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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_packet.h"
#include "nx_ip.h"
#include "nx_tcp.h"
#ifdef FEATURE_NX_IPV6
#include "nx_ipv6.h"
#endif /* FEATURE_NX_IPV6 */
#ifdef NX_IPSEC_ENABLE
#include "nx_ipsec.h"
#endif /* NX_IPSEC_ENABLE */
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_tcp_socket_retransmit PORTABLE C */
/* 6.4.3 */
/* AUTHOR */
/* */
/* Yuxin Zhou, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function retransmit a TCP packet. */
/* */
/* INPUT */
/* */
/* ip_ptr IP instance pointer */
/* socket_ptr Pointer to owning socket */
/* need_fast_retransmit Need fast retransmit or not */
/* */
/* OUTPUT */
/* */
/* None */
/* */
/* CALLS */
/* */
/* _nx_tcp_packet_send_probe Send zero window probe */
/* _nx_ip_checksum_compute Calculate TCP checksum */
/* _nx_ip_packet_send Resend the transmit packet */
/* _nx_ipv6_packet_send Resend the transmit packet */
/* */
/* CALLED BY */
/* */
/* _nx_tcp_fast_periodic_processing Process TCP packet for socket */
/* _nx_tcp_socket_state_ack_check Process ACK number */
/* */
/**************************************************************************/
VOID _nx_tcp_socket_retransmit(NX_IP *ip_ptr, NX_TCP_SOCKET *socket_ptr, UINT need_fast_retransmit)
{
NX_PACKET *packet_ptr;
ULONG window;
ULONG original_acknowledgment_number;
ULONG original_header_word_3;
ULONG original_header_word_4;
ULONG available;
ULONG window_size;
/* If the receiver winodw is zero, we enter the zero window probe phase
RFC 793 Sec 3.7, p42: keep send new data.
In the zero window probe phase, we send the zero window probe, and increase
exponentially the interval between successive probes.
RFC 1122 Sec 4.2.2.17, p92. */
if (socket_ptr -> nx_tcp_socket_tx_window_advertised == 0)
{
/* Pickup the head of the transmit queue. */
packet_ptr = socket_ptr -> nx_tcp_socket_transmit_sent_head;
if (packet_ptr)
{
/* Get one byte from send queue. */
/* Pick up the pointer to the head of the TCP packet. */
/*lint -e{927} -e{826} suppress cast of pointer to pointer, since it is necessary */
NX_TCP_HEADER *header_ptr = (NX_TCP_HEADER *)packet_ptr -> nx_packet_prepend_ptr;
NX_CHANGE_ULONG_ENDIAN(header_ptr -> nx_tcp_header_word_3);
NX_CHANGE_ULONG_ENDIAN(header_ptr -> nx_tcp_sequence_number);
/* Get sequence number and first byte. */
socket_ptr -> nx_tcp_socket_zero_window_probe_data = *(packet_ptr -> nx_packet_prepend_ptr + ((header_ptr -> nx_tcp_header_word_3 >> 28) << 2));
/* Now set zero window probe started. */
socket_ptr -> nx_tcp_socket_zero_window_probe_has_data = NX_TRUE;
socket_ptr -> nx_tcp_socket_zero_window_probe_sequence = header_ptr -> nx_tcp_sequence_number;
socket_ptr -> nx_tcp_socket_zero_window_probe_failure = 0;
NX_CHANGE_ULONG_ENDIAN(header_ptr -> nx_tcp_sequence_number);
NX_CHANGE_ULONG_ENDIAN(header_ptr -> nx_tcp_header_word_3);
}
else if (socket_ptr -> nx_tcp_socket_zero_window_probe_has_data == NX_FALSE)
{
return;
}
/* In the zero window probe phase, we send the zero window probe, and increase
exponentially the interval between successive probes. */
/* Increment the retry counter. */
socket_ptr -> nx_tcp_socket_timeout_retries++;
socket_ptr -> nx_tcp_socket_zero_window_probe_failure++;
/* 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 zero window probe. */
_nx_tcp_packet_send_probe(socket_ptr, socket_ptr -> nx_tcp_socket_zero_window_probe_sequence,
socket_ptr -> nx_tcp_socket_zero_window_probe_data);
return;
}
else if (socket_ptr -> nx_tcp_socket_zero_window_probe_has_data == NX_TRUE)
{
/* If advertised window isn't zero, reset zero window probe flag. */
socket_ptr -> nx_tcp_socket_zero_window_probe_has_data = NX_FALSE;
}
/* Increment the retry counter only if the receiver window is open. */
/* Increment the retry counter. */
socket_ptr -> nx_tcp_socket_timeout_retries++;
if ((need_fast_retransmit == NX_TRUE) || (socket_ptr -> nx_tcp_socket_fast_recovery == NX_FALSE))
{
/* Timed out on an outgoing packet. Enter slow start mode. */
/* Compute the flight size / 2 value. */
window = socket_ptr -> nx_tcp_socket_tx_outstanding_bytes >> 1;
/* Make sure we have at least 2 * MSS */
if (window < (socket_ptr -> nx_tcp_socket_connect_mss << 1))
{
window = socket_ptr -> nx_tcp_socket_connect_mss << 1;
}
/* Set the slow_start_threshold */
socket_ptr -> nx_tcp_socket_tx_slow_start_threshold = window;
/* Set the current window to be MSS size. */
socket_ptr -> nx_tcp_socket_tx_window_congestion = socket_ptr -> nx_tcp_socket_connect_mss;
/* Determine if this socket needs fast retransmit. */
if (need_fast_retransmit == NX_TRUE)
{
/* Update cwnd to ssthreshold plus 3 * MSS. */
socket_ptr -> nx_tcp_socket_tx_window_congestion += window + (socket_ptr -> nx_tcp_socket_connect_mss << 1);
/* Now TCP is in fast recovery procedure. */
socket_ptr -> nx_tcp_socket_fast_recovery = NX_TRUE;
/* Update the transmit sequence that enters fast transmit. */
socket_ptr -> nx_tcp_socket_tx_sequence_recover = socket_ptr -> nx_tcp_socket_tx_sequence - 1;
}
}
/* 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);
/* Get available size of packet that can be sent. */
available = socket_ptr -> nx_tcp_socket_tx_window_congestion;
/* Pickup the head of the transmit queue. */
packet_ptr = socket_ptr -> nx_tcp_socket_transmit_sent_head;
/* Determine if the packet has been released by the
application I/O driver. */
/*lint -e{923} suppress cast of ULONG to pointer. */
while (packet_ptr && (packet_ptr -> nx_packet_queue_next == (NX_PACKET *)NX_DRIVER_TX_DONE))
{
/* Update the ACK number in case it has changed since the data was originally transmitted. */
ULONG checksum;
NX_TCP_HEADER *header_ptr;
ULONG *source_ip = NX_NULL, *dest_ip = NX_NULL;
NX_PACKET *next_ptr;
#if defined(NX_DISABLE_TCP_TX_CHECKSUM) || defined(NX_ENABLE_INTERFACE_CAPABILITY) || defined(NX_IPSEC_ENABLE)
UINT compute_checksum = 1;
#endif /* defined(NX_DISABLE_TCP_TX_CHECKSUM) || defined(NX_ENABLE_INTERFACE_CAPABILITY) || defined(NX_IPSEC_ENABLE) */
#ifdef NX_DISABLE_TCP_TX_CHECKSUM
compute_checksum = 0;
#endif /* NX_DISABLE_TCP_TX_CHECKSUM */
if (packet_ptr -> nx_packet_length > (available + sizeof(NX_TCP_HEADER)))
{
/* This packet can not be sent. */
break;
}
/* Decrease the available size. */
available -= (packet_ptr -> nx_packet_length - (ULONG)sizeof(NX_TCP_HEADER));
/* Pickup next packet. */
next_ptr = packet_ptr -> nx_packet_union_next.nx_packet_tcp_queue_next;
#ifndef NX_DISABLE_IPV4
/* Is this an IPv4 connection? */
if (socket_ptr -> nx_tcp_socket_connect_ip.nxd_ip_version == NX_IP_VERSION_V4)
{
packet_ptr -> nx_packet_ip_version = NX_IP_VERSION_V4;
/* Get the source and destination addresses. */
source_ip = &socket_ptr -> nx_tcp_socket_connect_interface -> nx_interface_ip_address;
dest_ip = &socket_ptr -> nx_tcp_socket_connect_ip.nxd_ip_address.v4;
}
#endif /* !NX_DISABLE_IPV4 */
#ifdef FEATURE_NX_IPV6
if (socket_ptr -> nx_tcp_socket_connect_ip.nxd_ip_version == NX_IP_VERSION_V6)
{
/* Set the packet for IPv6 connectivity. */
packet_ptr -> nx_packet_ip_version = NX_IP_VERSION_V6;
/* Get the source and destination addresses. */
source_ip = socket_ptr -> nx_tcp_socket_ipv6_addr -> nxd_ipv6_address;
dest_ip = socket_ptr -> nx_tcp_socket_connect_ip.nxd_ip_address.v6;
}
#endif /* FEATURE_NX_IPV6 */
/* Pick up the pointer to the head of the TCP packet. */
/*lint -e{927} -e{826} suppress cast of pointer to pointer, since it is necessary */
header_ptr = (NX_TCP_HEADER *)packet_ptr -> nx_packet_prepend_ptr;
/* Record the original data. */
original_acknowledgment_number = header_ptr -> nx_tcp_acknowledgment_number;
original_header_word_3 = header_ptr -> nx_tcp_header_word_3;
original_header_word_4 = header_ptr -> nx_tcp_header_word_4;
/* Update the ACK number in the TCP header. */
header_ptr -> nx_tcp_acknowledgment_number = socket_ptr -> nx_tcp_socket_rx_sequence;
/* Convert to network byte order for checksum */
NX_CHANGE_ULONG_ENDIAN(header_ptr -> nx_tcp_acknowledgment_number);
/* Set window size. */
#ifdef NX_ENABLE_TCP_WINDOW_SCALING
window_size = socket_ptr -> nx_tcp_socket_rx_window_current >> socket_ptr -> nx_tcp_rcv_win_scale_value;
/* Make sure the window_size is less than 0xFFFF. */
if (window_size > 0xFFFF)
{
window_size = 0xFFFF;
}
#else
window_size = socket_ptr -> nx_tcp_socket_rx_window_current;
#endif /* NX_ENABLE_TCP_WINDOW_SCALING */
header_ptr -> nx_tcp_header_word_3 = NX_TCP_HEADER_SIZE | NX_TCP_ACK_BIT | NX_TCP_PSH_BIT | window_size;
/* Swap the content to network byte order. */
NX_CHANGE_ULONG_ENDIAN(header_ptr -> nx_tcp_header_word_3);
/* Convert back to host byte order to so we can zero out the checksum. */
NX_CHANGE_ULONG_ENDIAN(header_ptr -> nx_tcp_header_word_4);
/* Remember the last ACKed sequence and the last reported window size. */
socket_ptr -> nx_tcp_socket_rx_sequence_acked = socket_ptr -> nx_tcp_socket_rx_sequence;
socket_ptr -> nx_tcp_socket_rx_window_last_sent = socket_ptr -> nx_tcp_socket_rx_window_current;
/* Zero out existing checksum before computing new one. */
header_ptr -> nx_tcp_header_word_4 = header_ptr -> nx_tcp_header_word_4 & 0x0000FFFF;
/* Convert back to network byte order to so we can do the checksum. */
NX_CHANGE_ULONG_ENDIAN(header_ptr -> nx_tcp_header_word_4);
#ifdef NX_ENABLE_INTERFACE_CAPABILITY
if (socket_ptr -> nx_tcp_socket_connect_interface -> nx_interface_capability_flag & NX_INTERFACE_CAPABILITY_TCP_TX_CHECKSUM)
{
compute_checksum = 0;
}
#endif /* NX_ENABLE_INTERFACE_CAPABILITY */
#ifdef NX_IPSEC_ENABLE
if ((packet_ptr -> nx_packet_ipsec_sa_ptr != NX_NULL) &&
(((NX_IPSEC_SA *)(packet_ptr -> nx_packet_ipsec_sa_ptr)) -> nx_ipsec_sa_encryption_method != NX_CRYPTO_NONE))
{
compute_checksum = 1;
}
#endif /* NX_IPSEC_ENABLE */
#if defined(NX_DISABLE_TCP_TX_CHECKSUM) || defined(NX_ENABLE_INTERFACE_CAPABILITY) || defined(NX_IPSEC_ENABLE)
if (compute_checksum)
#endif /* defined(NX_DISABLE_TCP_TX_CHECKSUM) || defined(NX_ENABLE_INTERFACE_CAPABILITY) || defined(NX_IPSEC_ENABLE) */
{
/* Calculate the TCP checksum without protection. */
checksum = _nx_ip_checksum_compute(packet_ptr, NX_PROTOCOL_TCP,
packet_ptr -> nx_packet_length,
source_ip, dest_ip);
checksum = ~checksum & NX_LOWER_16_MASK;
/* Convert back to host byte order */
NX_CHANGE_ULONG_ENDIAN(header_ptr -> nx_tcp_header_word_4);
/* Move the checksum into header. */
header_ptr -> nx_tcp_header_word_4 = header_ptr -> nx_tcp_header_word_4 | (checksum << NX_SHIFT_BY_16);
/* Convert back to network byte order for transmit. */
NX_CHANGE_ULONG_ENDIAN(header_ptr -> nx_tcp_header_word_4);
}
#ifdef NX_ENABLE_INTERFACE_CAPABILITY
else
{
packet_ptr -> nx_packet_interface_capability_flag |= NX_INTERFACE_CAPABILITY_TCP_TX_CHECKSUM;
}
#endif /* NX_ENABLE_INTERFACE_CAPABILITY */
/* Determine if the retransmitted packet is identical to the original packet.
RFC1122, Section3.2.1.5, Page32-33. RFC1122, Section4.2.2.15, Page90-91. */
if ((header_ptr -> nx_tcp_acknowledgment_number == original_acknowledgment_number) &&
(header_ptr -> nx_tcp_header_word_3 == original_header_word_3) &&
(header_ptr -> nx_tcp_header_word_4 == original_header_word_4))
{
/* Yes, identical packet, update the identification flag. */
packet_ptr -> nx_packet_identical_copy = NX_TRUE;
}
#ifndef NX_DISABLE_TCP_INFO
/* Increment the TCP retransmit count. */
ip_ptr -> nx_ip_tcp_retransmit_packets++;
/* Increment the TCP retransmit count for the socket. */
socket_ptr -> nx_tcp_socket_retransmit_packets++;
#endif
#ifdef NX_ENABLE_VLAN
if (socket_ptr -> nx_tcp_socket_vlan_priority != NX_VLAN_PRIORITY_INVALID)
{
packet_ptr -> nx_packet_vlan_priority = socket_ptr -> nx_tcp_socket_vlan_priority;
}
#endif /* NX_ENABLE_VLAN */
/* If trace is enabled, insert this event into the trace buffer. */
NX_TRACE_IN_LINE_INSERT(NX_TRACE_INTERNAL_TCP_RETRY, ip_ptr, socket_ptr, packet_ptr, socket_ptr -> nx_tcp_socket_timeout_retries, NX_TRACE_INTERNAL_EVENTS, 0, 0);
/* Clear the queue next pointer. */
packet_ptr -> nx_packet_queue_next = NX_NULL;
/* Yes, the driver has finished with the packet at the head of the
transmit sent list... so it can be sent again! */
#ifndef NX_DISABLE_IPV4
/* Is this an IPv4 connection? */
if (socket_ptr -> nx_tcp_socket_connect_ip.nxd_ip_version == NX_IP_VERSION_V4)
{
_nx_ip_packet_send(ip_ptr, packet_ptr,
socket_ptr -> nx_tcp_socket_connect_ip.nxd_ip_address.v4,
socket_ptr -> nx_tcp_socket_type_of_service,
socket_ptr -> nx_tcp_socket_time_to_live, NX_IP_TCP,
socket_ptr -> nx_tcp_socket_fragment_enable,
socket_ptr -> nx_tcp_socket_next_hop_address);
}
#endif /* !NX_DISABLE_IPV4 */
#ifdef FEATURE_NX_IPV6
if (socket_ptr -> nx_tcp_socket_connect_ip.nxd_ip_version == NX_IP_VERSION_V6)
{
/* Handle for an IPv6 connection. */
/* Set the packet transmit interface before sending. */
packet_ptr -> nx_packet_address.nx_packet_ipv6_address_ptr = socket_ptr -> nx_tcp_socket_ipv6_addr;
_nx_ipv6_packet_send(ip_ptr, packet_ptr, NX_PROTOCOL_TCP,
packet_ptr -> nx_packet_length, ip_ptr -> nx_ipv6_hop_limit,
socket_ptr -> nx_tcp_socket_ipv6_addr -> nxd_ipv6_address,
socket_ptr -> nx_tcp_socket_connect_ip.nxd_ip_address.v6);
}
#endif /* FEATURE_NX_IPV6 */
/* Move to next packet. */
/* During fast recovery, only one packet is retransmitted at once. */
/* After a timeout, the sending data can be at most one SMSS. */
if ((next_ptr == (NX_PACKET *)NX_PACKET_ENQUEUED) ||
(socket_ptr -> nx_tcp_socket_fast_recovery == NX_TRUE))
{
break;
}
else
{
packet_ptr = next_ptr;
}
}
}
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