DHCP Option Information

Historically, DHCP option information has been stored in several places in Solaris DHCP, including the server's dhcptab file, the client's dhcptags file, and internal tables of in.dhcpd, snoop, dhcpinfo, and dhcpmgr. In an effort to begin consolidating option information, the Solaris 8 DHCP product has introduced the /etc/dhcp/inittab file. See dhcp_inittab(4) for detailed information about the file.

The inittab file is currently used on the Solaris DHCP client as a replacement for the dhcptags file. The dhcptags file was used to obtain information about option codes received in its DHCP packet. The inittab file now provides this information. In future releases, the in.dhcpd, snoop, and dhcpmgr programs on the DHCP server might use this file as well.

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Note -

Most sites using Solaris DHCP are not affected by this change. Your site is affected only if you are upgrading to Solaris 8, you previously created new DHCP options and modified the /etc/dhcp/dhcptags file, and want to retain the changes. When you upgrade, the upgrade log will notify you that your dhcptags file was modified and that you should make changes to the inittab file.

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Differences Between dhcptags and inittab

The inittab file contains more information than the dhcptags file, and the syntax used is different.

A sample dhcptags entry is:

33 StaticRt - IPList Static_Routes

where 33 is the numeric code that is passed in the DHCP packet, StaticRt is the option name, IPList indicates the expected data is a list of IP addresses, and Static_Routes is a more descriptive name.

The inittab file consists of one-line records describing each option. The format is similar to the format for defining symbols in dhcptab. The syntax of the inittab is described in the following table.

Table 13-3 DHCP inittab Syntax

Option	Description
option-name	Name of the option. The option name must be unique within its option category, and not overlap with other option names in the Standard, Site, and Vendor categories. For example, you cannot have two Site options with the same name, and you should not create a Site option with the same name as a Standard option.
category	Identifies the namespace in which the option belongs. Must be one of Standard, Site, Vendor, Field, or Internal.
code	Identifies the option when it is sent over the network. In most cases, the code uniquely identifies the option, without a category. However, in the case of internal categories like Field or Internal, a code might be used for other purposes and thus might not be globally unique. The code should be unique within the option's category, and not overlap with codes in the Standard and Site fields.
type	Describes the data associated with this option. Valid types are IP, Ascii, Octet, Number, Bool, Unumber8, Unumber16, Unumber32, Snumber8, Snumber16, and Snumber32. For numbers, a preceding `U' or `S' indicates whether the number is unsigned or signed, and the trailing number indicates the number of bits in the number.
granularity	Describes how many units of data make up a whole value for this option. In the case of Number, granularity describes the number of bytes in the number.
maximum	Describes how many whole values are allowed for this option. 0 indicates an infinite number.
consumers	Describes which programs can use this information. This should be set to sdmi, where: s - snoop d - in.dhcpd m - dhcpmgr i - dhcpinfo

A sample inittab entry is:

StaticRt Standard, 33, IP, 2, 0, sdmi

This entry describes an option named StaticRt, which is in the Standard category and is option code 33. The expected data is a potentially infinite number of pairs of IP addresses because the type is IP, granularity is 2, and maximum is infinite (0). The consumers of this option are sdmi: snoop, in.dhcpd, dhcpmgr, and dhcpinfo.

Converting dhcptags Entries to inittab Entries

If you previously added entries to your dhcptags file, you must add corresponding entries to the new inittab file. The following example shows how a sample dhcptags entry might be expressed in inittab format.

Suppose you had added the following dhcptags entry for fax machines connected to the network:

128 FaxMchn - IP Fax_Machine

The code 128 means that it must be in the site category, the option name is FaxMchn, the data type is IP.

The corresponding inittab entry might be:

FaxMchn SITE, 128, IP, 1, 1, sdmi

The granularity of 1 and maximum of 1 indicate that one IP address is expected for this option.