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incubator-nuttx/net/tcp/tcp_timer.c

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/****************************************************************************
* net/tcp/tcp_timer.c
*
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (C) 2007-2010, 2015-2016, 2018, 2020 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 <assert.h>
#include <debug.h>
#include <time.h>
#include <stdlib.h>
#include <nuttx/net/netconfig.h>
#include <nuttx/net/net.h>
#include <nuttx/net/netdev.h>
#include <nuttx/net/netstats.h>
#include <nuttx/net/tcp.h>
#include "netdev/netdev.h"
#include "devif/devif.h"
#include "socket/socket.h"
#include "tcp/tcp.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Per RFC 1122: "... an ACK should not be excessively delayed; in
* particular, the delay MUST be less than 0.5 seconds ..."
*
* NOTE: We only have 0.5 timing resolution here so the delay will be
* between 0.5 and 1.0 seconds, and may be delayed further, depending on the
* polling rate of the the driver (often 1 second).
*/
#define ACK_DELAY (1)
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: tcp_get_timeout
*
* Description:
* Gets the time of the next timeout
*
* Input Parameters:
* conn - The TCP "connection" to poll for TX data
*
* Returned Value:
* int - The time required for the next expiry (units: half-seconds)
*
* Assumptions:
* conn is not NULL.
* The connection (conn) is bound to the polling device (dev).
*
****************************************************************************/
static int tcp_get_timeout(FAR struct tcp_conn_s *conn)
{
int timeout = conn->timer;
#ifdef CONFIG_NET_TCP_KEEPALIVE
if (timeout == 0)
{
/* The conn->keeptimer units is decisecond and the timeout
* units is half-seconds, therefore they need to be unified.
*/
timeout = conn->keeptimer / DSEC_PER_HSEC;
}
else if (conn->keeptimer > 0 && timeout > conn->keeptimer / DSEC_PER_HSEC)
{
timeout = conn->keeptimer / DSEC_PER_HSEC;
}
#endif
return timeout;
}
/****************************************************************************
* Name: tcp_timer_expiry
*
* Description:
* Handle a TCP timer expiration for the provided TCP connection
* Restart a TCP timer if need to
*
* Input Parameters:
* arg - The TCP "connection" to poll for TX data
*
* Returned Value:
* None
*
* Assumptions:
* arg is not NULL.
* The connection (arg) is bound to the polling device (dev).
*
****************************************************************************/
static void tcp_timer_expiry(FAR void *arg)
{
FAR struct tcp_conn_s *conn = NULL;
net_lock();
while ((conn = tcp_nextconn(conn)) != NULL)
{
if (conn == arg)
{
conn->timeout = true;
netdev_txnotify_dev(conn->dev);
break;
}
}
net_unlock();
}
/****************************************************************************
* Name: tcp_xmit_probe
*
* Description:
* TCP retransmission probe packet
*
* Input Parameters:
* dev - The device driver structure to use in the send operation
* conn - The TCP "connection" to poll for TX data
*
* Returned Value:
* None
*
* Assumptions:
* dev is not NULL.
* conn is not NULL.
*
****************************************************************************/
static void tcp_xmit_probe(FAR struct net_driver_s *dev,
FAR struct tcp_conn_s *conn)
{
/* And send the probe.
* The packet we send must have these properties:
*
* - TCP_ACK flag (only) is set.
* - Sequence number is the sequence number of
* previously ACKed data, i.e., the expected
* sequence number minus one.
*
* tcp_send() will send the TCP sequence number as
* conn->sndseq. Rather than creating a new
* interface, we spoof tcp_end() here:
*/
uint16_t hdrlen = tcpip_hdrsize(conn);
uint32_t saveseq = tcp_getsequence(conn->sndseq);
tcp_setsequence(conn->sndseq, saveseq - 1);
tcp_send(dev, conn, TCP_ACK, hdrlen);
tcp_setsequence(conn->sndseq, saveseq);
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: tcp_update_timer
*
* Description:
* Update the TCP timer for the provided TCP connection,
* The timeout is accurate
*
* Input Parameters:
* conn - The TCP "connection" to poll for TX data
*
* Returned Value:
* None
*
* Assumptions:
* conn is not NULL.
* The connection (conn) is bound to the polling device (dev).
*
****************************************************************************/
void tcp_update_timer(FAR struct tcp_conn_s *conn)
{
sclock_t timeout = tcp_get_timeout(conn);
if (timeout > 0)
{
#ifdef CONFIG_NET_SOLINGER
/* Re-update tcp timeout */
if (conn->ltimeout != 0)
{
sclock_t ticks = conn->ltimeout - clock_systime_ticks();
if (ticks <= 0)
{
timeout = 0;
}
else if (timeout > TICK2HSEC(ticks))
{
timeout = TICK2HSEC(ticks);
}
}
#endif
if (work_available(&conn->work) ||
TICK2HSEC(work_timeleft(&conn->work)) != timeout)
{
work_queue(LPWORK, &conn->work, tcp_timer_expiry,
conn, HSEC2TICK(timeout));
}
}
else
{
work_cancel(LPWORK, &conn->work);
}
}
/****************************************************************************
* Name: tcp_update_retrantimer
*
* Description:
* Update the retransmit TCP timer for the provided TCP connection,
* The timeout is accurate
*
* Input Parameters:
* conn - The TCP "connection" to poll for TX data
* timeout - Time for the next timeout
*
* Returned Value:
* None
*
* Assumptions:
* conn is not NULL.
* The connection (conn) is bound to the polling device (dev).
*
****************************************************************************/
void tcp_update_retrantimer(FAR struct tcp_conn_s *conn, int timeout)
{
conn->timer = timeout;
tcp_update_timer(conn);
}
/****************************************************************************
* Name: tcp_update_keeptimer
*
* Description:
* Update the keeplive TCP timer for the provided TCP connection,
* The timeout is accurate
*
* Input Parameters:
* conn - The TCP "connection" to poll for TX data
* timeout - Time for the next timeout
*
* Returned Value:
* None
*
* Assumptions:
* conn is not NULL.
* The connection (conn) is bound to the polling device (dev).
*
****************************************************************************/
#ifdef CONFIG_NET_TCP_KEEPALIVE
void tcp_update_keeptimer(FAR struct tcp_conn_s *conn, int timeout)
{
conn->keeptimer = timeout;
tcp_update_timer(conn);
}
#endif
/****************************************************************************
* Name: tcp_stop_timer
*
* Description:
* Stop TCP timer for the provided TCP connection
* When the connection is closed
*
* Input Parameters:
* conn - The TCP "connection" to poll for TX data
*
* Returned Value:
* None
*
* Assumptions:
* conn is not NULL.
*
****************************************************************************/
void tcp_stop_timer(FAR struct tcp_conn_s *conn)
{
work_cancel(LPWORK, &conn->work);
}
/****************************************************************************
* Name: tcp_set_zero_probe
*
* Description:
* Update the TCP probe timer for the provided TCP connection,
* The timeout is accurate
*
* Input Parameters:
* conn - The TCP "connection" to poll for TX data
* flags - Set of connection events
*
* Returned Value:
* None
*
* Assumptions:
* conn is not NULL.
*
****************************************************************************/
void tcp_set_zero_probe(FAR struct tcp_conn_s *conn, uint16_t flags)
{
if ((conn->tcpstateflags & TCP_ESTABLISHED) &&
((flags & TCP_NEWDATA) == 0) && conn->tx_unacked <= 0 &&
(flags & (TCP_POLL | TCP_REXMIT | TCP_ACKDATA)) &&
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
!(sq_empty(&conn->write_q)) &&
#endif
!conn->timeout && !conn->zero_probe)
{
tcp_update_retrantimer(conn, TCP_RTO_MIN);
conn->zero_probe = true;
}
}
/****************************************************************************
* Name: tcp_timer
*
* Description:
* Handle a TCP timer expiration for the provided TCP connection
*
* Input Parameters:
* dev - The device driver structure to use in the send operation
* conn - The TCP "connection" to poll for TX data
*
* Returned Value:
* None
*
* Assumptions:
* The network is locked.
* dev is not NULL.
* conn is not NULL.
* The connection (conn) is bound to the polling device (dev).
*
****************************************************************************/
void tcp_timer(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn)
{
int hsec = tcp_get_timeout(conn);
uint16_t result;
uint8_t hdrlen;
/* NOTE: It is important to decrease conn->timer at "hsec" pace,
* not faster. Excessive (false) decrements of conn->timer are not allowed
* here. Otherwise, it breaks TCP timings and leads to TCP spurious
* retransmissions and other issues due to premature timeouts.
*/
DEBUGASSERT(dev != NULL && conn != NULL && dev == conn->dev);
/* Set up for the callback. We can't know in advance if the application
* is going to send a IPv4 or an IPv6 packet, so this setup may not
* actually be used. Furthermore, the TCP logic is required to call
* tcp_ip_select() prior to sending any packets.
* We will try to set the correct value here basic on the binding of
* the connection.
*/
tcp_ip_select(conn);
hdrlen = tcpip_hdrsize(conn);
/* Increase the TCP sequence number */
tcp_nextsequence();
/* Reset the length variables. */
dev->d_len = 0;
dev->d_sndlen = 0;
if (conn->tcpstateflags == TCP_CLOSED)
{
/* Nothing to be done */
return;
}
#ifdef CONFIG_NET_SOLINGER
/* Send reset immediately if linger timeout */
if (conn->ltimeout != 0 &&
((sclock_t)(conn->ltimeout - clock_systime_ticks()) <= 0))
{
conn->tcpstateflags = TCP_CLOSED;
ninfo("TCP state: TCP_CLOSED\n");
/* We call tcp_callback() with TCP_TIMEDOUT to
* inform the application that the connection has
* timed out.
*/
tcp_callback(dev, conn, TCP_TIMEDOUT);
/* We also send a reset packet to the remote host. */
tcp_send(dev, conn, TCP_RST | TCP_ACK, hdrlen);
goto done;
}
else
#endif
/* 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)
{
/* Check if the timer exceeds the timeout value */
if (conn->timer <= hsec)
{
/* Set the timer to zero value */
conn->timer = 0;
conn->tcpstateflags = TCP_CLOSED;
/* Notify upper layers about the timeout */
tcp_callback(dev, conn, TCP_TIMEDOUT);
ninfo("TCP state: TCP_CLOSED\n");
}
else
{
/* No timeout. Just update the decremented timer */
conn->timer -= hsec;
}
}
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->tx_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;
/* Check for a timeout on connection in the TCP_SYN_RCVD state.
* On such timeouts, we would normally resend the SYNACK until
* the ACK is received, completing the 3-way handshake. But if
* the retry count elapsed, then we must assume that no ACK is
* forthcoming and terminate the attempted connection.
*/
if (conn->tcpstateflags == TCP_SYN_RCVD &&
conn->nrtx >= TCP_MAXSYNRTX)
{
FAR struct tcp_conn_s *listener;
conn->tcpstateflags = TCP_CLOSED;
ninfo("TCP state: TCP_SYN_RCVD->TCP_CLOSED\n");
/* Find the listener for this connection. */
#if defined(CONFIG_NET_IPv4) && defined(CONFIG_NET_IPv6)
listener = tcp_findlistener(&conn->u, conn->lport,
conn->domain);
#else
listener = tcp_findlistener(&conn->u, conn->lport);
#endif
if (listener != NULL)
{
/* We call tcp_callback() for the connection with
* TCP_TIMEDOUT to inform the listener that the
* connection has timed out.
*/
tcp_callback(dev, listener, TCP_TIMEDOUT);
}
/* We also send a reset packet to the remote host. */
tcp_send(dev, conn, TCP_RST | TCP_ACK, hdrlen);
/* Finally, we must free this TCP connection structure */
conn->crefs = 0;
tcp_free(conn);
return;
}
/* Otherwise, check for a timeout on an established connection.
* If the retry count is exceeded in this case, we should
* close the connection.
*/
else if (
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
# ifdef CONFIG_NET_SENDFILE
(!conn->sendfile && conn->expired > 0) ||
(conn->sendfile && conn->nrtx >= TCP_MAXRTX) ||
# else
conn->expired > 0 ||
# endif
#else
conn->nrtx >= TCP_MAXRTX ||
#endif
(conn->tcpstateflags == TCP_SYN_SENT &&
conn->nrtx >= TCP_MAXSYNRTX)
)
{
conn->tcpstateflags = TCP_CLOSED;
ninfo("TCP state: TCP_CLOSED\n");
/* We call tcp_callback() with TCP_TIMEDOUT to
* inform the application that the connection has
* timed out.
*/
tcp_callback(dev, conn, TCP_TIMEDOUT);
/* We also send a reset packet to the remote host. */
tcp_send(dev, conn, TCP_RST | TCP_ACK, 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.
*/
#if !defined(CONFIG_NET_TCP_WRITE_BUFFERS)
tcp_setsequence(conn->sndseq, conn->rexmit_seq);
#else
/* REVISIT for the buffered mode */
#endif
tcp_synack(dev, conn, TCP_ACK | TCP_SYN);
goto done;
case TCP_SYN_SENT:
/* In the SYN_SENT state, we retransmit out SYN. */
#if !defined(CONFIG_NET_TCP_WRITE_BUFFERS)
tcp_setsequence(conn->sndseq, conn->rexmit_seq);
#else
/* REVISIT for the buffered mode */
#endif
tcp_synack(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);
#ifdef CONFIG_NET_TCP_CC_NEWRENO
/* If conn is TCP_INFR, it should enter to slow start */
if (conn->flags & TCP_INFR)
{
conn->flags &= ~TCP_INFR;
}
/* update the max_cwnd */
conn->max_cwnd = (conn->max_cwnd + 7 * conn->cwnd) >> 3;
/* reset cwnd and ssthresh, refers to RFC5861. */
conn->ssthresh =
MAX(conn->tx_unacked / 2, 2 * conn->mss);
conn->cwnd = conn->mss;
#endif
goto done;
case TCP_FIN_WAIT_1:
case TCP_CLOSING:
case TCP_LAST_ACK:
/* In all these states we should retransmit a FINACK. */
#if !defined(CONFIG_NET_TCP_WRITE_BUFFERS)
tcp_setsequence(conn->sndseq, conn->rexmit_seq);
#else
/* REVISIT for the buffered mode */
#endif
tcp_send(dev, conn, TCP_FIN | TCP_ACK, hdrlen);
goto done;
}
}
}
/* The connection does not have outstanding data. Check if the TCP
* connection has been established.
*/
else if ((conn->tcpstateflags & TCP_STATE_MASK) == TCP_ESTABLISHED)
{
#ifdef CONFIG_NET_TCP_KEEPALIVE
/* Is this an established connected with KeepAlive enabled? */
if (conn->keepalive)
{
/* Yes... has the idle period elapsed with no data or ACK
* received from the remote peer?
*/
if (conn->keeptimer > hsec * DSEC_PER_HSEC)
{
/* Will not yet decrement to zero */
conn->keeptimer -= hsec * DSEC_PER_HSEC;
}
else
{
/* Yes.. Has the retry count expired? */
if (conn->keepretries >= conn->keepcnt)
{
/* Yes... stop the network monitor, closing the
* connection and all sockets associated with the
* connection.
*/
tcp_stop_monitor(conn, TCP_ABORT);
}
else
{
tcp_xmit_probe(dev, conn);
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
/* Increment the un-ACKed sequence number */
conn->sndseq_max++;
#endif
/* Update for the next probe */
conn->keeptimer = conn->keepintvl;
conn->keepretries++;
}
goto done;
}
}
#endif
/* Is this an established connected with
* Zero window probe enabled?
*/
if (conn->zero_probe)
{
if (conn->timer > hsec)
{
/* Will not yet decrement to zero */
conn->timer -= hsec;
}
else
{
/* Yes.. Has the retry count expired? */
if (conn->nrtx >= TCP_MAXRTX)
{
/* Yes... stop the network monitor, closing the
* connection and all sockets associated with the
* connection.
*/
conn->zero_probe = false;
tcp_stop_monitor(conn, TCP_ABORT);
}
else
{
tcp_xmit_probe(dev, conn);
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
/* Increment the un-ACKed sequence number */
conn->sndseq_max++;
#endif
/* Update for the next probe */
conn->nrtx++;
conn->timer = MIN((TCP_RTO_MIN << conn->nrtx),
TCP_RTO_MAX);
}
goto done;
}
}
#ifdef CONFIG_NET_TCP_DELAYED_ACK
/* Handle delayed acknowledgments. Is there a segment with a
* delayed acknowledgment?
*/
if (conn->rx_unackseg > 0)
{
/* Increment the ACK delay. */
conn->rx_acktimer += hsec;
/* Per RFC 1122: "...an ACK should not be excessively
* delayed; in particular, the delay must be less than
* 0.5 seconds..."
*/
if (conn->rx_acktimer >= ACK_DELAY)
{
/* Reset the delayed ACK state and send the ACK
* packet.
*/
conn->rx_unackseg = 0;
conn->rx_acktimer = 0;
tcp_synack(dev, conn, TCP_ACK);
goto done;
}
}
#endif
/* There was no need for a retransmission and there was no
* need to probe the remote peer and there was no need to
* send a delayed ACK. We poll the application for new
* outgoing data.
*/
result = tcp_callback(dev, conn, TCP_POLL);
tcp_appsend(dev, conn, result);
goto done;
}
}
/* Nothing to be done */
dev->d_len = 0;
done:
tcp_update_timer(conn);
}
#endif /* CONFIG_NET && CONFIG_NET_TCP */
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