_fib(&m->external_addr, 32, sw_if_index, !is_del);
   }
-  /* *INDENT-ON* */
 
   return 0;
 }
@@ -1658,7 +1616,6 @@ snat_interface_add_del_output_feature (u32 sw_if_index,
       return VNET_API_ERROR_UNSUPPORTED;
     }
 
-  /* *INDENT-OFF* */
   pool_foreach (i, sm->interfaces)
    {
     if (i->sw_if_index == sw_if_index)
@@ -1667,13 +1624,11 @@ snat_interface_add_del_output_feature (u32 sw_if_index,
         return VNET_API_ERROR_VALUE_EXIST;
       }
   }
-  /* *INDENT-ON* */
 
   update_per_vrf_sessions_vec (fib_index, is_del);
 
   if (!is_inside)
     {
-      /* *INDENT-OFF* */
       vec_foreach (outside_fib, sm->outside_fibs)
         {
           if (outside_fib->fib_index == fib_index)
@@ -1689,7 +1644,6 @@ snat_interface_add_del_output_feature (u32 sw_if_index,
               goto feature_set;
             }
         }
-      /* *INDENT-ON* */
       if (!is_del)
 	{
 	  vec_add2 (sm->outside_fibs, outside_fib, 1);
@@ -1755,7 +1709,6 @@ fq:
     sm->fq_out2in_index =
       vlib_frame_queue_main_init (sm->out2in_node_index, 0);
 
-  /* *INDENT-OFF* */
   pool_foreach (i, sm->output_feature_interfaces)
    {
     if (i->sw_if_index == sw_if_index)
@@ -1768,7 +1721,6 @@ fq:
         goto fib;
       }
   }
-  /* *INDENT-ON* */
 
   if (is_del)
     {
@@ -1790,7 +1742,6 @@ fib:
   if (is_inside)
     return 0;
 
-  /* *INDENT-OFF* */
   vec_foreach (ap, sm->addresses)
     snat_add_del_addr_to_fib(&ap->addr, 32, sw_if_index, !is_del);
 
@@ -1801,7 +1752,6 @@ fib:
 
     snat_add_del_addr_to_fib(&m->external_addr, 32, sw_if_index, !is_del);
   }
-  /* *INDENT-ON* */
 
   return 0;
 }
@@ -1819,7 +1769,6 @@ snat_set_workers (uword * bitmap)
     return VNET_API_ERROR_INVALID_WORKER;
 
   vec_free (sm->workers);
-  /* *INDENT-OFF* */
   clib_bitmap_foreach (i, bitmap)
     {
       vec_add1(sm->workers, i);
@@ -1827,7 +1776,6 @@ snat_set_workers (uword * bitmap)
       sm->per_thread_data[sm->first_worker_index + i].thread_index = i;
       j++;
     }
-  /* *INDENT-ON* */
 
   sm->port_per_thread = (0xffff - 1024) / _vec_len (sm->workers);
 
@@ -1860,7 +1808,6 @@ snat_update_outside_fib (ip4_main_t * im, uword opaque,
       return;
     }
 
-  /* *INDENT-OFF* */
   pool_foreach (i, sm->interfaces)
      {
       if (i->sw_if_index == sw_if_index)
@@ -1880,7 +1827,6 @@ snat_update_outside_fib (ip4_main_t * im, uword opaque,
           match = 1;
         }
     }
-  /* *INDENT-ON* */
 
   if (!match)
     return;
@@ -2564,61 +2510,69 @@ nat44_ed_get_worker_in2out_cb (vlib_buffer_t *b, ip4_header_t *ip,
   clib_bihash_kv_16_8_t kv16, value16;
 
   u32 fib_index = rx_fib_index;
-  if (PREDICT_FALSE (is_output))
-    {
-      fib_index = sm->outside_fib_index;
-      nat_outside_fib_t *outside_fib;
-      fib_node_index_t fei = FIB_NODE_INDEX_INVALID;
-      fib_prefix_t pfx = {
-	.fp_proto = FIB_PROTOCOL_IP4,
-	.fp_len = 32,
-	.fp_addr = {
-		    .ip4.as_u32 = ip->dst_address.as_u32,
-		    }
-	,
-      };
-
-      switch (vec_len (sm->outside_fibs))
+  if (b)
+    {
+      if (PREDICT_FALSE (is_output))
 	{
-	case 0:
 	  fib_index = sm->outside_fib_index;
-	  break;
-	case 1:
-	  fib_index = sm->outside_fibs[0].fib_index;
-	  break;
-	default:
-            /* *INDENT-OFF* */
-            vec_foreach (outside_fib, sm->outside_fibs)
-              {
-                fei = fib_table_lookup (outside_fib->fib_index, &pfx);
-                if (FIB_NODE_INDEX_INVALID != fei)
-                  {
-                    if (fib_entry_get_resolving_interface (fei) != ~0)
-                      {
-                        fib_index = outside_fib->fib_index;
-                        break;
-                      }
-                  }
-              }
-            /* *INDENT-ON* */
-	  break;
+	  nat_outside_fib_t *outside_fib;
+	  fib_node_index_t fei = FIB_NODE_INDEX_INVALID;
+	  fib_prefix_t pfx = {
+		  .fp_proto = FIB_PROTOCOL_IP4,
+		  .fp_len = 32,
+		  .fp_addr = {
+			  .ip4.as_u32 = ip->dst_address.as_u32,
+		  } ,
+	  };
+
+	  switch (vec_len (sm->outside_fibs))
+	    {
+	    case 0:
+	      fib_index = sm->outside_fib_index;
+	      break;
+	    case 1:
+	      fib_index = sm->outside_fibs[0].fib_index;
+	      break;
+	    default:
+	      vec_foreach (outside_fib, sm->outside_fibs)
+		{
+		  fei = fib_table_lookup (outside_fib->fib_index, &pfx);
+		  if (FIB_NODE_INDEX_INVALID != fei)
+		    {
+		      if (fib_entry_get_resolving_interface (fei) != ~0)
+			{
+			  fib_index = outside_fib->fib_index;
+			  break;
+			}
+		    }
+		}
+	      break;
+	    }
 	}
-    }
 
-  if (b)
-    {
       init_ed_k (&kv16, ip->src_address, vnet_buffer (b)->ip.reass.l4_src_port,
 		 ip->dst_address, vnet_buffer (b)->ip.reass.l4_dst_port,
 		 fib_index, ip->protocol);
 
-      if (PREDICT_TRUE (
-	    !clib_bihash_search_16_8 (&sm->flow_hash, &kv16, &value16)))
+      if (!clib_bihash_search_16_8 (&sm->flow_hash, &kv16, &value16))
 	{
 	  next_worker_index = ed_value_get_thread_index (&value16);
 	  vnet_buffer2 (b)->nat.cached_session_index =
 	    ed_value_get_session_index (&value16);
 	  goto out;
 	}
+
+      // dst NAT
+      init_ed_k (&kv16, ip->dst_address, vnet_buffer (b)->ip.reass.l4_dst_port,
+		 ip->src_address, vnet_buffer (b)->ip.reass.l4_src_port,
+		 rx_fib_index, ip->protocol);
+      if (!clib_bihash_search_16_8 (&sm->flow_hash, &kv16, &value16))
+	{
+	  next_worker_index = ed_value_get_thread_index (&value16);
+	  vnet_buffer2 (b)->nat.cached_dst_nat_session_index =
+	    ed_value_get_session_index (&value16);
+	  goto out;
+	}
     }
 
   hash = ip->src_address.as_u32 + (ip->src_address.as_u32 >> 8) +
@@ -3234,7 +3188,6 @@ VLIB_NODE_FN (nat_default_node) (vlib_main_t * vm,
   return 0;
 }
 
-/* *INDENT-OFF* */
 VLIB_REGISTER_NODE (nat_default_node) = {
   .name = "nat-default",
   .vector_size = sizeof (u32),
@@ -3255,7 +3208,6 @@ VLIB_REGISTER_NODE (nat_default_node) = {
     [NAT_NEXT_OUT2IN_CLASSIFY] = "nat44-out2in-worker-handoff",
   },
 };
-/* *INDENT-ON* */
 
 void
 nat_6t_l3_l4_csum_calc (nat_6t_flow_t *f)
diff --git a/src/plugins/nat/nat44-ed/nat44_ed_in2out.c b/src/plugins/nat/nat44-ed/nat44_ed_in2out.c
index fe1a6d94f4c..6658e5b2b23 100644
--- a/src/plugins/nat/nat44-ed/nat44_ed_in2out.c
+++ b/src/plugins/nat/nat44-ed/nat44_ed_in2out.c
@@ -505,6 +505,7 @@ slow_path_ed (vlib_main_t *vm, snat_main_t *sm, vlib_buffer_t *b,
 			rx_fib_index, proto);
   nat_6t_flow_saddr_rewrite_set (&s->i2o, outside_addr.as_u32);
   nat_6t_flow_daddr_rewrite_set (&s->i2o, daddr.as_u32);
+
   if (NAT_PROTOCOL_ICMP == nat_proto)
     {
       nat_6t_flow_icmp_id_rewrite_set (&s->i2o, outside_port);
@@ -654,10 +655,11 @@ nat_not_translate_output_feature_fwd (snat_main_t * sm, ip4_header_t * ip,
 }
 
 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, f64 now)
+nat44_ed_not_translate_output_feature (snat_main_t *sm, vlib_buffer_t *b,
+				       ip4_header_t *ip, u16 src_port,
+				       u16 dst_port, u32 thread_index,
+				       u32 rx_sw_if_index, u32 tx_sw_if_index,
+				       f64 now, int is_multi_worker)
 {
   clib_bihash_kv_16_8_t kv, value;
   snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
@@ -685,6 +687,26 @@ nat44_ed_not_translate_output_feature (snat_main_t * sm, ip4_header_t * ip,
     }
 
   /* dst NAT check */
+  if (is_multi_worker &&
+      PREDICT_TRUE (!pool_is_free_index (
+	tsm->sessions, vnet_buffer2 (b)->nat.cached_dst_nat_session_index)))
+    {
+      nat_6t_t lookup;
+      lookup.fib_index = rx_fib_index;
+      lookup.proto = ip->protocol;
+      lookup.daddr.as_u32 = ip->src_address.as_u32;
+      lookup.dport = src_port;
+      lookup.saddr.as_u32 = ip->dst_address.as_u32;
+      lookup.sport = dst_port;
+      s = pool_elt_at_index (
+	tsm->sessions, vnet_buffer2 (b)->nat.cached_dst_nat_session_index);
+      if (PREDICT_TRUE (nat_6t_t_eq (&s->i2o.match, &lookup)))
+	{
+	  goto skip_dst_nat_lookup;
+	}
+      s = NULL;
+    }
+
   init_ed_k (&kv, ip->dst_address, dst_port, ip->src_address, src_port,
 	     rx_fib_index, ip->protocol);
   if (!clib_bihash_search_16_8 (&sm->flow_hash, &kv, &value))
@@ -694,6 +716,7 @@ nat44_ed_not_translate_output_feature (snat_main_t * sm, ip4_header_t * ip,
 	pool_elt_at_index (tsm->sessions,
 			   ed_value_get_session_index (&value));
 
+    skip_dst_nat_lookup:
       if (is_fwd_bypass_session (s))
 	return 0;
 
@@ -714,7 +737,8 @@ icmp_in2out_ed_slow_path (snat_main_t *sm, vlib_buffer_t *b, ip4_header_t *ip,
 			  icmp46_header_t *icmp, u32 sw_if_index,
 			  u32 rx_fib_index, vlib_node_runtime_t *node,
 			  u32 next, f64 now, u32 thread_index,
-			  nat_protocol_t nat_proto, snat_session_t **s_p)
+			  nat_protocol_t nat_proto, snat_session_t **s_p,
+			  int is_multi_worker)
 {
   vlib_main_t *vm = vlib_get_main ();
   u16 checksum;
@@ -736,8 +760,8 @@ icmp_in2out_ed_slow_path (snat_main_t *sm, vlib_buffer_t *b, ip4_header_t *ip,
   if (vnet_buffer (b)->sw_if_index[VLIB_TX] != ~0)
     {
       if (PREDICT_FALSE (nat44_ed_not_translate_output_feature (
-	    sm, ip, lookup_sport, lookup_dport, thread_index, sw_if_index,
-	    vnet_buffer (b)->sw_if_index[VLIB_TX], now)))
+	    sm, b, ip, lookup_sport, lookup_dport, thread_index, sw_if_index,
+	    vnet_buffer (b)->sw_if_index[VLIB_TX], now, is_multi_worker)))
 	{
 	  return next;
 	}
@@ -1236,10 +1260,11 @@ nat44_ed_in2out_fast_path_node_fn_inline (vlib_main_t *vm,
 }
 
 static inline uword
-nat44_ed_in2out_slow_path_node_fn_inline (vlib_main_t * vm,
-					  vlib_node_runtime_t * node,
-					  vlib_frame_t * frame,
-					  int is_output_feature)
+nat44_ed_in2out_slow_path_node_fn_inline (vlib_main_t *vm,
+					  vlib_node_runtime_t *node,
+					  vlib_frame_t *frame,
+					  int is_output_feature,
+					  int is_multi_worker)
 {
   u32 n_left_from, *from;
   snat_main_t *sm = &snat_main;
@@ -1315,9 +1340,9 @@ nat44_ed_in2out_slow_path_node_fn_inline (vlib_main_t * vm,
 
       if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_ICMP))
 	{
-	  next[0] = icmp_in2out_ed_slow_path (sm, b0, ip0, icmp0, sw_if_index0,
-					      rx_fib_index0, node, next[0],
-					      now, thread_index, proto0, &s0);
+	  next[0] = icmp_in2out_ed_slow_path (
+	    sm, b0, ip0, icmp0, sw_if_index0, rx_fib_index0, node, next[0],
+	    now, thread_index, proto0, &s0, is_multi_worker);
 	  if (NAT_NEXT_DROP != next[0] && s0 &&
 	      NAT_ED_TRNSL_ERR_SUCCESS !=
 		(translation_error = nat_6t_flow_buf_translate (
@@ -1354,12 +1379,11 @@ nat44_ed_in2out_slow_path_node_fn_inline (vlib_main_t * vm,
 	{
 	  if (is_output_feature)
 	    {
-	      if (PREDICT_FALSE
-		  (nat44_ed_not_translate_output_feature
-		   (sm, ip0, vnet_buffer (b0)->ip.reass.l4_src_port,
+	      if (PREDICT_FALSE (nat44_ed_not_translate_output_feature (
+		    sm, b0, 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],
-		    now)))
+		    sw_if_index0, vnet_buffer (b0)->sw_if_index[VLIB_TX], now,
+		    is_multi_worker)))
 		goto trace0;
 
 	      /*
@@ -1523,7 +1547,14 @@ VLIB_NODE_FN (nat44_ed_in2out_slowpath_node) (vlib_main_t * vm,
 					      vlib_node_runtime_t *
 					      node, vlib_frame_t * frame)
 {
-  return nat44_ed_in2out_slow_path_node_fn_inline (vm, node, frame, 0);
+  if (snat_main.num_workers > 1)
+    {
+      return nat44_ed_in2out_slow_path_node_fn_inline (vm, node, frame, 0, 1);
+    }
+  else
+    {
+      return nat44_ed_in2out_slow_path_node_fn_inline (vm, node, frame, 0, 0);
+    }
 }
 
 VLIB_REGISTER_NODE (nat44_ed_in2out_slowpath_node) = {
@@ -1542,7 +1573,14 @@ VLIB_NODE_FN (nat44_ed_in2out_output_slowpath_node) (vlib_main_t * vm,
 						     * node,
 						     vlib_frame_t * frame)
 {
-  return nat44_ed_in2out_slow_path_node_fn_inline (vm, node, frame, 1);
+  if (snat_main.num_workers > 1)
+    {
+      return nat44_ed_in2out_slow_path_node_fn_inline (vm, node, frame, 1, 1);
+    }
+  else
+    {
+      return nat44_ed_in2out_slow_path_node_fn_inline (vm, node, frame, 1, 0);
+    }
 }
 
 VLIB_REGISTER_NODE (nat44_ed_in2out_output_slowpath_node) = {
diff --git a/src/plugins/nat/test/test_nat44_ed.py b/src/plugins/nat/test/test_nat44_ed.py
index 7040cb7266e..5e382aae855 100644
--- a/src/plugins/nat/test/test_nat44_ed.py
+++ b/src/plugins/nat/test/test_nat44_ed.py
@@ -1926,22 +1926,35 @@ class TestNAT44ED(NAT44EDTestCase):
 
         pkts = []
         for i in range(x):
+            info = self.create_packet_info(self.pg0, self.pg1)
+            payload = self.info_to_payload(info)
             p = (Ether(dst=self.pg0.local_mac, src=self.pg0.remote_mac) /
                  IP(src=self.pg0.remote_hosts[i].ip4,
                      dst=self.pg1.remote_ip4) /
-                 UDP(sport=7000+i, dport=80+i))
+                 UDP(sport=7000+i, dport=8000+i) /
+                 Raw(payload))
+            info.data = p
             pkts.append(p)
 
         self.pg0.add_stream(pkts)
         self.pg_enable_capture(self.pg_interfaces)
         self.pg_start()
         recvd = self.pg1.get_capture(len(pkts))
-        for (p_sent, p_recvd) in zip(pkts, recvd):
+        for p_recvd in recvd:
+            payload_info = self.payload_to_info(p_recvd[Raw])
+            packet_index = payload_info.index
+            info = self._packet_infos[packet_index]
+            self.assertTrue(info is not None)
+            self.assertEqual(packet_index, info.index)
+            p_sent = info.data
             packed = socket.inet_aton(p_sent[IP].src)
             numeric = struct.unpack("!L", packed)[0]
             numeric = socket.htonl(numeric)
             a = nat_addresses[(numeric-1) % len(nat_addresses)]
-            self.assertEqual(a, p_recvd[IP].src, "Packet not translated")
+            self.assertEqual(
+                a, p_recvd[IP].src,
+                "Invalid packet (src IP %s translated to %s, but expected %s)"
+                % (p_sent[IP].src, p_recvd[IP].src, a))
 
 
 class TestNAT44EDMW(TestNAT44ED):
diff --git a/src/vnet/buffer.h b/src/vnet/buffer.h
index 37db4130514..00e9aa698c6 100644
--- a/src/vnet/buffer.h
+++ b/src/vnet/buffer.h
@@ -480,8 +480,11 @@ typedef struct
   struct
   {
     u32 arc_next;
-    /* cached session index from previous node */
-    u32 cached_session_index;
+    union
+    {
+      u32 cached_session_index;
+      u32 cached_dst_nat_session_index;
+    };
   } nat;
 
   union