\" $NetBSD: linkaddr.3,v 1.13 2017/07/03 21:32:49 wiz Exp $
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\" @(#)linkaddr.3 8.1 (Berkeley) 7/28/93
\"
Dd December 7, 2016
Dt LINK_ADDR 3
Os
Sh NAME
Nm link_addr ,
Nm link_ntoa
Nd elementary address specification routines for link level access
Sh LIBRARY
Lb libc
Sh SYNOPSIS
In sys/types.h
In sys/socket.h
In net/if_dl.h
Ft void
Fn link_addr "const char *addr" "struct sockaddr_dl *sdl"
Ft char *
Fn link_ntoa "const struct sockaddr_dl *sdl"
Sh DESCRIPTION
The routine
Fn link_addr
interprets character strings representing link-level addresses,
returning binary information suitable for use in system calls.
The routine
Fn link_ntoa
takes a link-level address and returns an
Tn ASCII
string representing some of the information present, including the
link level address itself, and the interface name or number, if present.
This facility is experimental and is still subject to change.
Pp
Prior to a call to
Fn link_addr ,
Fa sdl->sdl_len
must be initialized to the size of the link-level socket structure,
typically
Fa sizeof(struct sockaddr_dl) .
Pp
For
Fn link_addr ,
the string
Fa addr
may contain
an optional network interface identifier of the form
Dq "name unit-number" ,
suitable for the first argument to
Xr ifconfig 8 ,
followed in all cases by a colon and
an interface address in the form of
groups of hexadecimal digits
separated by periods.
Each group represents a byte of address;
address bytes are filled left to right from
low order bytes through high order bytes.
Pp
\" A regular expression may make this format clearer:
\" .Bd -literal -offset indent
\" ([a-z]+[0-9]+:)?[0-9a-f]+(\e.[0-9a-f]+)*
\" .Ed
\" .Pp
Thus
Li le0:8.0.9.13.d.30
represents an ethernet address
to be transmitted on the first Lance ethernet interface.
Sh RETURN VALUES
Fn link_ntoa
always returns a null terminated string.
Fn link_addr
has no return value (See
Sx BUGS ) .
Sh SEE ALSO
Xr ethers 3 ,
Xr iso 4
Sh HISTORY
The
Fn link_addr
and
Fn link_ntoa
functions appeared in
Bx 4.3 Reno .
Sh BUGS
The returned string for
Fn link_ntoa
resides in a static memory area.
If it would overflow this area,
Fn link_ntoa
silently truncates the result.
Pp
The function
Fn link_addr
should diagnose improperly formed input, and there should be an unambiguous
way to recognize this.
Pp
If the
Va sdl_len
field of the link socket address
Fa sdl
is 0,
Fn link_ntoa
will not insert a colon before the interface address bytes.
If this translated address is given to
Fn link_addr
without inserting an initial colon,
the latter will not interpret it correctly.
