118 lines
2.8 KiB
Groff
118 lines
2.8 KiB
Groff
.\" $NetBSD: ethers.3,v 1.8 1999/03/22 19:44:50 garbled Exp $
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.\"
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.\" Written by roland@frob.com. Public domain.
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.\"
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.Dd November 2, 1997
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.Dt ETHERS 3
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.Os
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.Sh NAME
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.Nm ether_ntoa ,
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.Nm ether_aton ,
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.Nm ether_ntohost ,
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.Nm ether_hostton ,
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.Nm ether_line ,
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.Nd get ethers entry
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.Fd #include <net/if_ether.h>
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.Ft char *
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.Fn ether_ntoa "struct ether_addr *e"
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.Ft struct ether_addr *
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.Fn ether_aton "const char *s"
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.Ft int
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.Fn ether_ntohost "char *hostname" "struct ether_addr *e"
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.Ft int
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.Fn ether_hostton "const char *hostname" "struct ether_addr *e"
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.Ft int
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.Fn ether_line "const char *line" "struct ether_addr *e" "char *hostname"
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.Sh DESCRIPTION
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Ethernet addresses are represented by the
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following structure:
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.Bd -literal -offset indent
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struct ether_addr {
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u_char ether_addr_octet[6];
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};
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.Ed
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.Pp
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The
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.Fn ether_ntoa
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function converts this structure into an ASCII string of the form
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``xx:xx:xx:xx:xx:xx'', consisting of 6 hexadecimal numbers separated
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by colons. It returns a pointer to a static buffer that is reused for
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each call.
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The
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.Fn ether_aton
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converts an ASCII string of the same form and to a structure
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containing the 6 octets of the address. It returns a pointer to a
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static structure that is reused for each call.
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.Pp
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The
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.Fn ether_ntohost
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and
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.Fn ether_hostton
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functions interrogate the data base mapping host names to Ethernet
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addresses,
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.Pa /etc/ethers .
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The
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.Fn ether_ntohost
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function looks up the given Ethernet address and writes the associated
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host name into the character buffer passed.
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The
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.Fn ether_hostton
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function looks up the given host name and writes the associated
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Ethernet address into the structure passed. Both functions return
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zero if they find the requested host name or address, and -1 if not.
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Each call reads
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.Pa /etc/ethers
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from the beginning; if a + appears alone on a line in the file, then
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.Fn ether_hostton
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will consult the
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.Pa ethers.byname
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YP map, and
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.Fn ether_ntohost
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will consult the
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.Pa ethers.byaddr
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YP map.
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.Pp
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The
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.Fn ether_line
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function parses a line from the
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.Pa /etc/ethers
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file and fills in the passed ``struct ether_addr'' and character
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buffer with the Ethernet address and host name on the line. It
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returns zero if the line was successfully parsed and -1 if not.
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.Pp
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The
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.Fa hostname
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buffer for
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.Fn ether_line
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and
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.Fn ether_ntohost
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should be at least
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.Dv MAXHOSTNAMELEN
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+ 1
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characters long, to prevent a buffer overflow during parsing.
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.Sh FILES
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.Bl -tag -width /etc/ethers -compact
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.It Pa /etc/ethers
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.El
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.Sh SEE ALSO
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.Xr ethers 5
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.Sh HISTORY
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The
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.Fn ether_ntoa ,
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.Fn ether_aton ,
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.Fn ether_ntohost ,
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.Fn ether_hostton ,
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and
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.Fn ether_line
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functions were adopted from
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.Tn SunOS
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and appeared in
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.Nx 1.0 .
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.Sh BUGS
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The data space used by these functions is static; if future use
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requires the data, it should be copied before any subsequent calls to
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these functions overwrite it.
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