NAT44: nat44_del_session and nat44_user_session_details API update (VPP-1271)
[vpp.git] / src / plugins / nat / out2in.c
index 52adc8a..c7eece8 100755 (executable)
@@ -25,6 +25,7 @@
 #include <nat/nat.h>
 #include <nat/nat_ipfix_logging.h>
 #include <nat/nat_det.h>
+#include <nat/nat_reass.h>
 
 #include <vppinfra/hash.h>
 #include <vppinfra/error.h>
@@ -78,16 +79,41 @@ static u8 * format_snat_out2in_worker_handoff_trace (u8 * s, va_list * args)
   return s;
 }
 
+typedef struct {
+  u32 sw_if_index;
+  u32 next_index;
+  u8 cached;
+} nat44_out2in_reass_trace_t;
+
+static u8 * format_nat44_out2in_reass_trace (u8 * s, va_list * args)
+{
+  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
+  CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
+  nat44_out2in_reass_trace_t * t = va_arg (*args, nat44_out2in_reass_trace_t *);
+
+  s = format (s, "NAT44_OUT2IN_REASS: sw_if_index %d, next index %d, status %s",
+              t->sw_if_index, t->next_index,
+              t->cached ? "cached" : "translated");
+
+  return s;
+}
+
 vlib_node_registration_t snat_out2in_node;
 vlib_node_registration_t snat_out2in_fast_node;
 vlib_node_registration_t snat_out2in_worker_handoff_node;
 vlib_node_registration_t snat_det_out2in_node;
+vlib_node_registration_t nat44_out2in_reass_node;
 
 #define foreach_snat_out2in_error                       \
 _(UNSUPPORTED_PROTOCOL, "Unsupported protocol")         \
 _(OUT2IN_PACKETS, "Good out2in packets processed")      \
+_(OUT_OF_PORTS, "Out of ports")                         \
 _(BAD_ICMP_TYPE, "unsupported ICMP type")               \
-_(NO_TRANSLATION, "No translation")
+_(NO_TRANSLATION, "No translation")                     \
+_(MAX_SESSIONS_EXCEEDED, "Maximum sessions exceeded")   \
+_(DROP_FRAGMENT, "Drop fragment")                       \
+_(MAX_REASS, "Maximum reassemblies exceeded")           \
+_(MAX_FRAG, "Maximum fragments per reassembly exceeded")
 
 typedef enum {
 #define _(sym,str) SNAT_OUT2IN_ERROR_##sym,
@@ -106,6 +132,8 @@ typedef enum {
   SNAT_OUT2IN_NEXT_DROP,
   SNAT_OUT2IN_NEXT_LOOKUP,
   SNAT_OUT2IN_NEXT_ICMP_ERROR,
+  SNAT_OUT2IN_NEXT_REASS,
+  SNAT_OUT2IN_NEXT_IN2OUT,
   SNAT_OUT2IN_N_NEXT,
 } snat_out2in_next_t;
 
@@ -132,78 +160,39 @@ create_session_for_static_mapping (snat_main_t *sm,
                                    u32 thread_index)
 {
   snat_user_t *u;
-  snat_user_key_t user_key;
   snat_session_t *s;
-  clib_bihash_kv_8_8_t kv0, value0;
-  dlist_elt_t * per_user_translation_list_elt;
-  dlist_elt_t * per_user_list_head_elt;
+  clib_bihash_kv_8_8_t kv0;
   ip4_header_t *ip0;
+  udp_header_t *udp0;
 
-  ip0 = vlib_buffer_get_current (b0);
-
-  user_key.addr = in2out.addr;
-  user_key.fib_index = in2out.fib_index;
-  kv0.key = user_key.as_u64;
-
-  /* Ever heard of the "user" = inside ip4 address before? */
-  if (clib_bihash_search_8_8 (&sm->user_hash, &kv0, &value0))
+  if (PREDICT_FALSE (maximum_sessions_exceeded(sm, thread_index)))
     {
-      /* no, make a new one */
-      pool_get (sm->per_thread_data[thread_index].users, u);
-      memset (u, 0, sizeof (*u));
-      u->addr = in2out.addr;
-      u->fib_index = in2out.fib_index;
-
-      pool_get (sm->per_thread_data[thread_index].list_pool,
-                per_user_list_head_elt);
-
-      u->sessions_per_user_list_head_index = per_user_list_head_elt -
-        sm->per_thread_data[thread_index].list_pool;
-
-      clib_dlist_init (sm->per_thread_data[thread_index].list_pool,
-                       u->sessions_per_user_list_head_index);
-
-      kv0.value = u - sm->per_thread_data[thread_index].users;
+      b0->error = node->errors[SNAT_OUT2IN_ERROR_MAX_SESSIONS_EXCEEDED];
+      return 0;
+    }
 
-      /* add user */
-      clib_bihash_add_del_8_8 (&sm->user_hash, &kv0, 1 /* is_add */);
+  ip0 = vlib_buffer_get_current (b0);
+  udp0 = ip4_next_header (ip0);
 
-      /* add non-traslated packets worker lookup */
-      kv0.value = thread_index;
-      clib_bihash_add_del_8_8 (&sm->worker_by_in, &kv0, 1);
-    }
-  else
+  u = nat_user_get_or_create (sm, &in2out.addr, in2out.fib_index, thread_index);
+  if (!u)
     {
-      u = pool_elt_at_index (sm->per_thread_data[thread_index].users,
-                             value0.value);
+      clib_warning ("create NAT user failed");
+      return 0;
     }
 
-  pool_get (sm->per_thread_data[thread_index].sessions, s);
-  memset (s, 0, sizeof (*s));
+  s = nat_session_alloc_or_recycle (sm, u, thread_index);
+  if (!s)
+    {
+      clib_warning ("create NAT session failed");
+      return 0;
+    }
 
   s->outside_address_index = ~0;
   s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING;
-  s->ext_host_addr.as_u32 = ip0->dst_address.as_u32;
-  u->nstaticsessions++;
-
-  /* Create list elts */
-  pool_get (sm->per_thread_data[thread_index].list_pool,
-            per_user_translation_list_elt);
-  clib_dlist_init (sm->per_thread_data[thread_index].list_pool,
-                   per_user_translation_list_elt -
-                   sm->per_thread_data[thread_index].list_pool);
-
-  per_user_translation_list_elt->value =
-    s - sm->per_thread_data[thread_index].sessions;
-  s->per_user_index =
-    per_user_translation_list_elt - sm->per_thread_data[thread_index].list_pool;
-  s->per_user_list_head_index = u->sessions_per_user_list_head_index;
-
-  clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
-                      s->per_user_list_head_index,
-                      per_user_translation_list_elt -
-                      sm->per_thread_data[thread_index].list_pool);
-
+  s->ext_host_addr.as_u32 = ip0->src_address.as_u32;
+  s->ext_host_port = udp0->src_port;
+  user_session_increment (sm, u, 1 /* static */);
   s->in2out = in2out;
   s->out2in = out2in;
   s->in2out.protocol = out2in.protocol;
@@ -211,13 +200,14 @@ create_session_for_static_mapping (snat_main_t *sm,
   /* Add to translation hashes */
   kv0.key = s->in2out.as_u64;
   kv0.value = s - sm->per_thread_data[thread_index].sessions;
-  if (clib_bihash_add_del_8_8 (&sm->in2out, &kv0, 1 /* is_add */))
+  if (clib_bihash_add_del_8_8 (&sm->per_thread_data[thread_index].in2out, &kv0,
+                               1 /* is_add */))
       clib_warning ("in2out key add failed");
 
   kv0.key = s->out2in.as_u64;
-  kv0.value = s - sm->per_thread_data[thread_index].sessions;
 
-  if (clib_bihash_add_del_8_8 (&sm->out2in, &kv0, 1 /* is_add */))
+  if (clib_bihash_add_del_8_8 (&sm->per_thread_data[thread_index].out2in, &kv0,
+                               1 /* is_add */))
       clib_warning ("out2in key add failed");
 
   /* log NAT event */
@@ -275,6 +265,164 @@ snat_out2in_error_t icmp_get_key(ip4_header_t *ip0,
   return -1; /* success */
 }
 
+static_always_inline int
+icmp_get_ed_key(ip4_header_t *ip0, nat_ed_ses_key_t *p_key0)
+{
+  icmp46_header_t *icmp0;
+  nat_ed_ses_key_t key0;
+  icmp_echo_header_t *echo0, *inner_echo0 = 0;
+  ip4_header_t *inner_ip0;
+  void *l4_header = 0;
+  icmp46_header_t *inner_icmp0;
+
+  icmp0 = (icmp46_header_t *) ip4_next_header (ip0);
+  echo0 = (icmp_echo_header_t *)(icmp0+1);
+
+  if (!icmp_is_error_message (icmp0))
+    {
+      key0.proto = IP_PROTOCOL_ICMP;
+      key0.l_addr = ip0->dst_address;
+      key0.r_addr = ip0->src_address;
+      key0.l_port = key0.r_port = echo0->identifier;
+    }
+  else
+    {
+      inner_ip0 = (ip4_header_t *)(echo0+1);
+      l4_header = ip4_next_header (inner_ip0);
+      key0.proto = inner_ip0->protocol;
+      key0.l_addr = inner_ip0->src_address;
+      key0.r_addr = inner_ip0->dst_address;
+      switch (ip_proto_to_snat_proto (inner_ip0->protocol))
+        {
+        case SNAT_PROTOCOL_ICMP:
+          inner_icmp0 = (icmp46_header_t*)l4_header;
+          inner_echo0 = (icmp_echo_header_t *)(inner_icmp0+1);
+          key0.l_port = key0.r_port = inner_echo0->identifier;
+          break;
+        case SNAT_PROTOCOL_UDP:
+        case SNAT_PROTOCOL_TCP:
+          key0.l_port = ((tcp_udp_header_t*)l4_header)->src_port;
+          key0.r_port = ((tcp_udp_header_t*)l4_header)->dst_port;
+          break;
+        default:
+          return -1;
+        }
+    }
+  *p_key0 = key0;
+  return 0;
+}
+
+static int
+next_src_nat (snat_main_t * sm, ip4_header_t * ip, u32 proto, u16 src_port,
+              u32 thread_index)
+{
+  snat_session_key_t key;
+  clib_bihash_kv_8_8_t kv, value;
+
+  key.addr = ip->src_address;
+  key.port = src_port;
+  key.protocol = proto;
+  key.fib_index = sm->inside_fib_index;
+  kv.key = key.as_u64;
+
+  if (!clib_bihash_search_8_8 (&sm->per_thread_data[thread_index].in2out, &kv,
+                               &value))
+    return 1;
+
+  return 0;
+}
+
+static void
+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, 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];
+  f64 now = vlib_time_now (sm->vlib_main);
+
+  if (ip->protocol == IP_PROTOCOL_ICMP)
+    {
+      if (icmp_get_ed_key (ip, &key))
+        return;
+    }
+  else if (ip->protocol == IP_PROTOCOL_UDP || ip->protocol == IP_PROTOCOL_TCP)
+    {
+      udp = ip4_next_header(ip);
+      key.r_addr = ip->src_address;
+      key.l_addr = ip->dst_address;
+      key.proto = ip->protocol;
+      key.l_port = udp->dst_port;
+      key.r_port = udp->src_port;
+    }
+  else
+    {
+      key.r_addr = ip->src_address;
+      key.l_addr = ip->dst_address;
+      key.proto = ip->protocol;
+      key.l_port = key.r_port = 0;
+    }
+  key.fib_index = 0;
+  kv.key[0] = key.as_u64[0];
+  kv.key[1] = key.as_u64[1];
+
+  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");
+    }
+
+  if (ip->protocol == IP_PROTOCOL_TCP)
+    {
+      tcp_header_t *tcp = ip4_next_header(ip);
+      if (nat44_set_tcp_session_state_o2i (sm, s, tcp, thread_index))
+        return;
+    }
+  /* 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);
+  /* Accounting */
+  s->last_heard = now;
+  s->total_pkts++;
+}
+
 /**
  * Get address and port values to be used for ICMP packet translation
  * and create session if needed
@@ -290,11 +438,11 @@ snat_out2in_error_t icmp_get_key(ip4_header_t *ip0,
  * @param e                      optional parameter
  */
 u32 icmp_match_out2in_slow(snat_main_t *sm, vlib_node_runtime_t *node,
-                           u32 thread_index, vlib_buffer_t *b0, u8 *p_proto,
+                           u32 thread_index, vlib_buffer_t *b0,
+                           ip4_header_t *ip0, u8 *p_proto,
                            snat_session_key_t *p_value,
                            u8 *p_dont_translate, void *d, void *e)
 {
-  ip4_header_t *ip0;
   icmp46_header_t *icmp0;
   u32 sw_if_index0;
   u32 rx_fib_index0;
@@ -307,7 +455,6 @@ u32 icmp_match_out2in_slow(snat_main_t *sm, vlib_node_runtime_t *node,
   u32 next0 = ~0;
   int err;
 
-  ip0 = vlib_buffer_get_current (b0);
   icmp0 = (icmp46_header_t *) ip4_next_header (ip0);
   sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
   rx_fib_index0 = ip4_fib_table_get_index_for_sw_if_index (sw_if_index0);
@@ -325,22 +472,37 @@ u32 icmp_match_out2in_slow(snat_main_t *sm, vlib_node_runtime_t *node,
 
   kv0.key = key0.as_u64;
 
-  if (clib_bihash_search_8_8 (&sm->out2in, &kv0, &value0))
+  if (clib_bihash_search_8_8 (&sm->per_thread_data[thread_index].out2in, &kv0,
+                              &value0))
     {
       /* Try to match static mapping by external address and port,
          destination address and port in packet */
-      if (snat_static_mapping_match(sm, key0, &sm0, 1, &is_addr_only))
+      if (snat_static_mapping_match(sm, key0, &sm0, 1, &is_addr_only, 0, 0))
         {
-          /* Don't NAT packet aimed at the intfc address */
-          if (PREDICT_FALSE(is_interface_addr(sm, node, sw_if_index0,
-                                              ip0->dst_address.as_u32)))
+          if (!sm->forwarding_enabled)
+            {
+              /* Don't NAT packet aimed at the intfc address */
+              if (PREDICT_FALSE(is_interface_addr(sm, node, sw_if_index0,
+                                                  ip0->dst_address.as_u32)))
+                {
+                  dont_translate = 1;
+                  goto out;
+                }
+              b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+              next0 = SNAT_OUT2IN_NEXT_DROP;
+              goto out;
+            }
+          else
             {
               dont_translate = 1;
+              if (next_src_nat(sm, ip0, key0.protocol, key0.port, thread_index))
+                {
+                  next0 = SNAT_OUT2IN_NEXT_IN2OUT;
+                  goto out;
+                }
+              create_bypass_for_fwd(sm, ip0, rx_fib_index0, thread_index);
               goto out;
             }
-          b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
-          next0 = SNAT_OUT2IN_NEXT_DROP;
-          goto out;
         }
 
       if (PREDICT_FALSE(icmp0->type != ICMP4_echo_reply &&
@@ -372,8 +534,34 @@ u32 icmp_match_out2in_slow(snat_main_t *sm, vlib_node_runtime_t *node,
           goto out;
         }
 
-      s0 = pool_elt_at_index (sm->per_thread_data[thread_index].sessions,
-                              value0.value);
+      if (PREDICT_FALSE (value0.value == ~0ULL))
+        {
+          nat_ed_ses_key_t key;
+          clib_bihash_kv_16_8_t s_kv, s_value;
+
+          key.as_u64[0] = 0;
+          key.as_u64[1] = 0;
+          if (icmp_get_ed_key (ip0, &key))
+            {
+              b0->error = node->errors[SNAT_OUT2IN_ERROR_UNSUPPORTED_PROTOCOL];
+              next0 = SNAT_OUT2IN_NEXT_DROP;
+              goto out;
+            }
+          key.fib_index = rx_fib_index0;
+          s_kv.key[0] = key.as_u64[0];
+          s_kv.key[1] = key.as_u64[1];
+          if (!clib_bihash_search_16_8 (&sm->out2in_ed, &s_kv, &s_value))
+            s0 = pool_elt_at_index (sm->per_thread_data[thread_index].sessions,
+                                    s_value.value);
+          else
+           {
+              next0 = SNAT_OUT2IN_NEXT_DROP;
+              goto out;
+           }
+        }
+      else
+        s0 = pool_elt_at_index (sm->per_thread_data[thread_index].sessions,
+                                value0.value);
     }
 
 out:
@@ -400,11 +588,11 @@ out:
  * @param e                      optional parameter
  */
 u32 icmp_match_out2in_fast(snat_main_t *sm, vlib_node_runtime_t *node,
-                           u32 thread_index, vlib_buffer_t *b0, u8 *p_proto,
+                           u32 thread_index, vlib_buffer_t *b0,
+                           ip4_header_t *ip0, u8 *p_proto,
                            snat_session_key_t *p_value,
                            u8 *p_dont_translate, void *d, void *e)
 {
-  ip4_header_t *ip0;
   icmp46_header_t *icmp0;
   u32 sw_if_index0;
   u32 rx_fib_index0;
@@ -415,7 +603,6 @@ u32 icmp_match_out2in_fast(snat_main_t *sm, vlib_node_runtime_t *node,
   u32 next0 = ~0;
   int err;
 
-  ip0 = vlib_buffer_get_current (b0);
   icmp0 = (icmp46_header_t *) ip4_next_header (ip0);
   sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
   rx_fib_index0 = ip4_fib_table_get_index_for_sw_if_index (sw_if_index0);
@@ -429,7 +616,7 @@ u32 icmp_match_out2in_fast(snat_main_t *sm, vlib_node_runtime_t *node,
     }
   key0.fib_index = rx_fib_index0;
 
-  if (snat_static_mapping_match(sm, key0, &sm0, 1, &is_addr_only))
+  if (snat_static_mapping_match(sm, key0, &sm0, 1, &is_addr_only, 0, 0))
     {
       /* Don't NAT packet aimed at the intfc address */
       if (is_interface_addr(sm, node, sw_if_index0, ip0->dst_address.as_u32))
@@ -486,7 +673,7 @@ static inline u32 icmp_out2in (snat_main_t *sm,
 
   echo0 = (icmp_echo_header_t *)(icmp0+1);
 
-  next0_tmp = sm->icmp_match_out2in_cb(sm, node, thread_index, b0,
+  next0_tmp = sm->icmp_match_out2in_cb(sm, node, thread_index, b0, ip0,
                                        &protocol, &sm0, &dont_translate, d, e);
   if (next0_tmp != ~0)
     next0 = next0_tmp;
@@ -511,6 +698,9 @@ static inline u32 icmp_out2in (snat_main_t *sm,
                          dst_address /* changed member */);
   ip0->checksum = ip_csum_fold (sum0);
 
+  if (icmp0->checksum == 0)
+    icmp0->checksum = 0xffff;
+
   if (!icmp_is_error_message (icmp0))
     {
       new_id0 = sm0.port;
@@ -602,27 +792,25 @@ static inline u32 icmp_out2in_slow_path (snat_main_t *sm,
       s0->last_heard = now;
       s0->total_pkts++;
       s0->total_bytes += vlib_buffer_length_in_chain (sm->vlib_main, b0);
-      /* Per-user LRU list maintenance for dynamic translation */
-      if (!snat_is_session_static (s0))
-        {
-          clib_dlist_remove (sm->per_thread_data[thread_index].list_pool,
-                             s0->per_user_index);
-          clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
-                              s0->per_user_list_head_index,
-                              s0->per_user_index);
-        }
+      /* Per-user LRU list maintenance */
+      clib_dlist_remove (sm->per_thread_data[thread_index].list_pool,
+                         s0->per_user_index);
+      clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
+                          s0->per_user_list_head_index,
+                          s0->per_user_index);
     }
   return next0;
 }
 
-static void
+static snat_session_t *
 snat_out2in_unknown_proto (snat_main_t *sm,
                            vlib_buffer_t * b,
                            ip4_header_t * ip,
                            u32 rx_fib_index,
                            u32 thread_index,
                            f64 now,
-                           vlib_main_t * vm)
+                           vlib_main_t * vm,
+                           vlib_node_runtime_t * node)
 {
   clib_bihash_kv_8_8_t kv, value;
   clib_bihash_kv_16_8_t s_kv, s_value;
@@ -633,9 +821,7 @@ snat_out2in_unknown_proto (snat_main_t *sm,
   nat_ed_ses_key_t key;
   snat_session_t * s;
   snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
-  snat_user_key_t u_key;
   snat_user_t *u;
-  dlist_elt_t *head, *elt;
 
   old_addr = ip->dst_address.as_u32;
 
@@ -643,7 +829,7 @@ snat_out2in_unknown_proto (snat_main_t *sm,
   key.r_addr = ip->src_address;
   key.fib_index = rx_fib_index;
   key.proto = ip->protocol;
-  key.rsvd = 0;
+  key.r_port = 0;
   key.l_port = 0;
   s_kv.key[0] = key.as_u64[0];
   s_kv.key[1] = key.as_u64[1];
@@ -655,70 +841,54 @@ snat_out2in_unknown_proto (snat_main_t *sm,
     }
   else
     {
+      if (PREDICT_FALSE (maximum_sessions_exceeded(sm, thread_index)))
+        {
+          b->error = node->errors[SNAT_OUT2IN_ERROR_MAX_SESSIONS_EXCEEDED];
+          return 0;
+        }
+
       m_key.addr = ip->dst_address;
       m_key.port = 0;
       m_key.protocol = 0;
       m_key.fib_index = rx_fib_index;
       kv.key = m_key.as_u64;
       if (clib_bihash_search_8_8 (&sm->static_mapping_by_external, &kv, &value))
-        return;
+        {
+          b->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+          return 0;
+        }
 
       m = pool_elt_at_index (sm->static_mappings, value.value);
 
       new_addr = ip->dst_address.as_u32 = m->local_addr.as_u32;
 
-      u_key.addr = ip->src_address;
-      u_key.fib_index = m->fib_index;
-      kv.key = u_key.as_u64;
-
-      /* Ever heard of the "user" = src ip4 address before? */
-      if (clib_bihash_search_8_8 (&sm->user_hash, &kv, &value))
+      u = nat_user_get_or_create (sm, &ip->src_address, m->fib_index,
+                                  thread_index);
+      if (!u)
         {
-          /* no, make a new one */
-          pool_get (tsm->users, u);
-          memset (u, 0, sizeof (*u));
-          u->addr = ip->src_address;
-          u->fib_index = rx_fib_index;
-
-          pool_get (tsm->list_pool, head);
-          u->sessions_per_user_list_head_index = head - tsm->list_pool;
-
-          clib_dlist_init (tsm->list_pool,
-                           u->sessions_per_user_list_head_index);
-
-          kv.value = u - tsm->users;
-
-          /* add user */
-          clib_bihash_add_del_8_8 (&sm->user_hash, &kv, 1);
-        }
-      else
-        {
-          u = pool_elt_at_index (tsm->users, value.value);
+          clib_warning ("create NAT user failed");
+          return 0;
         }
 
       /* Create a new session */
-      pool_get (tsm->sessions, s);
-      memset (s, 0, sizeof (*s));
+      s = nat_session_alloc_or_recycle (sm, u, thread_index);
+      if (!s)
+        {
+          clib_warning ("create NAT session failed");
+          return 0;
+        }
 
       s->ext_host_addr.as_u32 = ip->src_address.as_u32;
       s->flags |= SNAT_SESSION_FLAG_UNKNOWN_PROTO;
       s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING;
+      s->flags |= SNAT_SESSION_FLAG_ENDPOINT_DEPENDENT;
       s->outside_address_index = ~0;
       s->out2in.addr.as_u32 = old_addr;
       s->out2in.fib_index = rx_fib_index;
       s->in2out.addr.as_u32 = new_addr;
       s->in2out.fib_index = m->fib_index;
       s->in2out.port = s->out2in.port = ip->protocol;
-      u->nstaticsessions++;
-
-      /* Create list elts */
-      pool_get (tsm->list_pool, elt);
-      clib_dlist_init (tsm->list_pool, elt - tsm->list_pool);
-      elt->value = s - tsm->sessions;
-      s->per_user_index = elt - tsm->list_pool;
-      s->per_user_list_head_index = u->sessions_per_user_list_head_index;
-      clib_dlist_addtail (tsm->list_pool, s->per_user_list_head_index,
-                          s->per_user_index);
+      user_session_increment (sm, u, 1 /* static */);
 
       /* Add to lookup tables */
       s_kv.value = s - tsm->sessions;
@@ -748,6 +918,8 @@ snat_out2in_unknown_proto (snat_main_t *sm,
   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 s;
 }
 
 static snat_session_t *
@@ -757,7 +929,8 @@ snat_out2in_lb (snat_main_t *sm,
                 u32 rx_fib_index,
                 u32 thread_index,
                 f64 now,
-                vlib_main_t * vm)
+                vlib_main_t * vm,
+                vlib_node_runtime_t * node)
 {
   nat_ed_ses_key_t key;
   clib_bihash_kv_16_8_t s_kv, s_value;
@@ -766,14 +939,15 @@ snat_out2in_lb (snat_main_t *sm,
   snat_session_t *s = 0;
   snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
   snat_session_key_t e_key, l_key;
-  clib_bihash_kv_8_8_t kv, value;
   u32 old_addr, new_addr;
   u32 proto = ip_proto_to_snat_proto (ip->protocol);
   u16 new_port, old_port;
   ip_csum_t sum;
-  snat_user_key_t u_key;
   snat_user_t *u;
-  dlist_elt_t *head, *elt;
+  u32 address_index;
+  snat_session_key_t eh_key;
+  twice_nat_type_t twice_nat;
+  u8 lb;
 
   old_addr = ip->dst_address.as_u32;
 
@@ -781,7 +955,7 @@ snat_out2in_lb (snat_main_t *sm,
   key.r_addr = ip->src_address;
   key.fib_index = rx_fib_index;
   key.proto = ip->protocol;
-  key.rsvd = 0;
+  key.r_port = udp->src_port;
   key.l_port = udp->dst_port;
   s_kv.key[0] = key.as_u64[0];
   s_kv.key[1] = key.as_u64[1];
@@ -792,69 +966,68 @@ snat_out2in_lb (snat_main_t *sm,
     }
   else
     {
+      if (PREDICT_FALSE (maximum_sessions_exceeded(sm, thread_index)))
+        {
+          b->error = node->errors[SNAT_OUT2IN_ERROR_MAX_SESSIONS_EXCEEDED];
+          return 0;
+        }
+
       e_key.addr = ip->dst_address;
       e_key.port = udp->dst_port;
       e_key.protocol = proto;
       e_key.fib_index = rx_fib_index;
-      if (snat_static_mapping_match(sm, e_key, &l_key, 1, 0))
+      if (snat_static_mapping_match(sm, e_key, &l_key, 1, 0, &twice_nat, &lb))
         return 0;
 
-      u_key.addr = l_key.addr;
-      u_key.fib_index = l_key.fib_index;
-      kv.key = u_key.as_u64;
-
-      /* Ever heard of the "user" = src ip4 address before? */
-      if (clib_bihash_search_8_8 (&sm->user_hash, &kv, &value))
-        {
-          /* no, make a new one */
-          pool_get (tsm->users, u);
-          memset (u, 0, sizeof (*u));
-          u->addr = l_key.addr;
-          u->fib_index = l_key.fib_index;
-
-          pool_get (tsm->list_pool, head);
-          u->sessions_per_user_list_head_index = head - tsm->list_pool;
-
-          clib_dlist_init (tsm->list_pool,
-                           u->sessions_per_user_list_head_index);
-
-          kv.value = u - tsm->users;
+      u = nat_user_get_or_create (sm, &l_key.addr, l_key.fib_index,
+                                  thread_index);
+      if (!u)
+      {
+        clib_warning ("create NAT user failed");
+        return 0;
+      }
 
-          /* add user */
-          if (clib_bihash_add_del_8_8 (&sm->user_hash, &kv, 1))
-            clib_warning ("user key add failed");
-        }
-      else
+      s = nat_session_alloc_or_recycle (sm, u, thread_index);
+      if (!s)
         {
-          u = pool_elt_at_index (tsm->users, value.value);
+          clib_warning ("create NAT session failed");
+          return 0;
         }
 
-      /* Create a new session */
-      pool_get (tsm->sessions, s);
-      memset (s, 0, sizeof (*s));
-
       s->ext_host_addr.as_u32 = ip->src_address.as_u32;
+      s->ext_host_port = udp->src_port;
       s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING;
-      s->flags |= SNAT_SESSION_FLAG_LOAD_BALANCING;
+      if (lb)
+        s->flags |= SNAT_SESSION_FLAG_LOAD_BALANCING;
+      s->flags |= SNAT_SESSION_FLAG_ENDPOINT_DEPENDENT;
       s->outside_address_index = ~0;
       s->out2in = e_key;
       s->in2out = l_key;
-      u->nstaticsessions++;
-
-      /* Create list elts */
-      pool_get (tsm->list_pool, elt);
-      clib_dlist_init (tsm->list_pool, elt - tsm->list_pool);
-      elt->value = s - tsm->sessions;
-      s->per_user_index = elt - tsm->list_pool;
-      s->per_user_list_head_index = u->sessions_per_user_list_head_index;
-      clib_dlist_addtail (tsm->list_pool, s->per_user_list_head_index,
-                          s->per_user_index);
+      user_session_increment (sm, u, 1 /* static */);
 
       /* Add to lookup tables */
       s_kv.value = s - tsm->sessions;
       if (clib_bihash_add_del_16_8 (&sm->out2in_ed, &s_kv, 1))
         clib_warning ("out2in-ed key add failed");
 
+      if (twice_nat == TWICE_NAT ||
+          (twice_nat == TWICE_NAT_SELF &&
+           ip->src_address.as_u32 == l_key.addr.as_u32))
+        {
+          eh_key.protocol = proto;
+          if (snat_alloc_outside_address_and_port (sm->twice_nat_addresses, 0,
+                                                   thread_index, &eh_key,
+                                                   &address_index,
+                                                   sm->port_per_thread,
+                                                   sm->per_thread_data[thread_index].snat_thread_index))
+            {
+              b->error = node->errors[SNAT_OUT2IN_ERROR_OUT_OF_PORTS];
+              return 0;
+            }
+          key.r_addr.as_u32 = s->ext_host_nat_addr.as_u32 = eh_key.addr.as_u32;
+          key.r_port = s->ext_host_nat_port = eh_key.port;
+          s->flags |= SNAT_SESSION_FLAG_TWICE_NAT;
+        }
       key.l_addr = l_key.addr;
       key.fib_index = l_key.fib_index;
       key.l_port = l_key.port;
@@ -869,8 +1042,14 @@ snat_out2in_lb (snat_main_t *sm,
   /* Update IP checksum */
   sum = ip->checksum;
   sum = ip_csum_update (sum, old_addr, new_addr, ip4_header_t, dst_address);
+  if (is_twice_nat_session (s))
+    sum = ip_csum_update (sum, ip->src_address.as_u32,
+                          s->ext_host_nat_addr.as_u32, ip4_header_t,
+                          src_address);
   ip->checksum = ip_csum_fold (sum);
 
+  vnet_buffer(b)->sw_if_index[VLIB_TX] = s->in2out.fib_index;
+
   if (PREDICT_TRUE(proto == SNAT_PROTOCOL_TCP))
     {
       old_port = tcp->dst_port;
@@ -880,20 +1059,40 @@ snat_out2in_lb (snat_main_t *sm,
       sum = tcp->checksum;
       sum = ip_csum_update (sum, old_addr, new_addr, ip4_header_t, dst_address);
       sum = ip_csum_update (sum, old_port, new_port, ip4_header_t, length);
+      if (is_twice_nat_session (s))
+        {
+          sum = ip_csum_update (sum, ip->src_address.as_u32,
+                                s->ext_host_nat_addr.as_u32, ip4_header_t,
+                                dst_address);
+          sum = ip_csum_update (sum, tcp->src_port, s->ext_host_nat_port,
+                                ip4_header_t, length);
+          tcp->src_port = s->ext_host_nat_port;
+          ip->src_address.as_u32 = s->ext_host_nat_addr.as_u32;
+        }
       tcp->checksum = ip_csum_fold(sum);
+      if (nat44_set_tcp_session_state_o2i (sm, s, tcp, thread_index))
+        return s;
     }
   else
     {
       udp->dst_port = s->in2out.port;
+      if (is_twice_nat_session (s))
+        {
+          udp->src_port = s->ext_host_nat_port;
+          ip->src_address.as_u32 = s->ext_host_nat_addr.as_u32;
+        }
       udp->checksum = 0;
     }
 
-  vnet_buffer(b)->sw_if_index[VLIB_TX] = s->in2out.fib_index;
-
   /* Accounting */
   s->last_heard = now;
   s->total_pkts++;
   s->total_bytes += vlib_buffer_length_in_chain (vm, b);
+  /* 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 s;
 }
 
@@ -993,8 +1192,11 @@ snat_out2in_node_fn (vlib_main_t * vm,
 
           if (PREDICT_FALSE (proto0 == ~0))
             {
-              snat_out2in_unknown_proto(sm, b0, ip0, rx_fib_index0,
-                                        thread_index, now, vm);
+              s0 = snat_out2in_unknown_proto(sm, b0, ip0, rx_fib_index0,
+                                             thread_index, now, vm, node);
+             if (!sm->forwarding_enabled)
+               if (!s0)
+                 next0 = SNAT_OUT2IN_NEXT_DROP;
               goto trace0;
             }
 
@@ -1006,6 +1208,12 @@ snat_out2in_node_fn (vlib_main_t * vm,
               goto trace0;
             }
 
+          if (PREDICT_FALSE (ip4_is_fragment (ip0)))
+            {
+              next0 = SNAT_OUT2IN_NEXT_REASS;
+              goto trace0;
+            }
+
           key0.addr = ip0->dst_address;
           key0.port = udp0->dst_port;
           key0.protocol = proto0;
@@ -1013,22 +1221,42 @@ snat_out2in_node_fn (vlib_main_t * vm,
 
           kv0.key = key0.as_u64;
 
-          if (clib_bihash_search_8_8 (&sm->out2in, &kv0, &value0))
+          if (clib_bihash_search_8_8 (&sm->per_thread_data[thread_index].out2in,
+                                      &kv0, &value0))
             {
               /* Try to match static mapping by external address and port,
                  destination address and port in packet */
-              if (snat_static_mapping_match(sm, key0, &sm0, 1, 0))
+              if (snat_static_mapping_match(sm, key0, &sm0, 1, 0, 0, 0))
                 {
-                  b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
                   /*
                    * Send DHCP packets to the ipv4 stack, or we won't
                    * be able to use dhcp client on the outside interface
                    */
-                  if (proto0 != SNAT_PROTOCOL_UDP
-                      || (udp0->dst_port
-                          != clib_host_to_net_u16(UDP_DST_PORT_dhcp_to_client)))
-                    next0 = SNAT_OUT2IN_NEXT_DROP;
-                  goto trace0;
+                 if (PREDICT_FALSE (proto0 == SNAT_PROTOCOL_UDP
+                     && (udp0->dst_port ==
+                         clib_host_to_net_u16(UDP_DST_PORT_dhcp_to_client))))
+                   {
+                     vnet_feature_next
+                       (vnet_buffer (b0)->sw_if_index[VLIB_RX], &next0, b0);
+                     goto trace0;
+                   }
+
+                  if (!sm->forwarding_enabled)
+                    {
+                      b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+                      next0 = SNAT_OUT2IN_NEXT_DROP;
+                      goto trace0;
+                    }
+                  else
+                    {
+                      if (next_src_nat(sm, ip0, proto0, udp0->src_port, thread_index))
+                        {
+                          next0 = SNAT_OUT2IN_NEXT_IN2OUT;
+                          goto trace0;
+                        }
+                      create_bypass_for_fwd(sm, ip0, rx_fib_index0, thread_index);
+                      goto trace0;
+                    }
                 }
 
               /* Create session initiated by host from external network */
@@ -1036,7 +1264,6 @@ snat_out2in_node_fn (vlib_main_t * vm,
                                                      thread_index);
               if (!s0)
                 {
-                  b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
                   next0 = SNAT_OUT2IN_NEXT_DROP;
                   goto trace0;
                 }
@@ -1045,8 +1272,10 @@ snat_out2in_node_fn (vlib_main_t * vm,
             {
               if (PREDICT_FALSE (value0.value == ~0ULL))
                 {
-                  s0 = snat_out2in_lb(sm, b0, ip0, rx_fib_index0, thread_index, now,
-                                 vm);
+                  s0 = snat_out2in_lb(sm, b0, ip0, rx_fib_index0, thread_index,
+                                      now, vm, node);
+                  if (!s0)
+                    next0 = SNAT_OUT2IN_NEXT_DROP;
                   goto trace0;
                 }
               else
@@ -1095,15 +1324,12 @@ snat_out2in_node_fn (vlib_main_t * vm,
           s0->last_heard = now;
           s0->total_pkts++;
           s0->total_bytes += vlib_buffer_length_in_chain (vm, b0);
-          /* Per-user LRU list maintenance for dynamic translation */
-          if (!snat_is_session_static (s0))
-            {
-              clib_dlist_remove (sm->per_thread_data[thread_index].list_pool,
-                                 s0->per_user_index);
-              clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
-                                  s0->per_user_list_head_index,
-                                  s0->per_user_index);
-            }
+          /* Per-user LRU list maintenance */
+          clib_dlist_remove (sm->per_thread_data[thread_index].list_pool,
+                             s0->per_user_index);
+          clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
+                              s0->per_user_list_head_index,
+                              s0->per_user_index);
         trace0:
 
           if (PREDICT_FALSE((node->flags & VLIB_NODE_FLAG_TRACE)
@@ -1144,8 +1370,11 @@ snat_out2in_node_fn (vlib_main_t * vm,
 
           if (PREDICT_FALSE (proto1 == ~0))
             {
-              snat_out2in_unknown_proto(sm, b1, ip1, rx_fib_index1,
-                                        thread_index, now, vm);
+              s1 = snat_out2in_unknown_proto(sm, b1, ip1, rx_fib_index1,
+                                             thread_index, now, vm, node);
+             if (!sm->forwarding_enabled)
+               if (!s1)
+                 next1 = SNAT_OUT2IN_NEXT_DROP;
               goto trace1;
             }
 
@@ -1157,6 +1386,12 @@ snat_out2in_node_fn (vlib_main_t * vm,
               goto trace1;
             }
 
+          if (PREDICT_FALSE (ip4_is_fragment (ip1)))
+            {
+              next1 = SNAT_OUT2IN_NEXT_REASS;
+              goto trace1;
+            }
+
           key1.addr = ip1->dst_address;
           key1.port = udp1->dst_port;
           key1.protocol = proto1;
@@ -1164,22 +1399,42 @@ snat_out2in_node_fn (vlib_main_t * vm,
 
           kv1.key = key1.as_u64;
 
-          if (clib_bihash_search_8_8 (&sm->out2in, &kv1, &value1))
+          if (clib_bihash_search_8_8 (&sm->per_thread_data[thread_index].out2in,
+                                      &kv1, &value1))
             {
               /* Try to match static mapping by external address and port,
                  destination address and port in packet */
-              if (snat_static_mapping_match(sm, key1, &sm1, 1, 0))
+              if (snat_static_mapping_match(sm, key1, &sm1, 1, 0, 0, 0))
                 {
-                  b1->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
                   /*
                    * Send DHCP packets to the ipv4 stack, or we won't
                    * be able to use dhcp client on the outside interface
                    */
-                  if (proto1 != SNAT_PROTOCOL_UDP
-                      || (udp1->dst_port
-                          != clib_host_to_net_u16(UDP_DST_PORT_dhcp_to_client)))
-                    next1 = SNAT_OUT2IN_NEXT_DROP;
-                  goto trace1;
+                 if (PREDICT_FALSE (proto1 == SNAT_PROTOCOL_UDP
+                     && (udp1->dst_port ==
+                         clib_host_to_net_u16(UDP_DST_PORT_dhcp_to_client))))
+                   {
+                     vnet_feature_next
+                       (vnet_buffer (b1)->sw_if_index[VLIB_RX], &next1, b1);
+                     goto trace1;
+                   }
+
+                  if (!sm->forwarding_enabled)
+                    {
+                      b1->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+                      next1 = SNAT_OUT2IN_NEXT_DROP;
+                      goto trace1;
+                    }
+                  else
+                    {
+                      if (next_src_nat(sm, ip1, proto1, udp1->src_port, thread_index))
+                        {
+                          next1 = SNAT_OUT2IN_NEXT_IN2OUT;
+                          goto trace1;
+                        }
+                      create_bypass_for_fwd(sm, ip1, rx_fib_index1, thread_index);
+                      goto trace1;
+                    }
                 }
 
               /* Create session initiated by host from external network */
@@ -1187,7 +1442,6 @@ snat_out2in_node_fn (vlib_main_t * vm,
                                                      thread_index);
               if (!s1)
                 {
-                  b1->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
                   next1 = SNAT_OUT2IN_NEXT_DROP;
                   goto trace1;
                 }
@@ -1196,8 +1450,10 @@ snat_out2in_node_fn (vlib_main_t * vm,
             {
               if (PREDICT_FALSE (value1.value == ~0ULL))
                 {
-                  s1 = snat_out2in_lb(sm, b1, ip1, rx_fib_index1, thread_index, now,
-                                 vm);
+                  s1 = snat_out2in_lb(sm, b1, ip1, rx_fib_index1, thread_index,
+                                      now, vm, node);
+                  if (!s1)
+                    next1 = SNAT_OUT2IN_NEXT_DROP;
                   goto trace1;
                 }
               else
@@ -1246,15 +1502,12 @@ snat_out2in_node_fn (vlib_main_t * vm,
           s1->last_heard = now;
           s1->total_pkts++;
           s1->total_bytes += vlib_buffer_length_in_chain (vm, b1);
-          /* Per-user LRU list maintenance for dynamic translation */
-          if (!snat_is_session_static (s1))
-            {
-              clib_dlist_remove (sm->per_thread_data[thread_index].list_pool,
-                                 s1->per_user_index);
-              clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
-                                  s1->per_user_list_head_index,
-                                  s1->per_user_index);
-            }
+          /* Per-user LRU list maintenance */
+          clib_dlist_remove (sm->per_thread_data[thread_index].list_pool,
+                             s1->per_user_index);
+          clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
+                              s1->per_user_list_head_index,
+                              s1->per_user_index);
         trace1:
 
           if (PREDICT_FALSE((node->flags & VLIB_NODE_FLAG_TRACE)
@@ -1321,8 +1574,11 @@ snat_out2in_node_fn (vlib_main_t * vm,
 
           if (PREDICT_FALSE (proto0 == ~0))
             {
-              snat_out2in_unknown_proto(sm, b0, ip0, rx_fib_index0,
-                                        thread_index, now, vm);
+              s0 = snat_out2in_unknown_proto(sm, b0, ip0, rx_fib_index0,
+                                             thread_index, now, vm, node);
+             if (!sm->forwarding_enabled)
+               if (!s0)
+                 next0 = SNAT_OUT2IN_NEXT_DROP;
               goto trace00;
             }
 
@@ -1344,6 +1600,12 @@ snat_out2in_node_fn (vlib_main_t * vm,
               goto trace00;
             }
 
+          if (PREDICT_FALSE (ip4_is_fragment (ip0)))
+            {
+              next0 = SNAT_OUT2IN_NEXT_REASS;
+              goto trace00;
+            }
+
           key0.addr = ip0->dst_address;
           key0.port = udp0->dst_port;
           key0.protocol = proto0;
@@ -1351,23 +1613,42 @@ snat_out2in_node_fn (vlib_main_t * vm,
 
           kv0.key = key0.as_u64;
 
-          if (clib_bihash_search_8_8 (&sm->out2in, &kv0, &value0))
+          if (clib_bihash_search_8_8 (&sm->per_thread_data[thread_index].out2in,
+                                      &kv0, &value0))
             {
               /* Try to match static mapping by external address and port,
                  destination address and port in packet */
-              if (snat_static_mapping_match(sm, key0, &sm0, 1, 0))
+              if (snat_static_mapping_match(sm, key0, &sm0, 1, 0, 0, 0))
                 {
-                  b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
                   /*
                    * Send DHCP packets to the ipv4 stack, or we won't
                    * be able to use dhcp client on the outside interface
                    */
-                  if (proto0 != SNAT_PROTOCOL_UDP
-                      || (udp0->dst_port
-                          != clib_host_to_net_u16(UDP_DST_PORT_dhcp_to_client)))
-
-                    next0 = SNAT_OUT2IN_NEXT_DROP;
-                  goto trace00;
+                 if (PREDICT_FALSE (proto0 == SNAT_PROTOCOL_UDP
+                     && (udp0->dst_port ==
+                         clib_host_to_net_u16(UDP_DST_PORT_dhcp_to_client))))
+                   {
+                     vnet_feature_next
+                       (vnet_buffer (b0)->sw_if_index[VLIB_RX], &next0, b0);
+                     goto trace00;
+                   }
+
+                  if (!sm->forwarding_enabled)
+                    {
+                      b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+                      next0 = SNAT_OUT2IN_NEXT_DROP;
+                      goto trace00;
+                    }
+                  else
+                    {
+                      if (next_src_nat(sm, ip0, proto0, udp0->src_port, thread_index))
+                        {
+                          next0 = SNAT_OUT2IN_NEXT_IN2OUT;
+                          goto trace00;
+                        }
+                      create_bypass_for_fwd(sm, ip0, rx_fib_index0, thread_index);
+                      goto trace00;
+                    }
                 }
 
               /* Create session initiated by host from external network */
@@ -1375,8 +1656,7 @@ snat_out2in_node_fn (vlib_main_t * vm,
                                                      thread_index);
               if (!s0)
                 {
-                  b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
-                    next0 = SNAT_OUT2IN_NEXT_DROP;
+                  next0 = SNAT_OUT2IN_NEXT_DROP;
                   goto trace00;
                 }
             }
@@ -1384,8 +1664,10 @@ snat_out2in_node_fn (vlib_main_t * vm,
             {
               if (PREDICT_FALSE (value0.value == ~0ULL))
                 {
-                  s0 = snat_out2in_lb(sm, b0, ip0, rx_fib_index0, thread_index, now,
-                                 vm);
+                  s0 = snat_out2in_lb(sm, b0, ip0, rx_fib_index0, thread_index,
+                                      now, vm, node);
+                  if (!s0)
+                    next0 = SNAT_OUT2IN_NEXT_DROP;
                   goto trace00;
                 }
               else
@@ -1434,15 +1716,12 @@ snat_out2in_node_fn (vlib_main_t * vm,
           s0->last_heard = now;
           s0->total_pkts++;
           s0->total_bytes += vlib_buffer_length_in_chain (vm, b0);
-          /* Per-user LRU list maintenance for dynamic translation */
-          if (!snat_is_session_static (s0))
-            {
-              clib_dlist_remove (sm->per_thread_data[thread_index].list_pool,
-                                 s0->per_user_index);
-              clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
-                                  s0->per_user_list_head_index,
-                                  s0->per_user_index);
-            }
+          /* Per-user LRU list maintenance */
+          clib_dlist_remove (sm->per_thread_data[thread_index].list_pool,
+                             s0->per_user_index);
+          clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
+                              s0->per_user_list_head_index,
+                              s0->per_user_index);
         trace00:
 
           if (PREDICT_FALSE((node->flags & VLIB_NODE_FLAG_TRACE)
@@ -1493,10 +1772,313 @@ VLIB_REGISTER_NODE (snat_out2in_node) = {
     [SNAT_OUT2IN_NEXT_DROP] = "error-drop",
     [SNAT_OUT2IN_NEXT_LOOKUP] = "ip4-lookup",
     [SNAT_OUT2IN_NEXT_ICMP_ERROR] = "ip4-icmp-error",
+    [SNAT_OUT2IN_NEXT_REASS] = "nat44-out2in-reass",
+    [SNAT_OUT2IN_NEXT_IN2OUT] = "nat44-in2out",
   },
 };
 VLIB_NODE_FUNCTION_MULTIARCH (snat_out2in_node, snat_out2in_node_fn);
 
+static uword
+nat44_out2in_reass_node_fn (vlib_main_t * vm,
+                            vlib_node_runtime_t * node,
+                            vlib_frame_t * frame)
+{
+  u32 n_left_from, *from, *to_next;
+  snat_out2in_next_t next_index;
+  u32 pkts_processed = 0;
+  snat_main_t *sm = &snat_main;
+  f64 now = vlib_time_now (vm);
+  u32 thread_index = vlib_get_thread_index ();
+  snat_main_per_thread_data_t *per_thread_data =
+    &sm->per_thread_data[thread_index];
+  u32 *fragments_to_drop = 0;
+  u32 *fragments_to_loopback = 0;
+
+  from = vlib_frame_vector_args (frame);
+  n_left_from = frame->n_vectors;
+  next_index = node->cached_next_index;
+
+  while (n_left_from > 0)
+    {
+      u32 n_left_to_next;
+
+      vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
+
+      while (n_left_from > 0 && n_left_to_next > 0)
+       {
+          u32 bi0, sw_if_index0, proto0, rx_fib_index0, new_addr0, old_addr0;
+         vlib_buffer_t *b0;
+          u32 next0;
+          u8 cached0 = 0;
+          ip4_header_t *ip0;
+          nat_reass_ip4_t *reass0;
+          udp_header_t * udp0;
+          tcp_header_t * tcp0;
+          snat_session_key_t key0, sm0;
+          clib_bihash_kv_8_8_t kv0, value0;
+          snat_session_t * s0 = 0;
+          u16 old_port0, new_port0;
+          ip_csum_t sum0;
+
+          /* speculatively enqueue b0 to the current next frame */
+         bi0 = from[0];
+         to_next[0] = bi0;
+         from += 1;
+         to_next += 1;
+         n_left_from -= 1;
+         n_left_to_next -= 1;
+
+         b0 = vlib_get_buffer (vm, bi0);
+          next0 = SNAT_OUT2IN_NEXT_LOOKUP;
+
+          sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
+          rx_fib_index0 = fib_table_get_index_for_sw_if_index (FIB_PROTOCOL_IP4,
+                                                               sw_if_index0);
+
+          if (PREDICT_FALSE (nat_reass_is_drop_frag(0)))
+            {
+              next0 = SNAT_OUT2IN_NEXT_DROP;
+              b0->error = node->errors[SNAT_OUT2IN_ERROR_DROP_FRAGMENT];
+              goto trace0;
+            }
+
+          ip0 = (ip4_header_t *) vlib_buffer_get_current (b0);
+          udp0 = ip4_next_header (ip0);
+          tcp0 = (tcp_header_t *) udp0;
+          proto0 = ip_proto_to_snat_proto (ip0->protocol);
+
+          reass0 = nat_ip4_reass_find_or_create (ip0->src_address,
+                                                 ip0->dst_address,
+                                                 ip0->fragment_id,
+                                                 ip0->protocol,
+                                                 1,
+                                                 &fragments_to_drop);
+
+          if (PREDICT_FALSE (!reass0))
+            {
+              next0 = SNAT_OUT2IN_NEXT_DROP;
+              b0->error = node->errors[SNAT_OUT2IN_ERROR_MAX_REASS];
+              goto trace0;
+            }
+
+          if (PREDICT_FALSE (ip4_is_first_fragment (ip0)))
+            {
+              key0.addr = ip0->dst_address;
+              key0.port = udp0->dst_port;
+              key0.protocol = proto0;
+              key0.fib_index = rx_fib_index0;
+              kv0.key = key0.as_u64;
+
+              if (clib_bihash_search_8_8 (&per_thread_data->out2in, &kv0, &value0))
+                {
+                  /* Try to match static mapping by external address and port,
+                     destination address and port in packet */
+                  if (snat_static_mapping_match(sm, key0, &sm0, 1, 0, 0, 0))
+                    {
+                      /*
+                       * Send DHCP packets to the ipv4 stack, or we won't
+                       * be able to use dhcp client on the outside interface
+                       */
+                      if (PREDICT_FALSE (proto0 == SNAT_PROTOCOL_UDP
+                          && (udp0->dst_port
+                              == clib_host_to_net_u16(UDP_DST_PORT_dhcp_to_client))))
+                       {
+                          vnet_feature_next
+                            (vnet_buffer (b0)->sw_if_index[VLIB_RX],
+                             &next0, b0);
+                          goto trace0;
+                        }
+
+                      if (!sm->forwarding_enabled)
+                        {
+                          b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+                          next0 = SNAT_OUT2IN_NEXT_DROP;
+                          goto trace0;
+                        }
+                      else
+                        {
+                          if (next_src_nat(sm, ip0, proto0, udp0->src_port, thread_index))
+                            {
+                              next0 = SNAT_OUT2IN_NEXT_IN2OUT;
+                              goto trace0;
+                            }
+                          create_bypass_for_fwd(sm, ip0, rx_fib_index0, thread_index);
+                          goto trace0;
+                        }
+                    }
+
+                  /* Create session initiated by host from external network */
+                  s0 = create_session_for_static_mapping(sm, b0, sm0, key0, node,
+                                                         thread_index);
+                  if (!s0)
+                    {
+                      b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+                      next0 = SNAT_OUT2IN_NEXT_DROP;
+                      goto trace0;
+                    }
+                  reass0->sess_index = s0 - per_thread_data->sessions;
+                  reass0->thread_index = thread_index;
+                }
+              else
+                {
+                  s0 = pool_elt_at_index (per_thread_data->sessions,
+                                          value0.value);
+                  reass0->sess_index = value0.value;
+                }
+              nat_ip4_reass_get_frags (reass0, &fragments_to_loopback);
+            }
+          else
+            {
+              if (PREDICT_FALSE (reass0->sess_index == (u32) ~0))
+                {
+                  if (nat_ip4_reass_add_fragment (reass0, bi0))
+                    {
+                      b0->error = node->errors[SNAT_OUT2IN_ERROR_MAX_FRAG];
+                      next0 = SNAT_OUT2IN_NEXT_DROP;
+                      goto trace0;
+                    }
+                  cached0 = 1;
+                  goto trace0;
+                }
+              s0 = pool_elt_at_index (per_thread_data->sessions,
+                                      reass0->sess_index);
+            }
+
+          old_addr0 = ip0->dst_address.as_u32;
+          ip0->dst_address = s0->in2out.addr;
+          new_addr0 = ip0->dst_address.as_u32;
+          vnet_buffer(b0)->sw_if_index[VLIB_TX] = s0->in2out.fib_index;
+
+          sum0 = ip0->checksum;
+          sum0 = ip_csum_update (sum0, old_addr0, new_addr0,
+                                 ip4_header_t,
+                                 dst_address /* changed member */);
+          ip0->checksum = ip_csum_fold (sum0);
+
+          if (PREDICT_FALSE (ip4_is_first_fragment (ip0)))
+            {
+              if (PREDICT_TRUE(proto0 == SNAT_PROTOCOL_TCP))
+                {
+                  old_port0 = tcp0->dst_port;
+                  tcp0->dst_port = s0->in2out.port;
+                  new_port0 = tcp0->dst_port;
+
+                  sum0 = tcp0->checksum;
+                  sum0 = ip_csum_update (sum0, old_addr0, new_addr0,
+                                         ip4_header_t,
+                                         dst_address /* changed member */);
+
+                  sum0 = ip_csum_update (sum0, old_port0, new_port0,
+                                         ip4_header_t /* cheat */,
+                                         length /* changed member */);
+                  tcp0->checksum = ip_csum_fold(sum0);
+                }
+              else
+                {
+                  old_port0 = udp0->dst_port;
+                  udp0->dst_port = s0->in2out.port;
+                  udp0->checksum = 0;
+                }
+            }
+
+          /* Accounting */
+          s0->last_heard = now;
+          s0->total_pkts++;
+          s0->total_bytes += vlib_buffer_length_in_chain (vm, b0);
+          /* Per-user LRU list maintenance */
+          clib_dlist_remove (sm->per_thread_data[thread_index].list_pool,
+                             s0->per_user_index);
+          clib_dlist_addtail (sm->per_thread_data[thread_index].list_pool,
+                              s0->per_user_list_head_index,
+                              s0->per_user_index);
+
+        trace0:
+          if (PREDICT_FALSE((node->flags & VLIB_NODE_FLAG_TRACE)
+                            && (b0->flags & VLIB_BUFFER_IS_TRACED)))
+            {
+              nat44_out2in_reass_trace_t *t =
+                 vlib_add_trace (vm, node, b0, sizeof (*t));
+              t->cached = cached0;
+              t->sw_if_index = sw_if_index0;
+              t->next_index = next0;
+            }
+
+          if (cached0)
+            {
+              n_left_to_next++;
+              to_next--;
+            }
+          else
+            {
+              pkts_processed += next0 != SNAT_OUT2IN_NEXT_DROP;
+
+              /* verify speculative enqueue, maybe switch current next frame */
+              vlib_validate_buffer_enqueue_x1 (vm, node, next_index,
+                                               to_next, n_left_to_next,
+                                               bi0, next0);
+            }
+
+         if (n_left_from == 0 && vec_len (fragments_to_loopback))
+           {
+             from = vlib_frame_vector_args (frame);
+             u32 len = vec_len (fragments_to_loopback);
+             if (len <= VLIB_FRAME_SIZE)
+               {
+                 clib_memcpy (from, fragments_to_loopback, sizeof (u32) * len);
+                 n_left_from = len;
+                 vec_reset_length (fragments_to_loopback);
+               }
+             else
+               {
+                 clib_memcpy (from,
+                               fragments_to_loopback + (len - VLIB_FRAME_SIZE),
+                               sizeof (u32) * VLIB_FRAME_SIZE);
+                 n_left_from = VLIB_FRAME_SIZE;
+                 _vec_len (fragments_to_loopback) = len - VLIB_FRAME_SIZE;
+               }
+           }
+       }
+
+      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
+    }
+
+  vlib_node_increment_counter (vm, nat44_out2in_reass_node.index,
+                               SNAT_OUT2IN_ERROR_OUT2IN_PACKETS,
+                               pkts_processed);
+
+  nat_send_all_to_node (vm, fragments_to_drop, node,
+                        &node->errors[SNAT_OUT2IN_ERROR_DROP_FRAGMENT],
+                        SNAT_OUT2IN_NEXT_DROP);
+
+  vec_free (fragments_to_drop);
+  vec_free (fragments_to_loopback);
+  return frame->n_vectors;
+}
+
+VLIB_REGISTER_NODE (nat44_out2in_reass_node) = {
+  .function = nat44_out2in_reass_node_fn,
+  .name = "nat44-out2in-reass",
+  .vector_size = sizeof (u32),
+  .format_trace = format_nat44_out2in_reass_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+
+  .n_errors = ARRAY_LEN(snat_out2in_error_strings),
+  .error_strings = snat_out2in_error_strings,
+
+  .n_next_nodes = SNAT_OUT2IN_N_NEXT,
+
+  /* edit / add dispositions here */
+  .next_nodes = {
+    [SNAT_OUT2IN_NEXT_DROP] = "error-drop",
+    [SNAT_OUT2IN_NEXT_LOOKUP] = "ip4-lookup",
+    [SNAT_OUT2IN_NEXT_ICMP_ERROR] = "ip4-icmp-error",
+    [SNAT_OUT2IN_NEXT_REASS] = "nat44-out2in-reass",
+    [SNAT_OUT2IN_NEXT_IN2OUT] = "nat44-in2out",
+  },
+};
+VLIB_NODE_FUNCTION_MULTIARCH (nat44_out2in_reass_node,
+                              nat44_out2in_reass_node_fn);
+
 /**************************/
 /*** deterministic mode ***/
 /**************************/
@@ -1980,6 +2562,8 @@ VLIB_REGISTER_NODE (snat_det_out2in_node) = {
     [SNAT_OUT2IN_NEXT_DROP] = "error-drop",
     [SNAT_OUT2IN_NEXT_LOOKUP] = "ip4-lookup",
     [SNAT_OUT2IN_NEXT_ICMP_ERROR] = "ip4-icmp-error",
+    [SNAT_OUT2IN_NEXT_REASS] = "nat44-out2in-reass",
+    [SNAT_OUT2IN_NEXT_IN2OUT] = "nat44-in2out",
   },
 };
 VLIB_NODE_FUNCTION_MULTIARCH (snat_det_out2in_node, snat_det_out2in_node_fn);
@@ -1999,11 +2583,11 @@ VLIB_NODE_FUNCTION_MULTIARCH (snat_det_out2in_node, snat_det_out2in_node_fn);
  * @param e                      optional parameter
  */
 u32 icmp_match_out2in_det(snat_main_t *sm, vlib_node_runtime_t *node,
-                          u32 thread_index, vlib_buffer_t *b0, u8 *p_proto,
+                          u32 thread_index, vlib_buffer_t *b0,
+                          ip4_header_t *ip0, u8 *p_proto,
                           snat_session_key_t *p_value,
                           u8 *p_dont_translate, void *d, void *e)
 {
-  ip4_header_t *ip0;
   icmp46_header_t *icmp0;
   u32 sw_if_index0;
   u8 protocol;
@@ -2019,7 +2603,6 @@ u32 icmp_match_out2in_det(snat_main_t *sm, vlib_node_runtime_t *node,
   snat_det_session_t * ses0 = 0;
   ip4_address_t out_addr;
 
-  ip0 = vlib_buffer_get_current (b0);
   icmp0 = (icmp46_header_t *) ip4_next_header (ip0);
   echo0 = (icmp_echo_header_t *)(icmp0+1);
   sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
@@ -2371,7 +2954,7 @@ snat_out2in_fast_node_fn (vlib_main_t * vm,
           key0.port = udp0->dst_port;
           key0.fib_index = rx_fib_index0;
 
-          if (snat_static_mapping_match(sm, key0, &sm0, 1, 0))
+          if (snat_static_mapping_match(sm, key0, &sm0, 1, 0, 0, 0))
             {
               b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
               goto trace00;
@@ -2473,6 +3056,8 @@ VLIB_REGISTER_NODE (snat_out2in_fast_node) = {
     [SNAT_OUT2IN_NEXT_LOOKUP] = "ip4-lookup",
     [SNAT_OUT2IN_NEXT_DROP] = "error-drop",
     [SNAT_OUT2IN_NEXT_ICMP_ERROR] = "ip4-icmp-error",
+    [SNAT_OUT2IN_NEXT_REASS] = "nat44-out2in-reass",
+    [SNAT_OUT2IN_NEXT_IN2OUT] = "nat44-in2out",
   },
 };
 VLIB_NODE_FUNCTION_MULTIARCH (snat_out2in_fast_node, snat_out2in_fast_node_fn);