.\" Copyright (c) 1995 Bill Paul . .\" Copyright (c) 2007 Robert N. M. Watson .\" 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: head/lib/libc/net/ethers.3 224701 2011-08-08 03:09:03Z hrs $ .\" .Dd October 30, 2007 .Dt ETHERS 3 .Os .Sh NAME .Nm ethers , .Nm ether_line , .Nm ether_aton , .Nm ether_aton_r , .Nm ether_ntoa , .Nm ether_ntoa_r , .Nm ether_ntohost , .Nm ether_hostton .Nd Ethernet address conversion and lookup routines .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In sys/types.h .In sys/socket.h .In net/ethernet.h .Ft int .Fn ether_line "const char *l" "struct ether_addr *e" "char *hostname" .Ft struct ether_addr * .Fn ether_aton "const char *a" .Ft struct ether_addr * .Fn ether_aton_r "const char *a" "struct ether_addr *e" .Ft char * .Fn ether_ntoa "const struct ether_addr *n" .Ft char * .Fn ether_ntoa_r "const struct ether_addr *n" "char *buf" .Ft int .Fn ether_ntohost "char *hostname" "const struct ether_addr *e" .Ft int .Fn ether_hostton "const char *hostname" "struct ether_addr *e" .Sh DESCRIPTION These functions operate on ethernet addresses using an .Vt ether_addr structure, which is defined in the header file .In net/ethernet.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 .Fa l , an .Tn ASCII string in .Xr ethers 5 format and sets .Fa e to the ethernet address specified in the string and .Fa h to the hostname. This function is used to parse lines from .Pa /etc/ethers into their component parts. .Pp The .Fn ether_aton and .Fn ether_aton_r functions convert .Tn ASCII representation of ethernet addresses into .Vt ether_addr structures. Likewise, the .Fn ether_ntoa and .Fn ether_ntoa_r functions convert ethernet addresses specified as .Vt ether_addr structures into .Tn ASCII strings. .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. The .Fn ether_ntohost function converts from ethernet address to hostname, and .Fn ether_hostton converts from hostname to ethernet address. .Sh RETURN VALUES The .Fn ether_line function returns zero on success and non-zero if it was unable to parse any part of the supplied line .Fa l . It returns the extracted ethernet address in the supplied .Vt ether_addr structure .Fa e and the hostname in the supplied string .Fa h . .Pp On success, .Fn ether_ntoa and .Fn ether_ntoa_r functions return a pointer to a string containing an .Tn ASCII representation of an ethernet address. If it is unable to convert the supplied .Vt ether_addr structure, it returns a .Dv NULL pointer. .Fn ether_ntoa stores the result in a static buffer; .Fn ether_ntoa_r stores the result in a user-passed buffer. .Pp Likewise, .Fn ether_aton and .Fn ether_aton_r return a pointer to an .Vt ether_addr structure on success and a .Dv NULL pointer on failure. .Fn ether_aton stores the result in a static buffer; .Fn ether_aton_r stores the result in a user-passed buffer. .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 ensure that the hostname strings passed to 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 ethers 5 , .Xr yp 8 .Sh HISTORY This particular implementation of the .Nm library functions were written for and first appeared in .Fx 2.1 . Thread-safe function variants first appeared in .Fx 7.0 . .Sh BUGS 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. .Pp .Fn ether_ntoa_r accepts a character buffer pointer, but not a buffer length. The caller must ensure adequate space is available in the buffer in order to avoid a buffer overflow.