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incubator-nuttx/net/tcp/tcp_appsend.c

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/****************************************************************************
* net/tcp/tcp_appsend.c
*
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (C) 2007-2010, 2014 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 <inttypes.h>
#include <stdint.h>
#include <assert.h>
#include <debug.h>
#include <nuttx/net/netconfig.h>
#include <nuttx/net/netdev.h>
#include <nuttx/net/tcp.h>
#include "devif/devif.h"
#include "tcp/tcp.h"
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: tcp_appsend
*
* Description:
* Handle application or TCP protocol response. If this function is called
* with dev->d_sndlen > 0, then this is an application attempting to send
* packet.
*
* Input Parameters:
* dev - The device driver structure to use in the send operation
* conn - The TCP connection structure holding connection information
* result - App result event sent
*
* Returned Value:
* None
*
* Assumptions:
* The network is locked.
*
****************************************************************************/
void tcp_appsend(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
uint16_t result)
{
uint8_t hdrlen;
ninfo("result: %04x d_sndlen: %d conn->tx_unacked: %" PRId32 "\n",
result, dev->d_sndlen, (uint32_t)conn->tx_unacked);
/* Need to update the recv window? */
if (tcp_should_send_recvwindow(conn))
{
result |= TCP_SNDACK;
#ifdef CONFIG_NET_TCP_DELAYED_ACK
conn->rx_unackseg = 0;
#endif
}
#ifdef CONFIG_NET_TCP_DELAYED_ACK
/* Did the caller request that an ACK be sent? */
else if ((result & TCP_SNDACK) != 0)
{
/* Yes.. Handle delayed acknowledgments */
/* Reset the ACK timer in any event. */
conn->rx_acktimer = 0;
/* Per RFC 1122: "...in a stream of full-sized segments there
* SHOULD be an ACK for at least every second segment."
*
* NOTES:
* 1. If there is a data payload or other flags to be sent with the
* outgoing packet, then we may as well include the ACK too.
* 2. The RFC refers to full-size segments. It is not clear what
* "full-size" means. Does that mean that the payload is the size
* of the MSS? Payload size is not considered other there being
* a payload or or not. Should there be some special action for
* small payloads of size < MSS?
* 3. Experimentation shows that Windows and Linux behave somewhat
* differently; they delay the ACKs for many more segments (6 or
* more). Delaying for more segments would provide less network
* traffic and better performance but seems non-compliant.
*/
if (conn->rx_unackseg > 0 || dev->d_sndlen > 0 ||
result != TCP_SNDACK)
{
/* Reset the delayed ACK state and send the ACK with this packet. */
conn->rx_unackseg = 0;
}
else
{
/* This is only an ACK and there is no pending delayed ACK and
* no TX data is being sent. Indicate that there is one un-ACKed
* segment and don't send anything now.
*/
conn->rx_unackseg = 1;
return;
}
}
/* If there are data to be sent in the same direction as the ACK before
* the second data packet is received and the delay timer expires, the ACK
* is piggybacked with the data segment and sent immediately.
*/
else if (dev->d_sndlen > 0 && conn->rx_unackseg > 0)
{
result |= TCP_SNDACK;
conn->rx_unackseg = 0;
}
#endif
/* Get the IP header length associated with the IP domain configured for
* this TCP connection.
*/
hdrlen = tcpip_hdrsize(conn);
/* Check If the device went down */
if ((result & NETDEV_DOWN) != 0)
{
/* If so, make sure that the connection is marked closed
* and do not try to send anything.
*/
dev->d_sndlen = 0;
conn->tcpstateflags = TCP_CLOSED;
ninfo("TCP state: NETDEV_DOWN\n");
}
/* Check for connection aborted */
else if ((result & TCP_ABORT) != 0)
{
dev->d_sndlen = 0;
conn->tcpstateflags = TCP_CLOSED;
ninfo("TCP state: TCP_CLOSED\n");
tcp_send(dev, conn, TCP_RST | TCP_ACK, hdrlen);
}
/* Check for connection closed */
else if ((result & TCP_CLOSE) != 0)
{
conn->tcpstateflags = TCP_FIN_WAIT_1;
conn->tx_unacked = 1;
conn->nrtx = 0;
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
conn->sndseq_max = tcp_getsequence(conn->sndseq) + 1;
#endif
ninfo("TCP state: TCP_FIN_WAIT_1\n");
dev->d_sndlen = 0;
tcp_send(dev, conn, TCP_FIN | TCP_ACK, hdrlen);
}
/* None of the above */
else
{
/* The application cannot send more than what is allowed by the
* MSS (the minimum of the MSS and the available window).
*/
DEBUGASSERT(dev->d_sndlen <= conn->mss);
#if !defined(CONFIG_NET_TCP_WRITE_BUFFERS) || defined(CONFIG_NET_SENDFILE)
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
if (conn->sendfile)
{
#endif
/* If d_sndlen > 0, the application has data to be sent. */
if (dev->d_sndlen > 0)
{
/* Remember how much data we send out now so that we know
* when everything has been acknowledged. Just increment the
* amount of data sent. This will be needed in sequence number
* calculations and we know that this is not a re-transmission.
* Retransmissions do not go through this path.
*/
conn->tx_unacked += dev->d_sndlen;
}
conn->nrtx = 0;
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
}
#endif
#endif
/* Then handle the rest of the operation just as for the rexmit case */
tcp_rexmit(dev, conn, result);
}
}
/****************************************************************************
* Name: tcp_rexmit
*
* Description:
* Handle application retransmission
*
* Input Parameters:
* dev - The device driver structure to use in the send operation
* conn - The TCP connection structure holding connection information
* result - App result event sent
*
* Returned Value:
* None
*
* Assumptions:
* The network is locked.
*
****************************************************************************/
void tcp_rexmit(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
uint16_t result)
{
uint8_t hdrlen;
ninfo("result: %04x d_sndlen: %d conn->tx_unacked: %" PRId32 "\n",
result, dev->d_sndlen, (uint32_t)conn->tx_unacked);
/* Get the IP header length associated with the IP domain configured for
* this TCP connection.
*/
hdrlen = tcpip_hdrsize(conn);
/* If the application has data to be sent, or if the incoming packet had
* new data in it, we must send out a packet.
*/
#if defined(CONFIG_NET_TCP_WRITE_BUFFERS) && defined(CONFIG_NET_SENDFILE)
if (conn->sendfile)
#endif
{
#if !defined(CONFIG_NET_TCP_WRITE_BUFFERS) || defined(CONFIG_NET_SENDFILE)
if ((result & TCP_REXMIT) != 0 &&
dev->d_sndlen > 0 && conn->tx_unacked > 0 &&
conn->rexmit_seq > 0)
{
uint32_t saveseq;
/* According to RFC 6298 (5.4), retransmit the earliest segment
* that has not been acknowledged by the TCP receiver.
*/
saveseq = tcp_getsequence(conn->sndseq);
tcp_setsequence(conn->sndseq, conn->rexmit_seq);
tcp_send(dev, conn, TCP_ACK | TCP_PSH, dev->d_sndlen + hdrlen);
tcp_setsequence(conn->sndseq, saveseq);
return;
}
#endif
}
#if defined(CONFIG_NET_TCP_WRITE_BUFFERS)
if (dev->d_sndlen > 0)
#else
if (dev->d_sndlen > 0 && conn->tx_unacked > 0)
#endif
{
uint32_t seq;
/* We always set the ACK flag in response packets adding the length of
* the IP and TCP headers.
*/
tcp_send(dev, conn, TCP_ACK | TCP_PSH, dev->d_sndlen + hdrlen);
/* Advance sndseq */
seq = tcp_getsequence(conn->sndseq);
tcp_setsequence(conn->sndseq, seq + dev->d_sndlen);
}
/* If there is no data to send, just send out a pure ACK if one is
* requested.
*/
else if ((result & TCP_SNDACK) != 0)
{
tcp_send(dev, conn, TCP_ACK, hdrlen);
}
/* There is nothing to do -- drop the packet */
else
{
dev->d_len = 0;
}
}
#endif /* CONFIG_NET && CONFIG_NET_TCP */
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