1 /***************************************************************************
2 * Copyright (c) 2024 Microsoft Corporation
3 *
4 * This program and the accompanying materials are made available under the
5 * terms of the MIT License which is available at
6 * https://opensource.org/licenses/MIT.
7 *
8 * SPDX-License-Identifier: MIT
9 **************************************************************************/
10
11
12 /**************************************************************************/
13 /**************************************************************************/
14 /** */
15 /** NetX Component */
16 /** */
17 /** Transmission Control Protocol (TCP) */
18 /** */
19 /**************************************************************************/
20 /**************************************************************************/
21
22 #define NX_SOURCE_CODE
23
24
25 /* Include necessary system files. */
26
27 #include "nx_api.h"
28 #include "nx_ip.h"
29 #include "nx_tcp.h"
30
31
32 /**************************************************************************/
33 /* */
34 /* FUNCTION RELEASE */
35 /* */
36 /* _nx_tcp_socket_state_syn_received PORTABLE C */
37 /* 6.1 */
38 /* AUTHOR */
39 /* */
40 /* Yuxin Zhou, Microsoft Corporation */
41 /* */
42 /* DESCRIPTION */
43 /* */
44 /* This function processes packets during the SYN RECEIVED state, */
45 /* which is the state after the initial SYN message was responded to */
46 /* with an SYN/ACK message. The expected value here is an ACK, which */
47 /* will move us into an ESTABLISHED state ready for sending and */
48 /* receiving of TCP data. */
49 /* */
50 /* INPUT */
51 /* */
52 /* socket_ptr Pointer to owning socket */
53 /* tcp_header_ptr Pointer to packet header */
54 /* */
55 /* OUTPUT */
56 /* */
57 /* None */
58 /* */
59 /* CALLS */
60 /* */
61 /* _nx_tcp_socket_thread_resume Resume suspended thread */
62 /* _nx_tcp_packet_send_rst Send RST packet */
63 /* */
64 /* CALLED BY */
65 /* */
66 /* _nx_tcp_socket_packet_process Process TCP packet for socket */
67 /* */
68 /* RELEASE HISTORY */
69 /* */
70 /* DATE NAME DESCRIPTION */
71 /* */
72 /* 05-19-2020 Yuxin Zhou Initial Version 6.0 */
73 /* 09-30-2020 Yuxin Zhou Modified comment(s), */
74 /* resulting in version 6.1 */
75 /* */
76 /**************************************************************************/
_nx_tcp_socket_state_syn_received(NX_TCP_SOCKET * socket_ptr,NX_TCP_HEADER * tcp_header_ptr)77 VOID _nx_tcp_socket_state_syn_received(NX_TCP_SOCKET *socket_ptr, NX_TCP_HEADER *tcp_header_ptr)
78 {
79
80
81 /* Determine if the incoming message is an ACK message. If it is and
82 if it is proper, move into the ESTABLISHED state. */
83 if (tcp_header_ptr -> nx_tcp_header_word_3 & NX_TCP_ACK_BIT)
84 {
85
86 if (tcp_header_ptr -> nx_tcp_acknowledgment_number == socket_ptr -> nx_tcp_socket_tx_sequence)
87 {
88
89 /* If trace is enabled, insert this event into the trace buffer. */
90 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);
91
92 /* Save the window size. */
93 socket_ptr -> nx_tcp_socket_tx_window_advertised =
94 tcp_header_ptr -> nx_tcp_header_word_3 & NX_LOWER_16_MASK;
95
96 #ifdef NX_ENABLE_TCP_WINDOW_SCALING
97
98 /* The window size advertised in the SYN packet is NEVER scaled. Therefore there is no
99 need to apply the scale shift. However validate snd_win_scale and rcv_win_scale. */
100 if (socket_ptr -> nx_tcp_snd_win_scale_value == 0xFF)
101 {
102
103 /* Peer does not support window scale option. */
104 socket_ptr -> nx_tcp_snd_win_scale_value = 0;
105 socket_ptr -> nx_tcp_rcv_win_scale_value = 0;
106
107 /* Since peer does not offer window scaling feature, make sure
108 our default window size for this connection does not exceed 65535 bytes. */
109 if (socket_ptr -> nx_tcp_socket_rx_window_maximum > 65535)
110 {
111 socket_ptr -> nx_tcp_socket_rx_window_default = 65535;
112 socket_ptr -> nx_tcp_socket_rx_window_current = 65535;
113 }
114 }
115
116 /* Updated the window size. */
117 socket_ptr -> nx_tcp_socket_tx_window_advertised <<= socket_ptr -> nx_tcp_snd_win_scale_value;
118
119 #endif /* NX_ENABLE_TCP_WINDOW_SCALING */
120
121 /* Set the initial slow start threshold to be the advertised window size. */
122 socket_ptr -> nx_tcp_socket_tx_slow_start_threshold = socket_ptr -> nx_tcp_socket_tx_window_advertised;
123
124 /* Set the initial congestion control window size. */
125 /* Section 3.1, Page 5, RFC5681. */
126 if (socket_ptr -> nx_tcp_socket_timeout_retries > 0)
127 {
128
129 /* Set the initial congestion control window size to be the mss. */
130 socket_ptr -> nx_tcp_socket_tx_window_congestion = socket_ptr -> nx_tcp_socket_connect_mss;
131 }
132 else
133 {
134 socket_ptr -> nx_tcp_socket_tx_window_congestion = (socket_ptr -> nx_tcp_socket_connect_mss << 2);
135 if (socket_ptr -> nx_tcp_socket_connect_mss > 1095)
136 {
137 socket_ptr -> nx_tcp_socket_tx_window_congestion -= socket_ptr -> nx_tcp_socket_connect_mss;
138 }
139 if (socket_ptr -> nx_tcp_socket_connect_mss > 2190)
140 {
141 socket_ptr -> nx_tcp_socket_tx_window_congestion -= socket_ptr -> nx_tcp_socket_connect_mss;
142 }
143 }
144
145 /* Move into the ESTABLISHED state. */
146 socket_ptr -> nx_tcp_socket_state = NX_TCP_ESTABLISHED;
147 #ifndef NX_DISABLE_EXTENDED_NOTIFY_SUPPORT
148
149 /* If registered with the TCP socket, call the application's connection completion callback function. */
150 if (socket_ptr -> nx_tcp_establish_notify)
151 {
152
153 /* Call the application's establish callback function. */
154 (socket_ptr -> nx_tcp_establish_notify)(socket_ptr);
155 }
156 #endif
157
158
159 #ifdef NX_ENABLE_TCP_KEEPALIVE
160 /* Is the keepalive feature enabled on this socket? */
161 if (socket_ptr -> nx_tcp_socket_keepalive_enabled)
162 {
163 /* Setup the TCP Keepalive timer to initial values. */
164 socket_ptr -> nx_tcp_socket_keepalive_timeout = NX_TCP_KEEPALIVE_INITIAL;
165 socket_ptr -> nx_tcp_socket_keepalive_retries = 0;
166 }
167 #endif
168 /* Update the value of nx_tcp_socket_rx_sequence_acked */
169 socket_ptr -> nx_tcp_socket_rx_sequence_acked = socket_ptr -> nx_tcp_socket_rx_sequence;
170
171 /* Determine if we need to wake a thread suspended on the connection. */
172 if (socket_ptr -> nx_tcp_socket_connect_suspended_thread)
173 {
174
175 /* Resume the suspended thread. */
176 _nx_tcp_socket_thread_resume(&(socket_ptr -> nx_tcp_socket_connect_suspended_thread), NX_SUCCESS);
177 }
178 }
179 /* Check for an invalid ACK message that signals an error on the other side. */
180 else
181 {
182
183 /* Invalid response was received, it is likely that the other side still
184 thinks a previous connection is active. Send a reset (RST) message to
185 the other side to clear any previous connection. */
186
187 /* Send the RST packet. */
188 _nx_tcp_packet_send_rst(socket_ptr, tcp_header_ptr);
189 }
190 }
191 }
192
193
