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System Administration Commands dhcpagent(1M)
NAME
dhcpagent - Dynamic Host Configuration Protocol (DHCP)
client daemon
SYNOPSIS
dhcpagent [-a] [ -d n] [-f] [-v]
DESCRIPTION
dhcpagent implements the client half of the Dynamic Host
Configuration Protocol (DHCP) for machines running Solaris
software.
The dhcpagent daemon obtains configuration parameters for
the client (local) machine's network interfaces from a DHCP
server. These parameters may include a lease on an IP
address, which gives the client machine use of the address
for the period of the lease, which may be infinite. If the
client wishes to use the IP address for a period longer than
the lease, it must negotiate an extension using DHCP. For
this reason, dhcpagent must run as a daemon, terminating
only when the client machine powers down.
The dhcpagent daemon is controlled through ifconfig(1M) in
much the same way that the init(1M) daemon is controlled by
telinit(1M). dhcpagent can be invoked as a user process,
albeit one requiring root privileges, but this is not neces-
sary, as ifconfig(1M) will start it automatically.
When invoked, dhcpagent enters a passive state while it
awaits instructions fromifconfig(1M). When it receives a
command to configure an interface, it starts DHCP. Once DHCP
is complete, dhcpagent may be queried for the values of the
various network parameters. In addition, if DHCP was used to
obtain a lease on an address for an interface, the interface
is configured and brought up. When a lease is obtained, it
is automatically renewed as necessary. If the lease cannot
be renewed, dhcpagent will take the interface down at the
end of the lease. If the configured interface is found to be
unplumbed, marked down, or to have a different IP address,
subnet mask, or broadcast address from those obtained from
DHCP, the interface is abandoned by DHCP control.
In addition to DHCP, dhcpagent also supports BOOTP. See RFC
951, Bootstrap Protocol. Configuration parameters obtained
from a BOOTP server are treated identically to those
received from a DHCP server, except that the IP address
received from a BOOTP server always has an infinite lease.
DHCP also acts as a mechanism to configure other information
needed by the client, for example, the domain name and
addresses of routers. Aside from the IP address, netmask,
broadcast address and default router, the agent does not
SunOS 5.10 Last change: 10 Feb 2006 1
System Administration Commands dhcpagent(1M)
directly configure the workstation, but instead acts as a
database which may be interrogated by other programs, and in
particular by dhcpinfo(1).
On clients with a single interface, this is quite straight-
forward. Clients with multiple interfaces may present diffi-
culties, as it is possible that some information arriving on
different interfaces may need to be merged, or may be incon-
sistent. Furthermore, the configuration of the interfaces is
asynchronous, so requests may arrive while some or all of
the interfaces are still unconfigured. To handle these
cases, one interface may be designated as primary, which
makes it the authoritative source for the values of DHCP
parameters in the case where no specific interface is
requested. See dhcpinfo(1) and ifconfig(1M) for details.
The dhcpagent daemon can be configured to request a particu-
lar host name. See the REQUEST_HOSTNAME description in the
FILES section. When first configuring a client to request a
host name, you must perform the following steps as root to
ensure that the full DHCP negotiation takes place:
# pkill dhcpagent
# rm /etc/dhcp/interface.dhc
# reboot
All DHCP packets sent by dhcpagent include a vendor class
identifier (RFC 2132, option code 60). This identifier is
the same as the platform name returned by the uname -i com-
mand, except:
o Any commas in the platform name are changed to periods.
o If the name does not start with a stock symbol and a
comma, it is automatically prefixed with SUNW.
Messages
The dhcpagent daemon writes information and error messages
in five categories:
critical Critical messages indicate severe
conditions that prevent proper
operation.
errors Error messages are important, some-
times unrecoverable events due to
resource exhaustion and other unex-
pected failure of system calls;
ignoring errors may lead to degraded
SunOS 5.10 Last change: 10 Feb 2006 2
System Administration Commands dhcpagent(1M)
functionality.
warnings Warnings indicate less severe prob-
lems, and in most cases, describe
unusual or incorrect datagrams
received from servers, or requests
for service that cannot be provided.
informational Informational messages provide key
pieces of information that can be
useful to debugging a DHCP confi-
guration at a site. Informational
messages are generally controlled by
the -v option. However, certain
critical pieces of information, such
as the IP address obtained, are
always provided.
debug Debugging messages, which may be
generated at two different levels of
verbosity, are chiefly of benefit to
persons having access to source
code, but may be useful as well in
debugging difficult DHCP configura-
tion problems. Debugging messages
are only generated when using the -d
option.
When dhcpagent is run without the -f option, all messages
are sent to the system logger syslog(3C) at the appropriate
matching priority and with a facility identifier LOG_DAEMON.
When dhcpagent is run with the -f option, all messages are
directed to standard error.
DHCP Events and User-Defined Actions
If an executable (binary or script) is placed at
/etc/dhcp/eventhook, the dhcpagent deamon will automatically
run that program when any of the following events occur:
BOUND
This event occurs during interface configuration. The
event program is invoked when dhcpagent receives the ACK
SunOS 5.10 Last change: 10 Feb 2006 3
System Administration Commands dhcpagent(1M)
reply from the DHCP server for the lease request of an
address, indicating successful configuration.
EXTEND
This event occurs during lease extension. The event pro-
gram is invoked just after dhcpagent receives the ACK
reply from the DHCP server for the renew request.
EXPIRE
This event occurs during lease expiration. The event
program is invoked just before the leased address is
removed from an interface and the interface is marked as
down.
DROP
This event occurs during the period when an interface is
dropped. The event program is invoked just before the
interface is removed from DHCP control.
RELEASE
This event occurs during the period when a leased
address is released. The event program is invoked just
before dhcpagent relinquishes the address on an inter-
face and sends the RELEASE packet to the DHCP server.
The system does not provide a default event program. The
file /etc/dhcp/eventhook is owned by the root and its mode
must be 755.
The event program will be passed two arguments, the inter-
face name and the event name, respectively.
The event program can use the dhcpinfo(1) utility to fetch
additional information about the interface. While the event
program is invoked on every event defined above, it can
ignore those events in which it is not interested. The event
program runs with the same privileges and environment as
dhcpagent itself, except that stdin, stdout, and stderr are
SunOS 5.10 Last change: 10 Feb 2006 4
System Administration Commands dhcpagent(1M)
redirected to /dev/null. Note that this means that the event
program runs with root privileges.
If an invocation of the event program does not exit after 55
seconds, it is sent a SIGTERM signal. If does not exit
within the next three seconds, it is terminated by a SIGKILL
signal.
See EXAMPLES for an example event program.
OPTIONS
The following options are supported:
-a Adopt a configured interface. This option is for
use with diskless DHCP clients. In the case of
diskless DHCP, DHCP has already been performed on
the network interface providing the operating sys-
tem image prior to running dhcpagent. This option
instructs the agent to take over control of the
interface. It is intended primarily for use in boot
scripts.
The effect of this option depends on whether the
interface is being adopted.
If the interface is being adopted, the following
conditions apply:
o dhcpagent uses the client id specified in
/chosen:<client_id>, as published by the PROM
or as specified on a boot(1M) command line. If
this value is not present, the client id is
undefined. The DHCP server then determines
what to use as a client id. It is an error
condition if the interface is an Infiniband
interface and the PROM value is not present.
If the interface is not being adopted:
o dhcpagent uses the value stored in
/etc/default/dhcpagent. If this value is not
present, the client id is undefined. If the
interface is Infiniband and there is no value
in /etc/default/dhcpagent, a client id is gen-
erated as described by the draft document on
DHCP over Infiniband, available at:
http://www.ietf.org
SunOS 5.10 Last change: 10 Feb 2006 5
System Administration Commands dhcpagent(1M)
-d n Set debug level to n. Two levels of debugging are
currently available, 1 and 2; the latter is more
verbose.
-f Run in the foreground instead of as a daemon pro-
cess. When this option is used, messages are sent
to standard error instead of to syslog(3C).
-v Provide verbose output useful for debugging site
configuration problems.
EXAMPLES
Example 1: Example Event Program
The following script is stored in the file
/etc/dhcp/eventhook, owned by root with a mode of 755. It is
invoked upon the occurrence of the events listed in the
file.
#!/bin/sh
(
echo "Interface name: " $1
echo "Event: " $2
case $2 in
"BOUND")
echo "Address acquired from server " `/sbin/dhcpinfo -i $1 ServerID`
;;
"EXTEND")
echo "Lease extended for " `'sbin/dhcpinfo -i $1 LeaseTim`" seconds"
;;
"EXPIRE" | "DROP" | "RELEASE")
;;
esac
) >/var/run/dhcp_eventhook_output 2>&1
Note the redirection of stdout and stderr to a file.
FILES
/etc/dhcp/if.dhc
Contains the configuration for interface. The mere
SunOS 5.10 Last change: 10 Feb 2006 6
System Administration Commands dhcpagent(1M)
existence of this file does not imply that the confi-
guration is correct, since the lease may have expired.
/etc/default/dhcpagent
Contains default values for tunable parameters. All
values may be qualified with the interface they apply to
by prepending the interface name and a period (".") to
the interface parameter name. The parameters include:
RELEASE_ON_SIGTERM
Indicates that a RELEASE rather than a DROP should
be performed on managed interfaces when the agent
terminates.
OFFER_WAIT
Indicates how long to wait between checking for
valid OFFERs after sending a DISCOVER.
ARP_WAIT
Indicates how long to wait for clients to respond to
an ARP request before concluding the address in the
ARP request is unused.
IGNORE_FAILED_ARP
Specifies whether or not the agent should assume an
address is available, in the unlikely event that ARP
cannot be performed on that address.
CLIENT_ID
Indicates the value that should be used to uniquely
identify the client to the server. By default, the
value is interpreted as an NVT ASCII string, but you
can prepend 0x to the value to indicate a binary
string. Thus, "Sun" and "0x53756E" are equivalent.
SunOS 5.10 Last change: 10 Feb 2006 7
System Administration Commands dhcpagent(1M)
PARAM_REQUEST_LIST
Specifies a list of comma-separated integer values
of options for which the client would like values.
REQUEST_HOSTNAME
Indicates the client requests the DHCP server to map
the client's leased IP address to the host name
associated with the network interface that performs
DHCP on the client. The host name must be specified
in the /etc/hostname.interface file for the relevant
interface on a line of the form
inet hostname
where hostname is the host name requested.
/etc/dhcp/eventhook
Location of a DHCP event program.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsr |
|_____________________________|_____________________________|
| Interface Stability | Evolving |
|_____________________________|_____________________________|
SEE ALSO
dhcpinfo(1), ifconfig(1M), init(1M), syslog(3C), attri-
butes(5), dhcp(5)
System Administration Guide: IP Services
Croft, B. and Gilmore, J.,Bootstrap Protocol (BOOTP)RFC 951,
Network Working Group, September 1985.
SunOS 5.10 Last change: 10 Feb 2006 8
System Administration Commands dhcpagent(1M)
Droms, R., Dynamic Host Configuration Protocol, RFC 2131,
Network Working Group, March 1997.
NOTES
The dhcpagent daemon can be used on logical interfaces just
as with physical interfaces. However, each logical interface
must first be configured with a unique client id by setting
the /etc/default/dhcpagent CLIENT_ID parameter (see descrip-
tion above).
For example, inserting the entry:
hme0:1.CLIENT_ID=orangutan
...in /etc/default/dhcpagent will cause dhcpagent to use the
client id orangutan when managing the lease for hme0:1. As
with physical interfaces, the /etc/hostname.hme0:1 and
/etc/dhcp.hme0:1 files must also be created in order for
hme0:1 to be automatically plumbed and configured at boot.
In addition, unlike physical interfaces, dhcpagent does not
add or remove default routes associated with logical inter-
faces.
SunOS 5.10 Last change: 10 Feb 2006 9
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