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