NAME
link_addr,
link_ntoa —
elementary address specification routines for link level
access
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/types.h>
#include <sys/socket.h>
#include <net/if_dl.h>
void
link_addr(
const
char *addr,
struct
sockaddr_dl *sdl);
char *
link_ntoa(
const
struct sockaddr_dl *sdl);
DESCRIPTION
The routine
link_addr() interprets character strings
representing link-level addresses, returning binary information suitable for
use in system calls. The routine
link_ntoa() takes a
link-level address and returns an 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.
Prior to a call to
link_addr(),
sdl->sdl_len must be initialized to the size of the
link-level socket structure, typically
sizeof(struct
sockaddr_dl).
For
link_addr(), the string
addr may
contain an optional network interface identifier of the form “name
unit-number”, suitable for the first argument to
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.
Thus
le0:8.0.9.13.d.30
represents an ethernet address to
be transmitted on the first Lance ethernet interface.
RETURN VALUES
link_ntoa() always returns a null terminated string.
link_addr() has no return value (See
BUGS).
SEE ALSO
ethers(3),
iso(4)
HISTORY
The
link_addr() and
link_ntoa() functions
appeared in
4.3BSD-Reno.
BUGS
The returned string for
link_ntoa() resides in a static memory
area. If it would overflow this area,
link_ntoa() silently
truncates the result.
The function
link_addr() should diagnose improperly formed
input, and there should be an unambiguous way to recognize this.
If the
sdl_len field of the link socket address
sdl is 0,
link_ntoa() will not insert
a colon before the interface address bytes. If this translated address is
given to
link_addr() without inserting an initial colon, the
latter will not interpret it correctly.