1 /**************************************************************************/
2 /* */
3 /* Copyright (c) Microsoft Corporation. All rights reserved. */
4 /* */
5 /* This software is licensed under the Microsoft Software License */
6 /* Terms for Microsoft Azure RTOS. Full text of the license can be */
7 /* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
8 /* and in the root directory of this software. */
9 /* */
10 /**************************************************************************/
11
12
13 /**************************************************************************/
14 /**************************************************************************/
15 /** */
16 /** NetX Component */
17 /** */
18 /** Transmission Control Protocol (TCP) */
19 /** */
20 /**************************************************************************/
21 /**************************************************************************/
22
23 #define NX_SOURCE_CODE
24
25
26 /* Include necessary system files. */
27
28 #include "nx_api.h"
29 #include "nx_tcp.h"
30
31 #ifdef NX_ENABLE_TCP_WINDOW_SCALING
32
33 /**************************************************************************/
34 /* */
35 /* FUNCTION RELEASE */
36 /* */
37 /* _nx_tcp_window_scaling_option_get PORTABLE C */
38 /* 6.1 */
39 /* AUTHOR */
40 /* */
41 /* Yuxin Zhou, Microsoft Corporation */
42 /* */
43 /* DESCRIPTION */
44 /* */
45 /* This internal function searches for the Window Scale option. */
46 /* If found, first check the option length, if option length is not */
47 /* valid, it returns NX_FALSE to the caller, else it set the window */
48 /* scale size and returns NX_TRUE to the caller. Otherwise, */
49 /* NX_TRUE is returned. */
50 /* */
51 /* INPUT */
52 /* */
53 /* option_ptr Pointer to option area */
54 /* option_area_size Size of option area */
55 /* window_scale window scale size */
56 /* */
57 /* OUTPUT */
58 /* */
59 /* NX_FALSE TCP option is invalid */
60 /* NX_TRUE TCP option is valid */
61 /* */
62 /* CALLS */
63 /* */
64 /* None */
65 /* */
66 /* CALLED BY */
67 /* */
68 /* _nx_tcp_packet_process TCP packet processing */
69 /* _nx_tcp_server_socket_relisten Socket relisten processing */
70 /* */
71 /* RELEASE HISTORY */
72 /* */
73 /* DATE NAME DESCRIPTION */
74 /* */
75 /* 05-19-2020 Yuxin Zhou Initial Version 6.0 */
76 /* 09-30-2020 Yuxin Zhou Modified comment(s), */
77 /* resulting in version 6.1 */
78 /* */
79 /**************************************************************************/
_nx_tcp_window_scaling_option_get(UCHAR * option_ptr,ULONG option_area_size,ULONG * window_scale)80 UINT _nx_tcp_window_scaling_option_get(UCHAR *option_ptr, ULONG option_area_size, ULONG *window_scale)
81 {
82
83 ULONG option_length;
84
85
86 /* Set invalid window scaling, in case the SYN message does not contain Window Scaling feature. */
87 *window_scale = 0xFF;
88
89 /* Loop through the option area looking for the window scaling option. */
90 while (option_area_size >= 3)
91 {
92
93 /* Is the current character the window scaling type? */
94 if (*option_ptr == NX_TCP_RWIN_KIND)
95 {
96
97 /* Yes, we found it! */
98
99 /* Move the pointer forward by one. */
100 option_ptr++;
101
102 /* Check the option length, if option length is not equal to 3, return NX_FALSE. */
103 if (*option_ptr++ != 3)
104 {
105 return(NX_FALSE);
106 }
107
108 /* Get the window scale size. */
109 *window_scale = (ULONG)*option_ptr;
110
111 if (*window_scale > 14)
112 {
113
114 /* Make sure window scale is limited to 14, per RFC 1323 pp.11 */
115 *window_scale = 14;
116 }
117
118 break;
119 }
120
121 /* Otherwise, process relative to the option type. */
122
123 /* Check for end of list. */
124 if (*option_ptr == NX_TCP_EOL_KIND)
125 {
126
127 /* Yes, end of list, get out! */
128 break;
129 }
130
131 /* Check for NOP. */
132 if (*option_ptr == NX_TCP_NOP_KIND)
133 {
134 /* One character option! Skip this option and move to the next entry. */
135 option_ptr++;
136
137 option_area_size--;
138 }
139 else
140 {
141
142 /* Derive the option length. All options *fields* area 32-bits,
143 but the options themselves may be padded by NOP's. Determine
144 the option size based on alignment of the option ptr */
145 option_length = *(option_ptr + 1);
146
147 if (option_length == 0)
148 {
149 /* Illegal option length. */
150 return(NX_FALSE);
151 }
152
153 /* Move the option pointer forward. */
154 option_ptr = option_ptr + option_length;
155
156 /* Determine if this is greater than the option area size. */
157 if (option_length > option_area_size)
158 {
159 return(NX_FALSE);
160 }
161 else
162 {
163 option_area_size = option_area_size - option_length;
164 }
165 }
166 }
167
168 /* Return. */
169 return(NX_TRUE);
170 }
171 #endif /* NX_ENABLE_TCP_WINDOW_SCALING */
172
173
