Supplying Additional Information

To perform its second function, delivering application and system-level information, the Solaris DHCP client uses another program, dhcpinfo(1). Since the agent does not know about these services, any configuration information it receives via the DHCP protocol is stored, waiting to be retrieved by dhcpinfo.

The dhcpinfo command takes a command line argument with a specified parameter, interrogates the agent as to the value of that parameter, and echoes the result to its standard output as a (human readable) text string. However, the chief consumer of the dhcpinfo answers is not the user, but the Solaris 2 startup scripts, since the output lends itself easily to shell command substitution and output redirection.

Data supplied by DHCP can be host-wide or interface-specific. On a client with a single DHCP-configurable interface, this distinction is meaningless. But on a host with many interfaces, questions of interpretation arise regarding dhcpinfo parameters. For example, the agent could configure two interfaces and find that the NIS+ domain name returned for the two differs. This situation is resolved by dividing interfaces into two categories: the primary interface and secondary interfaces.

The primary interface is the preferred one for a host-wide configuration. When dhcpinfo is asked for a value, it consults the primary interface. It does the same in the case of interface-specific data. The values returned are those that were received on the primary interface. For example, if dhcpinfo is asked for the IP address, it echoes the IP address of the primary interface to standard output. An interface is designated as primary by command line arguments to ifconfig.

The dhcpinfo command allows other command line options to override this default behavior. One of these options allows an interface name to be explicitly specified. In that case, the values returned are those delivered by DHCP for that interface.

Because much of the host-wide data is critically important to successful booting of a Solaris 2 client, the designation of an interface as primary implies that the system cannot boot unless the agent can configure that interface. The ifconfig command is instructed by command line arguments to wait indefinitely until dhcpagent has finished configuring the primary interface.