http: unify client/server state machines

Type: improvement

Change-Id: I57a816fbed8b681dec201edc8d5950a34a555a2b
Signed-off-by: Filip Tehlar <ftehlar@cisco.com>

2 files changed, 350 insertions, 327 deletions

diff --git a/src/plugins/http/http.c b/src/plugins/http/http.c
index d404e734d48..4797308666e 100644
--- a/src/plugins/http/http.c
+++ b/src/plugins/http/http.c
@@ -47,6 +47,42 @@ const http_buffer_type_t msg_to_buf_type[] = {
   [HTTP_MSG_DATA_PTR] = HTTP_BUFFER_PTR,
 };
 
+u8 *
+format_http_state (u8 *s, va_list *va)
+{
+  http_state_t state = va_arg (*va, http_state_t);
+
+  switch (state)
+    {
+    case HTTP_STATE_IDLE:
+      return format (s, "idle");
+    case HTTP_STATE_WAIT_APP_METHOD:
+      return format (s, "wait app method");
+    case HTTP_STATE_WAIT_SERVER_REPLY:
+      return format (s, "wait server reply");
+    case HTTP_STATE_CLIENT_IO_MORE_DATA:
+      return format (s, "client io more data");
+    case HTTP_STATE_WAIT_CLIENT_METHOD:
+      return format (s, "wait client method");
+    case HTTP_STATE_WAIT_APP_REPLY:
+      return format (s, "wait app reply");
+    case HTTP_STATE_APP_IO_MORE_DATA:
+      return format (s, "app io more data");
+    default:
+      break;
+    }
+  return format (s, "unknown");
+}
+
+static inline void
+http_state_change (http_conn_t *hc, http_state_t state)
+{
+  HTTP_DBG (1, "changing http state %U -> %U", format_http_state,
+	    hc->http_state, format_http_state, state);
+  ASSERT (hc->http_state != state);
+  hc->http_state = state;
+}
+
 static inline http_worker_t *
 http_worker_get (u32 thread_index)
 {
@@ -164,7 +200,7 @@ http_ts_accept_callback (session_t *ts)
   hc->c_flags |= TRANSPORT_CONNECTION_F_NO_LOOKUP;
 
   hc->state = HTTP_CONN_STATE_ESTABLISHED;
-  hc->http_state = HTTP_STATE_WAIT_METHOD;
+  http_state_change (hc, HTTP_STATE_WAIT_CLIENT_METHOD);
 
   ts->session_state = SESSION_STATE_READY;
   ts->opaque = hc_index;
@@ -249,7 +285,7 @@ http_ts_connected_callback (u32 http_app_index, u32 ho_hc_index, session_t *ts,
   hc->c_c_index = new_hc_index;
   hc->c_flags |= TRANSPORT_CONNECTION_F_NO_LOOKUP;
   hc->state = HTTP_CONN_STATE_ESTABLISHED;
-  hc->http_state = HTTP_STATE_WAIT_APP;
+  http_state_change (hc, HTTP_STATE_WAIT_APP_METHOD);
 
   ts->session_state = SESSION_STATE_READY;
   ts->opaque = new_hc_index;
@@ -265,6 +301,9 @@ http_ts_connected_callback (u32 http_app_index, u32 ho_hc_index, session_t *ts,
   as->session_type = session_type_from_proto_and_ip (
     TRANSPORT_PROTO_HTTP, session_type_is_ip4 (ts->session_type));
 
+  HTTP_DBG (1, "half-open hc index %d,  hc index %d", ho_hc_index,
+	    new_hc_index);
+
   app_wrk = app_worker_get (hc->h_pa_wrk_index);
   if (!app_wrk)
     {
@@ -309,7 +348,7 @@ http_ts_reset_callback (session_t *ts)
 
   hc->state = HTTP_CONN_STATE_CLOSED;
   http_buffer_free (&hc->tx_buf);
-  hc->http_state = HTTP_STATE_WAIT_METHOD;
+  http_state_change (hc, HTTP_STATE_WAIT_CLIENT_METHOD);
   session_transport_reset_notify (&hc->connection);
 
   http_disconnect_transport (hc);
@@ -342,7 +381,7 @@ static const char *http_request_template = "GET %s HTTP/1.1\r\n"
 					   "Accept: */*\r\n";
 
 static u32
-send_data (http_conn_t *hc, u8 *data, u32 length, u32 offset)
+http_send_data (http_conn_t *hc, u8 *data, u32 length, u32 offset)
 {
   const u32 max_burst = 64 << 10;
   session_t *ts;
@@ -364,7 +403,7 @@ send_data (http_conn_t *hc, u8 *data, u32 length, u32 offset)
 }
 
 static void
-send_error (http_conn_t *hc, http_status_code_t ec)
+http_send_error (http_conn_t *hc, http_status_code_t ec)
 {
   http_main_t *hm = &http_main;
   u8 *data;
@@ -376,12 +415,12 @@ send_error (http_conn_t *hc, http_status_code_t ec)
   now = clib_timebase_now (&hm->timebase);
   data = format (0, http_error_template, http_status_code_str[ec],
 		 format_clib_timebase_time, now);
-  send_data (hc, data, vec_len (data), 0);
+  http_send_data (hc, data, vec_len (data), 0);
   vec_free (data);
 }
 
 static int
-read_http_message (http_conn_t *hc)
+http_read_message (http_conn_t *hc)
 {
   u32 max_deq, cursize;
   session_t *ts;
@@ -426,11 +465,148 @@ v_find_index (u8 *vec, u32 offset, char *str)
   return -1;
 }
 
-/**
- * waiting for request method from peer - parse request method and data
- */
+static int
+http_parse_header (http_conn_t *hc, int *content_length)
+{
+  unformat_input_t input;
+  int i, len;
+  u8 *line;
+
+  i = v_find_index (hc->rx_buf, hc->rx_buf_offset, CONTENT_LEN_STR);
+  if (i < 0)
+    {
+      clib_warning ("cannot find '%s' in the header!", CONTENT_LEN_STR);
+      return -1;
+    }
+
+  hc->rx_buf_offset = i;
+
+  i = v_find_index (hc->rx_buf, hc->rx_buf_offset, "\n");
+  if (i < 0)
+    {
+      clib_warning ("end of line missing; incomplete data");
+      return -1;
+    }
+
+  len = i - hc->rx_buf_offset;
+  line = vec_new (u8, len);
+  clib_memcpy (line, hc->rx_buf + hc->rx_buf_offset, len);
+
+  unformat_init_vector (&input, line);
+  if (!unformat (&input, CONTENT_LEN_STR "%d", content_length))
+    {
+      clib_warning ("failed to unformat content length!");
+      return -1;
+    }
+  unformat_free (&input);
+
+  /* skip rest of the header */
+  hc->rx_buf_offset += len;
+  i = v_find_index (hc->rx_buf, hc->rx_buf_offset, "<html>");
+  if (i < 0)
+    {
+      clib_warning ("<html> tag not found");
+      return -1;
+    }
+  hc->rx_buf_offset = i;
+
+  return 0;
+}
+
 static http_sm_result_t
-state_srv_wait_method (http_conn_t *hc, transport_send_params_t *sp)
+http_state_wait_server_reply (http_conn_t *hc, transport_send_params_t *sp)
+{
+  int i, rv, content_length;
+  http_msg_t msg = {};
+  app_worker_t *app_wrk;
+  session_t *as;
+  http_status_code_t ec;
+
+  rv = http_read_message (hc);
+
+  /* Nothing yet, wait for data or timer expire */
+  if (rv)
+    return HTTP_SM_STOP;
+
+  if (vec_len (hc->rx_buf) < 8)
+    {
+      ec = HTTP_STATUS_BAD_REQUEST;
+      goto error;
+    }
+
+  if ((i = v_find_index (hc->rx_buf, 0, "200 OK")) >= 0)
+    {
+      msg.type = HTTP_MSG_REPLY;
+      msg.content_type = HTTP_CONTENT_TEXT_HTML;
+      msg.code = HTTP_STATUS_OK;
+      msg.data.type = HTTP_MSG_DATA_INLINE;
+      msg.data.len = 0;
+
+      rv = http_parse_header (hc, &content_length);
+      if (rv)
+	{
+	  clib_warning ("failed to parse http reply");
+	  session_transport_closing_notify (&hc->connection);
+	  http_disconnect_transport (hc);
+	  return -1;
+	}
+      msg.data.len = content_length;
+      u32 dlen = vec_len (hc->rx_buf) - hc->rx_buf_offset;
+      as = session_get_from_handle (hc->h_pa_session_handle);
+      svm_fifo_seg_t segs[2] = { { (u8 *) &msg, sizeof (msg) },
+				 { &hc->rx_buf[hc->rx_buf_offset], dlen } };
+
+      rv = svm_fifo_enqueue_segments (as->rx_fifo, segs, 2,
+				      0 /* allow partial */);
+      if (rv < 0)
+	{
+	  clib_warning ("error enqueue");
+	  return HTTP_SM_ERROR;
+	}
+
+      hc->rx_buf_offset += dlen;
+      hc->to_recv = content_length - dlen;
+
+      if (hc->rx_buf_offset == vec_len (hc->rx_buf))
+	{
+	  vec_reset_length (hc->rx_buf);
+	  hc->rx_buf_offset = 0;
+	}
+
+      if (hc->to_recv == 0)
+	{
+	  hc->rx_buf_offset = 0;
+	  vec_reset_length (hc->rx_buf);
+	  http_state_change (hc, HTTP_STATE_WAIT_CLIENT_METHOD);
+	}
+      else
+	{
+	  http_state_change (hc, HTTP_STATE_CLIENT_IO_MORE_DATA);
+	}
+
+      app_wrk = app_worker_get_if_valid (as->app_wrk_index);
+      app_worker_rx_notify (app_wrk, as);
+      return HTTP_SM_STOP;
+    }
+  else
+    {
+      HTTP_DBG (0, "Unknown http method %v", hc->rx_buf);
+      ec = HTTP_STATUS_METHOD_NOT_ALLOWED;
+      goto error;
+    }
+  return HTTP_SM_STOP;
+
+error:
+
+  http_send_error (hc, ec);
+  session_transport_closing_notify (&hc->connection);
+  http_disconnect_transport (hc);
+
+  return HTTP_SM_ERROR;
+}
+
+static http_sm_result_t
+http_state_wait_client_method (http_conn_t *hc, transport_send_params_t *sp)
 {
   http_status_code_t ec;
   app_worker_t *app_wrk;
@@ -440,7 +616,7 @@ state_srv_wait_method (http_conn_t *hc, transport_send_params_t *sp)
   u32 len;
   u8 *buf;
 
-  rv = read_http_message (hc);
+  rv = http_read_message (hc);
 
   /* Nothing yet, wait for data or timer expire */
   if (rv)
@@ -464,6 +640,7 @@ state_srv_wait_method (http_conn_t *hc, transport_send_params_t *sp)
 	  goto error;
 	}
 
+      HTTP_DBG (0, "GET method %v", hc->rx_buf);
       len = i - hc->rx_buf_offset - 1;
     }
   else if ((i = v_find_index (hc->rx_buf, 0, "POST ")) >= 0)
@@ -471,10 +648,11 @@ state_srv_wait_method (http_conn_t *hc, transport_send_params_t *sp)
       hc->method = HTTP_REQ_POST;
       hc->rx_buf_offset = i + 6;
       len = vec_len (hc->rx_buf) - hc->rx_buf_offset - 1;
+      HTTP_DBG (0, "POST method %v", hc->rx_buf);
     }
   else
     {
-      HTTP_DBG (0, "Unknown http method");
+      HTTP_DBG (0, "Unknown http method %v", hc->rx_buf);
       ec = HTTP_STATUS_METHOD_NOT_ALLOWED;
       goto error;
     }
@@ -501,7 +679,7 @@ state_srv_wait_method (http_conn_t *hc, transport_send_params_t *sp)
     }
 
   vec_free (hc->rx_buf);
-  hc->http_state = HTTP_STATE_WAIT_APP;
+  http_state_change (hc, HTTP_STATE_WAIT_APP_REPLY);
 
   app_wrk = app_worker_get_if_valid (as->app_wrk_index);
   if (app_wrk)
@@ -511,26 +689,23 @@ state_srv_wait_method (http_conn_t *hc, transport_send_params_t *sp)
 
 error:
 
-  send_error (hc, ec);
+  http_send_error (hc, ec);
   session_transport_closing_notify (&hc->connection);
   http_disconnect_transport (hc);
 
   return HTTP_SM_ERROR;
 }
 
-/**
- * waiting for data from app
- */
 static http_sm_result_t
-state_srv_wait_app (http_conn_t *hc, transport_send_params_t *sp)
+http_state_wait_app_reply (http_conn_t *hc, transport_send_params_t *sp)
 {
   http_main_t *hm = &http_main;
-  http_status_code_t ec;
-  http_msg_t msg;
-  session_t *as;
   u8 *header;
   u32 offset;
   f64 now;
+  session_t *as;
+  http_status_code_t sc;
+  http_msg_t msg;
   int rv;
 
   as = session_get_from_handle (hc->h_pa_session_handle);
@@ -538,21 +713,17 @@ state_srv_wait_app (http_conn_t *hc, transport_send_params_t *sp)
   rv = svm_fifo_dequeue (as->tx_fifo, sizeof (msg), (u8 *) &msg);
   ASSERT (rv == sizeof (msg));
 
-  if (msg.type != HTTP_MSG_REPLY || msg.data.type > HTTP_MSG_DATA_PTR)
+  if (msg.data.type > HTTP_MSG_DATA_PTR)
     {
-      clib_warning ("unexpected msg type from app %u", msg.type);
-      ec = HTTP_STATUS_INTERNAL_ERROR;
+      clib_warning ("no data");
+      sc = HTTP_STATUS_INTERNAL_ERROR;
       goto error;
     }
 
-  ec = msg.code;
-
-  switch (msg.code)
+  if (msg.type != HTTP_MSG_REPLY)
     {
-    case HTTP_STATUS_OK:
-    case HTTP_STATUS_MOVED:
-      break;
-    default:
+      clib_warning ("unexpected message type %d", msg.type);
+      sc = HTTP_STATUS_INTERNAL_ERROR;
       goto error;
     }
 
@@ -588,221 +759,111 @@ state_srv_wait_app (http_conn_t *hc, transport_send_params_t *sp)
       /* Location: http(s)://new-place already queued up as data */
       break;
     default:
-      goto error;
+      return HTTP_SM_ERROR;
     }
 
-  offset = send_data (hc, header, vec_len (header), 0);
+  offset = http_send_data (hc, header, vec_len (header), 0);
   if (offset != vec_len (header))
     {
       clib_warning ("couldn't send response header!");
-      ec = HTTP_STATUS_INTERNAL_ERROR;
+      sc = HTTP_STATUS_INTERNAL_ERROR;
       goto error;
     }
   vec_free (header);
 
   /* Start sending the actual data */
-  hc->http_state = HTTP_STATE_IO_MORE_DATA;
+  http_state_change (hc, HTTP_STATE_APP_IO_MORE_DATA);
 
   ASSERT (sp->max_burst_size >= offset);
   sp->max_burst_size -= offset;
-
   return HTTP_SM_CONTINUE;
 
 error:
-
-  send_error (hc, ec);
-  hc->http_state = HTTP_STATE_WAIT_METHOD;
+  clib_warning ("unexpected msg type from app %u", msg.type);
+  http_send_error (hc, sc);
+  http_state_change (hc, HTTP_STATE_WAIT_CLIENT_METHOD);
   session_transport_closing_notify (&hc->connection);
   http_disconnect_transport (hc);
-
   return HTTP_SM_STOP;
 }
 
 static http_sm_result_t
-state_srv_send_more_data (http_conn_t *hc, transport_send_params_t *sp)
+http_state_wait_app_method (http_conn_t *hc, transport_send_params_t *sp)
 {
-  u32 max_send = 64 << 10, n_segs;
-  http_buffer_t *hb = &hc->tx_buf;
-  svm_fifo_seg_t *seg;
-  session_t *ts;
-  int sent = 0;
-
-  max_send = clib_min (max_send, sp->max_burst_size);
-  ts = session_get_from_handle (hc->h_tc_session_handle);
-  if ((seg = http_buffer_get_segs (hb, max_send, &n_segs)))
-    sent = svm_fifo_enqueue_segments (ts->tx_fifo, seg, n_segs,
-				      1 /* allow partial */);
-
-  if (sent > 0)
-    {
-      /* Ask scheduler to notify app of deq event if needed */
-      sp->bytes_dequeued += http_buffer_drain (hb, sent);
-      sp->max_burst_size -= sent;
-    }
-
-  /* Not finished sending all data */
-  if (!http_buffer_is_drained (hb))
-    {
-      if (sent && svm_fifo_set_event (ts->tx_fifo))
-	session_send_io_evt_to_thread (ts->tx_fifo, SESSION_IO_EVT_TX);
-
-      if (svm_fifo_max_enqueue (ts->tx_fifo) < HTTP_FIFO_THRESH)
-	{
-	  /* Deschedule http session and wait for deq notification if
-	   * underlying ts tx fifo almost full */
-	  svm_fifo_add_want_deq_ntf (ts->tx_fifo, SVM_FIFO_WANT_DEQ_NOTIF);
-	  transport_connection_deschedule (&hc->connection);
-	  sp->flags |= TRANSPORT_SND_F_DESCHED;
-	}
-    }
-  else
-    {
-      if (sent && svm_fifo_set_event (ts->tx_fifo))
-	session_send_io_evt_to_thread (ts->tx_fifo, SESSION_IO_EVT_TX_FLUSH);
-
-      /* Finished transaction, back to HTTP_STATE_WAIT_METHOD */
-      hc->http_state = HTTP_STATE_WAIT_METHOD;
-      http_buffer_free (&hc->tx_buf);
-    }
-
-  return HTTP_SM_STOP;
-}
-
-static int
-parse_http_header (http_conn_t *hc, int *content_length)
-{
-  unformat_input_t input;
-  int i, len;
-  u8 *line;
-
-  if ((i = v_find_index (hc->rx_buf, hc->rx_buf_offset, "200 OK") < 0))
-    {
-      clib_warning ("bad response code");
-      return -1;
-    }
-
-  i = v_find_index (hc->rx_buf, hc->rx_buf_offset, CONTENT_LEN_STR);
-  if (i < 0)
-    {
-      clib_warning ("cannot find '%s' in the header!", CONTENT_LEN_STR);
-      return -1;
-    }
-
-  hc->rx_buf_offset = i;
+  http_status_code_t sc;
+  http_msg_t msg;
+  session_t *as;
+  u8 *buf = 0, *request;
+  u32 offset;
+  int rv;
 
-  i = v_find_index (hc->rx_buf, hc->rx_buf_offset, "\n");
-  if (i < 0)
-    {
-      clib_warning ("end of line missing; incomplete data");
-      return -1;
-    }
+  as = session_get_from_handle (hc->h_pa_session_handle);
 
-  len = i - hc->rx_buf_offset;
-  line = vec_new (u8, len);
-  clib_memcpy (line, hc->rx_buf + hc->rx_buf_offset, len);
+  rv = svm_fifo_dequeue (as->tx_fifo, sizeof (msg), (u8 *) &msg);
+  ASSERT (rv == sizeof (msg));
 
-  unformat_init_vector (&input, line);
-  if (!unformat (&input, CONTENT_LEN_STR "%d", content_length))
+  if (msg.data.type > HTTP_MSG_DATA_PTR)
     {
-      clib_warning ("failed to unformat content length!");
-      return -1;
+      clib_warning ("no data");
+      sc = HTTP_STATUS_INTERNAL_ERROR;
+      goto error;
     }
-  unformat_free (&input);
 
-  /* skip rest of the header */
-  hc->rx_buf_offset += len;
-  i = v_find_index (hc->rx_buf, hc->rx_buf_offset, "<html>");
-  if (i < 0)
+  if (msg.type != HTTP_MSG_REQUEST)
     {
-      clib_warning ("<html> tag not found");
-      return -1;
+      clib_warning ("unexpected message type %d", msg.type);
+      sc = HTTP_STATUS_INTERNAL_ERROR;
+      goto error;
     }
-  hc->rx_buf_offset = i;
 
-  return 0;
-}
-
-static int
-state_cln_wait_method (http_conn_t *hc, transport_send_params_t *sp)
-{
-  session_t *as;
-  http_msg_t msg;
-  app_worker_t *app_wrk;
-  int rv, content_length;
-
-  rv = read_http_message (hc);
-  if (rv)
-    return HTTP_SM_STOP;
+  sc = msg.code;
 
-  msg.type = HTTP_MSG_REPLY;
-  msg.content_type = HTTP_CONTENT_TEXT_HTML;
-  msg.code = HTTP_STATUS_OK;
-  msg.data.type = HTTP_MSG_DATA_INLINE;
-  msg.data.len = 0;
-
-  rv = parse_http_header (hc, &content_length);
-  if (rv)
-    {
-      clib_warning ("failed to parse http reply");
-      session_transport_closing_notify (&hc->connection);
-      http_disconnect_transport (hc);
-      return -1;
-    }
-
-  msg.data.len = content_length;
-  u32 dlen = vec_len (hc->rx_buf) - hc->rx_buf_offset;
-  as = session_get_from_handle (hc->h_pa_session_handle);
-  svm_fifo_seg_t segs[2] = { { (u8 *) &msg, sizeof (msg) },
-			     { &hc->rx_buf[hc->rx_buf_offset], dlen } };
+  vec_validate (buf, msg.data.len - 1);
+  rv = svm_fifo_dequeue (as->tx_fifo, msg.data.len, buf);
+  ASSERT (rv == msg.data.len);
 
-  rv = svm_fifo_enqueue_segments (as->rx_fifo, segs, 2, 0 /* allow partial */);
-  if (rv < 0)
+  request = format (0, http_request_template, buf);
+  offset = http_send_data (hc, request, vec_len (request), 0);
+  if (offset != vec_len (request))
     {
-      clib_warning ("error enqueue");
-      return HTTP_SM_ERROR;
+      clib_warning ("sending request failed!");
+      sc = HTTP_STATUS_INTERNAL_ERROR;
+      goto error;
     }
-  hc->rx_buf_offset += dlen;
-  hc->http_state = HTTP_STATE_IO_MORE_DATA;
-  hc->to_recv = content_length - dlen;
 
-  if (hc->rx_buf_offset == vec_len (hc->rx_buf))
-    {
-      vec_reset_length (hc->rx_buf);
-      hc->rx_buf_offset = 0;
-    }
+  http_state_change (hc, HTTP_STATE_WAIT_SERVER_REPLY);
 
-  if (hc->to_recv == 0)
-    {
-      hc->rx_buf_offset = 0;
-      vec_reset_length (hc->rx_buf);
-      hc->http_state = HTTP_STATE_WAIT_APP;
-    }
+  vec_free (buf);
+  vec_free (request);
 
-  app_wrk = app_worker_get_if_valid (as->app_wrk_index);
-  if (app_wrk)
-    app_worker_rx_notify (app_wrk, as);
+  return HTTP_SM_CONTINUE;
 
+error:
+  clib_warning ("unexpected msg type from app %u", msg.type);
+  http_send_error (hc, sc);
+  session_transport_closing_notify (&hc->connection);
+  http_disconnect_transport (hc);
   return HTTP_SM_STOP;
 }
 
-static int
-cln_drain_rx_buf (http_conn_t *hc, session_t *ts, session_t *as)
+static void
+http_app_enqueue (http_conn_t *hc, session_t *as)
 {
   app_worker_t *app_wrk;
-  u32 max_enq, n_enq, dlen = vec_len (hc->rx_buf) - hc->rx_buf_offset;
+  u32 dlen, max_enq, n_enq;
   int rv;
 
+  dlen = vec_len (hc->rx_buf) - hc->rx_buf_offset;
+  if (!dlen)
+    return;
+
   max_enq = svm_fifo_max_enqueue (as->rx_fifo);
   n_enq = clib_min (max_enq, dlen);
   rv = svm_fifo_enqueue (as->rx_fifo, n_enq, &hc->rx_buf[hc->rx_buf_offset]);
   if (rv < 0)
-    {
-      clib_warning ("enqueue failed");
-      return -1;
-    }
+    return;
 
   hc->rx_buf_offset += rv;
-
   if (hc->rx_buf_offset >= vec_len (hc->rx_buf))
     {
       vec_reset_length (hc->rx_buf);
@@ -811,149 +872,124 @@ cln_drain_rx_buf (http_conn_t *hc, session_t *ts, session_t *as)
 
   app_wrk = app_worker_get_if_valid (as->app_wrk_index);
   ASSERT (app_wrk);
-
   app_worker_rx_notify (app_wrk, as);
-  return 1;
 }
 
 static http_sm_result_t
-state_cln_recv_more_data (http_conn_t *hc, transport_send_params_t *sp)
+http_state_client_io_more_data (http_conn_t *hc, transport_send_params_t *sp)
 {
-  session_t *as;
+  session_t *as, *ts;
   u32 max_deq;
-  session_t *ts;
-  int n_read, rv;
+  int n_read;
 
   as = session_get_from_handle (hc->h_pa_session_handle);
   ts = session_get_from_handle (hc->h_tc_session_handle);
 
-  u32 dlen = vec_len (hc->rx_buf) - hc->rx_buf_offset;
-  if (dlen)
-    {
-      rv = cln_drain_rx_buf (hc, ts, as);
-      if (rv < 0)
-	{
-	  clib_warning ("drain rx error!");
-	  return HTTP_SM_ERROR;
-	}
-      goto maybe_reschedule;
-    }
+  http_app_enqueue (hc, as);
 
   if (hc->to_recv == 0)
     {
-      ASSERT (vec_len (hc->rx_buf) == 0);
-      ASSERT (hc->rx_buf_offset == 0);
-      hc->http_state = HTTP_STATE_WAIT_APP;
+      http_state_change (hc, HTTP_STATE_WAIT_CLIENT_METHOD);
       return HTTP_SM_STOP;
     }
 
   max_deq = svm_fifo_max_dequeue (ts->rx_fifo);
-  if (max_deq == 0)
-    return HTTP_SM_STOP;
-
-  ASSERT (vec_len (hc->rx_buf) == 0);
-  ASSERT (hc->rx_buf_offset == 0);
+  if (max_deq > 0)
+    {
+      vec_validate (hc->rx_buf, max_deq - 1);
+      n_read = svm_fifo_dequeue (ts->rx_fifo, max_deq, hc->rx_buf);
+      ASSERT (n_read == max_deq);
 
-  vec_validate (hc->rx_buf, max_deq - 1);
-  n_read = svm_fifo_dequeue (ts->rx_fifo, max_deq, hc->rx_buf);
-  ASSERT (n_read == max_deq);
+      if (svm_fifo_is_empty (ts->rx_fifo))
+	svm_fifo_unset_event (ts->rx_fifo);
 
-  if (svm_fifo_is_empty (ts->rx_fifo))
-    svm_fifo_unset_event (ts->rx_fifo);
-
-  hc->to_recv -= n_read;
-  vec_set_len (hc->rx_buf, max_deq);
+      hc->to_recv -= n_read;
+      vec_set_len (hc->rx_buf, n_read);
+    }
 
-maybe_reschedule:
   if (hc->rx_buf_offset < vec_len (hc->rx_buf) ||
       svm_fifo_max_dequeue_cons (ts->rx_fifo))
     {
-      /* TODO is the flag really needed? */
-      if (svm_fifo_set_event (ts->rx_fifo))
 	session_enqueue_notify (ts);
     }
   return HTTP_SM_CONTINUE;
 }
 
 static http_sm_result_t
-state_cln_wait_app (http_conn_t *hc, transport_send_params_t *sp)
+http_state_app_io_more_data (http_conn_t *hc, transport_send_params_t *sp)
 {
-  session_t *as;
-  http_msg_t msg;
-  http_status_code_t ec;
-  u8 *buf = 0, *request;
-  u32 offset;
-  int rv;
-
-  as = session_get_from_handle (hc->h_pa_session_handle);
-  rv = svm_fifo_dequeue (as->tx_fifo, sizeof (msg), (u8 *) &msg);
-  ASSERT (rv == sizeof (msg));
-  if (msg.type != HTTP_MSG_REQUEST || msg.data.type > HTTP_MSG_DATA_PTR)
-    {
-      clib_warning ("unexpected msg type from app %u", msg.type);
-      ec = HTTP_STATUS_INTERNAL_ERROR;
-      goto error;
-    }
+  u32 max_send = 64 << 10, n_segs;
+  http_buffer_t *hb = &hc->tx_buf;
+  svm_fifo_seg_t *seg;
+  session_t *ts;
+  int sent = 0;
 
-  vec_validate (buf, msg.data.len - 1);
-  rv = svm_fifo_dequeue (as->tx_fifo, msg.data.len, buf);
-  ASSERT (rv == msg.data.len);
+  max_send = clib_min (max_send, sp->max_burst_size);
+  ts = session_get_from_handle (hc->h_tc_session_handle);
+  if ((seg = http_buffer_get_segs (hb, max_send, &n_segs)))
+    sent = svm_fifo_enqueue_segments (ts->tx_fifo, seg, n_segs,
+				      1 /* allow partial */);
 
-  request = format (0, http_request_template, buf);
-  offset = send_data (hc, request, vec_len (request), 0);
-  if (offset != vec_len (request))
+  if (sent > 0)
     {
-      clib_warning ("sending request failed!");
-      ec = HTTP_STATUS_INTERNAL_ERROR;
-      goto error;
+      /* Ask scheduler to notify app of deq event if needed */
+      sp->bytes_dequeued += http_buffer_drain (hb, sent);
+      sp->max_burst_size -= sent;
     }
 
-  hc->http_state = HTTP_STATE_WAIT_METHOD;
+  /* Not finished sending all data */
+  if (!http_buffer_is_drained (hb))
+    {
+      if (sent && svm_fifo_set_event (ts->tx_fifo))
+	session_send_io_evt_to_thread (ts->tx_fifo, SESSION_IO_EVT_TX);
 
-  vec_free (buf);
-  vec_free (request);
+      if (svm_fifo_max_enqueue (ts->tx_fifo) < HTTP_FIFO_THRESH)
+	{
+	  /* Deschedule http session and wait for deq notification if
+	   * underlying ts tx fifo almost full */
+	  svm_fifo_add_want_deq_ntf (ts->tx_fifo, SVM_FIFO_WANT_DEQ_NOTIF);
+	  transport_connection_deschedule (&hc->connection);
+	  sp->flags |= TRANSPORT_SND_F_DESCHED;
+	}
+    }
+  else
+    {
+      if (sent && svm_fifo_set_event (ts->tx_fifo))
+	session_send_io_evt_to_thread (ts->tx_fifo, SESSION_IO_EVT_TX_FLUSH);
 
-  return HTTP_SM_CONTINUE;
+      /* Finished transaction, back to HTTP_STATE_WAIT_METHOD */
+      http_state_change (hc, HTTP_STATE_WAIT_CLIENT_METHOD);
+      http_buffer_free (&hc->tx_buf);
+    }
 
-error:
-  send_error (hc, ec);
-  session_transport_closing_notify (&hc->connection);
-  http_disconnect_transport (hc);
   return HTTP_SM_STOP;
 }
 
 typedef http_sm_result_t (*http_sm_handler) (http_conn_t *,
 					     transport_send_params_t *sp);
 
-static http_sm_handler srv_state_funcs[HTTP_N_STATES] = {
-  /* Waiting for GET, POST, etc. */
-  state_srv_wait_method,
-  /* Wait for data from app */
-  state_srv_wait_app,
-  /* Send more data */
-  state_srv_send_more_data,
-};
-
-static http_sm_handler cln_state_funcs[HTTP_N_STATES] = {
-  /* wait for reply */
-  state_cln_wait_method,
-  /* wait for data from app */
-  state_cln_wait_app,
-  /* receive more data */
-  state_cln_recv_more_data,
+static http_sm_handler state_funcs[HTTP_N_STATES] = {
+  0, /* idle state */
+  http_state_wait_app_method,
+  http_state_wait_client_method,
+  http_state_wait_server_reply,
+  http_state_wait_app_reply,
+  http_state_client_io_more_data,
+  http_state_app_io_more_data,
 };
 
 static void
 http_req_run_state_machine (http_conn_t *hc, transport_send_params_t *sp)
 {
   http_sm_result_t res;
-  http_sm_handler *state_fn =
-    hc->is_client ? cln_state_funcs : srv_state_funcs;
   do
     {
-      res = state_fn[hc->http_state](hc, sp);
+      res = state_funcs[hc->http_state](hc, sp);
       if (res == HTTP_SM_ERROR)
-	return;
+	{
+	  HTTP_DBG (1, "error in state machine %d", res);
+	  return;
+	}
     }
   while (res == HTTP_SM_CONTINUE);
 
@@ -962,33 +998,15 @@ http_req_run_state_machine (http_conn_t *hc, transport_send_params_t *sp)
 }
 
 static int
-http_ts_server_rx_callback (session_t *ts, http_conn_t *hc)
+http_ts_rx_callback (session_t *ts)
 {
-  if (hc->http_state != HTTP_STATE_WAIT_METHOD)
-    {
-      clib_warning ("tcp data in req state %u", hc->http_state);
-      return 0;
-    }
-
-  http_req_run_state_machine (hc, 0);
-
-  if (hc->state == HTTP_CONN_STATE_TRANSPORT_CLOSED)
-    {
-      if (!svm_fifo_max_dequeue_cons (ts->rx_fifo))
-	session_transport_closing_notify (&hc->connection);
-    }
-  return 0;
-}
+  http_conn_t *hc;
 
-static int
-http_ts_client_rx_callback (session_t *ts, http_conn_t *hc)
-{
-  if (hc->http_state != HTTP_STATE_WAIT_METHOD &&
-      hc->http_state != HTTP_STATE_IO_MORE_DATA)
+  hc = http_conn_get_w_thread (ts->opaque, ts->thread_index);
+  if (!hc)
     {
-      clib_warning ("http in unexpected state %d (ts %d)", hc->http_state,
-		    ts->session_index);
-      return 0;
+      clib_warning ("http connection not found (ts %d)", ts->opaque);
+      return -1;
     }
 
   http_req_run_state_machine (hc, 0);
@@ -1001,17 +1019,6 @@ http_ts_client_rx_callback (session_t *ts, http_conn_t *hc)
   return 0;
 }
 
-static int
-http_ts_rx_callback (session_t *ts)
-{
-  http_conn_t *hc;
-
-  hc = http_conn_get_w_thread (ts->opaque, ts->thread_index);
-  if (hc->is_client)
-    return http_ts_client_rx_callback (ts, hc);
-  return http_ts_server_rx_callback (ts, hc);
-}
-
 int
 http_ts_builtin_tx_callback (session_t *ts)
 {
@@ -1142,10 +1149,11 @@ http_transport_connect (transport_endpoint_cfg_t *tep)
   hc = http_conn_get_w_thread (hc_index, 0);
   hc->h_pa_wrk_index = sep->app_wrk_index;
   hc->h_pa_app_api_ctx = sep->opaque;
-  hc->is_client = 1;
   hc->state = HTTP_CONN_STATE_CONNECTING;
   cargs->api_context = hc_index;
 
+  HTTP_DBG (1, "hc ho_index %x", hc_index);
+
   if ((error = vnet_connect (cargs)))
     return error;
 
@@ -1273,12 +1281,14 @@ http_app_tx_callback (void *session, transport_send_params_t *sp)
   u32 max_burst_sz, sent;
   http_conn_t *hc;
 
+  HTTP_DBG (1, "app session conn index %x", as->connection_index);
+
   hc = http_conn_get_w_thread (as->connection_index, as->thread_index);
-  if (hc->http_state < HTTP_STATE_WAIT_APP)
+  if (!http_state_is_tx_valid (hc))
     {
       if (hc->state != HTTP_CONN_STATE_CLOSED)
-	clib_warning ("app data req state %u session state %u", hc->http_state,
-		      hc->state);
+	clib_warning ("app data req state '%U' session state %u",
+		      format_http_state, hc->http_state, hc->state);
       svm_fifo_dequeue_drop_all (as->tx_fifo);
       return 0;
     }
diff --git a/src/plugins/http/http.h b/src/plugins/http/http.h
index 50203dcd2f9..dbae5ac4611 100644
--- a/src/plugins/http/http.h
+++ b/src/plugins/http/http.h
@@ -61,9 +61,13 @@ typedef enum http_conn_state_
 
 typedef enum http_state_
 {
-  HTTP_STATE_WAIT_METHOD,
-  HTTP_STATE_WAIT_APP,
-  HTTP_STATE_IO_MORE_DATA,
+  HTTP_STATE_IDLE = 0,
+  HTTP_STATE_WAIT_APP_METHOD,
+  HTTP_STATE_WAIT_CLIENT_METHOD,
+  HTTP_STATE_WAIT_SERVER_REPLY,
+  HTTP_STATE_WAIT_APP_REPLY,
+  HTTP_STATE_CLIENT_IO_MORE_DATA,
+  HTTP_STATE_APP_IO_MORE_DATA,
   HTTP_N_STATES,
 } http_state_t;
 
@@ -232,7 +236,6 @@ typedef struct http_tc_
   u8 *rx_buf;
   u32 rx_buf_offset;
   http_buffer_t tx_buf;
-  u8 is_client;
   u32 to_recv;
   u32 bytes_dequeued;
 } http_conn_t;
@@ -263,6 +266,16 @@ typedef struct http_main_
   u32 fifo_size;
 } http_main_t;
 
+static inline int
+http_state_is_tx_valid (http_conn_t *hc)
+{
+  http_state_t state = hc->http_state;
+  return (state == HTTP_STATE_APP_IO_MORE_DATA ||
+	  state == HTTP_STATE_CLIENT_IO_MORE_DATA ||
+	  state == HTTP_STATE_WAIT_APP_REPLY ||
+	  state == HTTP_STATE_WAIT_APP_METHOD);
+}
+
 #endif /* SRC_PLUGINS_HTTP_HTTP_H_ */
 
 /*