/**************************************************************************** * net/tcp/tcp_timer.c * Poll for the availability of TCP TX data * * 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 "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) /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * 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 * hsec - The polling interval in units of halves of a second * * Returned Value: * None * * Assumptions: * The network is locked. * ****************************************************************************/ void tcp_timer(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn, int hsec) { uint16_t result; uint8_t hdrlen; /* 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_ipv4_select() or tcp_ipv6_select() prior to sending any packets. * We will try to set the correct value here basic on the binding of * the connection. */ #ifdef CONFIG_NET_IPv4 #ifdef CONFIG_NET_IPv6 if (conn->domain == PF_INET) #endif { hdrlen = IPv4TCP_HDRLEN; tcp_ipv4_select(dev); } #endif /* CONFIG_NET_IPv4 */ #ifdef CONFIG_NET_IPv6 #ifdef CONFIG_NET_IPv4 else #endif { hdrlen = IPv6TCP_HDRLEN; tcp_ipv6_select(dev); } #endif /* CONFIG_NET_IPv6 */ /* 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) { unsigned int newtimer; /* Increment the connection timer */ newtimer = (unsigned int)conn->timer + hsec; /* Check if the timer exceeds the timeout value */ if (newtimer >= (TCP_TIME_WAIT_TIMEOUT * HSEC_PER_SEC)) { /* Set the timer to the maximum value */ conn->timer = TCP_TIME_WAIT_TIMEOUT * HSEC_PER_SEC; /* The TCP connection was established and, hence, should be bound * to a device. Make sure that the polling device is the one that * we are bound to. * * If not, then we will catch the timeout on the next poll from * the correct device. */ DEBUGASSERT(conn->dev != NULL); if (dev != conn->dev) { ninfo("TCP: TCP_CLOSED pending\n"); } else { conn->tcpstateflags = TCP_CLOSED; /* Notify upper layers about the timeout */ result = tcp_callback(dev, conn, TCP_TIMEDOUT); ninfo("TCP state: TCP_CLOSED\n"); } } else { /* No timeout. Just update the incremented timer */ conn->timer = newtimer; } } 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; /* The TCP is connected and, hence, should be bound to a * device. Make sure that the polling device is the one that * we are bound to. * * If not, then we will catch the timeout on the next poll * from the correct device. */ DEBUGASSERT(conn->dev != NULL); if (dev != conn->dev) { ninfo("TCP: TCP_CLOSED pending\n"); goto done; } /* 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->lport, conn->domain); #else listener = tcp_findlistener(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. */ result = 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 */ tcp_free(conn); goto done; } /* 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 conn->expired > 0 || #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. */ 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, 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_synack(dev, conn, TCP_ACK | TCP_SYN); goto done; case TCP_SYN_SENT: /* In the SYN_SENT state, we retransmit out SYN. */ 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); 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, 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) { /* The TCP connection is established and, hence, should be bound * to a device. Make sure that the polling device is the one that * we are bound to. */ DEBUGASSERT(conn->dev != NULL); if (dev == conn->dev) { #ifdef CONFIG_NET_TCP_KEEPALIVE /* Is this an established connected with KeepAlive enabled? */ if (conn->keepalive) { socktimeo_t timeo; uint32_t saveseq; /* If this is the first probe, then the keepstart time is * the time that the last ACK or data was received from the * remote. * * On subsequent retries, keepstart is the time that the * last probe was sent. */ if (conn->keepretries > 0) { timeo = (socktimeo_t)conn->keepintvl; } else { timeo = (socktimeo_t)conn->keepidle; } /* Yes... has the idle period elapsed with no data or ACK * received from the remote peer? */ if (net_timeo(conn->keeptime, timeo)) { /* 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 { unsigned int tcpiplen; /* No.. we need to send another probe. * Get the size of the IP and TCP header. */ #ifdef CONFIG_NET_IPv4 #ifdef CONFIG_NET_IPv6 if (conn->domain == PF_INET) #endif { tcpiplen = IPv4_HDRLEN + TCP_HDRLEN; } #endif #ifdef CONFIG_NET_IPv6 #ifdef CONFIG_NET_IPv4 else #endif { tcpiplen = IPv6_HDRLEN + TCP_HDRLEN; } #endif /* And send the probe (along with a garbage byte). * The packet we sned 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. * - The data payload is one or two bytes. * * tcp_send() will send the TCP sequence number as * conn->sndseq. Rather than creating a new * interface, we spoof tcp_end() here: */ saveseq = tcp_getsequence(conn->sndseq); tcp_setsequence(conn->sndseq, saveseq - 1); tcp_send(dev, conn, TCP_ACK, tcpiplen + 1); tcp_setsequence(conn->sndseq, saveseq); /* Increment the number of un-ACKed bytes due to * the dummy byte that we just sent. */ conn->tx_unacked++; #ifdef CONFIG_NET_TCP_WRITE_BUFFERS /* Increment the un-ACKed sequence number */ conn->sndseq_max++; #endif /* Update for the next probe */ conn->keeptime = clock_systime_ticks(); conn->keepretries++; } goto done; } } #endif #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: return; } #endif /* CONFIG_NET && CONFIG_NET_TCP */