gen.subproj/if_indextoname.3

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