net/linkaddr.3

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  35 .\"     From: @(#)linkaddr.3    8.1 (Berkeley) 7/28/93
  36 .\" $FreeBSD: src/lib/libc/net/linkaddr.3,v 1.12 2001/10/01 16:08:56 ru Exp $
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  38 .Dd June 17, 1996
  39 .Dt LINK_ADDR 3
  40 .Os
  41 .Sh NAME
  42 .Nm link_addr ,
  43 .Nm link_ntoa
  44 .Nd elementary address specification routines for link level access
  45 .Sh LIBRARY
  46 .Lb libc
  47 .Sh SYNOPSIS
  48 .In sys/types.h
  49 .In sys/socket.h
  50 .In net/if_dl.h
  51 .Ft void
  52 .Fn link_addr "const char *addr" "struct sockaddr_dl *sdl"
  53 .Ft char *
  54 .Fn link_ntoa "const struct sockaddr_dl *sdl"
  55 .Sh DESCRIPTION
  56 The routine
  57 .Fn link_addr
  58 interprets character strings representing
  59 link-level addresses, returning binary information suitable
  60 for use in system calls.
  61 The routine
  62 .Fn link_ntoa
  63 takes
  64 a link-level
  65 address and returns an
  66 .Tn ASCII
  67 string representing some of the information present,
  68 including the link level address itself, and the interface name
  69 or number, if present.
  70 This facility is experimental and is
  71 still subject to change.
  72 .Pp
  73 For
  74 .Fn link_addr ,
  75 the string
  76 .Fa addr
  77 may contain
  78 an optional network interface identifier of the form
  79 .Dq "name unit-number" ,
  80 suitable for the first argument to
  81 .Xr ifconfig 8 ,
  82 followed in all cases by a colon and
  83 an interface address in the form of
  84 groups of hexadecimal digits
  85 separated by periods.
  86 Each group represents a byte of address;
  87 address bytes are filled left to right from
  88 low order bytes through high order bytes.
  89 .Pp
  90 .\" A regular expression may make this format clearer:
  91 .\" .Bd -literal -offset indent
  92 .\" ([a-z]+[0-9]+:)?[0-9a-f]+(\e.[0-9a-f]+)*
  93 .\" .Ed
  94 .\" .Pp
  95 Thus
  96 .Li le0:8.0.9.13.d.30
  97 represents an ethernet address
  98 to be transmitted on the first Lance ethernet interface.
  99 .Pp
 100 The direct use of these functions is deprecated in favor of the
 101 .Xr addr2ascii 3
 102 interface; however, portable programs cannot rely on the latter as it is
 103 not yet widely implemented.
 104 .Sh RETURN VALUES
 105 .Fn link_ntoa
 106 always returns a null terminated string.
 107 .Fn link_addr
 108 has no return value.
 109 (See
 110 .Sx BUGS . )
 111 .Sh SEE ALSO
 112 .Xr addr2ascii 3
 113 .\" .Xr iso 4
 114 .Sh HISTORY
 115 The
 116 .Fn link_addr
 117 and
 118 .Fn link_ntoa
 119 functions appeared in
 120 .Bx 4.3 Reno  .
 121 .Sh BUGS
 122 The returned values for link_ntoa
 123 reside in a static memory area.
 124 .Pp
 125 The function
 126 .Fn link_addr
 127 should diagnose improperly formed input, and there should be an unambiguous
 128 way to recognize this.
 129 .Pp
 130 If the
 131 .Va sdl_len
 132 field of the link socket address
 133 .Fa sdl
 134 is 0,
 135 .Fn link_ntoa
 136 will not insert a colon before the interface address bytes.
 137 If this translated address is given to
 138 .Fn link_addr
 139 without inserting an initial colon,
 140 the latter will not interpret it correctly.