DHCP Request Packet Validation Exit Program

The Dynamic Host Configuration Protocol (DHCP) Request Packet Validation exit program provides additional control for restricting which incoming DHCP and Bootstrap Protocol (BOOTP) message request packets from client hosts are processed by the DHCP server, and which should be rejected. Any restrictions that are imposed by the exit program are in addition to any validation that is performed by the DHCP server program through its configuration options. When an exit program is added to the exit point, it is called by the DHCP server each time an incoming DHCP or BOOTP request packet is received, but before any processing of the packet has taken place. The packet data is passed to the exit program just as it was received off the network without any additional formatting or data conversion. The exit program sets the allow operation parameter to indicate whether the DHCP server should continue with normal processing of the request packet. If the exit program indicates that the request packet should be rejected, the DHCP server will discard the packet without any further processing.

Note: Since this is an exit point of the DHCP server, the exit program can only be used to restrict BOOTP packets if the DHCP server is running. It cannot be used to restrict BOOTP packets from being processed by the BOOTP server.

Authorities and Locks

None.

Required Parameter Group

Request packet

INPUT; CHAR(*)

The DHCP or BOOTP message request packet that was initiated from some client host and received by the DHCP server. It is in its initial form, which is how it comes off of the network.

The formats of the packets are defined and maintained by the Internet Engineering Task Force (IETF) standards body. Refer to the following IETF Request For Comments (RFC) documents for the specifications:

• RFC 951, Bootstrap Protocol (BOOTP)
• RFC 1542, Clarifications and Extensions for the Bootstrap Protocol
• RFC 2131, Dynamic Host Configuration Protocol
• RFC 2132, DHCP Options and BOOTP Vendor Extensions

Note: Since the packet is presented to the exit program just as it was received from the network, it should be noted that any data areas of the packet that are defined as type string or character by the RFCs will be US-ASCII. On the iSeries, it is recommended that this data be treated as CCSID 819.

Length of request packet

INPUT; BINARY(4)

The length (in bytes) of the request packet.

Allow operation

OUTPUT; BINARY(4)

Whether the DHCP server should continue processing the request packet, or whether it should be rejected. The possible values are:

0	The request packet should be rejected
1	Processing of the request packet should be allowed to continue