/*************************************************************************** * Copyright (c) 2024 Microsoft Corporation * * 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_tcp.h" #ifdef NX_ENABLE_HTTP_PROXY #include "nx_http_proxy_client.h" #endif /* NX_ENABLE_HTTP_PROXY */ /**************************************************************************/ /* */ /* FUNCTION RELEASE */ /* */ /* _nx_tcp_socket_state_syn_sent PORTABLE C */ /* 6.2.0 */ /* 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 */ /* _nx_http_proxy_client_connect Connect with HTTP Proxy */ /* */ /* 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 */ /* 10-31-2022 Wenhui Xie Modified comment(s), and */ /* supported HTTP Proxy, */ /* resulting in version 6.2.0 */ /* */ /**************************************************************************/ 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; #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 #ifdef NX_ENABLE_HTTP_PROXY /* Check if the HTTP Proxy is started and waiting for TCP socket connection. */ if ((socket_ptr -> nx_tcp_socket_ip_ptr -> nx_ip_http_proxy_enable) && (socket_ptr -> nx_tcp_socket_http_proxy_state == NX_HTTP_PROXY_STATE_WAITING)) { /* TCP connection established, start the HTTP Proxy connection. */ _nx_http_proxy_client_connect(socket_ptr); } else #endif /* NX_ENABLE_HTTP_PROXY */ { #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 /* 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); } }