bootpgw(1Mtcp)

bootpgw -- Internet Boot Protocol gateway

Synopsis

in.bootpgw [ -i ] [ -s ] [ -t timeout ] [ -D debug_level ] [ -h hop_cnt ] [ -a gw_addr ] [ -w wait_tm ] server

Description

bootpgw implements a simple BOOTP gateway which can be used to forward requests and responses between clients on one subnet and a BOOTP or DHCP server (that is, bootpd(1Mtcp) or dhcpd(1Mtcp) on another subnet. While either bootpd or bootpgw will forward BOOTREPLY packets, only bootpgw will forward BOOTREQUEST packets.

One host on each network segment is normally configured to run bootpgw from inetd by including the following line in the file /etc/inetd.conf:

   bootps dgram/i udp wait root /usr/sbin/in.bootpgw in.bootpgw server

The /i option to the socket type (sock_type) ``dgram'' is required in order to identify the interface on which a packet was received (by activating the IP_RECVIFINDEX option on the socket).

This mode of operation is referred to as ``inetd mode'' and causes 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 -t option controls this timeout (see ``Options'').

It is also possible to run bootpgw in ``standalone mode'' (without inetd) by simply invoking it from a shell like any other regular command. This is not very useful for bootpgw which has very little start up delay because it does not read a configuration file.

bootpgw automatically detects whether it was invoked from inetd or from a shell and automatically selects the appropriate mode. The -s or -i option may be used to force standalone or inetd mode, respectively (see ``Options'').

Options

-a gw_addr: Specifies what address to fill in for the gateway address. Since more than one address can be assigned to an interface, bootpgw will forward packets to the address specified.
-D debug_level: Sets the debug_level variable that controls the amount of debugging messages generated. For example, -D 1 will set the debugging level to 1. Recognized values are 0, 1, 2, and 3 or greater. Zero generates no messages and 1 to 3 generate increasing amounts of messages. Specifying an integer over 3 has the same result as specifying 3. For compatibility with older versions of bootpgw, the option -d (without an argument) will simply increment the debug level by one.
-h hop_cnt: Sets the maximum number of hops allowed for requests; bootpgw increments the hop count of the BOOTREQUEST packet. The packet is dropped if the hop_cnt limit is reached. The default hop_cnt is 4.
-i: Force inetd mode. This option is obsolete, but remains for compatibility with older versions of bootpgw.
-s: Force standalone mode. This option is obsolete, but remains for compatibility with older versions of bootpgw.
-t timeout: Specifies the timeout value (in minutes) that a bootpgw process will wait for a BOOTP packet before exiting. If no packets are received for timeout minutes, then the program will exit. A timeout value of zero means ``run forever''. In standalone mode, this option is forced to zero.
-w wait_tm: Sets the minimum number of seconds a client must wait before bootpgw will forward its BOOTREQUEST packet. The default wait_tm value is 3.

server specifies the name of a BOOTP server to which bootpgw will forward all BOOTREQUEST packets it receives.

Operation

bootpgw listens for any packets sent to the bootps port and forwards any BOOTREPLY packets.

When bootpgw is started, it determines the address of a BOOTP server whose name is provided as a command line parameter. When 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.

During initialization, bootpgw determines the UDP port numbers to be used by calling getservbyname (see getservent(3N)) (which normally uses /etc/services). Two service names (and port numbers) are used:

bootps: BOOTP server listening port
bootpc: BOOTP client destination port

If the port numbers cannot be determined using getservbyname, then the values default to bootps=67 and bootpc=68.

Files

/etc/services: internet service numbers

References

bootp(1Mtcp), bootpd(1Mtcp), bootpef(1Mtcp), bootptab(4tcp), dhcpd(1Mtcp), inetd(1Mtcp), inetd.conf(4tcp), tftpd(1Mtcp)