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LINK_ADDR(3)		     Library Functions Manual		    LINK_ADDR(3)

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.

     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
     The  link_ntoa()  function  always  returns  a null terminated string.  The
     link_addr() function has no return value.	(See "BUGS".)

SEE ALSO
     getnameinfo(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.

FreeBSD 14.3			February 28, 2007		    LINK_ADDR(3)

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<https://man.freebsd.org/cgi/man.cgi?query=link_addr&manpath=FreeBSD+14.3-RELEASE+and+Ports>

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