NAT44: active-passive HA (VPP-1571)

session synchronization so that we can build a plain active-passive HA NAT pair

Change-Id: I21db200491081ca46b7af3e82afc677c1985abf4
Signed-off-by: Matus Fabian <matfabia@cisco.com>

1 files changed, 1179 insertions, 0 deletions

diff --git a/src/plugins/nat/nat_ha.c b/src/plugins/nat/nat_ha.c
new file mode 100644
index 00000000000..a7eaf6ec5d0
--- /dev/null
+++ b/src/plugins/nat/nat_ha.c
@@ -0,0 +1,1179 @@
+/*
+ * Copyright (c) 2019 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "nat_ha.h"
+#include <vnet/udp/udp.h>
+#include <nat/nat.h>
+#include <vppinfra/atomics.h>
+
+/* number of retries */
+#define NAT_HA_RETRIES 3
+
+#define foreach_nat_ha_counter           \
+_(RECV_ADD, "add-event-recv", 0)         \
+_(RECV_DEL, "del-event-recv", 1)         \
+_(RECV_REFRESH, "refresh-event-recv", 2) \
+_(SEND_ADD, "add-event-send", 3)         \
+_(SEND_DEL, "del-event-send", 4)         \
+_(SEND_REFRESH, "refresh-event-send", 5) \
+_(RECV_ACK, "ack-recv", 6)               \
+_(SEND_ACK, "ack-send", 7)               \
+_(RETRY_COUNT, "retry-count", 8)         \
+_(MISSED_COUNT, "missed-count", 9)
+
+/* NAT HA protocol version */
+#define NAT_HA_VERSION 0x01
+
+/* NAT HA protocol flags */
+#define NAT_HA_FLAG_ACK 0x01
+
+/* NAT HA event types */
+typedef enum
+{
+  NAT_HA_ADD = 1,
+  NAT_HA_DEL,
+  NAT_HA_REFRESH,
+} nat_ha_event_type_t;
+
+/* NAT HA protocol header */
+typedef struct
+{
+  /* version */
+  u8 version;
+  /* flags */
+  u8 flags;
+  /* event count */
+  u16 count;
+  /* sequence number */
+  u32 sequence_number;
+  /* thread index where events originated */
+  u32 thread_index;
+} __attribute__ ((packed)) nat_ha_message_header_t;
+
+/* NAT HA protocol event data */
+typedef struct
+{
+  /* event type */
+  u8 event_type;
+  /* session data */
+  u8 protocol;
+  u16 flags;
+  u32 in_addr;
+  u32 out_addr;
+  u16 in_port;
+  u16 out_port;
+  u32 eh_addr;
+  u32 ehn_addr;
+  u16 eh_port;
+  u16 ehn_port;
+  u32 fib_index;
+  u32 total_pkts;
+  u64 total_bytes;
+} __attribute__ ((packed)) nat_ha_event_t;
+
+typedef enum
+{
+#define _(N, s, v) NAT_HA_COUNTER_##N = v,
+  foreach_nat_ha_counter
+#undef _
+  NAT_HA_N_COUNTERS
+} nat_ha_counter_t;
+
+/* data waiting for ACK */
+typedef struct
+{
+  /* sequence number */
+  u32 seq;
+  /* retry count */
+  u32 retry_count;
+  /* next retry time */
+  f64 retry_timer;
+  /* 1 if HA resync */
+  u8 is_resync;
+  /* packet data */
+  u8 *data;
+} nat_ha_resend_entry_t;
+
+/* per thread data */
+typedef struct
+{
+  /* buffer under construction */
+  vlib_buffer_t *state_sync_buffer;
+  /* frame containing NAT HA buffers */
+  vlib_frame_t *state_sync_frame;
+  /* number of events */
+  u16 state_sync_count;
+  /* next event offset */
+  u32 state_sync_next_event_offset;
+  /* data waiting for ACK */
+  nat_ha_resend_entry_t *resend_queue;
+} nat_ha_per_thread_data_t;
+
+/* NAT HA settings */
+typedef struct nat_ha_main_s
+{
+  /* local IP address and UDP port */
+  ip4_address_t src_ip_address;
+  u16 src_port;
+  /* failvoer IP address and UDP port */
+  ip4_address_t dst_ip_address;
+  u16 dst_port;
+  /* path MTU between local and failover */
+  u32 state_sync_path_mtu;
+  /* number of seconds after which to send session counters refresh */
+  u32 session_refresh_interval;
+  /* counters */
+  vlib_simple_counter_main_t counters[NAT_HA_N_COUNTERS];
+  vlib_main_t *vlib_main;
+  /* sequence number counter */
+  u32 sequence_number;
+  /* 1 if resync in progress */
+  u8 in_resync;
+  /* number of remaing ACK for resync */
+  u32 resync_ack_count;
+  /* number of missed ACK for resync */
+  u32 resync_ack_missed;
+  /* resync data */
+  nat_ha_resync_event_cb_t event_callback;
+  u32 client_index;
+  u32 pid;
+  /* call back functions for received HA events on failover */
+  nat_ha_sadd_cb_t sadd_cb;
+  nat_ha_sdel_cb_t sdel_cb;
+  nat_ha_sref_cb_t sref_cb;
+  /* per thread data */
+  u32 num_workers;
+  nat_ha_per_thread_data_t *per_thread_data;
+  /* worker handoff frame-queue index */
+  u32 fq_index;
+} nat_ha_main_t;
+
+nat_ha_main_t nat_ha_main;
+vlib_node_registration_t nat_ha_process_node;
+vlib_node_registration_t nat_ha_worker_node;
+vlib_node_registration_t nat_ha_node;
+vlib_node_registration_t nat_ha_handoff_node;
+
+static void
+nat_ha_resync_fin (void)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+
+  /* if no more resync ACK remainig we are done */
+  if (ha->resync_ack_count)
+    return;
+
+  ha->in_resync = 0;
+  nat_log_info ("resync completed with result %s",
+		ha->resync_ack_missed ? "FAILED" : "SUCESS");
+  if (ha->event_callback)
+    ha->event_callback (ha->client_index, ha->pid, ha->resync_ack_missed);
+}
+
+/* cache HA NAT data waiting for ACK */
+static int
+nat_ha_resend_queue_add (u32 seq, u8 * data, u8 data_len, u8 is_resync,
+			 u32 thread_index)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  nat_ha_per_thread_data_t *td = &ha->per_thread_data[thread_index];
+  nat_ha_resend_entry_t *entry;
+  f64 now = vlib_time_now (ha->vlib_main);
+
+  vec_add2 (td->resend_queue, entry, 1);
+  clib_memset (entry, 0, sizeof (*entry));
+  entry->retry_timer = now + 2.0;
+  entry->seq = seq;
+  entry->is_resync = is_resync;
+  vec_add (entry->data, data, data_len);
+
+  return 0;
+}
+
+static_always_inline void
+nat_ha_ack_recv (u32 seq, u32 thread_index)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  nat_ha_per_thread_data_t *td = &ha->per_thread_data[thread_index];
+  u32 i;
+
+  vec_foreach_index (i, td->resend_queue)
+  {
+    if (td->resend_queue[i].seq != seq)
+      continue;
+
+    vlib_increment_simple_counter (&ha->counters[NAT_HA_COUNTER_RECV_ACK],
+				   thread_index, 0, 1);
+    /* ACK received remove cached data */
+    if (td->resend_queue[i].is_resync)
+      {
+	clib_atomic_fetch_sub (&ha->resync_ack_count, 1);
+	nat_ha_resync_fin ();
+      }
+    vec_free (td->resend_queue[i].data);
+    vec_del1 (td->resend_queue, i);
+    nat_log_debug ("ACK for seq %d received", clib_net_to_host_u32 (seq));
+
+    return;
+  }
+}
+
+/* scan non-ACKed HA NAT for retry */
+static void
+nat_ha_resend_scan (f64 now, u32 thread_index)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  nat_ha_per_thread_data_t *td = &ha->per_thread_data[thread_index];
+  u32 i, *del, *to_delete = 0;
+  vlib_main_t *vm = ha->vlib_main;
+  vlib_buffer_t *b = 0;
+  vlib_frame_t *f;
+  u32 bi, *to_next;
+  ip4_header_t *ip;
+
+  vec_foreach_index (i, td->resend_queue)
+  {
+    if (td->resend_queue[i].retry_timer > now)
+      continue;
+
+    /* maximum retry reached delete cached data */
+    if (td->resend_queue[i].retry_count >= NAT_HA_RETRIES)
+      {
+	nat_log_notice ("seq %d missed",
+			clib_net_to_host_u32 (td->resend_queue[i].seq));
+	if (td->resend_queue[i].is_resync)
+	  {
+	    clib_atomic_fetch_add (&ha->resync_ack_missed, 1);
+	    clib_atomic_fetch_sub (&ha->resync_ack_count, 1);
+	    nat_ha_resync_fin ();
+	  }
+	vec_add1 (to_delete, i);
+	vlib_increment_simple_counter (&ha->counters
+				       [NAT_HA_COUNTER_MISSED_COUNT],
+				       thread_index, 0, 1);
+	continue;
+      }
+
+    /* retry to send non-ACKed data */
+    nat_log_debug ("state sync seq %d resend",
+		   clib_net_to_host_u32 (td->resend_queue[i].seq));
+    td->resend_queue[i].retry_count++;
+    vlib_increment_simple_counter (&ha->counters[NAT_HA_COUNTER_RETRY_COUNT],
+				   thread_index, 0, 1);
+    if (vlib_buffer_alloc (vm, &bi, 1) != 1)
+      {
+	nat_log_warn ("HA NAT state sync can't allocate buffer");
+	return;
+      }
+    b = vlib_get_buffer (vm, bi);
+    b->current_length = vec_len (td->resend_queue[i].data);
+    b->flags |= VLIB_BUFFER_TOTAL_LENGTH_VALID;
+    b->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
+    vnet_buffer (b)->sw_if_index[VLIB_RX] = 0;
+    vnet_buffer (b)->sw_if_index[VLIB_TX] = 0;
+    ip = vlib_buffer_get_current (b);
+    clib_memcpy (ip, td->resend_queue[i].data,
+		 vec_len (td->resend_queue[i].data));
+    f = vlib_get_frame_to_node (vm, ip4_lookup_node.index);
+    to_next = vlib_frame_vector_args (f);
+    to_next[0] = bi;
+    f->n_vectors = 1;
+    vlib_put_frame_to_node (vm, ip4_lookup_node.index, f);
+    td->resend_queue[i].retry_timer = now + 2.0;
+  }
+
+  vec_foreach (del, to_delete)
+  {
+    vec_free (td->resend_queue[*del].data);
+    vec_del1 (td->resend_queue, *del);
+  }
+  vec_free (to_delete);
+}
+
+void
+nat_ha_init (vlib_main_t * vm, nat_ha_sadd_cb_t sadd_cb,
+	     nat_ha_sdel_cb_t sdel_cb, nat_ha_sref_cb_t sref_cb)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  vlib_thread_main_t *tm = vlib_get_thread_main ();
+  vlib_thread_registration_t *tr;
+  uword *p;
+
+  ha->src_ip_address.as_u32 = 0;
+  ha->src_port = 0;
+  ha->dst_ip_address.as_u32 = 0;
+  ha->dst_port = 0;
+  ha->in_resync = 0;
+  ha->resync_ack_count = 0;
+  ha->resync_ack_missed = 0;
+  ha->vlib_main = vm;
+  ha->sadd_cb = sadd_cb;
+  ha->sdel_cb = sdel_cb;
+  ha->sref_cb = sref_cb;
+  ha->num_workers = 0;
+  vec_validate (ha->per_thread_data, tm->n_vlib_mains - 1);
+  ha->fq_index = ~0;
+  p = hash_get_mem (tm->thread_registrations_by_name, "workers");
+  if (p)
+    {
+      tr = (vlib_thread_registration_t *) p[0];
+      if (tr)
+	ha->num_workers = tr->count;
+    }
+
+#define _(N, s, v) ha->counters[v].name = s;          \
+  ha->counters[v].stat_segment_name = "/nat44/ha/" s; \
+  vlib_validate_simple_counter(&ha->counters[v], 0);  \
+  vlib_zero_simple_counter(&ha->counters[v], 0);
+  foreach_nat_ha_counter
+#undef _
+}
+
+int
+nat_ha_set_listener (ip4_address_t * addr, u16 port, u32 path_mtu)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+
+  /* unregister previously set UDP port */
+  if (ha->src_port)
+    udp_unregister_dst_port (ha->vlib_main, ha->src_port, 1);
+
+  ha->src_ip_address.as_u32 = addr->as_u32;
+  ha->src_port = port;
+  ha->state_sync_path_mtu = path_mtu;
+
+  if (port)
+    {
+      /* if multiple worker threads first go to handoff node */
+      if (ha->num_workers > 1)
+	{
+	  if (ha->fq_index == ~0)
+	    ha->fq_index = vlib_frame_queue_main_init (nat_ha_node.index, 0);
+	  udp_register_dst_port (ha->vlib_main, port,
+				 nat_ha_handoff_node.index, 1);
+	}
+      else
+	{
+	  udp_register_dst_port (ha->vlib_main, port, nat_ha_node.index, 1);
+	}
+      nat_log_info ("HA listening on port %d for state sync", port);
+    }
+
+  return 0;
+}
+
+void
+nat_ha_get_listener (ip4_address_t * addr, u16 * port, u32 * path_mtu)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+
+  addr->as_u32 = ha->src_ip_address.as_u32;
+  *port = ha->src_port;
+  *path_mtu = ha->state_sync_path_mtu;
+}
+
+int
+nat_ha_set_failover (ip4_address_t * addr, u16 port,
+		     u32 session_refresh_interval)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+
+  ha->dst_ip_address.as_u32 = addr->as_u32;
+  ha->dst_port = port;
+  ha->session_refresh_interval = session_refresh_interval;
+
+  vlib_process_signal_event (ha->vlib_main, nat_ha_process_node.index, 1, 0);
+
+  return 0;
+}
+
+void
+nat_ha_get_failover (ip4_address_t * addr, u16 * port,
+		     u32 * session_refresh_interval)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+
+  addr->as_u32 = ha->dst_ip_address.as_u32;
+  *port = ha->dst_port;
+  *session_refresh_interval = ha->session_refresh_interval;
+}
+
+static_always_inline void
+nat_ha_recv_add (nat_ha_event_t * event, f64 now, u32 thread_index)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  ip4_address_t in_addr, out_addr, eh_addr, ehn_addr;
+  u32 fib_index;
+  u16 flags;
+
+  vlib_increment_simple_counter (&ha->counters[NAT_HA_COUNTER_RECV_ADD],
+				 thread_index, 0, 1);
+
+  in_addr.as_u32 = event->in_addr;
+  out_addr.as_u32 = event->out_addr;
+  eh_addr.as_u32 = event->eh_addr;
+  ehn_addr.as_u32 = event->ehn_addr;
+  fib_index = clib_net_to_host_u32 (event->fib_index);
+  flags = clib_net_to_host_u16 (event->flags);
+
+  ha->sadd_cb (&in_addr, event->in_port, &out_addr, event->out_port, &eh_addr,
+	       event->eh_port, &ehn_addr, event->ehn_port, event->protocol,
+	       fib_index, flags, thread_index);
+}
+
+static_always_inline void
+nat_ha_recv_del (nat_ha_event_t * event, u32 thread_index)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  ip4_address_t out_addr, eh_addr;
+  u32 fib_index;
+
+  vlib_increment_simple_counter (&ha->counters[NAT_HA_COUNTER_RECV_DEL],
+				 thread_index, 0, 1);
+
+  out_addr.as_u32 = event->out_addr;
+  eh_addr.as_u32 = event->eh_addr;
+  fib_index = clib_net_to_host_u32 (event->fib_index);
+
+  ha->sdel_cb (&out_addr, event->out_port, &eh_addr, event->eh_port,
+	       event->protocol, fib_index, thread_index);
+}
+
+static_always_inline void
+nat_ha_recv_refresh (nat_ha_event_t * event, f64 now, u32 thread_index)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  ip4_address_t out_addr, eh_addr;
+  u32 fib_index, total_pkts;
+  u64 total_bytes;
+
+  vlib_increment_simple_counter (&ha->counters[NAT_HA_COUNTER_RECV_REFRESH],
+				 thread_index, 0, 1);
+
+  out_addr.as_u32 = event->out_addr;
+  eh_addr.as_u32 = event->eh_addr;
+  fib_index = clib_net_to_host_u32 (event->fib_index);
+  total_pkts = clib_net_to_host_u32 (event->total_pkts);
+  total_bytes = clib_net_to_host_u64 (event->total_bytes);
+
+  ha->sref_cb (&out_addr, event->out_port, &eh_addr, event->eh_port,
+	       event->protocol, fib_index, total_pkts, total_bytes,
+	       thread_index);
+}
+
+/* process received NAT HA event */
+static_always_inline void
+nat_ha_event_process (nat_ha_event_t * event, f64 now, u32 thread_index)
+{
+  switch (event->event_type)
+    {
+    case NAT_HA_ADD:
+      nat_ha_recv_add (event, now, thread_index);
+      break;
+    case NAT_HA_DEL:
+      nat_ha_recv_del (event, thread_index);
+      break;
+    case NAT_HA_REFRESH:
+      nat_ha_recv_refresh (event, now, thread_index);
+      break;
+    default:
+      nat_log_notice ("Unsupported HA event type %d", event->event_type);
+      break;
+    }
+}
+
+static inline void
+nat_ha_header_create (vlib_buffer_t * b, u32 * offset, u32 thread_index)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  nat_ha_message_header_t *h;
+  ip4_header_t *ip;
+  udp_header_t *udp;
+  u32 sequence_number;
+
+  b->current_data = 0;
+  b->current_length = sizeof (*ip) + sizeof (*udp) + sizeof (*h);
+  b->flags |= VLIB_BUFFER_TOTAL_LENGTH_VALID;
+  b->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
+  vnet_buffer (b)->sw_if_index[VLIB_RX] = 0;
+  vnet_buffer (b)->sw_if_index[VLIB_TX] = 0;
+  ip = vlib_buffer_get_current (b);
+  udp = (udp_header_t *) (ip + 1);
+  h = (nat_ha_message_header_t *) (udp + 1);
+
+  /* IP header */
+  ip->ip_version_and_header_length = 0x45;
+  ip->ttl = 254;
+  ip->protocol = IP_PROTOCOL_UDP;
+  ip->flags_and_fragment_offset =
+    clib_host_to_net_u16 (IP4_HEADER_FLAG_DONT_FRAGMENT);
+  ip->src_address.as_u32 = ha->src_ip_address.as_u32;
+  ip->dst_address.as_u32 = ha->dst_ip_address.as_u32;
+  /* UDP header */
+  udp->src_port = clib_host_to_net_u16 (ha->src_port);
+  udp->dst_port = clib_host_to_net_u16 (ha->dst_port);
+  udp->checksum = 0;
+
+  /* NAT HA protocol header */
+  h->version = NAT_HA_VERSION;
+  h->flags = 0;
+  h->count = 0;
+  h->thread_index = clib_host_to_net_u32 (thread_index);
+  sequence_number = clib_atomic_fetch_add (&ha->sequence_number, 1);
+  h->sequence_number = clib_host_to_net_u32 (sequence_number);
+
+  *offset =
+    sizeof (ip4_header_t) + sizeof (udp_header_t) +
+    sizeof (nat_ha_message_header_t);
+}
+
+static inline void
+nat_ha_send (vlib_frame_t * f, vlib_buffer_t * b, u8 is_resync,
+	     u32 thread_index)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  nat_ha_per_thread_data_t *td = &ha->per_thread_data[thread_index];
+  nat_ha_message_header_t *h;
+  ip4_header_t *ip;
+  udp_header_t *udp;
+  vlib_main_t *vm = vlib_mains[thread_index];
+
+  ip = vlib_buffer_get_current (b);
+  udp = ip4_next_header (ip);
+  h = (nat_ha_message_header_t *) (udp + 1);
+
+  h->count = clib_host_to_net_u16 (td->state_sync_count);
+
+  ip->length = clib_host_to_net_u16 (b->current_length);
+  ip->checksum = ip4_header_checksum (ip);
+  udp->length = clib_host_to_net_u16 (b->current_length - sizeof (*ip));
+
+  nat_ha_resend_queue_add (h->sequence_number, (u8 *) ip, b->current_length,
+			   is_resync, thread_index);
+
+  vlib_put_frame_to_node (vm, ip4_lookup_node.index, f);
+}
+
+/* add NAT HA protocol event */
+static_always_inline void
+nat_ha_event_add (nat_ha_event_t * event, u8 do_flush, u32 thread_index,
+		  u8 is_resync)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  nat_ha_per_thread_data_t *td = &ha->per_thread_data[thread_index];
+  vlib_main_t *vm = vlib_mains[thread_index];
+  vlib_buffer_t *b = 0;
+  vlib_frame_t *f;
+  u32 bi = ~0, offset;
+
+  b = td->state_sync_buffer;
+
+  if (PREDICT_FALSE (b == 0))
+    {
+      if (do_flush)
+	return;
+
+      if (vlib_buffer_alloc (vm, &bi, 1) != 1)
+	{
+	  nat_log_warn ("HA NAT state sync can't allocate buffer");
+	  return;
+	}
+
+      b = td->state_sync_buffer = vlib_get_buffer (vm, bi);
+      clib_memset (vnet_buffer (b), 0, sizeof (*vnet_buffer (b)));
+      VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b);
+      offset = 0;
+    }
+  else
+    {
+      bi = vlib_get_buffer_index (vm, b);
+      offset = td->state_sync_next_event_offset;
+    }
+
+  f = td->state_sync_frame;
+  if (PREDICT_FALSE (f == 0))
+    {
+      u32 *to_next;
+      f = vlib_get_frame_to_node (vm, ip4_lookup_node.index);
+      td->state_sync_frame = f;
+      to_next = vlib_frame_vector_args (f);
+      to_next[0] = bi;
+      f->n_vectors = 1;
+    }
+
+  if (PREDICT_FALSE (td->state_sync_count == 0))
+    nat_ha_header_create (b, &offset, thread_index);
+
+  if (PREDICT_TRUE (do_flush == 0))
+    {
+      clib_memcpy_fast (b->data + offset, event, sizeof (*event));
+      offset += sizeof (*event);
+      td->state_sync_count++;
+      b->current_length += sizeof (*event);
+
+      switch (event->event_type)
+	{
+	case NAT_HA_ADD:
+	  vlib_increment_simple_counter (&ha->counters
+					 [NAT_HA_COUNTER_SEND_ADD],
+					 thread_index, 0, 1);
+	  break;
+	case NAT_HA_DEL:
+	  vlib_increment_simple_counter (&ha->counters
+					 [NAT_HA_COUNTER_SEND_DEL],
+					 thread_index, 0, 1);
+	  break;
+	case NAT_HA_REFRESH:
+	  vlib_increment_simple_counter (&ha->counters
+					 [NAT_HA_COUNTER_SEND_REFRESH],
+					 thread_index, 0, 1);
+	  break;
+	default:
+	  break;
+	}
+    }
+
+  if (PREDICT_FALSE
+      (do_flush || offset + (sizeof (*event)) > ha->state_sync_path_mtu))
+    {
+      nat_ha_send (f, b, is_resync, thread_index);
+      td->state_sync_buffer = 0;
+      td->state_sync_frame = 0;
+      td->state_sync_count = 0;
+      offset = 0;
+      if (is_resync)
+	{
+	  clib_atomic_fetch_add (&ha->resync_ack_count, 1);
+	  nat_ha_resync_fin ();
+	}
+    }
+
+  td->state_sync_next_event_offset = offset;
+}
+
+#define skip_if_disabled()          \
+do {                                \
+  nat_ha_main_t *ha = &nat_ha_main; \
+  if (PREDICT_TRUE (!ha->dst_port)) \
+    return;                         \
+} while (0)
+
+void
+nat_ha_flush (u8 is_resync)
+{
+  skip_if_disabled ();
+  nat_ha_event_add (0, 1, 0, is_resync);
+}
+
+void
+nat_ha_sadd (ip4_address_t * in_addr, u16 in_port, ip4_address_t * out_addr,
+	     u16 out_port, ip4_address_t * eh_addr, u16 eh_port,
+	     ip4_address_t * ehn_addr, u16 ehn_port, u8 proto, u32 fib_index,
+	     u16 flags, u32 thread_index, u8 is_resync)
+{
+  nat_ha_event_t event;
+
+  skip_if_disabled ();
+
+  clib_memset (&event, 0, sizeof (event));
+  event.event_type = NAT_HA_ADD;
+  event.flags = clib_host_to_net_u16 (flags);
+  event.in_addr = in_addr->as_u32;
+  event.in_port = in_port;
+  event.out_addr = out_addr->as_u32;
+  event.out_port = out_port;
+  event.eh_addr = eh_addr->as_u32;
+  event.eh_port = eh_port;
+  event.ehn_addr = ehn_addr->as_u32;
+  event.ehn_port = ehn_port;
+  event.fib_index = clib_host_to_net_u32 (fib_index);
+  event.protocol = proto;
+  nat_ha_event_add (&event, 0, thread_index, is_resync);
+}
+
+void
+nat_ha_sdel (ip4_address_t * out_addr, u16 out_port, ip4_address_t * eh_addr,
+	     u16 eh_port, u8 proto, u32 fib_index, u32 thread_index)
+{
+  nat_ha_event_t event;
+
+  skip_if_disabled ();
+
+  clib_memset (&event, 0, sizeof (event));
+  event.event_type = NAT_HA_DEL;
+  event.out_addr = out_addr->as_u32;
+  event.out_port = out_port;
+  event.eh_addr = eh_addr->as_u32;
+  event.eh_port = eh_port;
+  event.fib_index = clib_host_to_net_u32 (fib_index);
+  event.protocol = proto;
+  nat_ha_event_add (&event, 0, thread_index, 0);
+}
+
+void
+nat_ha_sref (ip4_address_t * out_addr, u16 out_port, ip4_address_t * eh_addr,
+	     u16 eh_port, u8 proto, u32 fib_index, u32 total_pkts,
+	     u64 total_bytes, u32 thread_index, f64 * last_refreshed, f64 now)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  nat_ha_event_t event;
+
+  skip_if_disabled ();
+
+  if ((*last_refreshed + ha->session_refresh_interval) > now)
+    return;
+
+  *last_refreshed = now;
+  clib_memset (&event, 0, sizeof (event));
+  event.event_type = NAT_HA_REFRESH;
+  event.out_addr = out_addr->as_u32;
+  event.out_port = out_port;
+  event.eh_addr = eh_addr->as_u32;
+  event.eh_port = eh_port;
+  event.fib_index = clib_host_to_net_u32 (fib_index);
+  event.protocol = proto;
+  event.total_pkts = clib_host_to_net_u32 (total_pkts);
+  event.total_bytes = clib_host_to_net_u64 (total_bytes);
+  nat_ha_event_add (&event, 0, thread_index, 0);
+}
+
+/* per thread process waiting for interrupt */
+static uword
+nat_ha_worker_fn (vlib_main_t * vm, vlib_node_runtime_t * rt,
+		  vlib_frame_t * f)
+{
+  u32 thread_index = vm->thread_index;
+  /* flush HA NAT data under construction */
+  nat_ha_event_add (0, 1, thread_index, 0);
+  /* scan if we need to resend some non-ACKed data */
+  nat_ha_resend_scan (vlib_time_now (vm), thread_index);
+  return 0;
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (nat_ha_worker_node) = {
+    .function = nat_ha_worker_fn,
+    .type = VLIB_NODE_TYPE_INPUT,
+    .state = VLIB_NODE_STATE_INTERRUPT,
+    .name = "nat-ha-worker",
+};
+/* *INDENT-ON* */
+
+/* periodically send interrupt to each thread */
+static uword
+nat_ha_process (vlib_main_t * vm, vlib_node_runtime_t * rt, vlib_frame_t * f)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  uword event_type;
+  uword *event_data = 0;
+  u32 ti;
+
+  vlib_process_wait_for_event (vm);
+  event_type = vlib_process_get_events (vm, &event_data);
+  if (event_type)
+    nat_log_info ("nat-ha-process: bogus kickoff event received");
+  vec_reset_length (event_data);
+
+  while (1)
+    {
+      vlib_process_wait_for_event_or_clock (vm, 1.0);
+      event_type = vlib_process_get_events (vm, &event_data);
+      vec_reset_length (event_data);
+      for (ti = 0; ti < vec_len (vlib_mains); ti++)
+	{
+	  if (ti >= vec_len (ha->per_thread_data))
+	    continue;
+
+	  vlib_node_set_interrupt_pending (vlib_mains[ti],
+					   nat_ha_worker_node.index);
+	}
+    }
+
+  return 0;
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (nat_ha_process_node) = {
+    .function = nat_ha_process,
+    .type = VLIB_NODE_TYPE_PROCESS,
+    .name = "nat-ha-process",
+};
+/* *INDENT-ON* */
+
+void
+nat_ha_get_resync_status (u8 * in_resync, u32 * resync_ack_missed)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+
+  *in_resync = ha->in_resync;
+  *resync_ack_missed = ha->resync_ack_missed;
+}
+
+int
+nat44_ha_resync (u32 client_index, u32 pid,
+		 nat_ha_resync_event_cb_t event_callback)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  snat_main_t *sm = &snat_main;
+  snat_session_t *ses;
+  snat_main_per_thread_data_t *tsm;
+
+  if (ha->in_resync)
+    return VNET_API_ERROR_IN_PROGRESS;
+
+  ha->in_resync = 1;
+  ha->resync_ack_count = 0;
+  ha->resync_ack_missed = 0;
+  ha->event_callback = event_callback;
+  ha->client_index = client_index;
+  ha->pid = pid;
+
+  /* *INDENT-OFF* */
+  vec_foreach (tsm, sm->per_thread_data)
+    {
+      pool_foreach (ses, tsm->sessions, ({
+        nat_ha_sadd (&ses->in2out.addr, ses->in2out.port,
+                     &ses->out2in.addr, ses->out2in.port,
+                     &ses->ext_host_addr, ses->ext_host_port,
+                     &ses->ext_host_nat_addr, ses->ext_host_nat_port,
+                     ses->in2out.protocol, ses->in2out.fib_index,
+                     ses->flags, 0, 1);
+      }));
+    }
+  /* *INDENT-ON* */
+
+  nat_ha_flush (1);
+
+  return 0;
+}
+
+typedef struct
+{
+  ip4_address_t addr;
+  u32 event_count;
+} nat_ha_trace_t;
+
+static u8 *
+format_nat_ha_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 *);
+  nat_ha_trace_t *t = va_arg (*args, nat_ha_trace_t *);
+
+  s =
+    format (s, "nat-ha: %u events from %U", t->event_count,
+	    format_ip4_address, &t->addr);
+
+  return s;
+}
+
+typedef enum
+{
+  NAT_HA_NEXT_IP4_LOOKUP,
+  NAT_HA_NEXT_DROP,
+  NAT_HA_N_NEXT,
+} nat_ha_next_t;
+
+#define foreach_nat_ha_error   \
+_(PROCESSED, "pkts-processed") \
+_(BAD_VERSION, "bad-version")
+
+typedef enum
+{
+#define _(sym, str) NAT_HA_ERROR_##sym,
+  foreach_nat_ha_error
+#undef _
+    NAT_HA_N_ERROR,
+} nat_ha_error_t;
+
+static char *nat_ha_error_strings[] = {
+#define _(sym, str) str,
+  foreach_nat_ha_error
+#undef _
+};
+
+/* process received HA NAT protocol messages */
+static uword
+nat_ha_node_fn (vlib_main_t * vm, vlib_node_runtime_t * node,
+		vlib_frame_t * frame)
+{
+  u32 n_left_from, *from, next_index, *to_next;
+  f64 now = vlib_time_now (vm);
+  u32 thread_index = vm->thread_index;
+  u32 pkts_processed = 0;
+  ip4_main_t *i4m = &ip4_main;
+  u8 host_config_ttl = i4m->host_config.ttl;
+  nat_ha_main_t *ha = &nat_ha_main;
+
+  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, next0, src_addr0, dst_addr0;;
+	  vlib_buffer_t *b0;
+	  nat_ha_message_header_t *h0;
+	  nat_ha_event_t *e0;
+	  u16 event_count0, src_port0, dst_port0, old_len0;
+	  ip4_header_t *ip0;
+	  udp_header_t *udp0;
+	  ip_csum_t sum0;
+
+	  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);
+	  h0 = vlib_buffer_get_current (b0);
+	  vlib_buffer_advance (b0, -sizeof (*udp0));
+	  udp0 = vlib_buffer_get_current (b0);
+	  vlib_buffer_advance (b0, -sizeof (*ip0));
+	  ip0 = vlib_buffer_get_current (b0);
+
+	  next0 = NAT_HA_NEXT_DROP;
+
+	  if (h0->version != NAT_HA_VERSION)
+	    {
+	      b0->error = node->errors[NAT_HA_ERROR_BAD_VERSION];
+	      goto done0;
+	    }
+
+	  event_count0 = clib_net_to_host_u16 (h0->count);
+	  /* ACK for previously send data */
+	  if (!event_count0 && (h0->flags & NAT_HA_FLAG_ACK))
+	    {
+	      nat_ha_ack_recv (h0->sequence_number, thread_index);
+	      b0->error = node->errors[NAT_HA_ERROR_PROCESSED];
+	      goto done0;
+	    }
+
+	  e0 = (nat_ha_event_t *) (h0 + 1);
+
+	  /* process each event */
+	  while (event_count0)
+	    {
+	      nat_ha_event_process (e0, now, thread_index);
+	      event_count0--;
+	      e0 = (nat_ha_event_t *) ((u8 *) e0 + sizeof (nat_ha_event_t));
+	    }
+
+	  next0 = NAT_HA_NEXT_IP4_LOOKUP;
+	  pkts_processed++;
+
+	  /* reply with ACK */
+	  b0->current_length = sizeof (*ip0) + sizeof (*udp0) + sizeof (*h0);
+
+	  src_addr0 = ip0->src_address.data_u32;
+	  dst_addr0 = ip0->dst_address.data_u32;
+	  ip0->src_address.data_u32 = dst_addr0;
+	  ip0->dst_address.data_u32 = src_addr0;
+	  old_len0 = ip0->length;
+	  ip0->length = clib_host_to_net_u16 (b0->current_length);
+
+	  sum0 = ip0->checksum;
+	  sum0 = ip_csum_update (sum0, ip0->ttl, host_config_ttl,
+				 ip4_header_t, ttl);
+	  ip0->ttl = host_config_ttl;
+	  sum0 =
+	    ip_csum_update (sum0, old_len0, ip0->length, ip4_header_t,
+			    length);
+	  ip0->checksum = ip_csum_fold (sum0);
+
+	  udp0->checksum = 0;
+	  src_port0 = udp0->src_port;
+	  dst_port0 = udp0->dst_port;
+	  udp0->src_port = dst_port0;
+	  udp0->dst_port = src_port0;
+	  udp0->length =
+	    clib_host_to_net_u16 (b0->current_length - sizeof (*ip0));
+
+	  h0->flags = NAT_HA_FLAG_ACK;
+	  h0->count = 0;
+	  vlib_increment_simple_counter (&ha->counters
+					 [NAT_HA_COUNTER_SEND_ACK],
+					 thread_index, 0, 1);
+
+	done0:
+	  if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
+			     && (b0->flags & VLIB_BUFFER_IS_TRACED)))
+	    {
+	      nat_ha_trace_t *t = vlib_add_trace (vm, node, b0, sizeof (*t));
+	      ip4_header_t *ip =
+		(void *) (b0->data + vnet_buffer (b0)->l3_hdr_offset);
+	      t->event_count = clib_net_to_host_u16 (h0->count);
+	      t->addr.as_u32 = ip->src_address.data_u32;
+	    }
+
+	  vlib_validate_buffer_enqueue_x1 (vm, node, next_index,
+					   to_next, n_left_to_next,
+					   bi0, next0);
+	}
+
+      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
+    }
+
+  vlib_node_increment_counter (vm, nat_ha_node.index,
+			       NAT_HA_ERROR_PROCESSED, pkts_processed);
+
+  return frame->n_vectors;
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (nat_ha_node) = {
+  .function = nat_ha_node_fn,
+  .name = "nat-ha",
+  .vector_size = sizeof (u32),
+  .format_trace = format_nat_ha_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+  .n_errors = ARRAY_LEN (nat_ha_error_strings),
+  .error_strings = nat_ha_error_strings,
+  .n_next_nodes = NAT_HA_N_NEXT,
+  .next_nodes = {
+     [NAT_HA_NEXT_IP4_LOOKUP] = "ip4-lookup",
+     [NAT_HA_NEXT_DROP] = "error-drop",
+  },
+};
+/* *INDENT-ON* */
+
+typedef struct
+{
+  u32 next_worker_index;
+  u8 in2out;
+} nat_ha_handoff_trace_t;
+
+#define foreach_nat_ha_handoff_error  \
+_(CONGESTION_DROP, "congestion drop") \
+_(SAME_WORKER, "same worker")         \
+_(DO_HANDOFF, "do handoff")
+
+typedef enum
+{
+#define _(sym,str) NAT_HA_HANDOFF_ERROR_##sym,
+  foreach_nat_ha_handoff_error
+#undef _
+    NAT44_HANDOFF_N_ERROR,
+} nat_ha_handoff_error_t;
+
+static char *nat_ha_handoff_error_strings[] = {
+#define _(sym,string) string,
+  foreach_nat_ha_handoff_error
+#undef _
+};
+
+static u8 *
+format_nat_ha_handoff_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 *);
+  nat_ha_handoff_trace_t *t = va_arg (*args, nat_ha_handoff_trace_t *);
+
+  s =
+    format (s, "NAT_HA_WORKER_HANDOFF: next-worker %d", t->next_worker_index);
+
+  return s;
+}
+
+/* do worker handoff based on thread_index in NAT HA protcol header */
+static uword
+nat_ha_handoff_node_fn (vlib_main_t * vm, vlib_node_runtime_t * node,
+			vlib_frame_t * frame)
+{
+  nat_ha_main_t *ha = &nat_ha_main;
+  vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b;
+  u32 n_enq, n_left_from, *from;
+  u16 thread_indices[VLIB_FRAME_SIZE], *ti;
+  u32 thread_index = vm->thread_index;
+  u32 do_handoff = 0, same_worker = 0;
+
+  from = vlib_frame_vector_args (frame);
+  n_left_from = frame->n_vectors;
+  vlib_get_buffers (vm, from, bufs, n_left_from);
+
+  b = bufs;
+  ti = thread_indices;
+
+  while (n_left_from > 0)
+    {
+      nat_ha_message_header_t *h0;
+
+      h0 = vlib_buffer_get_current (b[0]);
+      ti[0] = clib_net_to_host_u32 (h0->thread_index);
+
+      if (ti[0] != thread_index)
+	do_handoff++;
+      else
+	same_worker++;
+
+      if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
+			 && (b[0]->flags & VLIB_BUFFER_IS_TRACED)))
+	{
+	  nat_ha_handoff_trace_t *t =
+	    vlib_add_trace (vm, node, b[0], sizeof (*t));
+	  t->next_worker_index = ti[0];
+	}
+
+      n_left_from -= 1;
+      ti += 1;
+      b += 1;
+    }
+
+  n_enq =
+    vlib_buffer_enqueue_to_thread (vm, ha->fq_index, from, thread_indices,
+				   frame->n_vectors, 1);
+
+  if (n_enq < frame->n_vectors)
+    vlib_node_increment_counter (vm, node->node_index,
+				 NAT_HA_HANDOFF_ERROR_CONGESTION_DROP,
+				 frame->n_vectors - n_enq);
+  vlib_node_increment_counter (vm, node->node_index,
+			       NAT_HA_HANDOFF_ERROR_SAME_WORKER, same_worker);
+  vlib_node_increment_counter (vm, node->node_index,
+			       NAT_HA_HANDOFF_ERROR_DO_HANDOFF, do_handoff);
+  return frame->n_vectors;
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (nat_ha_handoff_node) = {
+  .function = nat_ha_handoff_node_fn,
+  .name = "nat-ha-handoff",
+  .vector_size = sizeof (u32),
+  .format_trace = format_nat_ha_handoff_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+  .n_errors = ARRAY_LEN(nat_ha_handoff_error_strings),
+  .error_strings = nat_ha_handoff_error_strings,
+  .n_next_nodes = 1,
+  .next_nodes = {
+    [0] = "error-drop",
+  },
+};
+/* *INDENT-ON* */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */