link_addr(3)

NAME

link_addr, link_ntoa - elementary address specification rou

tines 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 repre

senting linklevel 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.

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.

The direct use of these functions is deprecated in favor of

the
addr2ascii(3) interface; however, portable programs cannot

rely on the
latter as it is not yet widely implemented.

RETURN VALUES

The link_ntoa() function always returns a null terminated

string. The
link_addr() function has no return value. (See BUGS.)

SEE ALSO

addr2ascii(3)

HISTORY

The link_addr() and link_ntoa() functions appeared in

4.3BSD-Reno.

BUGS

The returned values for link_ntoa reside in a static memory

area.

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.

BSD June 17, 1996

BSD