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/***************************************************************************
* Copyright (c) 2024 Microsoft Corporation
* Copyright (c) 2025-present Eclipse ThreadX Contributors
*
* This program and the accompanying materials are made available under the
* terms of the MIT License which is available at
* https://opensource.org/licenses/MIT.
*
* SPDX-License-Identifier: MIT
**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** NetX Component */
/** */
/** Transmission Control Protocol (TCP) */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_SOURCE_CODE
/* Include necessary system files. */
#include "nx_api.h"
#include "nx_ip.h"
#ifdef FEATURE_NX_IPV6
#include "nx_ipv6.h"
#endif /* FEATURE_NX_IPV6 */
#include "nx_packet.h"
#include "nx_tcp.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_tcp_fast_periodic_processing PORTABLE C */
/* 6.4.3 */
/* AUTHOR */
/* */
/* Yuxin Zhou, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function processes the fast periodic TCP processing for */
/* sending delayed ACK messages for previous receive operations and */
/* for re-transmitting packets that have not been ACKed by the other */
/* side of the connection. */
/* */
/* INPUT */
/* */
/* ip_ptr Pointer to IP control block */
/* */
/* OUTPUT */
/* */
/* None */
/* */
/* CALLS */
/* */
/* _nx_tcp_packet_send_ack Send a delayed ACK */
/* _nx_tcp_packet_send_syn Send initial SYN again */
/* _nx_tcp_socket_connection_reset Reset connection on timeout */
/* _nx_tcp_socket_block_cleanup Cleanup the socket block */
/* _nx_tcp_socket_retransmit Retransmit packet */
/* */
/* CALLED BY */
/* */
/* _nx_ip_thread_entry IP helper thread */
/* */
/**************************************************************************/
VOID _nx_tcp_fast_periodic_processing(NX_IP *ip_ptr)
{
NX_TCP_SOCKET *socket_ptr;
ULONG sockets;
ULONG timer_rate;
/* Pickup this timer's periodic rate. */
timer_rate = _nx_tcp_fast_timer_rate;
/* Pickup the number of created TCP sockets. */
sockets = ip_ptr -> nx_ip_tcp_created_sockets_count;
/* Pickup the first socket. */
socket_ptr = ip_ptr -> nx_ip_tcp_created_sockets_ptr;
/* Loop through the created sockets. */
while (sockets--)
{
/* Determine if the socket is in an established or disconnect state and has delayed sending an ACK
from a previous receive packet event. */
if ((socket_ptr -> nx_tcp_socket_state >= NX_TCP_ESTABLISHED) &&
((socket_ptr -> nx_tcp_socket_rx_sequence != socket_ptr -> nx_tcp_socket_rx_sequence_acked) ||
(socket_ptr -> nx_tcp_socket_rx_window_last_sent < socket_ptr -> nx_tcp_socket_rx_window_current)))
{
/* Determine if the ACK has expired. */
if (socket_ptr -> nx_tcp_socket_delayed_ack_timeout <= timer_rate)
{
/* Send the delayed ACK, which also resets the ACK timeout. */
_nx_tcp_packet_send_ack(socket_ptr, socket_ptr -> nx_tcp_socket_tx_sequence);
}
else
{
/* No, it hasn't expired yet. Just decrement it for now. */
socket_ptr -> nx_tcp_socket_delayed_ack_timeout -= timer_rate;
}
}
/* Determine if a timeout is active. */
if (socket_ptr -> nx_tcp_socket_timeout)
{
/* Yes, a timeout is active. Determine if it has expired. */
if (socket_ptr -> nx_tcp_socket_timeout > timer_rate)
{
/* No, it hasn't expired yet. Just decrement the timeout value. */
socket_ptr -> nx_tcp_socket_timeout -= timer_rate;
}
else if (((socket_ptr -> nx_tcp_socket_timeout_retries >= socket_ptr -> nx_tcp_socket_timeout_max_retries) &&
(socket_ptr -> nx_tcp_socket_zero_window_probe_has_data == NX_FALSE)) ||
((socket_ptr -> nx_tcp_socket_zero_window_probe_failure >= socket_ptr -> nx_tcp_socket_timeout_max_retries) &&
(socket_ptr -> nx_tcp_socket_zero_window_probe_has_data == NX_TRUE))
)
{
/* Number of retries has been exceeded. */
/* Close the socket via a connection reset. */
_nx_tcp_socket_connection_reset(socket_ptr);
}
/* YUXIN MODIFIED HERE */
else if ((socket_ptr -> nx_tcp_socket_state == NX_TCP_SYN_SENT) ||
(socket_ptr -> nx_tcp_socket_state == NX_TCP_SYN_RECEIVED))
{
/* Yes, the timeout on the SYN message has expired. */
/* Increment the retry counter. */
socket_ptr -> nx_tcp_socket_timeout_retries++;
/* Setup the next timeout. */
socket_ptr -> nx_tcp_socket_timeout = socket_ptr -> nx_tcp_socket_timeout_rate <<
(socket_ptr -> nx_tcp_socket_timeout_retries * socket_ptr -> nx_tcp_socket_timeout_shift);
/* Send the initial SYN message again. Adjust the sequence number before and
after to ensure the same sequence as the initial SYN. */
_nx_tcp_packet_send_syn(socket_ptr, (socket_ptr -> nx_tcp_socket_tx_sequence - 1));
}
/* Has the TCP timeout for transmit packet or probing zero window expired? */
else if (socket_ptr -> nx_tcp_socket_transmit_sent_head ||
((socket_ptr -> nx_tcp_socket_tx_window_advertised == 0) &&
(socket_ptr -> nx_tcp_socket_state <= NX_TCP_CLOSE_WAIT)))
{
/* Update the transmit sequence that entered fast transmit. */
socket_ptr -> nx_tcp_socket_tx_sequence_recover = socket_ptr -> nx_tcp_socket_tx_sequence - 1;
/* Retransmit the packet. */
_nx_tcp_socket_retransmit(ip_ptr, socket_ptr, NX_FALSE);
/* Exit fast recovery procedure. */
socket_ptr -> nx_tcp_socket_fast_recovery = NX_FALSE;
socket_ptr -> nx_tcp_socket_tx_window_congestion = socket_ptr -> nx_tcp_socket_tx_slow_start_threshold;
}
else if ((socket_ptr -> nx_tcp_socket_state == NX_TCP_FIN_WAIT_1) ||
(socket_ptr -> nx_tcp_socket_state == NX_TCP_CLOSING) ||
(socket_ptr -> nx_tcp_socket_state == NX_TCP_LAST_ACK))
{
/* We have a timeout condition on sending the FIN... so it needs to be
retried. */
/* Increment the retry counter. */
socket_ptr -> nx_tcp_socket_timeout_retries++;
/* Setup the next timeout. */
socket_ptr -> nx_tcp_socket_timeout = socket_ptr -> nx_tcp_socket_timeout_rate <<
(socket_ptr -> nx_tcp_socket_timeout_retries * socket_ptr -> nx_tcp_socket_timeout_shift);
/* Send another FIN packet. */
_nx_tcp_packet_send_fin(socket_ptr, (socket_ptr -> nx_tcp_socket_tx_sequence - 1));
}
else if (socket_ptr -> nx_tcp_socket_state == NX_TCP_TIMED_WAIT)
{
/* Clean the transmission control block. */
_nx_tcp_socket_block_cleanup(socket_ptr);
}
}
/* Move to the next TCP socket. */
socket_ptr = socket_ptr -> nx_tcp_socket_created_next;
}
}
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