NAME
link_addr,
link_ntoa —
elementary address specification
routines for link level access
LIBRARY
library “libc”
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 routinelink_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.
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 lnc0:8.0.9.13.d.30 represents an
ethernet address to be transmitted on the first Lance ethernet
interface.
RETURN VALUES
The link_ntoa() function always returns a
null terminated string. The link_addr() function has
no return value. (See BUGS.)
SEE ALSO
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.