/**************************************************************************** * 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 * * Adapted for NuttX from logic in uIP which also has a BSD-like license: * * Original author Adam Dunkels * 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 #if defined(CONFIG_NET) && defined(CONFIG_NET_TCP) #include #include #include #include #include #include #include #include #include #include #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) { timeout = conn->keeptimer; } else if (conn->keeptimer > 0 && timeout > conn->keeptimer) { timeout = conn->keeptimer; } #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) { /* Will not yet decrement to zero */ conn->keeptimer -= 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 */