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1 | .\" $OpenBSD: if_indextoname.3,v 1.5 2002/03/07 22:41:12 millert Exp $ | ||
2 | .\" Copyright (c) 1983, 1991, 1993 | ||
3 | .\" The Regents of the University of California. All rights reserved. | ||
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33 | .\" From: @(#)rcmd.3 8.1 (Berkeley) 6/4/93 | ||
34 | .\" | ||
35 | .Dd May 21, 1998 | ||
36 | .Dt IF_NAMETOINDEX 3 | ||
37 | .Os | ||
38 | .Sh NAME | ||
39 | .Nm if_nametoindex , | ||
40 | .Nm if_indextoname , | ||
41 | .Nm if_nameindex , | ||
42 | .Nm if_freenameindex | ||
43 | .Nd convert interface index to name, and vice versa | ||
44 | .Sh SYNOPSIS | ||
45 | .Fd #include <net/if.h> | ||
46 | .Ft "unsigned int" | ||
47 | .Fn if_nametoindex "const char *ifname" | ||
48 | .Ft "char *" | ||
49 | .Fn if_indextoname "unsigned int ifindex" "char *ifname" | ||
50 | .Ft "struct if_nameindex *" | ||
51 | .Fn if_nameindex "void" | ||
52 | .Ft "void" | ||
53 | .Fn if_freenameindex "struct if_nameindex *ptr" | ||
54 | .Sh DESCRIPTION | ||
55 | These functions map interface indexes to interface names (such as | ||
56 | .Dq lo0 ) , | ||
57 | and vice versa. | ||
58 | .Pp | ||
59 | The | ||
60 | .Fn if_nametoindex | ||
61 | function converts an interface name specified by the | ||
62 | .Fa ifname | ||
63 | argument to an interface index (positive integer value). | ||
64 | If the specified interface does not exist, 0 will be returned. | ||
65 | .Pp | ||
66 | .Fn if_indextoname | ||
67 | converts an interface index specified by the | ||
68 | .Fa ifindex | ||
69 | argument to an interface name. | ||
70 | The | ||
71 | .Fa ifname | ||
72 | argument must point to a buffer of at least | ||
73 | .Dv IF_NAMESIZE | ||
74 | bytes into which the interface name corresponding to the specified index is | ||
75 | returned. | ||
76 | .Pf ( Dv IF_NAMESIZE | ||
77 | is also defined in | ||
78 | .Aq Pa net/if.h | ||
79 | and its value includes a terminating null byte at the end of the | ||
80 | interface name.) | ||
81 | This pointer is also the return value of the function. | ||
82 | If there is no interface corresponding to the specified index, | ||
83 | .Dv NULL | ||
84 | is returned. | ||
85 | .Pp | ||
86 | .Fn if_nameindex | ||
87 | returns an array of | ||
88 | .Fa if_nameindex | ||
89 | structures. | ||
90 | .Fa if_nametoindex | ||
91 | is also defined in | ||
92 | .Aq Pa net/if.h , | ||
93 | and is as follows: | ||
94 | .Bd -literal -offset | ||
95 | struct if_nameindex { | ||
96 | unsigned int if_index; /* 1, 2, ... */ | ||
97 | char *if_name; /* null terminated name: "le0", ... */ | ||
98 | }; | ||
99 | .Ed | ||
100 | .Pp | ||
101 | The end of the array of structures is indicated by a structure with | ||
102 | an | ||
103 | .Fa if_index | ||
104 | of 0 and an | ||
105 | .Fa if_name | ||
106 | of | ||
107 | .Dv NULL . | ||
108 | The function returns a null pointer on error. | ||
109 | The memory used for this array of structures along with the interface | ||
110 | names pointed to by the | ||
111 | .Fa if_name | ||
112 | members is obtained dynamically. | ||
113 | This memory is freed by the | ||
114 | .Fn if_freenameindex | ||
115 | function. | ||
116 | .Pp | ||
117 | .Fn if_freenameindex | ||
118 | takes a pointer that was returned by | ||
119 | .Fn if_nameindex | ||
120 | as argument | ||
121 | .Pq Fa ptr , | ||
122 | and it reclaims the region allocated. | ||
123 | .Sh DIAGNOSTICS | ||
124 | .Fn if_nametoindex | ||
125 | returns 0 on error, positive integer on success. | ||
126 | .Fn if_indextoname | ||
127 | and | ||
128 | .Fn if_nameindex | ||
129 | return | ||
130 | .Dv NULL | ||
131 | on errors. | ||
132 | .Sh SEE ALSO | ||
133 | .Xr getifaddrs 3 , | ||
134 | .Xr networking 4 | ||
135 | .Pp | ||
136 | R. Gilligan, S. Thomson, J. Bound, and W. Stevens, | ||
137 | ``Basic Socket Interface Extensions for IPv6,'' RFC2553, March 1999. | ||
138 | .Sh STANDARDS | ||
139 | These functions are defined in ``Basic Socket Interface Extensions for IPv6'' | ||
140 | .Pq RFC2533 . | ||