net/tcp and udp: Add logic to signal events when TCP or UDP read-ahead data is buffered.

Squashed commit of the following:

    net/tcp:  Add signal notification for the case when UDP read-ahead data is buffered.  This is basically of clone of the TCP notification logic with naming adapted for UDP.

    net/tcp:  Add signal notification for the case when TCP read-ahead data is buffered.

mm/iob/Kconfig

@@ -64,7 +64,7 @@ config IOB_NOTIFIER
 	default n
 	select SIG_NOTIFIER
 	---help---
-		Enable building of IOB notifier logic that will send a signla to
+		Enable building of IOB notifier logic that will send a signal to
 		a kernel thread when an IOB is available.  This is is a general
 		purpose notifier, but was developed specifically to support poll()
 		logic where the poll must wait for an IOB to become available.

net/tcp/Kconfig

@@ -66,8 +66,17 @@ config NET_TCP_READAHEAD
 		These settings are critical to the reasonable operation of read-
 		ahead buffering.
 
-if NET_TCP_READAHEAD
+config TCP_READAHEAD_NOTIFIER
-endif # NET_TCP_READAHEAD
+	bool "Support TCP read-ahead notifications"
+	default n
+	select SIG_NOTIFIER
+	depends on NET_TCP_READAHEAD && !DISABLE_POLL
+	---help---
+		Enable building of TCP read-ahead notifier logic that will send a
+		signal to a kernel thread when an TCP read-ahead data has been
+		buffered.  This is is a general purpose notifier, but was developed
+		specifically to support TCP poll() logic where the poll must wait
+		for incoming TCP data to be buffered.
 
 config NET_TCP_WRITE_BUFFERS
 	bool "Enable TCP/IP write buffering"

net/tcp/Make.defs

@@ -55,6 +55,9 @@ endif
 ifneq ($(CONFIG_DISABLE_POLL),y)
 ifeq ($(CONFIG_NET_TCP_READAHEAD),y)
 SOCK_CSRCS += tcp_netpoll.c
+ifeq ($(CONFIG_TCP_READAHEAD_NOTIFIER),y)
+SOCK_CSRCS += tcp_notifier.c
+endif
 endif
 endif
 

net/tcp/tcp.h

@@ -1542,6 +1542,85 @@ int tcp_pollsetup(FAR struct socket *psock, FAR struct pollfd *fds);
 int tcp_pollteardown(FAR struct socket *psock, FAR struct pollfd *fds);
 #endif
 
+/****************************************************************************
+ * Name: tcp_notifier_setup
+ *
+ * Description:
+ *   Set up to notify the specified PID with the provided signal number.
+ *
+ *   NOTE: To avoid race conditions, the caller should set the sigprocmask
+ *   to block signal delivery.  The signal will be delivered once the
+ *   signal is removed from the sigprocmask.
+ *
+ * Input Parameters:
+ *   pid   - The PID to be notified.  If a zero value is provided, then the
+ *           PID of the calling thread will be used.
+ *   signo - The signal number to use with the notification.
+ *   conn  - The TCP connection where read-ahead data is needed.
+ *
+ * Returned Value:
+ *   > 0   - The signal notification is in place.  The returned value is a
+ *           key that may be used later in a call to
+ *           tcp_notifier_teardown().
+ *   == 0  - There is already buffered read-ahead data.  No signal
+ *           notification will be provided.
+ *   < 0   - An unexpected error occurred and no signal will be sent.  The
+ *           returned value is a negated errno value that indicates the
+ *           nature of the failure.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_TCP_READAHEAD_NOTIFIER
+int tcp_notifier_setup(int pid, int signo, FAR struct tcp_conn_s *conn);
+#endif
+
+/****************************************************************************
+ * Name: tcp_notifier_teardown
+ *
+ * Description:
+ *   Eliminate a TCP read-ahead notification previously setup by
+ *   tcp_notifier_setup().  This function should only be called if the
+ *   notification should be aborted prior to the notification.  The
+ *   notification will automatically be torn down after the signal is sent.
+ *
+ * Input Parameters:
+ *   key - The key value returned from a previous call to
+ *         tcp_notifier_setup().
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; a negated errno value is returned on
+ *   any failure.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_TCP_READAHEAD_NOTIFIER
+int tcp_notifier_teardown(int key);
+#endif
+
+/****************************************************************************
+ * Name: tcp_notifier_signal
+ *
+ * Description:
+ *   Read-ahead data has been buffered.  Signal all threads waiting for
+ *   read-ahead data to become available.
+ *
+ *   When the read-ahead data becomes available, *all* of the waiters in
+ *   this thread will be signaled.  If there are multiple waiters then only
+ *   the highest priority thread will get the data.  Lower priority threads
+ *   will need to call tcp_notifier_setup() once again.
+ *
+ * Input Parameters:
+ *   conn  - The TCP connection where read-ahead data was just buffered.
+ *
+ * Returned Value:
+ *   None.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_TCP_READAHEAD_NOTIFIER
+void tcp_notifier_signal(FAR struct tcp_conn_s *conn);
+#endif
+
 #undef EXTERN
 #ifdef __cplusplus
 }

net/tcp/tcp_callback.c

@@ -273,6 +273,14 @@ uint16_t tcp_datahandler(FAR struct tcp_conn_s *conn, FAR uint8_t *buffer,
       return 0;
     }
 
+#ifdef CONFIG_TCP_READAHEAD_NOTIFIER
+  /* Provided notification(s) that additional TCP read-ahead data is
+   * available.
+   */
+
+  tcp_notifier_signal(conn);
+#endif
+
   ninfo("Buffered %d bytes\n", buflen);
   return buflen;
 }

net/tcp/tcp_notifier.c

@@ -0,0 +1,152 @@
+/****************************************************************************
+ * net/tcp/tcp_notifier.c
+ *
+ *   Copyright (C) 2018 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+
+#include <nuttx/signal.h>
+#include <nuttx/mm/iob.h>
+
+#include "tcp/tcp.h"
+
+#ifdef CONFIG_TCP_READAHEAD_NOTIFIER
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: tcp_notifier_setup
+ *
+ * Description:
+ *   Set up to notify the specified PID with the provided signal number.
+ *
+ *   NOTE: To avoid race conditions, the caller should set the sigprocmask
+ *   to block signal delivery.  The signal will be delivered once the
+ *   signal is removed from the sigprocmask.
+ *
+ * Input Parameters:
+ *   pid   - The PID to be notified.  If a zero value is provided, then the
+ *           PID of the calling thread will be used.
+ *   signo - The signal number to use with the notification.
+ *   conn  - The TCP connection where read-ahead data is needed.
+ *
+ * Returned Value:
+ *   > 0   - The signal notification is in place.  The returned value is a
+ *           key that may be used later in a call to
+ *           tcp_notifier_teardown().
+ *   == 0  - There is already buffered read-ahead data.  No signal
+ *           notification will be provided.
+ *   < 0   - An unexpected error occurred and no signal will be sent.  The
+ *           returned value is a negated errno value that indicates the
+ *           nature of the failure.
+ *
+ ****************************************************************************/
+
+int tcp_notifier_setup(int pid, int signo, FAR struct tcp_conn_s *conn)
+{
+  /* If there is already buffered read-ahead data, then return zero without
+   * setting up the notification.
+   */
+
+  if (conn->readahead.qh_head != NULL)
+    {
+      return 0;
+    }
+
+  /* Otherwise, this is just a simple wrapper around nxsig_notifer_setup(). */
+
+  return nxsig_notifier_setup(pid, signo, NXSIG_TCP_READAHEAD, conn);
+}
+
+/****************************************************************************
+ * Name: tcp_notifier_teardown
+ *
+ * Description:
+ *   Eliminate a TCP read-ahead notification previously setup by
+ *   tcp_notifier_setup().  This function should only be called if the
+ *   notification should be aborted prior to the notification.  The
+ *   notification will automatically be torn down after the signal is sent.
+ *
+ * Input Parameters:
+ *   key - The key value returned from a previous call to
+ *         tcp_notifier_setup().
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; a negated errno value is returned on
+ *   any failure.
+ *
+ ****************************************************************************/
+
+int tcp_notifier_teardown(int key)
+{
+  /* This is just a simple wrapper around nxsig_notifier_teardown(). */
+
+  return nxsig_notifier_teardown(key);
+}
+
+/****************************************************************************
+ * Name: tcp_notifier_signal
+ *
+ * Description:
+ *   Read-ahead data has been buffered.  Signal all threads waiting for
+ *   read-ahead data to become available.
+ *
+ *   When the read-ahead data becomes available, *all* of the waiters in
+ *   this thread will be signaled.  If there are multiple waiters then only
+ *   the highest priority thread will get the data.  Lower priority threads
+ *   will need to call tcp_notifier_setup() once again.
+ *
+ * Input Parameters:
+ *   conn  - The TCP connection where read-ahead data was just buffered.
+ *
+ * Returned Value:
+ *   None.
+ *
+ ****************************************************************************/
+
+void tcp_notifier_signal(FAR struct tcp_conn_s *conn)
+{
+  /* This is just a simple wrapper around nxsig_notifier_signal(). */
+
+  return nxsig_notifier_signal(NXSIG_TCP_READAHEAD, conn);
+}
+
+#endif /* CONFIG_TCP_READAHEAD_NOTIFIER */

net/udp/Kconfig

@@ -57,6 +57,18 @@ config NET_UDP_READAHEAD
 	select NET_READAHEAD
 	select MM_IOB
 
+config UDP_READAHEAD_NOTIFIER
+	bool "Support UDP read-ahead notifications"
+	default n
+	select SIG_NOTIFIER
+	depends on NET_UDP_READAHEAD && !DISABLE_POLL
+	---help---
+		Enable building of UDP read-ahead notifier logic that will send a
+		signal to a kernel thread when an UDP read-ahead data has been
+		buffered.  This is is a general purpose notifier, but was developed
+		specifically to support UDP poll() logic where the poll must wait
+		for incoming UDP data to be buffered.
+
 config NET_UDP_WRITE_BUFFERS
 	bool "Enable UDP/IP write buffering"
 	default n

net/udp/Make.defs

@@ -55,6 +55,9 @@ endif
 ifneq ($(CONFIG_DISABLE_POLL),y)
 ifeq ($(CONFIG_NET_UDP_READAHEAD),y)
 SOCK_CSRCS += udp_netpoll.c
+ifeq ($(CONFIG_UDP_READAHEAD_NOTIFIER),y)
+SOCK_CSRCS += udp_notifier.c
+endif
 endif
 endif
 

net/udp/udp.h

@@ -643,6 +643,85 @@ int udp_pollsetup(FAR struct socket *psock, FAR struct pollfd *fds);
 int udp_pollteardown(FAR struct socket *psock, FAR struct pollfd *fds);
 #endif
 
+/****************************************************************************
+ * Name: udp_notifier_setup
+ *
+ * Description:
+ *   Set up to notify the specified PID with the provided signal number.
+ *
+ *   NOTE: To avoid race conditions, the caller should set the sigprocmask
+ *   to block signal delivery.  The signal will be delivered once the
+ *   signal is removed from the sigprocmask.
+ *
+ * Input Parameters:
+ *   pid   - The PID to be notified.  If a zero value is provided, then the
+ *           PID of the calling thread will be used.
+ *   signo - The signal number to use with the notification.
+ *   conn  - The UDP connection where read-ahead data is needed.
+ *
+ * Returned Value:
+ *   > 0   - The signal notification is in place.  The returned value is a
+ *           key that may be used later in a call to
+ *           udp_notifier_teardown().
+ *   == 0  - There is already buffered read-ahead data.  No signal
+ *           notification will be provided.
+ *   < 0   - An unexpected error occurred and no signal will be sent.  The
+ *           returned value is a negated errno value that indicates the
+ *           nature of the failure.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_UDP_READAHEAD_NOTIFIER
+int udp_notifier_setup(int pid, int signo, FAR struct udp_conn_s *conn);
+#endif
+
+/****************************************************************************
+ * Name: udp_notifier_teardown
+ *
+ * Description:
+ *   Eliminate a UDP read-ahead notification previously setup by
+ *   udp_notifier_setup().  This function should only be called if the
+ *   notification should be aborted prior to the notification.  The
+ *   notification will automatically be torn down after the signal is sent.
+ *
+ * Input Parameters:
+ *   key - The key value returned from a previous call to
+ *         udp_notifier_setup().
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; a negated errno value is returned on
+ *   any failure.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_UDP_READAHEAD_NOTIFIER
+int udp_notifier_teardown(int key);
+#endif
+
+/****************************************************************************
+ * Name: udp_notifier_signal
+ *
+ * Description:
+ *   Read-ahead data has been buffered.  Signal all threads waiting for
+ *   read-ahead data to become available.
+ *
+ *   When the read-ahead data becomes available, *all* of the waiters in
+ *   this thread will be signaled.  If there are multiple waiters then only
+ *   the highest priority thread will get the data.  Lower priority threads
+ *   will need to call udp_notifier_setup() once again.
+ *
+ * Input Parameters:
+ *   conn  - The UDP connection where read-ahead data was just buffered.
+ *
+ * Returned Value:
+ *   None.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_UDP_READAHEAD_NOTIFIER
+void udp_notifier_signal(FAR struct udp_conn_s *conn);
+#endif
+
 #undef EXTERN
 #ifdef __cplusplus
 }

net/udp/udp_callback.c

@@ -224,6 +224,14 @@ static uint16_t udp_datahandler(FAR struct net_driver_s *dev, FAR struct udp_con
       return 0;
     }
 
+#ifdef CONFIG_UDP_READAHEAD_NOTIFIER
+  /* Provided notification(s) that additional UDP read-ahead data is
+   * available.
+   */
+
+  udp_notifier_signal(conn);
+#endif
+
   ninfo("Buffered %d bytes\n", buflen);
   return buflen;
 }

net/udp/udp_notifier.c

@@ -0,0 +1,152 @@
+/****************************************************************************
+ * net/udp/udp_notifier.c
+ *
+ *   Copyright (C) 2018 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+
+#include <nuttx/signal.h>
+#include <nuttx/mm/iob.h>
+
+#include "udp/udp.h"
+
+#ifdef CONFIG_UDP_READAHEAD_NOTIFIER
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: udp_notifier_setup
+ *
+ * Description:
+ *   Set up to notify the specified PID with the provided signal number.
+ *
+ *   NOTE: To avoid race conditions, the caller should set the sigprocmask
+ *   to block signal delivery.  The signal will be delivered once the
+ *   signal is removed from the sigprocmask.
+ *
+ * Input Parameters:
+ *   pid   - The PID to be notified.  If a zero value is provided, then the
+ *           PID of the calling thread will be used.
+ *   signo - The signal number to use with the notification.
+ *   conn  - The UDP connection where read-ahead data is needed.
+ *
+ * Returned Value:
+ *   > 0   - The signal notification is in place.  The returned value is a
+ *           key that may be used later in a call to
+ *           udp_notifier_teardown().
+ *   == 0  - There is already buffered read-ahead data.  No signal
+ *           notification will be provided.
+ *   < 0   - An unexpected error occurred and no signal will be sent.  The
+ *           returned value is a negated errno value that indicates the
+ *           nature of the failure.
+ *
+ ****************************************************************************/
+
+int udp_notifier_setup(int pid, int signo, FAR struct udp_conn_s *conn)
+{
+  /* If there is already buffered read-ahead data, then return zero without
+   * setting up the notification.
+   */
+
+  if (conn->readahead.qh_head != NULL)
+    {
+      return 0;
+    }
+
+  /* Otherwise, this is just a simple wrapper around nxsig_notifer_setup(). */
+
+  return nxsig_notifier_setup(pid, signo, NXSIG_UDP_READAHEAD, conn);
+}
+
+/****************************************************************************
+ * Name: udp_notifier_teardown
+ *
+ * Description:
+ *   Eliminate a UDP read-ahead notification previously setup by
+ *   udp_notifier_setup().  This function should only be called if the
+ *   notification should be aborted prior to the notification.  The
+ *   notification will automatically be torn down after the signal is sent.
+ *
+ * Input Parameters:
+ *   key - The key value returned from a previous call to
+ *         udp_notifier_setup().
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; a negated errno value is returned on
+ *   any failure.
+ *
+ ****************************************************************************/
+
+int udp_notifier_teardown(int key)
+{
+  /* This is just a simple wrapper around nxsig_notifier_teardown(). */
+
+  return nxsig_notifier_teardown(key);
+}
+
+/****************************************************************************
+ * Name: udp_notifier_signal
+ *
+ * Description:
+ *   Read-ahead data has been buffered.  Signal all threads waiting for
+ *   read-ahead data to become available.
+ *
+ *   When the read-ahead data becomes available, *all* of the waiters in
+ *   this thread will be signaled.  If there are multiple waiters then only
+ *   the highest priority thread will get the data.  Lower priority threads
+ *   will need to call udp_notifier_setup() once again.
+ *
+ * Input Parameters:
+ *   conn  - The UDP connection where read-ahead data was just buffered.
+ *
+ * Returned Value:
+ *   None.
+ *
+ ****************************************************************************/
+
+void udp_notifier_signal(FAR struct udp_conn_s *conn)
+{
+  /* This is just a simple wrapper around nxsig_notifier_signal(). */
+
+  return nxsig_notifier_signal(NXSIG_UDP_READAHEAD, conn);
+}
+
+#endif /* CONFIG_UDP_READAHEAD_NOTIFIER */