HardenedBSD/libexec/bootpd/bootpd.8

.\" Copyright (c) 1988, 1989, 1991 Carnegie Mellon University
.\"
.\" $FreeBSD$
.\"
.Dd May 21, 2019
.Dt BOOTPD 8
.Os
.Sh NAME
.Nm bootpd , bootpgw
.Nd Internet Boot Protocol server/gateway
.Sh SYNOPSIS
.Nm
.Op Fl i | s
.Op Fl c Ar chdir-path
.Op Fl d Ar level
.Op Fl h Ar hostname
.Op Fl t Ar timeout
.Oo
.Ar bootptab
.Op Ar dumpfile
.Oc
.Nm bootpgw
.Op Fl i | s
.Op Fl d Ar level
.Op Fl h Ar hostname
.Op Fl t Ar timeout
.Ar server
.Sh DESCRIPTION
The
.Nm
utility
implements an Internet Bootstrap Protocol (BOOTP) server as defined in
RFC951, RFC1532, and RFC1533.
The
.Nm bootpgw
utility implements a simple BOOTP gateway which can be used to forward
requests and responses between clients on one subnet and a
BOOTP server (i.e.\&
.Nm )
on another subnet.
While either
.Nm
or
.Nm bootpgw
will forward BOOTREPLY packets, only
.Nm bootpgw
will forward BOOTREQUEST packets.
.Pp
One host on each network segment is normally configured to run either
.Nm
or
.Nm bootpgw
from
.Xr inetd 8
by including one of the following lines in the file
.Pa /etc/inetd.conf :
.Pp
.Dl bootps dgram udp wait root /usr/libexec/bootpd bootpd /etc/bootptab
.Dl bootps dgram udp wait root /usr/libexec/bootpgw bootpgw server
.Pp
This mode of operation is referred to as "inetd mode" and causes
.Nm
(or
.Nm bootpgw )
to be started only when a boot request arrives.
If it does not
receive another packet within fifteen minutes of the last one
it received, it will exit to conserve system resources.
The
.Fl t
option controls this timeout (see OPTIONS).
.Pp
It is also possible to run
.Nm
(or
.Nm bootpgw )
in "standalone mode" (without
.Xr inetd 8 )
by simply invoking it from a shell like any other regular command.
Standalone mode is particularly useful when
.Nm
is used with a large configuration database, where the start up
delay might otherwise prevent timely response to client requests.
(Automatic start up in standalone mode can be done by invoking
.Nm
from within
.Pa /etc/rc.local ,
for example.)
Standalone mode is less useful for
.Nm bootpgw
which
has very little start up delay because
it does not read a configuration file.
.Pp
Either program automatically detects whether it was invoked from inetd
or from a shell and automatically selects the appropriate mode.
The
.Fl s
or
.Fl i
option may be used to force standalone or inetd mode respectively
(see OPTIONS).
.Sh OPTIONS
The following options are available:
.Bl -tag -width indent
.It Fl a
Skip ARP table modifications.
.It Fl t Ar timeout
Specify the
.Ar timeout
value (in minutes) that a
.Nm
or
.Nm bootpgw
process will wait for a BOOTP packet before exiting.
If no packets are received for
.Ar timeout
minutes, then the program will exit.
A timeout value of zero means "run forever".
In standalone mode, this option is forced to zero.
.It Fl d Ar debug-level
Set the
.Ar debug-level
variable that controls the amount of debugging messages generated.
For example,
.Fl d Ns 4
or
.Fl d
4 will set the debugging level to 4.
For compatibility with older versions of
.Nm ,
omitting the numeric parameter (i.e., just
.Fl d )
will simply increment the debug level by one.
.It Fl c Ar chdir-path
Set the current directory used by
.Nm
while checking the existence and size of client boot files.
This is
useful when client boot files are specified as relative pathnames, and
.Nm
needs to use the same current directory as the TFTP server
(typically
.Pa /tftpboot ) .
This option is not recognized by
.Nm bootpgw .
.It Fl h Ar hostname
Specify the hostname corresponding to the IP address to listen on.
By default,
.Nm
listens on the IP address corresponding to the machine's hostname, as
returned by
.Xr gethostname 3 .
.It Fl i
Force inetd mode.
This option is obsolete, but remains for
compatibility with older versions of
.Nm .
.It Fl s
Force standalone mode.
This option is obsolete, but remains for
compatibility with older versions of
.Nm .
.It Ar bootptab
Specify the name of the configuration file from which
.Nm
loads its database of known clients and client options
.No ( Nm
only).
.It Ar dumpfile
Specify the name of the file that
.Nm
will dump its internal database into when it receives a
SIGUSR1 signal
.No ( Nm
only).
This option is only recognized if
.Nm
was compiled with the -DDEBUG flag.
.It Ar server
Specify the name of a BOOTP server to which
.Nm bootpgw
will forward all BOOTREQUEST packets it receives
.Pf ( Nm bootpgw
only).
.El
.Sh OPERATION
Both
.Nm
and
.Nm bootpgw
operate similarly in that both listen for any packets sent to the
.Em bootps
port, and both simply forward any BOOTREPLY packets.
They differ in their handling of BOOTREQUEST packets.
.Pp
When
.Nm bootpgw
is started, it determines the address of a BOOTP server
whose name is provided as a command line parameter.
When
.Nm bootpgw
receives a BOOTREQUEST packet, it sets the "gateway address"
and "hop count" fields in the packet and forwards the packet
to the BOOTP server at the address determined earlier.
Requests are forwarded only if they indicate that
the client has been waiting for at least three seconds.
.Pp
When
.Nm
is started it reads a configuration file, (normally
.Pa /etc/bootptab )
that initializes the internal database of known clients and client
options.
This internal database is reloaded
from the configuration file when
.Nm
receives a hangup signal (SIGHUP) or when it discovers that the
configuration file has changed.
.Pp
When
.Nm
receives a BOOTREQUEST packet, it
.\" checks the modification time of the
.\" configuration file and reloads the database if necessary.  Then it
looks for a database entry matching the client request.
If the client is known,
.Nm
composes a BOOTREPLY packet using the database entry found above,
and sends the reply to the client (possibly using a gateway).
If the client is unknown, the request is discarded
(with a notice if debug > 0).
.Pp
If
.Nm
is compiled with the -DDEBUG option, receipt of a SIGUSR1 signal causes
it to dump its internal database to the file
.Pa /tmp/bootpd.dump
or the dumpfile specified as a command line parameter.
.Pp
During initialization, both programs
determine the UDP port numbers to be used by calling
.Xr getservbyname 3
(which normally uses
.Pa /etc/services ) .
Two service names (and port numbers) are used:
.Pp
.Dl bootps BOOTP Server listening port
.Dl bootpc BOOTP Client destination port
.Pp
If the port numbers cannot be determined using
.Xr getservbyname 3
then the values default to bootps=67 and bootpc=68.
.Sh FILES
.Bl -tag -width /tmp/bootpd.dump -compact
.It Pa /etc/bootptab
Database file read by
.Nm .
.It Pa /tmp/bootpd.dump
Debugging dump file created by
.Nm .
.It Pa /etc/services
Internet service numbers.
.It Pa /tftpboot
Current directory typically used by the TFTP server and
.Nm .
.El
.Sh "SEE ALSO"
.Xr bootptab 5 ,
.Xr inetd 8 ,
.Xr tftpd 8
.Pp
DARPA Internet Request For Comments:
.Bl -tag -width RFC1533 -compact
.It RFC951
Bootstrap Protocol
.It RFC1532
Clarifications and Extensions for the Bootstrap Protocol
.It RFC1533
DHCP Options and BOOTP Vendor Extensions
.El
.Sh AUTHORS
This distribution is currently maintained by
.An Walter L. Wimer Aq Mt walt+@cmu.edu .
.Pp
The original BOOTP server was created by
.An Bill Croft
at Stanford University in January 1986.
.Pp
The current version of
.Nm
is primarily the work of
.An David Kovar ,
.An Drew D. Perkins ,
and
.An Walter L. Wimer ,
at Carnegie Mellon University.
.Pp
Enhancements and bug-fixes have been contributed by:
.Pp
(in alphabetical order)
.Pp
.An -split
.An Danny Backx Aq Mt db@sunbim.be
.An John Brezak Aq Mt brezak@ch.hp.com
.An Frank da Cruz Aq Mt fdc@cc.columbia.edu
.An David R. Linn Aq Mt drl@vuse.vanderbilt.edu
.An Jim McKim Aq Mt mckim@lerc.nasa.gov
.An Gordon W. Ross Aq Mt gwr@mc.com
.An Jason Zions Aq Mt jazz@hal.com .
.Sh BUGS
Individual host entries must not exceed 1024 characters.