NAME    [Toc]    [Back]

     link_addr, link_ntoa - elementary address specification routines for link
     level access

LIBRARY    [Toc]    [Back]

     Standard C Library (libc, -lc)

SYNOPSIS    [Toc]    [Back]

     #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    [Toc]    [Back]

     The routine link_addr() interprets character strings representing 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.

     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    [Toc]    [Back]

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

SEE ALSO    [Toc]    [Back]

     ethers(3), iso(4)

HISTORY    [Toc]    [Back]

     The link_addr() and link_ntoa() functions appeared in 4.3BSD-Reno.

BUGS    [Toc]    [Back]

     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                              July 28, 1993                             BSD