net/FreeBSD/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 1.14 2004/07/03 22:30:08 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 The
 106 .Fn link_ntoa
 107 function
 108 always returns a null terminated string.
 109 The
 110 .Fn link_addr
 111 function
 112 has no return value.
 113 (See
 114 .Sx BUGS . )
 115 .Sh SEE ALSO
 116 .Xr addr2ascii 3
 117 .\" .Xr iso 4
 118 .Sh HISTORY
 119 The
 120 .Fn link_addr
 121 and
 122 .Fn link_ntoa
 123 functions appeared in
 124 .Bx 4.3 Reno .
 125 .Sh BUGS
 126 The returned values for link_ntoa
 127 reside in a static memory area.
 128 .Pp
 129 The function
 130 .Fn link_addr
 131 should diagnose improperly formed input, and there should be an unambiguous
 132 way to recognize this.
 133 .Pp
 134 If the
 135 .Va sdl_len
 136 field of the link socket address
 137 .Fa sdl
 138 is 0,
 139 .Fn link_ntoa
 140 will not insert a colon before the interface address bytes.
 141 If this translated address is given to
 142 .Fn link_addr
 143 without inserting an initial colon,
 144 the latter will not interpret it correctly.