Fix for recvfrom() hang when the new CONFIG_NET_TCP_RECVDELAY is set to zero (from Max Holtzberg)

git-svn-id: https://nuttx.svn.sourceforge.net/svnroot/nuttx/trunk@5148 7fd9a85b-ad96-42d3-883c-3090e2eb8679

2 files changed, 22 insertions, 0 deletions

diff --git a/nuttx/ChangeLog b/nuttx/ChangeLog
index 5728e117f..1375bea43 100644
--- a/nuttx/ChangeLog
+++ b/nuttx/ChangeLog
@@ -3337,4 +3337,8 @@
 	* include/nuttx/usb/usb.h, arch/*/src/*usb.c, and arch/*/src/*otg*.c:
 	  Add hooks to to use common, external DMA buffer allocation
 	  implementation.
+	* net/recvfrom.c: Don't block in recvfrom if (1) read-ahead buffering
+	  is enabled and (2) some data was obtained from read-ahead buffers.
+	  Blocking is a bad idea in that case because there is no timeout!
+	  (submitted by Max Holtzberg).
 
diff --git a/nuttx/net/recvfrom.c b/nuttx/net/recvfrom.c
index 51027e0f8..78990fd39 100644
--- a/nuttx/net/recvfrom.c
+++ b/nuttx/net/recvfrom.c
@@ -1079,7 +1079,25 @@ static ssize_t tcp_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
 
   else
 #endif
+
+  /* We get here when we we decide that we need to setup the wait for incoming
+   * TCP/IP data.  Just a few more conditions to check:
+   *
+   * 1) Make sure thet there is buffer space to receive additional data
+   *    (state.rf_buflen > 0).  This could be zero, for example, if read-ahead
+   *    buffering was enabled and we filled the user buffer with data from
+   *    the read-ahead buffers.  Aand
+   * 2) if read-ahead buffering is enabled (CONFIG_NET_NTCP_READAHEAD_BUFFERS > 0)
+   *    and delay logic is disabled (CONFIG_NET_TCP_RECVDELAY == 0), then we
+   *    not want to wait if we already obtained some data from the read-ahead
+   *    buffer.  In that case, return now with what we have.
+   */
+
+#if CONFIG_NET_TCP_RECVDELAY == 0 && CONFIG_NET_NTCP_READAHEAD_BUFFERS > 0
+  if (state.rf_recvlen == 0 && state.rf_buflen > 0)
+#else
   if (state.rf_buflen > 0)
+#endif
     {
       struct uip_conn *conn = (struct uip_conn *)psock->s_conn;