[incubator-nuttx] 01/03: tcp: Extract MSS calculation from tcp_synack

[xi...@apache.org]

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commit 1f6fdf04b7dca14dd3afc77b3f35ebc0ad6828ff
Author: YAMAMOTO Takashi <ya...@midokura.com>
AuthorDate: Tue Jun 1 18:43:24 2021 +0900

    tcp: Extract MSS calculation from tcp_synack
    
    I plan to use it for recv window update decision logic.
---
 net/tcp/tcp.h      | 16 ++++++++++++++++
 net/tcp/tcp_send.c | 47 +++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/net/tcp/tcp.h b/net/tcp/tcp.h
index c83f832..b71c012 100644
--- a/net/tcp/tcp.h
+++ b/net/tcp/tcp.h
@@ -963,6 +963,22 @@ ssize_t tcp_sendfile(FAR struct socket *psock, FAR struct file *infile,
 void tcp_reset(FAR struct net_driver_s *dev);
 
 /****************************************************************************
+ * Name: tcp_rx_mss
+ *
+ * Description:
+ *   Return the MSS to advertize to the peer.
+ *
+ * Input Parameters:
+ *   dev  - The device driver structure
+ *
+ * Returned Value:
+ *   The MSS value.
+ *
+ ****************************************************************************/
+
+uint16_t tcp_rx_mss(FAR struct net_driver_s *dev);
+
+/****************************************************************************
  * Name: tcp_synack
  *
  * Description:
diff --git a/net/tcp/tcp_send.c b/net/tcp/tcp_send.c
index 050fd80..1079b13 100644
--- a/net/tcp/tcp_send.c
+++ b/net/tcp/tcp_send.c
@@ -553,6 +553,45 @@ void tcp_reset(FAR struct net_driver_s *dev)
 }
 
 /****************************************************************************
+ * Name: tcp_rx_mss
+ *
+ * Description:
+ *   Return the MSS to advertize to the peer.
+ *
+ * Input Parameters:
+ *   dev  - The device driver structure
+ *
+ * Returned Value:
+ *   The MSS value.
+ *
+ ****************************************************************************/
+
+uint16_t tcp_rx_mss(FAR struct net_driver_s *dev)
+{
+  uint16_t tcp_mss;
+
+#ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+  if (IFF_IS_IPv6(dev->d_flags))
+#endif
+    {
+      tcp_mss = TCP_IPv6_MSS(dev);
+    }
+#endif /* CONFIG_NET_IPv6 */
+
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+  else
+#endif
+    {
+      tcp_mss = TCP_IPv4_MSS(dev);
+    }
+#endif /* CONFIG_NET_IPv4 */
+
+  return tcp_mss;
+}
+
+/****************************************************************************
  * Name: tcp_synack
  *
  * Description:
@@ -588,10 +627,9 @@ void tcp_synack(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
   if (IFF_IS_IPv6(dev->d_flags))
 #endif
     {
-      /* Get the MSS value and offset TCP header address for this packet */
+      /* Get the offset TCP header address for this packet */
 
       tcp     = TCPIPv6BUF;
-      tcp_mss = TCP_IPv6_MSS(dev);
 
       /* Set the packet length for the TCP Maximum Segment Size */
 
@@ -604,10 +642,9 @@ void tcp_synack(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
   else
 #endif
     {
-      /* Get the MSS value and offset TCP header address for this packet */
+      /* Get the offset TCP header address for this packet */
 
       tcp     = TCPIPv4BUF;
-      tcp_mss = TCP_IPv4_MSS(dev);
 
       /* Set the packet length for the TCP Maximum Segment Size */
 
@@ -615,6 +652,8 @@ void tcp_synack(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
     }
 #endif /* CONFIG_NET_IPv4 */
 
+  tcp_mss = tcp_rx_mss(dev);
+
   /* Save the ACK bits */
 
   tcp->flags      = ack;