link_addr, link_ntoa -- elementary address specification routines for
link level access
Standard C Library (libc, -lc)
link_addr(const char *addr, struct sockaddr_dl *sdl);
link_ntoa(const struct sockaddr_dl *sdl);
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.
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 le0:126.96.36.199.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.
The link_ntoa() function always returns a null terminated string. The
link_addr() function has no return value. (See BUGS.)
The link_addr() and link_ntoa() functions appeared in 4.3BSD-Reno.
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 5.2.1 June 17, 1996 FreeBSD 5.2.1 [ Back ]