/****************************************************************************
* net/tcp/tcp_timer.c
* Poll for the availability of TCP TX data
*
* Copyright (C) 2007-2010 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Adapted for NuttX from logic in uIP which also has a BSD-like license:
*
* Original author Adam Dunkels <adam@dunkels.com>
* Copyright () 2001-2003, Adam Dunkels.
* All rights reserved.
*
* 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. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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>
#if defined(CONFIG_NET) && defined(CONFIG_NET_TCP)
#include <stdint.h>
#include <debug.h>
#include <nuttx/net/netconfig.h>
#include <nuttx/net/netdev.h>
#include <nuttx/net/netstats.h>
#include <nuttx/net/tcp.h>
#include "devif/devif.h"
#include "tcp/tcp.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Public Variables
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: tcp_timer
*
* Description:
* Handle a TCP timer expiration for the provided TCP connection
*
* Parameters:
* dev - The device driver structure to use in the send operation
* conn - The TCP "connection" to poll for TX data
* hsed - The polling interval in halves of a second
*
* Return:
* None
*
* Assumptions:
* Called from the interrupt level or with interrupts disabled.
*
****************************************************************************/
void tcp_timer(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
int hsec)
{
uint8_t result;
dev->d_snddata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN];
dev->d_appdata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN];
/* Increase the TCP sequence number */
tcp_nextsequence();
/* Reset the length variables. */
dev->d_len = 0;
dev->d_sndlen = 0;
/* Check if the connection is in a state in which we simply wait
* for the connection to time out. If so, we increase the
* connection's timer and remove the connection if it times
* out.
*/
if (conn->tcpstateflags == TCP_TIME_WAIT ||
conn->tcpstateflags == TCP_FIN_WAIT_2)
{
/* Increment the connection timer */
conn->timer += hsec;
if (conn->timer >= TCP_TIME_WAIT_TIMEOUT)
{
conn->tcpstateflags = TCP_CLOSED;
/* Notify upper layers about the timeout */
result = tcp_callback(dev, conn, TCP_TIMEDOUT);
nllvdbg("TCP state: TCP_CLOSED\n");
}
}
else if (conn->tcpstateflags != TCP_CLOSED)
{
/* If the connection has outstanding data, we increase the connection's
* timer and see if it has reached the RTO value in which case we
* retransmit.
*/
if (conn->unacked > 0)
{
/* The connection has outstanding data */
if (conn->timer > hsec)
{
/* Will not yet decrement to zero */
conn->timer -= hsec;
}
else
{
/* Will decrement to zero */
conn->timer = 0;
/* Should we close the connection? */
if (
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
conn->expired > 0 ||
#else
conn->nrtx == TCP_MAXRTX ||
#endif
((conn->tcpstateflags == TCP_SYN_SENT ||
conn->tcpstateflags == TCP_SYN_RCVD) &&
conn->nrtx == TCP_MAXSYNRTX)
)
{
conn->tcpstateflags = TCP_CLOSED;
nllvdbg("TCP state: TCP_CLOSED\n");
/* We call tcp_callback() with TCP_TIMEDOUT to
* inform the application that the connection has
* timed out.
*/
result = tcp_callback(dev, conn, TCP_TIMEDOUT);
/* We also send a reset packet to the remote host. */
tcp_send(dev, conn, TCP_RST | TCP_ACK, IPTCP_HDRLEN);
goto done;
}
/* Exponential backoff. */
conn->timer = TCP_RTO << (conn->nrtx > 4 ? 4: conn->nrtx);
(conn->nrtx)++;
/* Ok, so we need to retransmit. We do this differently
* depending on which state we are in. In ESTABLISHED, we
* call upon the application so that it may prepare the
* data for the retransmit. In SYN_RCVD, we resend the
* SYNACK that we sent earlier and in LAST_ACK we have to
* retransmit our FINACK.
*/
#ifdef CONFIG_NET_STATISTICS
g_netstats.tcp.rexmit++;
#endif
switch (conn->tcpstateflags & TCP_STATE_MASK)
{
case TCP_SYN_RCVD:
/* In the SYN_RCVD state, we should retransmit our
* SYNACK.
*/
tcp_ack(dev, conn, TCP_ACK | TCP_SYN);
goto done;
case TCP_SYN_SENT:
/* In the SYN_SENT state, we retransmit out SYN. */
tcp_ack(dev, conn, TCP_SYN);
goto done;
case TCP_ESTABLISHED:
/* In the ESTABLISHED state, we call upon the application
* to do the actual retransmit after which we jump into
* the code for sending out the packet.
*/
result = tcp_callback(dev, conn, TCP_REXMIT);
tcp_rexmit(dev, conn, result);
goto done;
case TCP_FIN_WAIT_1:
case TCP_CLOSING:
case TCP_LAST_ACK:
/* In all these states we should retransmit a FINACK. */
tcp_send(dev, conn, TCP_FIN | TCP_ACK, IPTCP_HDRLEN);
goto done;
}
}
}
/* The connection does not have outstanding data */
else if ((conn->tcpstateflags & TCP_STATE_MASK) == TCP_ESTABLISHED)
{
/* If there was no need for a retransmission, we poll the
* application for new data.
*/
result = tcp_callback(dev, conn, TCP_POLL);
tcp_appsend(dev, conn, result);
goto done;
}
}
/* Nothing to be done */
dev->d_len = 0;
done:
return;
}
#endif /* CONFIG_NET && CONFIG_NET_TCP */
