From 30070b06dfff52c05ff2f2f0f6c1d7eebd1af365 Mon Sep 17 00:00:00 2001
From: Masayuki Ishikawa <masayuki.ishikawa@gmail.com>
Date: Mon, 18 Dec 2017 12:11:52 +0000
Subject: [PATCH] Merged in masayuki2009/nuttx.nuttx/tcp_rcvwnd_control (pull
 request #555)

net/tcp: Introduce tcp receive window control based on I/O buffer

NOTE: The algorithm is still experimental but useful for http streaming.

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

Approved-by: Gregory Nutt <gnutt@nuttx.org>
---
 net/tcp/Kconfig    |  9 +++++++++
 net/tcp/tcp_send.c | 23 +++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/net/tcp/Kconfig b/net/tcp/Kconfig
index fac41794dcf..77cebe81fbe 100644
--- a/net/tcp/Kconfig
+++ b/net/tcp/Kconfig
@@ -192,4 +192,13 @@ config NET_SENDFILE
 		files out a TCP connection.
 
 endif # NET_TCP && !NET_TCP_NO_STACK
+
+config NET_TCP_RWND_CONTROL
+	bool "Receive window control based on IOBuffer"
+	default n
+	depends on MM_IOB && EXPERIMENTAL
+	---help---
+		Support receive window control based on I/O buffer.  This feature
+		is still experimental.
+
 endmenu # TCP/IP Networking
diff --git a/net/tcp/tcp_send.c b/net/tcp/tcp_send.c
index 6797c9d279a..b4e833aa9b0 100644
--- a/net/tcp/tcp_send.c
+++ b/net/tcp/tcp_send.c
@@ -54,6 +54,10 @@
 #include <nuttx/net/ip.h>
 #include <nuttx/net/tcp.h>
 
+#ifdef CONFIG_NET_TCP_RWND_CONTROL
+#  include <nuttx/semaphore.h>
+#endif
+
 #include "devif/devif.h"
 #include "inet/inet.h"
 #include "tcp/tcp.h"
@@ -309,6 +313,12 @@ static void tcp_sendcommon(FAR struct net_driver_s *dev,
                            FAR struct tcp_conn_s *conn,
                            FAR struct tcp_hdr_s *tcp)
 {
+#ifdef CONFIG_NET_TCP_RWND_CONTROL
+  extern sem_t g_qentry_sem;
+  int  qentry_sem_count;
+  uint32_t rwnd;
+#endif
+
   /* Copy the IP address into the IPv6 header */
 
 #ifdef CONFIG_NET_IPv6
@@ -341,6 +351,19 @@ static void tcp_sendcommon(FAR struct net_driver_s *dev,
   tcp->srcport  = conn->lport;
   tcp->destport = conn->rport;
 
+#ifdef CONFIG_NET_TCP_RWND_CONTROL
+  /* Update the TCP received window based on I/O buffer */
+  /* NOTE: This algorithm is still experimental */
+
+  if (OK == nxsem_getvalue(&g_qentry_sem, &qentry_sem_count))
+    {
+      rwnd = (qentry_sem_count * CONFIG_NET_ETH_TCP_RECVWNDO)
+             / CONFIG_IOB_NCHAINS;
+
+      NET_DEV_RCVWNDO(dev) = (uint16_t)rwnd;
+    }
+#endif
+
   /* Set the TCP window */
 
   if (conn->tcpstateflags & TCP_STOPPED)