xref: /freebsd/lib/libc/net/ethers.3 (revision 453196eb04d88ed1bc05b91f47e08e81facc7c35)

.\" Copyright (c) 1995
.\"	Bill Paul <wpaul@ctr.columbia.edu>.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by Bill Paul.
.\" 4. Neither the name of the author nor the names of any co-contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY Bill Paul AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     $FreeBSD$
.\"
.Dd April 12, 1995
.Dt ETHERS 3
.Os FreeBSD 2.1
.Sh NAME
.Nm ethers ,
.Nm ether_line ,
.Nm ether_aton ,
.Nm ether_ntoa ,
.Nm ether_ntohost ,
.Nm ether_hostton
.Nd Ethernet address conversion and lookup routines
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/socket.h>
.Fd #include <net/ethernet.h>
.Ft int
.Fn ether_line "char *l" "struct ether_addr *e" "char *hostname"
.Ft struct ether_addr *
.Fn ether_aton "char *a"
.Ft char *
.Fn ether_ntoa "struct ether_addr *n"
.Ft int
.Fn ether_ntohost "char *hostname" "struct ether_addr *e"
.Ft int
.Fn ether_hostton "char *hostname" "struct ether_addr *e"
.Sh DESCRIPTION
These functions operate on ethernet addresses using an
.Ar ether_addr
structure, which is defined in the header file
.Aq Pa netinet/if_ether.h :
.Bd -literal -offset indent
/*
 * The number of bytes in an ethernet (MAC) address.
 */
#define ETHER_ADDR_LEN		6

/*
 * Structure of a 48-bit Ethernet address.
 */
struct  ether_addr {
        u_char octet[ETHER_ADDR_LEN];
};
.Ed
.Pp
The function
.Fn ether_line
scans
.Ar l ,
an
.Tn ASCII
string in
.Xr ethers 5
format and sets
.Ar e
to the ethernet address specified in the string and
.Ar h
to the hostname. This function is used to parse lines from
.Pa /etc/ethers
into their component parts.
.Pp
The
.Fn ether_aton
function converts an
.Tn ASCII
representation of an ethernet address into an
.Ar ether_addr
structure. Likewise,
.Fn ether_ntoa
converts an ethernet address specified as an
.Ar ether_addr
structure into an
.Tn ASCII
string.
.Pp
The
.Fn ether_ntohost
and
.Fn ether_hostton
functions map ethernet addresses to their corresponding hostnames
as specified in the
.Pa /etc/ethers
database.
.Fn ether_ntohost
converts from ethernet address to hostname, and
.Fn ether_hostton
converts from hostname to ethernet address.
.Sh RETURN VALUES
.Fn ether_line
returns zero on success and non-zero if it was unable to parse
any part of the supplied line
.Ar l .
It returns the extracted ethernet address in the supplied
.Ar ether_addr
structure
.Ar e
and the hostname in the supplied string
.Ar h .
.Pp
On success,
.Fn ether_ntoa
returns a pointer to a string containing an
.Tn ASCII
representation of an ethernet address. If it is unable to convert
the supplied
.Ar ether_addr
structure, it returns a
.Dv NULL
pointer. Likewise,
.Fn ether_aton
returns a pointer to an
.Ar ether_addr
structure on success and a
.Dv NULL
pointer on failure.
.Pp
The
.Fn ether_ntohost
and
.Fn ether_hostton
functions both return zero on success or non-zero if they were
unable to find a match in the
.Pa /etc/ethers
database.
.Sh NOTES
The user must insure that the hostname strings passed to the
the
.Fn ether_line ,
.Fn ether_ntohost
and
.Fn ether_hostton
functions are large enough to contain the returned hostnames.
.Sh NIS INTERACTION
If the
.Pa /etc/ethers
contains a line with a single + in it, the
.Fn ether_ntohost
and
.Fn ether_hostton
functions will attempt to consult the NIS
.Pa ethers.byname
and
.Pa ethers.byaddr
maps in addition to the data in the
.Pa /etc/ethers
file.
.Sh SEE ALSO
.Xr yp 4 ,
.Xr ethers 5
.Sh BUGS
.Pp
The
.Fn ether_aton
and
.Fn ether_ntoa
functions returns values that are stored in static memory areas
which may be overwritten the next time they are called.
.Sh HISTORY
This particular implementation of the
.Nm ethers
library functions were written for and first appeared in
.Fx 2.1 .