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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** NetX Component */
/** */
/** Transmission Control Protocol (TCP) */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_SOURCE_CODE
/* Include necessary system files. */
#include "nx_api.h"
#include "nx_tcp.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_tcp_socket_state_syn_sent PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* Yuxin Zhou, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function processes packets during the SYN SENT state, which is */
/* the state of the socket immediately after the initial SYN is sent */
/* in the establishment of a TCP connection. We are expecting a SYN */
/* and an ACK from the other side of the connection in order to move */
/* into an established state. */
/* */
/* INPUT */
/* */
/* socket_ptr Pointer to owning socket */
/* tcp_header_ptr Pointer to packet header */
/* */
/* OUTPUT */
/* */
/* None */
/* */
/* CALLS */
/* */
/* _nx_tcp_packet_send_ack Send ACK packet */
/* _nx_tcp_packet_send_syn Send SYN packet */
/* _nx_tcp_packet_send_rst Send RST packet */
/* _nx_tcp_socket_thread_resume Resume suspended thread */
/* */
/* CALLED BY */
/* */
/* _nx_tcp_socket_packet_process Process TCP packet for socket */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 Yuxin Zhou Initial Version 6.0 */
/* 09-30-2020 Yuxin Zhou Modified comment(s), */
/* resulting in version 6.1 */
/* */
/**************************************************************************/
VOID _nx_tcp_socket_state_syn_sent(NX_TCP_SOCKET *socket_ptr, NX_TCP_HEADER *tcp_header_ptr, NX_PACKET *packet_ptr)
{
#ifndef TX_ENABLE_EVENT_TRACE
NX_PARAMETER_NOT_USED(packet_ptr);
#endif /* TX_ENABLE_EVENT_TRACE */
/* Check if a RST is present. */
if (tcp_header_ptr -> nx_tcp_header_word_3 & NX_TCP_RST_BIT)
{
/* Check if the ACK was acceptable. According to RFC 793, Section 3.9, Page 67. */
if ((tcp_header_ptr -> nx_tcp_header_word_3 & NX_TCP_ACK_BIT) &&
(tcp_header_ptr -> nx_tcp_acknowledgment_number == socket_ptr -> nx_tcp_socket_tx_sequence))
{
#ifndef NX_DISABLE_TCP_INFO
/* Increment the resets received count. */
(socket_ptr -> nx_tcp_socket_ip_ptr) -> nx_ip_tcp_resets_received++;
#endif
/* If trace is enabled, insert this event into the trace buffer. */
NX_TRACE_IN_LINE_INSERT(NX_TRACE_INTERNAL_TCP_RESET_RECEIVE, socket_ptr -> nx_tcp_socket_ip_ptr, socket_ptr, packet_ptr, tcp_header_ptr -> nx_tcp_sequence_number, NX_TRACE_INTERNAL_EVENTS, 0, 0);
/* Reset connection. */
_nx_tcp_socket_connection_reset(socket_ptr);
}
/* Finished processing, simply return! */
return;
}
/* Determine if a valid SYN/ACK is present. */
else if ((tcp_header_ptr -> nx_tcp_header_word_3 & NX_TCP_SYN_BIT) &&
(tcp_header_ptr -> nx_tcp_header_word_3 & NX_TCP_ACK_BIT) &&
(tcp_header_ptr -> nx_tcp_acknowledgment_number == socket_ptr -> nx_tcp_socket_tx_sequence))
{
/* Yes, this is a proper SYN/ACK message. We need to send an ACK
back the other direction before we go into the ESTABLISHED
state. */
/* Save the sequence number. */
socket_ptr -> nx_tcp_socket_rx_sequence = tcp_header_ptr -> nx_tcp_sequence_number + 1;
/* Save the window size. */
socket_ptr -> nx_tcp_socket_tx_window_advertised = tcp_header_ptr -> nx_tcp_header_word_3 & NX_LOWER_16_MASK;
#ifdef NX_ENABLE_TCP_WINDOW_SCALING
/* The window size advertised in the SYN packet is NEVER scaled. Therefore there is no
need to apply the scale shift. However validate snd_win_scale and rcv_win_scale. */
if (socket_ptr -> nx_tcp_snd_win_scale_value == 0xFF)
{
/* Peer does not support window scale option. */
socket_ptr -> nx_tcp_snd_win_scale_value = 0;
socket_ptr -> nx_tcp_rcv_win_scale_value = 0;
/* Since the peer does not offer window scaling feature, make sure
our default window size for this connection does not exceed 65535 bytes. */
if (socket_ptr -> nx_tcp_socket_rx_window_maximum > 65535)
{
socket_ptr -> nx_tcp_socket_rx_window_default = 65535;
socket_ptr -> nx_tcp_socket_rx_window_current = 65535;
}
}
#endif /* NX_ENABLE_TCP_WINDOW_SCALING */
/* Initialize the slow start threshold to be the advertised window size. */
socket_ptr -> nx_tcp_socket_tx_slow_start_threshold = socket_ptr -> nx_tcp_socket_tx_window_advertised;
/* Set the Initial transmit outstanding byte count. */
socket_ptr -> nx_tcp_socket_tx_outstanding_bytes = 0;
/* Set the initial congestion control window size. */
/* Section 3.1, Page 5, RFC5681. */
if (socket_ptr -> nx_tcp_socket_timeout_retries > 0)
{
/* Set the initial congestion control window size to be the mss. */
socket_ptr -> nx_tcp_socket_tx_window_congestion = socket_ptr -> nx_tcp_socket_connect_mss;
}
else
{
socket_ptr -> nx_tcp_socket_tx_window_congestion = (socket_ptr -> nx_tcp_socket_connect_mss << 2);
if (socket_ptr -> nx_tcp_socket_connect_mss > 1095)
{
socket_ptr -> nx_tcp_socket_tx_window_congestion -= socket_ptr -> nx_tcp_socket_connect_mss;
}
if (socket_ptr -> nx_tcp_socket_connect_mss > 2190)
{
socket_ptr -> nx_tcp_socket_tx_window_congestion -= socket_ptr -> nx_tcp_socket_connect_mss;
}
}
/* Send the ACK. */
_nx_tcp_packet_send_ack(socket_ptr, socket_ptr -> nx_tcp_socket_tx_sequence);
/* If trace is enabled, insert this event into the trace buffer. */
NX_TRACE_IN_LINE_INSERT(NX_TRACE_INTERNAL_TCP_STATE_CHANGE, socket_ptr -> nx_tcp_socket_ip_ptr, socket_ptr, socket_ptr -> nx_tcp_socket_state, NX_TCP_ESTABLISHED, NX_TRACE_INTERNAL_EVENTS, 0, 0);
/* Move to the ESTABLISHED state. */
socket_ptr -> nx_tcp_socket_state = NX_TCP_ESTABLISHED;
/* Clear the socket timeout. */
socket_ptr -> nx_tcp_socket_timeout = 0;
#ifndef NX_DISABLE_EXTENDED_NOTIFY_SUPPORT
/* Is a connection completion callback registered with the TCP socket? */
if (socket_ptr -> nx_tcp_establish_notify)
{
/* Call the application's establish callback function. */
(socket_ptr -> nx_tcp_establish_notify)(socket_ptr);
}
#endif
#ifdef NX_ENABLE_TCP_KEEPALIVE
/* Is the keepalive feature enabled on this socket? */
if (socket_ptr -> nx_tcp_socket_keepalive_enabled)
{
/* Setup the TCP Keepalive timer to initial values. */
socket_ptr -> nx_tcp_socket_keepalive_timeout = NX_TCP_KEEPALIVE_INITIAL;
socket_ptr -> nx_tcp_socket_keepalive_retries = 0;
}
#endif
/* Determine if we need to wake a thread suspended on the connection. */
if (socket_ptr -> nx_tcp_socket_connect_suspended_thread)
{
/* Resume the suspended thread. */
_nx_tcp_socket_thread_resume(&(socket_ptr -> nx_tcp_socket_connect_suspended_thread), NX_SUCCESS);
}
}
else if ((tcp_header_ptr -> nx_tcp_header_word_3 & NX_TCP_SYN_BIT) &&
(!(tcp_header_ptr -> nx_tcp_header_word_3 & NX_TCP_ACK_BIT)))
{
/* Simultaneous Connection Synchronization,
A SYN message was received. We need to send both a SYN and ACK and move to the SYN RECEIVED state. */
/* Save the sequence number. */
socket_ptr -> nx_tcp_socket_rx_sequence = tcp_header_ptr -> nx_tcp_sequence_number + 1;
/* Save the window size. */
socket_ptr -> nx_tcp_socket_tx_window_advertised = tcp_header_ptr -> nx_tcp_header_word_3 & NX_LOWER_16_MASK;
#ifdef NX_ENABLE_TCP_WINDOW_SCALING
socket_ptr -> nx_tcp_socket_tx_window_advertised <<= socket_ptr -> nx_tcp_rcv_win_scale_value;
#endif /* NX_ENABLE_TCP_WINDOW_SCALING */
/* Initialize the slow start threshold to be the advertised window size. */
socket_ptr -> nx_tcp_socket_tx_slow_start_threshold = socket_ptr -> nx_tcp_socket_tx_window_advertised;
/* Set the initial congestion control window size. */
/* Section 3.1, Page 5, RFC5681. */
socket_ptr -> nx_tcp_socket_tx_window_congestion = (socket_ptr -> nx_tcp_socket_connect_mss << 2);
if (socket_ptr -> nx_tcp_socket_connect_mss > 1095)
{
socket_ptr -> nx_tcp_socket_tx_window_congestion -= socket_ptr -> nx_tcp_socket_connect_mss;
}
if (socket_ptr -> nx_tcp_socket_connect_mss > 2190)
{
socket_ptr -> nx_tcp_socket_tx_window_congestion -= socket_ptr -> nx_tcp_socket_connect_mss;
}
/* Set the Initial transmit outstanding byte count. */
socket_ptr -> nx_tcp_socket_tx_outstanding_bytes = 0;
/* If trace is enabled, insert this event into the trace buffer. */
NX_TRACE_IN_LINE_INSERT(NX_TRACE_INTERNAL_TCP_STATE_CHANGE, socket_ptr -> nx_tcp_socket_ip_ptr, socket_ptr, socket_ptr -> nx_tcp_socket_state, NX_TCP_SYN_RECEIVED, NX_TRACE_INTERNAL_EVENTS, 0, 0);
/* Move to the SYN RECEIVED state. */
socket_ptr -> nx_tcp_socket_state = NX_TCP_SYN_RECEIVED;
/* Clear the timeout. */
socket_ptr -> nx_tcp_socket_timeout = 0;
/* Send the SYN packet. */
_nx_tcp_packet_send_syn(socket_ptr, (socket_ptr -> nx_tcp_socket_tx_sequence - 1));
}
/* Check for an invalid response to an attempted connection. */
else if ((tcp_header_ptr -> nx_tcp_header_word_3 & NX_TCP_ACK_BIT) &&
(tcp_header_ptr -> nx_tcp_acknowledgment_number != socket_ptr -> nx_tcp_socket_tx_sequence))
{
/* Invalid response was received, it is likely that the other side still
thinks a previous connection is active. Send a reset (RST) message to
the other side to clear any previous connection. */
/* Send the RST packet. */
_nx_tcp_packet_send_rst(socket_ptr, tcp_header_ptr);
}
}
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