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nuttx/net/tcp/tcp_input.c

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/****************************************************************************
* net/tcp/tcp_input.c
* Handling incoming TCP input
*
* Copyright (C) 2007-2014, 2017-2018 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 <string.h>
#include <assert.h>
#include <debug.h>
#include <nuttx/clock.h>
#include <nuttx/net/netconfig.h>
#include <nuttx/net/netdev.h>
#include <nuttx/net/netstats.h>
#include <nuttx/net/ip.h>
#include <nuttx/net/tcp.h>
#include "devif/devif.h"
#include "utils/utils.h"
#include "tcp/tcp.h"
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: tcp_input
*
* Description:
* Handle incoming TCP input
*
* Input Parameters:
* dev - The device driver structure containing the received TCP packet.
* domain - IP domain (PF_INET or PF_INET6)
* iplen - Lngth of the IP header (IPv4_HDRLEN or IPv6_HDRLEN).
*
* Returned Value:
* None
*
* Assumptions:
* The network is locked.
*
****************************************************************************/
static void tcp_input(FAR struct net_driver_s *dev, uint8_t domain,
unsigned int iplen)
{
FAR struct tcp_hdr_s *tcp;
FAR struct tcp_conn_s *conn = NULL;
unsigned int tcpiplen;
unsigned int hdrlen;
uint16_t tmp16;
uint16_t flags;
uint16_t result;
uint8_t opt;
int len;
int i;
#ifdef CONFIG_NET_STATISTICS
/* Bump up the count of TCP packets received */
g_netstats.tcp.recv++;
#endif
/* Get a pointer to the TCP header. The TCP header lies just after the
* the link layer header and the IP header.
*/
tcp = (FAR struct tcp_hdr_s *)&dev->d_buf[iplen + NET_LL_HDRLEN(dev)];
/* Get the size of the IP header and the TCP header.
*
* REVISIT: TCP header is *not* a constant! It can be larger if the
* TCP header includes options. The constant TCP_HDRLEN should be
* replaced with the macro TCP_OPT_HDRLEN(n) which will calculate the
* correct header length in all cases.
*/
tcpiplen = iplen + TCP_HDRLEN;
/* Get the size of the link layer header, the IP header, and the TCP header */
hdrlen = tcpiplen + NET_LL_HDRLEN(dev);
/* Start of TCP input header processing code. */
if (tcp_chksum(dev) != 0xffff)
{
/* Compute and check the TCP checksum. */
#ifdef CONFIG_NET_STATISTICS
g_netstats.tcp.drop++;
g_netstats.tcp.chkerr++;
#endif
nwarn("WARNING: Bad TCP checksum\n");
goto drop;
}
/* Demultiplex this segment. First check any active connections. */
conn = tcp_active(dev, tcp);
if (conn)
{
/* We found an active connection.. Check for the subsequent SYN
* arriving in TCP_SYN_RCVD state after the SYNACK packet was
* lost. To avoid other issues, reset any active connection
* where a SYN arrives in a state != TCP_SYN_RCVD.
*/
if ((conn->tcpstateflags & TCP_STATE_MASK) != TCP_SYN_RCVD &&
(tcp->flags & TCP_CTL) == TCP_SYN)
{
nwarn("WARNING: SYN in TCP_SYN_RCVD\n");
goto reset;
}
else
{
goto found;
}
}
/* If we didn't find an active connection that expected the packet,
* either (1) this packet is an old duplicate, or (2) this is a SYN packet
* destined for a connection in LISTEN. If the SYN flag isn't set,
* it is an old packet and we send a RST.
*/
if ((tcp->flags & TCP_CTL) == TCP_SYN)
{
/* This is a SYN packet for a connection. Find the connection
* listening on this port.
*/
tmp16 = tcp->destport;
#if defined(CONFIG_NET_IPv4) && defined(CONFIG_NET_IPv6)
if (tcp_islistener(tmp16, domain))
#else
if (tcp_islistener(tmp16))
#endif
{
/* We matched the incoming packet with a connection in LISTEN.
* We now need to create a new connection and send a SYNACK in
* response.
*/
/* First allocate a new connection structure and see if there is any
* user application to accept it.
*/
conn = tcp_alloc_accept(dev, tcp);
if (conn)
{
/* The connection structure was successfully allocated and has
* been initialized in the TCP_SYN_RECVD state. The expected
* sequence of events is then the rest of the 3-way handshake:
*
* 1. We just received a TCP SYN packet from a remote host.
* 2. We will send the SYN-ACK response below (perhaps
* repeatedly in the event of a timeout)
* 3. Then we expect to receive an ACK from the remote host
* indicated the TCP socket connection is ESTABLISHED.
*
* Possible failure:
*
* 1. The ACK is never received. This will be handled by
* a timeout managed by tcp_timer().
* 2. The listener "unlistens()". This will be handled by
* the failure of tcp_accept_connection() when the ACK is
* received.
*/
conn->crefs = 1;
}
if (!conn)
{
/* Either (1) all available connections are in use, or (2)
* there is no application in place to accept the connection.
* We drop packet and hope that the remote end will retransmit
* the packet at a time when we have more spare connections
* or someone waiting to accept the connection.
*/
#ifdef CONFIG_NET_STATISTICS
g_netstats.tcp.syndrop++;
#endif
nerr("ERROR: No free TCP connections\n");
goto drop;
}
net_incr32(conn->rcvseq, 1);
/* Parse the TCP MSS option, if present. */
if ((tcp->tcpoffset & 0xf0) > 0x50)
{
for (i = 0; i < ((tcp->tcpoffset >> 4) - 5) << 2 ; )
{
opt = dev->d_buf[hdrlen + i];
if (opt == TCP_OPT_END)
{
/* End of options. */
break;
}
else if (opt == TCP_OPT_NOOP)
{
/* NOP option. */
++i;
}
else if (opt == TCP_OPT_MSS &&
dev->d_buf[hdrlen + 1 + i] == TCP_OPT_MSS_LEN)
{
uint16_t tcp_mss = TCP_MSS(dev, iplen);
/* An MSS option with the right option length. */
tmp16 = ((uint16_t)dev->d_buf[hdrlen + 2 + i] << 8) |
(uint16_t)dev->d_buf[hdrlen + 3 + i];
conn->mss = tmp16 > tcp_mss ? tcp_mss : tmp16;
/* And we are done processing options. */
break;
}
else
{
/* All other options have a length field, so that we easily
* can skip past them.
*/
if (dev->d_buf[hdrlen + 1 + i] == 0)
{
/* If the length field is zero, the options are malformed
* and we don't process them further.
*/
break;
}
i += dev->d_buf[hdrlen + 1 + i];
}
}
}
/* Our response will be a SYNACK. */
tcp_ack(dev, conn, TCP_ACK | TCP_SYN);
return;
}
}
nwarn("WARNING: SYN with no listener (or old packet) .. reset\n");
/* This is (1) an old duplicate packet or (2) a SYN packet but with
* no matching listener found. Send RST packet in either case.
*/
reset:
/* We do not send resets in response to resets. */
if ((tcp->flags & TCP_RST) != 0)
{
goto drop;
}
#ifdef CONFIG_NET_STATISTICS
g_netstats.tcp.synrst++;
#endif
tcp_reset(dev);
return;
found:
/* Update the connection's window size */
conn->winsize = ((uint16_t)tcp->wnd[0] << 8) + (uint16_t)tcp->wnd[1];
flags = 0;
/* We do a very naive form of TCP reset processing; we just accept
* any RST and kill our connection. We should in fact check if the
* sequence number of this reset is within our advertised window
* before we accept the reset.
*/
if ((tcp->flags & TCP_RST) != 0)
{
FAR struct tcp_conn_s *listener = NULL;
/* An RST received during the 3-way connection handshake requires
* little more clean-up.
*/
if ((conn->tcpstateflags & TCP_STATE_MASK) == TCP_SYN_RCVD)
{
conn->tcpstateflags = TCP_CLOSED;
nwarn("WARNING: RESET in TCP_SYN_RCVD\n");
/* Notify the listener for the connection of the reset event */
#if defined(CONFIG_NET_IPv4) && defined(CONFIG_NET_IPv6)
listener = tcp_findlistener(conn->lport, domain);
#else
listener = tcp_findlistener(conn->lport);
#endif
/* We must free this TCP connection structure; this connection
* will never be established. There should only be one reference
* on this connection when we allocated for the connection.
*/
DEBUGASSERT(conn->crefs == 1);
conn->crefs = 0;
tcp_free(conn);
}
else
{
conn->tcpstateflags = TCP_CLOSED;
nwarn("WARNING: RESET TCP state: TCP_CLOSED\n");
/* Notify this connection of the reset event */
listener = conn;
}
/* Perform the TCP_ABORT callback and drop the packet */
if (listener != NULL)
{
(void)tcp_callback(dev, listener, TCP_ABORT);
}
goto drop;
}
/* Calculated the length of the data, if the application has sent
* any data to us.
*/
len = (tcp->tcpoffset >> 4) << 2;
/* d_len will contain the length of the actual TCP data. This is
* calculated by subtracting the length of the TCP header (in
* len) and the length of the IP header.
*/
dev->d_len -= (len + iplen);
#ifdef CONFIG_NET_TCP_KEEPALIVE
/* Check for a to KeepAlive probes. These packets have these properties:
*
* - TCP_ACK flag is set. SYN/FIN/RST never appear in a Keepalive probe.
* - 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.
*
* We would expect a KeepAlive only in the ESTABLISHED state and only after
* some time has elapsed with no network activity. If there is un-ACKed data,
* then we will let the normal TCP re-transmission logic handle that case.
*/
if ((tcp->flags & TCP_ACK) != 0 &&
(tcp->flags & (TCP_SYN | TCP_FIN | TCP_RST)) == 0 &&
(conn->tcpstateflags & TCP_STATE_MASK) == TCP_ESTABLISHED &&
(dev->d_len == 0 || dev->d_len == 1) &&
conn->unacked <= 0)
{
uint32_t ackseq;
uint32_t rcvseq;
/* Get the sequence number of that has just been acknowledged by this
* incoming packet.
*/
ackseq = tcp_getsequence(tcp->seqno);
rcvseq = tcp_getsequence(conn->rcvseq);
if (ackseq < rcvseq)
{
if (dev->d_len > 0)
{
/* Increment the received sequence number (perhaps including the
* discarded dummy byte in the probe).
*/
net_incr32(conn->rcvseq, dev->d_len);
}
/* And send a "normal" acknowledgment of the KeepAlive probe */
tcp_send(dev, conn, TCP_ACK, tcpiplen);
return;
}
}
#endif
/* Check if the sequence number of the incoming packet is what we are
* expecting next. If not, we send out an ACK with the correct numbers
* in, unless we are in the SYN_RCVD state and receive a SYN, in which
* case we should retransmit our SYNACK (which is done further down).
*/
if (!((((conn->tcpstateflags & TCP_STATE_MASK) == TCP_SYN_SENT) &&
((tcp->flags & TCP_CTL) == (TCP_SYN | TCP_ACK))) ||
(((conn->tcpstateflags & TCP_STATE_MASK) == TCP_SYN_RCVD) &&
((tcp->flags & TCP_CTL) == TCP_SYN))))
{
if ((dev->d_len > 0 || ((tcp->flags & (TCP_SYN | TCP_FIN)) != 0)) &&
memcmp(tcp->seqno, conn->rcvseq, 4) != 0)
{
tcp_send(dev, conn, TCP_ACK, tcpiplen);
return;
}
}
/* Check if the incoming segment acknowledges any outstanding data. If so,
* we update the sequence number, reset the length of the outstanding
* data, calculate RTT estimations, and reset the retransmission timer.
*/
if ((tcp->flags & TCP_ACK) != 0 && conn->unacked > 0)
{
uint32_t unackseq;
uint32_t ackseq;
/* The next sequence number is equal to the current sequence
* number (sndseq) plus the size of the outstanding, unacknowledged
* data (unacked).
*/
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
unackseq = conn->sndseq_max;
#else
unackseq = tcp_addsequence(conn->sndseq, conn->unacked);
#endif
/* Get the sequence number of that has just been acknowledged by this
* incoming packet.
*/
ackseq = tcp_getsequence(tcp->ackno);
/* Check how many of the outstanding bytes have been acknowledged. For
* most send operations, this should always be true. However,
* the send() API sends data ahead when it can without waiting for
* the ACK. In this case, the 'ackseq' could be less than then the
* new sequence number.
*/
if (ackseq <= unackseq)
{
/* Calculate the new number of outstanding, unacknowledged bytes */
conn->unacked = unackseq - ackseq;
}
else
{
/* What would it mean if ackseq > unackseq? The peer has ACKed
* more bytes than we think we have sent? Someone has lost it.
* Complain and reset the number of outstanding, unacknowledged
* bytes
*/
if ((conn->tcpstateflags & TCP_STATE_MASK) == TCP_ESTABLISHED)
{
nwarn("WARNING: ackseq > unackseq\n");
nwarn(" sndseq=%u unacked=%u unackseq=%u ackseq=%u\n",
tcp_getsequence(conn->sndseq), conn->unacked, unackseq,
ackseq);
conn->unacked = 0;
}
}
/* Update sequence number to the unacknowledge sequence number. If
* there is still outstanding, unacknowledged data, then this will
* be beyond ackseq.
*/
ninfo("sndseq: %08x->%08x unackseq: %08x new unacked: %d\n",
conn->sndseq, ackseq, unackseq, conn->unacked);
tcp_setsequence(conn->sndseq, ackseq);
/* Do RTT estimation, unless we have done retransmissions. */
if (conn->nrtx == 0)
{
signed char m;
m = conn->rto - conn->timer;
/* This is taken directly from VJs original code in his paper */
m = m - (conn->sa >> 3);
conn->sa += m;
if (m < 0)
{
m = -m;
}
m = m - (conn->sv >> 2);
conn->sv += m;
conn->rto = (conn->sa >> 3) + conn->sv;
}
/* Set the acknowledged flag. */
flags |= TCP_ACKDATA;
/* Reset the retransmission timer. */
conn->timer = conn->rto;
}
/* Do different things depending on in what state the connection is. */
switch (conn->tcpstateflags & TCP_STATE_MASK)
{
/* CLOSED and LISTEN are not handled here. CLOSE_WAIT is not
* implemented, since we force the application to close when the
* peer sends a FIN (hence the application goes directly from
* ESTABLISHED to LAST_ACK).
*/
case TCP_SYN_RCVD:
/* In SYN_RCVD we have sent out a SYNACK in response to a SYN, and
* we are waiting for an ACK that acknowledges the data we sent
* out the last time. Therefore, we want to have the TCP_ACKDATA
* flag set. If so, we enter the ESTABLISHED state.
*/
if ((flags & TCP_ACKDATA) != 0)
{
/* The three way handshake is complete and the TCP connection
* is now in the ESTABLISHED state.
*/
conn->tcpstateflags = TCP_ESTABLISHED;
/* Wake up any listener waiting for a connection on this port */
if (tcp_accept_connection(dev, conn, tcp->destport) != OK)
{
/* No more listener for current port. We can free conn here
* because it has not been shared with upper layers yet as
* handshake is not complete
*/
nwarn("WARNING: Listen canceled while waiting for ACK on port %d\n",
tcp->destport);
/* Free the connection structure */
conn->crefs = 0;
tcp_free(conn);
conn = NULL;
/* And send a reset packet to the remote host. */
goto reset;
}
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
conn->isn = tcp_getsequence(tcp->ackno);
tcp_setsequence(conn->sndseq, conn->isn);
conn->sent = 0;
conn->sndseq_max = 0;
#endif
conn->unacked = 0;
flags = TCP_CONNECTED;
ninfo("TCP state: TCP_ESTABLISHED\n");
if (dev->d_len > 0)
{
flags |= TCP_NEWDATA;
net_incr32(conn->rcvseq, dev->d_len);
}
dev->d_sndlen = 0;
result = tcp_callback(dev, conn, flags);
tcp_appsend(dev, conn, result);
return;
}
/* We need to retransmit the SYNACK */
if ((tcp->flags & TCP_CTL) == TCP_SYN)
{
tcp_ack(dev, conn, TCP_ACK | TCP_SYN);
return;
}
goto drop;
case TCP_SYN_SENT:
/* In SYN_SENT, we wait for a SYNACK that is sent in response to
* our SYN. The rcvseq is set to sequence number in the SYNACK
* plus one, and we send an ACK. We move into the ESTABLISHED
* state.
*/
if ((flags & TCP_ACKDATA) != 0 && (tcp->flags & TCP_CTL) == (TCP_SYN | TCP_ACK))
{
/* Parse the TCP MSS option, if present. */
if ((tcp->tcpoffset & 0xf0) > 0x50)
{
for (i = 0; i < ((tcp->tcpoffset >> 4) - 5) << 2 ; )
{
opt = dev->d_buf[hdrlen + i];
if (opt == TCP_OPT_END)
{
/* End of options. */
break;
}
else if (opt == TCP_OPT_NOOP)
{
/* NOP option. */
++i;
}
else if (opt == TCP_OPT_MSS &&
dev->d_buf[hdrlen + 1 + i] == TCP_OPT_MSS_LEN)
{
uint16_t tcp_mss = TCP_MSS(dev, iplen);
/* An MSS option with the right option length. */
tmp16 =
(dev->d_buf[hdrlen + 2 + i] << 8) |
dev->d_buf[hdrlen + 3 + i];
conn->mss = tmp16 > tcp_mss ? tcp_mss : tmp16;
/* And we are done processing options. */
break;
}
else
{
/* All other options have a length field, so that we
* easily can skip past them.
*/
if (dev->d_buf[hdrlen + 1 + i] == 0)
{
/* If the length field is zero, the options are
* malformed and we don't process them further.
*/
break;
}
i += dev->d_buf[hdrlen + 1 + i];
}
}
}
conn->tcpstateflags = TCP_ESTABLISHED;
memcpy(conn->rcvseq, tcp->seqno, 4);
net_incr32(conn->rcvseq, 1);
conn->unacked = 0;
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
conn->isn = tcp_getsequence(tcp->ackno);
tcp_setsequence(conn->sndseq, conn->isn);
#endif
dev->d_len = 0;
dev->d_sndlen = 0;
ninfo("TCP state: TCP_ESTABLISHED\n");
result = tcp_callback(dev, conn, TCP_CONNECTED | TCP_NEWDATA);
tcp_appsend(dev, conn, result);
return;
}
/* Inform the application that the connection failed */
(void)tcp_callback(dev, conn, TCP_ABORT);
/* The connection is closed after we send the RST */
conn->tcpstateflags = TCP_CLOSED;
ninfo("Connection failed - TCP state: TCP_CLOSED\n");
/* We do not send resets in response to resets. */
if ((tcp->flags & TCP_RST) != 0)
{
goto drop;
}
tcp_reset(dev);
return;
case TCP_ESTABLISHED:
/* In the ESTABLISHED state, we call upon the application to feed
* data into the d_buf. If the TCP_ACKDATA flag is set, the
* application should put new data into the buffer, otherwise we are
* retransmitting an old segment, and the application should put that
* data into the buffer.
*
* If the incoming packet is a FIN, we should close the connection on
* this side as well, and we send out a FIN and enter the LAST_ACK
* state. We require that there is no outstanding data; otherwise the
* sequence numbers will be screwed up.
*/
if ((tcp->flags & TCP_FIN) != 0 && (conn->tcpstateflags & TCP_STOPPED) == 0)
{
/* Needs to be investigated further.
* Windows often sends FIN packets together with the last ACK for
* the received data. So the socket layer has to get this ACK even
* if the connection is going to be closed.
*/
#if 0
if (conn->unacked > 0)
{
goto drop;
}
#endif
/* Update the sequence number and indicate that the connection has
* been closed.
*/
net_incr32(conn->rcvseq, dev->d_len + 1);
flags |= TCP_CLOSE;
if (dev->d_len > 0)
{
flags |= TCP_NEWDATA;
}
(void)tcp_callback(dev, conn, flags);
conn->tcpstateflags = TCP_LAST_ACK;
conn->unacked = 1;
conn->nrtx = 0;
ninfo("TCP state: TCP_LAST_ACK\n");
tcp_send(dev, conn, TCP_FIN | TCP_ACK, tcpiplen);
return;
}
/* Check the URG flag. If this is set, the segment carries urgent
* data that we must pass to the application.
*/
if ((tcp->flags & TCP_URG) != 0)
{
#ifdef CONFIG_NET_TCPURGDATA
dev->d_urglen = (tcp->urgp[0] << 8) | tcp->urgp[1];
if (dev->d_urglen > dev->d_len)
{
/* There is more urgent data in the next segment to come. */
dev->d_urglen = dev->d_len;
}
net_incr32(conn->rcvseq, dev->d_urglen);
dev->d_len -= dev->d_urglen;
dev->d_urgdata = dev->d_appdata;
dev->d_appdata += dev->d_urglen;
}
else
{
dev->d_urglen = 0;
#else /* CONFIG_NET_TCPURGDATA */
dev->d_appdata = ((FAR uint8_t *)dev->d_appdata) + ((tcp->urgp[0] << 8) |
tcp->urgp[1]);
dev->d_len -= (tcp->urgp[0] << 8) | tcp->urgp[1];
#endif /* CONFIG_NET_TCPURGDATA */
}
#ifdef CONFIG_NET_TCP_KEEPALIVE
/* If the established socket receives an ACK or any kind of data
* from the remote peer (whether we accept it or not), then reset
* the keep alive timer.
*/
if (conn->keepalive && (dev->d_len > 0 || (tcp->flags & TCP_ACK) != 0))
{
/* Reset the last known "alive" time.
*
* REVISIT: At this level, we don't actually know if keep-
* alive is enabled for this connection.
*/
conn->keeptime = clock_systimer();
conn->keepretries = 0;
}
#endif
/* If d_len > 0 we have TCP data in the packet, and we flag this
* by setting the TCP_NEWDATA flag. If the application has stopped
* the data flow using TCP_STOPPED, we must not accept any data
* packets from the remote host.
*/
if (dev->d_len > 0 && (conn->tcpstateflags & TCP_STOPPED) == 0)
{
flags |= TCP_NEWDATA;
}
/* If this packet constitutes an ACK for outstanding data (flagged
* by the TCP_ACKDATA flag), we should call the application since it
* might want to send more data. If the incoming packet had data
* from the peer (as flagged by the TCP_NEWDATA flag), the
* application must also be notified.
*
* When the application is called, the d_len field
* contains the length of the incoming data. The application can
* access the incoming data through the global pointer
* d_appdata, which usually points hdrlen bytes into the d_buf
* array.
*
* If the application wishes to send any data, this data should be
* put into the d_appdata and the length of the data should be
* put into d_len. If the application don't have any data to
* send, d_len must be set to 0.
*/
if ((flags & (TCP_NEWDATA | TCP_ACKDATA)) != 0)
{
/* Clear sndlen and remember the size in d_len. The application
* may modify d_len and we will need this value later when we
* update the sequence number.
*/
dev->d_sndlen = 0;
len = dev->d_len;
/* Provide the packet to the application */
result = tcp_callback(dev, conn, flags);
/* If the application successfully handled the incoming data,
* then TCP_SNDACK will be set in the result. In this case,
* we need to update the sequence number. The ACK will be
* send by tcp_appsend().
*/
if ((result & TCP_SNDACK) != 0)
{
/* Update the sequence number using the saved length */
net_incr32(conn->rcvseq, len);
}
/* Send the response, ACKing the data or not, as appropriate */
tcp_appsend(dev, conn, result);
return;
}
goto drop;
case TCP_LAST_ACK:
/* We can close this connection if the peer has acknowledged our
* FIN. This is indicated by the TCP_ACKDATA flag.
*/
if ((flags & TCP_ACKDATA) != 0)
{
conn->tcpstateflags = TCP_CLOSED;
ninfo("TCP_LAST_ACK TCP state: TCP_CLOSED\n");
(void)tcp_callback(dev, conn, TCP_CLOSE);
}
break;
case TCP_FIN_WAIT_1:
/* The application has closed the connection, but the remote host
* hasn't closed its end yet. Thus we stay in the FIN_WAIT_1 state
* until we receive a FIN from the remote.
*/
if (dev->d_len > 0)
{
net_incr32(conn->rcvseq, dev->d_len);
}
if ((tcp->flags & TCP_FIN) != 0)
{
if ((flags & TCP_ACKDATA) != 0)
{
conn->tcpstateflags = TCP_TIME_WAIT;
conn->timer = 0;
conn->unacked = 0;
ninfo("TCP state: TCP_TIME_WAIT\n");
}
else
{
conn->tcpstateflags = TCP_CLOSING;
ninfo("TCP state: TCP_CLOSING\n");
}
net_incr32(conn->rcvseq, 1);
(void)tcp_callback(dev, conn, TCP_CLOSE);
tcp_send(dev, conn, TCP_ACK, tcpiplen);
return;
}
else if ((flags & TCP_ACKDATA) != 0)
{
conn->tcpstateflags = TCP_FIN_WAIT_2;
conn->unacked = 0;
ninfo("TCP state: TCP_FIN_WAIT_2\n");
goto drop;
}
if (dev->d_len > 0)
{
tcp_send(dev, conn, TCP_ACK, tcpiplen);
return;
}
goto drop;
case TCP_FIN_WAIT_2:
if (dev->d_len > 0)
{
net_incr32(conn->rcvseq, dev->d_len);
}
if ((tcp->flags & TCP_FIN) != 0)
{
conn->tcpstateflags = TCP_TIME_WAIT;
conn->timer = 0;
ninfo("TCP state: TCP_TIME_WAIT\n");
net_incr32(conn->rcvseq, 1);
(void)tcp_callback(dev, conn, TCP_CLOSE);
tcp_send(dev, conn, TCP_ACK, tcpiplen);
return;
}
if (dev->d_len > 0)
{
tcp_send(dev, conn, TCP_ACK, tcpiplen);
return;
}
goto drop;
case TCP_TIME_WAIT:
tcp_send(dev, conn, TCP_ACK, tcpiplen);
return;
case TCP_CLOSING:
if ((flags & TCP_ACKDATA) != 0)
{
conn->tcpstateflags = TCP_TIME_WAIT;
conn->timer = 0;
ninfo("TCP state: TCP_TIME_WAIT\n");
}
default:
break;
}
drop:
dev->d_len = 0;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: tcp_ipv4_input
*
* Description:
* Handle incoming TCP input with IPv4 header
*
* Input Parameters:
* dev - The device driver structure containing the received TCP packet.
*
* Returned Value:
* None
*
* Assumptions:
* Called from the Ethernet driver with the network stack locked
*
****************************************************************************/
#ifdef CONFIG_NET_IPv4
void tcp_ipv4_input(FAR struct net_driver_s *dev)
{
/* Configure to receive an TCP IPv4 packet */
tcp_ipv4_select(dev);
/* Then process in the TCP IPv4 input */
tcp_input(dev, PF_INET, IPv4_HDRLEN);
}
#endif
/****************************************************************************
* Name: tcp_ipv6_input
*
* Description:
* Handle incoming TCP input with IPv4 header
*
* Input Parameters:
* dev - The device driver structure containing the received TCP packet.
*
* Returned Value:
* None
*
* Assumptions:
* Called from the Ethernet driver with the network stack locked
*
****************************************************************************/
#ifdef CONFIG_NET_IPv6
void tcp_ipv6_input(FAR struct net_driver_s *dev)
{
/* Configure to receive an TCP IPv6 packet */
tcp_ipv6_select(dev);
/* Then process in the TCP IPv6 input */
tcp_input(dev, PF_INET6, IPv6_HDRLEN);
}
#endif
#endif /* CONFIG_NET && CONFIG_NET_TCP */
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