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 /** NetX Component */
15 /** */
16 /** Internet Protocol version 6 Default Router Table (IPv6 router) */
17 /** */
18 /**************************************************************************/
19 /**************************************************************************/
20 #define NX_SOURCE_CODE
21
22
23 #include "nx_api.h"
24 #include "nx_ipv6.h"
25
26 #ifdef FEATURE_NX_IPV6
27
28 /**************************************************************************/
29 /* */
30 /* FUNCTION RELEASE */
31 /* */
32 /* _nxd_ipv6_find_max_prefix_length PORTABLE C */
33 /* 6.1 */
34 /* AUTHOR */
35 /* */
36 /* Yuxin Zhou, Microsoft Corporation */
37 /* */
38 /* DESCRIPTION */
39 /* */
40 /* This function finds the longest matching prefix between two IPv6 */
41 /* addresses. */
42 /* */
43 /* INPUT */
44 /* */
45 /* addr1 IPv6 address 1 */
46 /* addr2 IPv6 address 2 */
47 /* max_length Maximum length to match */
48 /* */
49 /* OUTPUT */
50 /* */
51 /* Number of matching bits */
52 /* */
53 /* CALLS */
54 /* */
55 /* None */
56 /* */
57 /* CALLED BY */
58 /* */
59 /* _nx_ipv6_source_selection */
60 /* */
61 /* NOTE */
62 /* */
63 /* */
64 /* RELEASE HISTORY */
65 /* */
66 /* DATE NAME DESCRIPTION */
67 /* */
68 /* 05-19-2020 Yuxin Zhou Initial Version 6.0 */
69 /* 09-30-2020 Yuxin Zhou Modified comment(s), */
70 /* resulting in version 6.1 */
71 /* */
72 /**************************************************************************/
_nxd_ipv6_find_max_prefix_length(ULONG * addr1,ULONG * addr2,UINT max_length)73 UINT _nxd_ipv6_find_max_prefix_length(ULONG *addr1, ULONG *addr2, UINT max_length)
74 {
75 UINT length = 0;
76 UINT i, j, bit, time;
77
78 for (i = 0; i < 4; i++)
79 {
80 if (addr1[i] == addr2[i])
81 {
82 length += 32;
83 }
84 /* Length shall not exceed max_length. Stop compare. */
85 else if (length + 31 < max_length)
86 {
87 break;
88 }
89 else
90 {
91 bit = 16;
92 time = 16;
93 for (j = 0; j < 5; j++)
94 {
95 time = time / 2;
96 if (addr1[i] >> bit == addr2[i] >> bit)
97 {
98 bit -= time;
99 if (time == 0)
100 {
101 length += (32 - bit);
102 }
103 }
104 else if (j == 4)
105 {
106 length += (31 - bit);
107 break;
108 }
109 else
110 {
111 bit += time;
112 }
113 }
114 break;
115 }
116 }
117
118
119 return(length);
120 }
121
122 #endif /* FEATURE_NX_IPV6 */
123
124
