dhcp-options.5

DHCP服务器源码

.B option routers \fIip-address\fR [\fB,\fR \fIip-address\fR...
]\fB;\fR
.RS 0.25i
.PP
The routers option specifies a list of IP addresses for routers on the
client's subnet.  Routers should be listed in order of preference.
.RE
.PP
.B option slp-directory-agent \fIboolean ip-address
[\fB,\fR \fIip-address\fR... ]\fB;\fR
.RS 0.25i
.PP
This option specifies two things: the IP addresses of one or more
Service Location Protocol Directory Agents, and whether the use of
these addresses is mandatory.   If the initial boolean value is true,
the SLP agent should just use the IP addresses given.   If the value
is false, the SLP agent may additionally do active or passive
multicast discovery of SLP agents (see RFC2165 for details).
.PP
Please note that in this option and the slp-service-scope option, the
term "SLP Agent" is being used to refer to a Service Location Protocol
agent running on a machine that is being configured using the DHCP
protocol.
.PP
Also, please be aware that some companies may refer to SLP as NDS.
If you have an NDS directory agent whose address you need to
configure, the slp-directory-agent option should work.
.RE
.PP
.B option slp-service-scope \fIboolean text\fR\fB;\fR
.RS 0.25i
.PP
The Service Location Protocol Service Scope Option specifies two
things: a list of service scopes for SLP, and whether the use of this
list is mandatory.  If the initial boolean value is true, the SLP
agent should only use the list of scopes provided in this option;
otherwise, it may use its own static configuration in preference to
the list provided in this option.
.PP
The text string should be a comma-separated list of scopes that the
SLP agent should use.   It may be omitted, in which case the SLP Agent
will use the aggregated list of scopes of all directory agents known
to the SLP agent.
.RE
.PP
.B option \fBsmtp-server\fR \fIip-address\fR [\fB,\fR
\fIip-address\fR... ]\fB;\fR
.RS 0.25i
.PP
The SMTP server option specifies a list of SMTP servers available to
the client.  Servers should be listed in order of preference.
.RE
.PP
.nf
.B option \fBstatic-routes\fR \fIip-address ip-address\fR
                  [\fB,\fR \fIip-address ip-address\fR...]\fB;\fR
.fi
.RS 0.25i
.PP
This option specifies a list of static routes that the client should
install in its routing cache.  If multiple routes to the same
destination are specified, they are listed in descending order of
priority.
.PP
The routes consist of a list of IP address pairs.  The first address
is the destination address, and the second address is the router for
the destination.
.PP
The default route (0.0.0.0) is an illegal destination for a static
route.  To specify the default route, use the
.B routers
option.   Also, please note that this option is not intended for
classless IP routing - it does not include a subnet mask.   Since
classless IP routing is now the most widely deployed routing standard,
this option is virtually useless, and is not implemented by any of the
popular DHCP clients, for example the Microsoft DHCP client.
.RE
.PP
.nf
.B option \fBstreettalk-directory-assistance-server\fR \fIip-address\fR
                                           [\fB,\fR \fIip-address\fR...]\fB;\fR
.fi
.RS 0.25i
.PP
The StreetTalk Directory Assistance (STDA) server option specifies a
list of STDA servers available to the client.  Servers should be
listed in order of preference.
.RE
.PP
.B option \fBstreettalk-server\fR \fIip-address\fR [\fB,\fR \fIip-address\fR... ]\fB;\fR
.RS 0.25i
.PP
The StreetTalk server option specifies a list of StreetTalk servers
available to the client.  Servers should be listed in order of
preference.
.RE
.PP
.B option subnet-mask \fIip-address\fR\fB;\fR
.RS 0.25i
.PP
The subnet mask option specifies the client's subnet mask as per RFC
950.  If no subnet mask option is provided anywhere in scope, as a
last resort dhcpd will use the subnet mask from the subnet declaration
for the network on which an address is being assigned.  However,
.I any
subnet-mask option declaration that is in scope for the address being
assigned will override the subnet mask specified in the subnet
declaration.
.RE
.PP
.B option \fBsubnet-selection\fR \fIstring\fR\fB;\fR
.RS 0.25i
.PP
Sent by the client if an address is required in a subnet other than the one
that would normally be selected (based on the relaying address of the
connected subnet the request is obtained from). See RFC3011. Note that the
option number used by this server is 118; this has not always been the
defined number, and some clients may use a different value. Use of this
option should be regarded as slightly experimental!
.RE
.PP
This option is not user configurable in the server.
.PP
.PP
.B option \fBswap-server\fR \fIip-address\fR\fB;\fR
.RS 0.25i
.PP
This specifies the IP address of the client's swap server.
.RE
.PP
.B option \fBtcp-keepalive-garbage\fR \fIflag\fR\fB;\fR
.RS 0.25i
.PP
This option specifies whether or not the client should send TCP
keepalive messages with an octet of garbage for compatibility with
older implementations.  A value of false indicates that a garbage octet
should not be sent. A value of true indicates that a garbage octet
should be sent.
.RE
.PP
.B option \fBtcp-keepalive-interval\fR \fIuint32\fR\fB;\fR
.RS 0.25i
.PP
This option specifies the interval (in seconds) that the client TCP
should wait before sending a keepalive message on a TCP connection.
The time is specified as a 32-bit unsigned integer.  A value of zero
indicates that the client should not generate keepalive messages on
connections unless specifically requested by an application.
.RE
.PP
.B option \fBtftp-server-name\fR \fItext\fR\fB;\fR
.RS 0.25i
.PP
This option is used to identify a TFTP server and, if supported by the
client, should have the same effect as the \fBserver-name\fR
declaration.   BOOTP clients are unlikely to support this option.
Some DHCP clients will support it, and others actually require it.
.RE
.PP
.B option time-offset \fIint32\fR\fB;\fR
.RS 0.25i
.PP
The time-offset option specifies the offset of the client's subnet in
seconds from Coordinated Universal Time (UTC).
.RE
.PP
.B option time-servers \fIip-address\fR [, \fIip-address\fR...
]\fB;\fR
.RS 0.25i
.PP
The time-server option specifies a list of RFC 868 time servers
available to the client.  Servers should be listed in order of
preference.
.RE
.PP
.B option \fBtrailer-encapsulation\fR \fIflag\fR\fB;\fR
.RS 0.25i
.PP
This option specifies whether or not the client should negotiate the
use of trailers (RFC 893 [14]) when using the ARP protocol.  A value
of false indicates that the client should not attempt to use trailers.  A
value of true means that the client should attempt to use trailers.
.RE
.PP
.B option \fBuap-servers\fR \fItext\fR\fB;\fR
.RS 0.25i
.PP
This option specifies a list of URLs, each pointing to a user
authentication service that is capable of processing authentication
requests encapsulated in the User Authentication Protocol (UAP).  UAP
servers can accept either HTTP 1.1 or SSLv3 connections.  If the list
includes a URL that does not contain a port component, the normal
default port is assumed (i.e., port 80 for http and port 443 for
https).  If the list includes a URL that does not contain a path
component, the path /uap is assumed.   If more than one URL is
specified in this list, the URLs are separated by spaces.
.RE
.PP
.B option \fBuser-class\fR \fIstring\fR\fB;\fR
.RS 0.25i
.PP
This option is used by some DHCP clients as a way for users to
specify identifying information to the client.   This can be used in a
similar way to the vendor-class-identifier option, but the value of
the option is specified by the user, not the vendor.   Most recent
DHCP clients have a way in the user interface to specify the value for
this identifier, usually as a text string.
.PP
.B option \fBvendor-class-identifier\fR \fIstring\fR\fB;\fR
.RS 0.25i
.PP
This option is used by some DHCP clients to identify the vendor
type and possibly the configuration of a DHCP client.  The information
is a string of bytes whose contents are specific to the vendor and are
not specified in a standard.   To see what vendor class identifier a
clients are sending, you can write the following in your DHCP server
configuration file:
.nf
.PP
set vendor-class option vendor-class-identifier;
.fi
.PP
This will result in all entries in the DHCP server lease database file
for clients that sent vendor-class-identifier options having a set
statement that looks something like this:
.nf
.PP
set vendor-class "SUNW.Ultra-5_10";
.fi
.PP
The vendor-class-identifier option is normally used by the DHCP server
to determine the options that are returned in the
.B vendor-encapsulated-options
option.   Please see the VENDOR ENCAPSULATED OPTIONS section of the
dhcpd.conf manual page for further information.
.RE
.PP
.B option \fBvendor-encapsulated-options\fR \fIstring\fR\fB;\fR
.RS 0.25i
.PP
The \fBvendor-encapsulated-options\fR option can contain either a
single vendor-specific value or one or more vendor-specific
suboptions.   This option is not normally specified in the DHCP server
configuration file - instead, a vendor class is defined for each
vendor, vendor class suboptions are defined, values for those
suboptions are defined, and the DHCP server makes up a response on
that basis.
.PP
Some default behaviours for well-known DHCP client vendors (currently,
the Microsoft Windows 2000 DHCP client) are configured automatically,
but otherwise this must be configured manually - see the VENDOR
ENCAPSULATED OPTIONS section of the \fIdhcpd.conf\fI manual page for
details.
.RE
.PP
.B option \fBwww-server\fR \fIip-address\fR [\fB,\fR
\fIip-address\fR... ]\fB;\fR
.RS 0.25i
.PP
The WWW server option specifies a list of WWW servers available
to the client.  Servers should be listed in order of preference.
.RE
.PP
.B option \fBx-display-manager\fR \fIip-address\fR [\fB,\fR \fIip-address\fR...
]\fB;\fR
.RS 0.25i
.PP
This option specifies a list of systems that are running the X Window
System Display Manager and are available to the client.  Addresses
should be listed in order of preference.
.RE
.SH RELAY AGENT INFORMATION OPTION
An IETF draft, draft-ietf-dhc-agent-options-11.txt, defines a series
of encapsulated options that a relay agent can add to a DHCP packet
when relaying it to the DHCP server.   The server can then make
address allocation decisions (or whatever other decisions it wants)
based on these options.   The server also returns these options in any
replies it sends through the relay agent, so that the relay agent can
use the information in these options for delivery or accounting
purposes.
.PP
The current draft defines two options.   To reference
these options in the dhcp server, specify the option space name,
"agent", followed by a period, followed by the option name.   It is
not normally useful to define values for these options in the server,
although it is permissible.   These options are not supported in the
client.
.PP
.B option \fBagent.circuit-id\fR \fIstring\fR\fB;\fR
.RS 0.25i
.PP
The circuit-id suboption encodes an agent-local identifier of the
circuit from which a DHCP client-to-server packet was received.  It is
intended for use by agents in relaying DHCP responses back to the
proper circuit.   The format of this option is currently defined to be
vendor-dependent, and will probably remain that way, although the
current draft allows for for the possibility of standardizing the
format in the future.
.RE
.PP
.B option \fBagent.remote-id\fR \fIstring\fR\fB;\fR
.RS 0.25i
.PP
The remote-id suboption encodes information about the remote host end
of a circuit.   Examples of what it might contain include caller ID
information, username information, remote ATM address, cable modem ID,
and similar things.   In principal, the meaning is not well-specified,
and it should generally be assumed to be an opaque object that is
administratively guaranteed to be unique to a particular remote end of
a circuit.
.RE
.SH THE CLIENT FQDN SUBOPTIONS
The Client FQDN option, currently defined in the Internet Draft
draft-ietf-dhc-fqdn-option-00.txt is not a standard yet, but is in
sufficiently wide use already that we have implemented it.   Due to
the complexity of the option format, we have implemented it as a
suboption space rather than a single option.   In general this
option should not be configured by the user - instead it should be
used as part of an automatic DNS update system.
.PP
.B option fqdn.no-client-update \fIflag\fB;
.RS 0.25i
.PP
When the client sends this, if it is true, it means the client will not
attempt to update its A record.   When sent by the server to the client,
it means that the client \fIshould not\fR update its own A record.
.RE
.PP
.B option fqdn.server-update \fIflag\fB;
.RS 0.25i
.PP
When the client sends this to the server, it is requesting that the server
update its A record.   When sent by the server, it means that the server
has updated (or is about to update) the client's A record.
.RE
.PP
.B option fqdn.encoded \fIflag\fB;
.RS 0.25i
.PP
If true, this indicates that the domain name included in the option is
encoded in DNS wire format, rather than as plain ASCII text.   The client
normally sets this to false if it doesn't support DNS wire format in the
FQDN option.   The server should always send back the same value that the
client sent.   When this value is set on the configuration side, it controls
the format in which the \fIfqdn.fqdn\fR suboption is encoded.
.RE
.PP
.B option fqdn.rcode1 \fIflag\fB;
.PP
.B option fqdn.rcode2 \fIflag\fB;
.RS 0.25i
.PP
These options specify the result of the updates of the A and PTR records,
respectively, and are only sent by the DHCP server to the DHCP client.
The values of these fields are those defined in the DNS protocol specification.
.RE
.PP
.B option fqdn.fqdn \fItext\fB;
.RS 0.25i
.PP
Specifies the domain name that the client wishes to use.   This can be a
fully-qualified domain name, or a single label.   If there is no trailing
'.' character in the name, it is not fully-qualified, and the server will
generally update that name in some locally-defined domain.
.RE
.PP
.B option fqdn.hostname \fI--never set--\fB;
.RS 0.25i
.PP
This option should never be set, but it can be read back using the \fBoption\fR
and \fBconfig-option\fR operators in an expression, in which case it returns
the first label in the \fBfqdn.fqdn\fR suboption - for example, if
the value of \fBfqdn.fqdn\fR is "foo.example.com.", then \fBfqdn.hostname\fR
will be "foo".
.RE
.PP
.B option fqdn.domainname \fI--never set--\fB;
.RS 0.25i
.PP
This option should never be set, but it can be read back using the \fBoption\fR