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incubator-nuttx/net/tcp/tcp_input.c

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/****************************************************************************
* net/tcp/tcp_input.c
* Handling incoming TCP input
*
* Copyright (C) 2007-2014, 2017-2019, 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 <inttypes.h>
#include <stdint.h>
#include <string.h>
#include <assert.h>
#include <debug.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"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define IPv4BUF ((FAR struct ipv4_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: tcp_trim_head
*
* Description:
* Trim the head of the TCP segment.
*
* Input Parameters:
* dev - The device driver structure containing the received TCP
* packet.
* tcp - The TCP header.
* trimlen - The length to trim in bytes.
*
* Returned Value:
* True if nothing was left.
*
* Assumptions:
* The network is locked.
*
****************************************************************************/
static bool tcp_trim_head(FAR struct net_driver_s *dev,
FAR struct tcp_hdr_s *tcp,
uint32_t trimlen)
{
uint32_t seq = tcp_getsequence(tcp->seqno);
uint16_t urg_ptr = (tcp->urgp[0] << 8) | tcp->urgp[1];
uint32_t urg_trimlen = 0;
uint8_t th_flags = tcp->flags;
DEBUGASSERT(trimlen > 0);
ninfo("Dropping %" PRIu32 " bytes: "
"seq=%" PRIu32 ", "
"tcp flags=%" PRIx8 ", "
"d_len=%" PRIu16 ", "
"urg_ptr=%" PRIu16 "\n",
trimlen,
seq,
th_flags,
dev->d_len,
urg_ptr);
if ((th_flags & TCP_SYN) != 0)
{
ninfo("Dropping SYN\n");
seq = TCP_SEQ_ADD(seq, 1);
urg_trimlen++;
trimlen--;
th_flags &= ~TCP_SYN;
}
if (trimlen > 0)
{
uint32_t len = trimlen;
if (len > dev->d_len)
{
len = dev->d_len;
}
ninfo("Dropping %" PRIu32 " bytes app data\n", len);
seq = TCP_SEQ_ADD(seq, len);
urg_trimlen += len;
dev->d_appdata += len;
dev->d_len -= len;
trimlen -= len;
}
if (trimlen > 0)
{
if ((th_flags & TCP_FIN) != 0)
{
ninfo("Dropping FIN\n");
seq = TCP_SEQ_ADD(seq, 1);
urg_trimlen++;
trimlen--;
th_flags &= ~TCP_FIN;
}
}
/* Update the header */
if ((th_flags & TCP_URG) != 0)
{
/* Adjust URG pointer */
if (urg_trimlen >= urg_ptr)
{
th_flags &= ~TCP_URG;
urg_ptr = 0;
}
else
{
urg_ptr -= urg_trimlen;
}
ninfo("Adjusting URG pointer by %" PRIu32 ", "
"new urg_ptr=%" PRIu16 "\n",
urg_trimlen, urg_ptr);
tcp->urgp[0] = (uint8_t)(urg_ptr >> 8);
tcp->urgp[1] = (uint8_t)urg_ptr;
}
tcp->flags = th_flags;
tcp_setsequence(tcp->seqno, seq);
if ((th_flags & (TCP_SYN | TCP_FIN)) == 0 && dev->d_len == 0)
{
ninfo("Dropped the entire segment\n");
return true;
}
DEBUGASSERT(trimlen == 0);
ninfo("Dropped the segment partially\n");
return false;
}
/****************************************************************************
* 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 - Length 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 and 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); /* ack SYN */
/* 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;
continue;
}
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;
}
#ifdef CONFIG_NET_TCP_WINDOW_SCALE
else if (opt == TCP_OPT_WS &&
dev->d_buf[hdrlen + 1 + i] == TCP_OPT_WS_LEN)
{
conn->snd_scale = dev->d_buf[hdrlen + 2 + i];
conn->rcv_scale = CONFIG_NET_TCP_WINDOW_SCALE_FACTOR;
conn->flags |= TCP_WSCALE;
}
#endif
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_synack(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 */
#ifdef CONFIG_NET_TCP_WINDOW_SCALE
conn->snd_wnd = (((uint32_t)tcp->wnd[0] << 8) + (uint32_t)tcp->wnd[1]) <<
conn->snd_scale;
#else
conn->snd_wnd = (((uint16_t)tcp->wnd[0] << 8) + (uint16_t)tcp->wnd[1]);
#endif
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)
{
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);
/* 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))))
{
uint32_t seq;
uint32_t rcvseq;
seq = tcp_getsequence(tcp->seqno);
rcvseq = tcp_getsequence(conn->rcvseq);
if (seq != rcvseq)
{
/* Trim the head of the segment */
if (TCP_SEQ_LT(seq, rcvseq))
{
uint32_t trimlen = TCP_SEQ_SUB(rcvseq, seq);
if (tcp_trim_head(dev, tcp, trimlen))
{
/* The segment was completely out of the window.
* E.g. a retransmit which was not necessary.
* E.g. a keep-alive segment.
*/
tcp_send(dev, conn, TCP_ACK, tcpiplen);
return;
}
}
else
{
/* We never queue out-of-order segments. */
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->tx_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 (tx_unacked).
*/
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
unackseq = conn->sndseq_max;
#else
unackseq = tcp_addsequence(conn->sndseq, conn->tx_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 (TCP_SEQ_LTE(ackseq, unackseq))
{
/* Calculate the new number of outstanding, unacknowledged bytes */
conn->tx_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=%" PRIu32 " tx_unacked=%" PRIu32
" unackseq=%" PRIu32 " ackseq=%" PRIu32 "\n",
tcp_getsequence(conn->sndseq),
(uint32_t)conn->tx_unacked,
unackseq, ackseq);
conn->tx_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: %08" PRIx32 "->%08" PRIx32
" unackseq: %08" PRIx32 " new tx_unacked: %" PRId32 "\n",
tcp_getsequence(conn->sndseq), ackseq, unackseq,
(uint32_t)conn->tx_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",
ntohs(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->tx_unacked = 0;
flags = TCP_CONNECTED;
ninfo("TCP state: TCP_ESTABLISHED\n");
if (dev->d_len > 0)
{
flags |= TCP_NEWDATA;
}
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_synack(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;
continue;
}
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;
}
#ifdef CONFIG_NET_TCP_WINDOW_SCALE
else if (opt == TCP_OPT_WS &&
dev->d_buf[hdrlen + 1 + i] == TCP_OPT_WS_LEN)
{
conn->snd_scale = dev->d_buf[hdrlen + 2 + i];
conn->rcv_scale = CONFIG_NET_TCP_WINDOW_SCALE_FACTOR;
conn->flags |= TCP_WSCALE;
}
#endif
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);
conn->rcv_adv = tcp_getsequence(conn->rcvseq);
net_incr32(conn->rcvseq, 1); /* ack SYN */
conn->tx_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 */
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->tx_unacked > 0)
{
goto drop;
}
#endif
/* Update the sequence number and indicate that the connection
* has been closed.
*/
flags |= TCP_CLOSE;
if (dev->d_len > 0)
{
flags |= TCP_NEWDATA;
}
result = tcp_callback(dev, conn, flags);
if ((result & TCP_CLOSE) != 0)
{
conn->tcpstateflags = TCP_LAST_ACK;
conn->tx_unacked = 1;
conn->nrtx = 0;
net_incr32(conn->rcvseq, 1); /* ack FIN */
#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
conn->sndseq_max = tcp_getsequence(conn->sndseq) + 1;
#endif
ninfo("TCP state: TCP_LAST_ACK\n");
tcp_send(dev, conn, TCP_FIN | TCP_ACK, tcpiplen);
}
else
{
ninfo("TCP: Dropped a FIN\n");
tcp_appsend(dev, conn, result);
}
return;
}
#ifdef CONFIG_NET_TCPURGDATA
/* 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)
{
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;
}
/* The d_len field contains the length of the incoming data.
* d_urgdata points to the "urgent" data at the beginning of
* the payload; d_appdata field points to the any "normal" data
* that may follow the urgent data.
*
* NOTE: If the urgent data continues in the next packet, then
* d_len will be zero and d_appdata will point past the end of
* the payload (which is OK).
*/
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
{
/* No urgent data */
dev->d_urglen = 0;
}
#else /* CONFIG_NET_TCPURGDATA */
/* Check the URG flag. If this is set, We must gracefully ignore
* and discard the urgent data.
*/
if ((tcp->flags & TCP_URG) != 0)
{
uint16_t urglen = (tcp->urgp[0] << 8) | tcp->urgp[1];
if (urglen > dev->d_len)
{
/* There is more urgent data in the next segment to come. */
urglen = dev->d_len;
}
/* The d_len field contains the length of the incoming data;
* The d_appdata field points to the any "normal" data that
* may follow the urgent data.
*
* NOTE: If the urgent data continues in the next packet, then
* d_len will be zero and d_appdata will point past the end of
* the payload (which is OK).
*/
net_incr32(conn->rcvseq, urglen);
dev->d_len -= urglen;
dev->d_appdata += urglen;
}
#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_systime_ticks();
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)
{
dev->d_sndlen = 0;
/* Provide the packet to the application */
result = tcp_callback(dev, conn, flags);
/* 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");
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->tx_unacked == 0)
{
conn->tcpstateflags = TCP_TIME_WAIT;
conn->timer = 0;
ninfo("TCP state: TCP_TIME_WAIT\n");
}
else
{
conn->tcpstateflags = TCP_CLOSING;
ninfo("TCP state: TCP_CLOSING\n");
}
net_incr32(conn->rcvseq, 1); /* ack FIN */
tcp_callback(dev, conn, TCP_CLOSE);
tcp_send(dev, conn, TCP_ACK, tcpiplen);
return;
}
else if ((flags & TCP_ACKDATA) != 0 && conn->tx_unacked == 0)
{
conn->tcpstateflags = TCP_FIN_WAIT_2;
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); /* ack FIN */
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)
{
FAR struct ipv4_hdr_s *ipv4 = IPv4BUF;
uint16_t iphdrlen;
/* Configure to receive an TCP IPv4 packet */
tcp_ipv4_select(dev);
/* Get the IP header length (accounting for possible options). */
iphdrlen = (ipv4->vhl & IPv4_HLMASK) << 2;
/* Then process in the TCP IPv4 input */
tcp_input(dev, PF_INET, iphdrlen);
}
#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.
* iplen - The size of the IPv6 header. This may be larger than
* IPv6_HDRLEN the IPv6 header if IPv6 extension headers are
* present.
*
* 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, unsigned int iplen)
{
/* Configure to receive an TCP IPv6 packet */
tcp_ipv6_select(dev);
/* Then process in the TCP IPv6 input */
tcp_input(dev, PF_INET6, iplen);
}
#endif
#endif /* CONFIG_NET && CONFIG_NET_TCP */
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