tcp: window update ack

Type: feature

Provide interface for sending Window Update ACK,
ensuring it will be sent only once, if RWND became non-zero,
after zero RWND has been advertised before.

Change-Id: I7f0d8af76d7763208625df68ab4ac3727fdaf449
Signed-off-by: Vladimir Kropylev <vladimir.kropylev@enea.com>
diff --git a/src/vnet/tcp/tcp_output.c b/src/vnet/tcp/tcp_output.c
index d3c4ca4..7cf85c3 100644
--- a/src/vnet/tcp/tcp_output.c
+++ b/src/vnet/tcp/tcp_output.c
@@ -505,6 +505,11 @@
 
   tcp_options_write ((u8 *) (th + 1), snd_opts);
   vnet_buffer (b)->tcp.connection_index = tc->c_c_index;
+
+  if (wnd == 0)
+    tcp_zero_rwnd_sent_on (tc);
+  else
+    tcp_zero_rwnd_sent_off (tc);
 }
 
 /**
@@ -1266,6 +1271,28 @@
 }
 
 /**
+ * Send Window Update ACK,
+ * ensuring that it will be sent once, if RWND became non-zero,
+ * after zero RWND has been advertised in ACK before
+ */
+void
+tcp_send_window_update_ack (tcp_connection_t * tc)
+{
+  tcp_worker_ctx_t *wrk = tcp_get_worker (tc->c_thread_index);
+  u32 win;
+
+  if (tcp_zero_rwnd_sent (tc))
+    {
+      win = tcp_window_to_advertise (tc, tc->state);
+      if (win > 0)
+	{
+	  tcp_zero_rwnd_sent_off (tc);
+	  tcp_program_ack (wrk, tc);
+	}
+    }
+}
+
+/**
  * Allocate a new buffer and build a new tcp segment
  *
  * @param wrk		tcp worker