dhcpagent(1M) System Administration Commands dhcpagent(1M)NAMEdhcpagent - Dynamic Host Configuration Protocol (DHCP) client daemon
SYNOPSISdhcpagent [-a] [ -d n] [-f] [-v]
DESCRIPTIONdhcpagent 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 parame‐
ters 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.
For IPv4, 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 necessary, as ifconfig(1M)
will start it automatically.
For IPv6, the dhcpagent daemon is invoked automatically by in.ndpd(1M).
It can also be controlled through ifconfig(1M), if necessary.
When invoked, dhcpagent enters a passive state while it awaits instruc‐
tions from ifconfig(1M) or in.ndpd(1M). When it receives a command to
configure an interface, it brings up the interface (if necessary) and
starts DHCP. Once DHCP is complete, dhcpagent can 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, it configures the
address for use. When a lease is obtained, it is automatically renewed
as necessary. If the lease cannot be renewed, dhcpagent will unconfig‐
ure the address, but the interface will be left up and dhcpagent will
attempt to acquire a new address lease. dhcpagent monitors system sus‐
pend/resume events and will validate any non-permanent leases with the
DHCP server upon resume. Similarly, dhcpagent monitors link up/down
events and will validate any non-permanent leases with the DHCP server
when the downed link is brought back up. The lease validation mechanism
will restart DHCP if the server indicates that the existing lease is no
longer valid. If the server cannot be contacted, then the existing
lease will continue. This behavior can be modified with the VERI‐
FIED_LEASE_ONLY parameter in the /etc/default/dhcpagent file. See the
description of this parameter below.
For IPv4, if the configured interface is found to be unplumbed, or to
have a different IP address, subnet mask, or broadcast address from
those obtained from DHCP, the interface is abandoned from DHCP control.
For IPv6, dhcpagent automatically plumbs and unplumbs logical inter‐
faces as necessary for the IPv6 addresses supplied by the server. The
IPv6 prefix length (netmask) is not set by the DHCPv6 protocol, but is
instead set by in.ndpd(1M) using prefix information obtained by Router
Advertisements. If any of the logical interfaces created by dhcpagent
is unplumbed, or configured with a different IP address, it will be
abandoned from DHCP control. If the link-local interface is unplumbed,
then all addresses configured by DHCP on that physical interface will
be removed.
In addition to DHCP, dhcpagent also supports BOOTP (IPv4 only). 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, and for IPv4 alone, the netmask, broadcast
address, and default router, the agent does not 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 straightforward.
Clients with multiple interfaces may present difficulties, as it is
possible that some information arriving on different interfaces may
need to be merged, or may be inconsistent. Furthermore, the configura‐
tion 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 ifcon‐
fig(1M) for details.
For IPv4, the dhcpagent daemon can be configured to request a particu‐
lar host name. See the REQUEST_HOSTNAME description in the FILES sec‐
tion. When first configuring a client to request a host name, you must
perform the following steps as root to ensure that the full DHCP nego‐
tiation 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; RFC 3315, option code 16). This identifier
is the same as the platform name returned by the uname -i command,
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 cat‐
egories:
critical
Critical messages indicate severe conditions that prevent proper
operation.
errors
Error messages are important, sometimes unrecoverable events due to
resource exhaustion and other unexpected failure of system calls;
ignoring errors may lead to degraded functionality.
warnings
Warnings indicate less severe problems, 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 configuration at a site. Informa‐
tional 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
configuration 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 and BOUND6
These events occur during interface configuration. The event pro‐
gram is invoked when dhcpagent receives the DHCPv4 ACK or DHCPv6
Reply message from the DHCP server for the lease request of an
address, indicating successful initial configuration of the inter‐
face. (See also the INFORM and INFORM6 events, which occur when
configuration parameters are obtained without address leases.)
EXTEND and EXTEND6
These events occur during lease extension. The event program is
invoked just after dhcpagent receives the DHCPv4 ACK or DHCPv6
Reply from the DHCP server for the DHCPv4 REQUEST (renew) message
or the DHCPv6 Renew or Rebind message.
Note that with DHCPv6, the server might choose to remove some
addresses, add new address leases, and ignore (allow to expire)
still other addresses in a given Reply message. The EXTEND6 event
occurs when a Reply is received that leaves one or more address
leases still valid, even if the Reply message does not extend the
lease for any address. The event program is invoked just before any
addresses are removed, but just after any new addresses are added.
Those to be removed will be marked with the IFF_DEPRECATED flag.
EXPIRE and EXPIRE6
These events occur during lease expiration. For DHCPv4, the event
program is invoked just before the leased address is removed from
an interface. For DHCPv6, the event program is invoked just before
the last remaining leased addresses are removed from the interface.
DROP and DROP6
These events occur during the period when an interface is dropped.
The event program is invoked just before the interface is removed
from DHCP control. If the interface has been abandoned due the user
unplumbing the interface, then this event will occur after the
user's action has taken place. The interface might not be present.
INFORM and INFORM6
These events occur when an interface acquires new or updated con‐
figuration information from a DHCP server by means of the DHCPv4
INFORM or the DHCPv6 Information-Request message. These messages
are sent using an ifconfig(1M) dhcp inform command or when the
DHCPv6 Router Advertisement O (letter 0) bit is set and the M bit
is not set. Thus, these events occur when the DHCP client does not
obtain an IP address lease from the server, and instead obtains
only configuration parameters.
LOSS6
This event occurs during lease expiration when one or more valid
leases still remain. The event program is invoked just before
expired addresses are removed. Those being removed will be marked
with the IFF_DEPRECATED flag.
Note that this event is not associated with the receipt of the
Reply message, which occurs only when one or more valid leases
remain, and occurs only with DHCPv6. If all leases have expired,
then the EXPIRE6 event occurs instead.
RELEASE and RELEASE6
This event occurs during the period when a leased address is
released. The event program is invoked just before dhcpagent relin‐
quishes the address on an interface and sends the DHCPv4 RELEASE or
DHCPv6 Release packet to the DHCP server.
The system does not provide a default event program. The file
/etc/dhcp/eventhook is expected to be owned by root and have a mode of
755.
The event program will be passed two arguments, the interface name and
the event name, respectively. For DHCPv6, the interface name is the
name of the physical interface.
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 redirected to /dev/null. Note that this means that the event pro‐
gram 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 IPv4 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 oper‐
ating system 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:
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:
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 generated as described by the draft document on DHCP
over Infiniband, available at:
http://www.ietf.org
-d n
Set debug level to n. Two levels of debugging are currently avail‐
able, 1 and 2; the latter is more verbose.
-f
Run in the foreground instead of as a daemon process. 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`
;;
"BOUND6")
echo "Addresses acquired from server " \
`/sbin/dhcpinfo -v6 -i $1 ServerID`
;;
"EXTEND")
echo "Lease extended for " \
`sbin/dhcpinfo -i $1 LeaseTim`" seconds"
;;
"EXTEND6")
echo "New lease information obtained on $i"
;;
"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
/etc/dhcp/if.dh6
Contains the configuration for interface. The mere existence of
this file does not imply that the configuration is correct, since
the lease might have expired. On start-up, dhcpagent confirms the
validity of the address using REQUEST (for DHCPv4) or Confirm
(DHCPv6).
/etc/dhcp/duid
/etc/dhcp/iaid
Contains persistent storage for DUID (DHCP Unique Identifier) and
IAID (Identity Association Identifier) values. The format of these
files is undocumented, and applications should not read from or
write to them.
/etc/default/dhcpagent
Contains default values for tunable parameters. All values may be
qualified with the interface they apply to by prepending the inter‐
face name and a period (".") to the interface parameter name. The
parameters include: the interface parameter name.
To configure IPv6 parameters, place the string .v6 between the
interface name (if any) and the parameter name. For example, to set
the global IPv6 parameter request list, use .v6.PARAM_REQUEST_LIST.
To set the CLIENT_ID (DUID) on hme0, use hme0.v6.CLIENT_ID.
The parameters include:
VERIFIED_LEASE_ONLY
Indicates that a RELEASE rather than a DROP should be performed
on managed interfaces when the agent terminates. Release causes
the client to discard the lease, and the server to make the
address available again. Drop causes the client to record the
lease in /etc/dhcp/interface.dhc or /etc/dhcp/interface.dh6 for
later use. In addition, when the link status changes to up or
when the system is resumed after a suspend, the client will
verify the lease with the server. If the server is unreachable
for verification, then the old lease will be discarded (even if
it has time remaining) and a new one obtained.
Enabling this option is often desirable on mobile systems, such
as laptops, to allow the system to recover quickly from moves.
OFFER_WAIT
Indicates how long to wait between checking for valid OFFERs
after sending a DISCOVER. For DHCPv6, sets the time to wait
between checking for valid Advertisements after sending a
Solicit.
CLIENT_ID
Indicates the value that should be used to uniquely identify
the client to the server. This value can take one of three
basic forms:
decimal,data...
0xHHHHH...
"string...."
The first form is an RFC 3315 DUID. This is legal for both IPv4
DHCP and DHCPv6. For IPv4, an RFC 4361 Client ID is constructed
from this value. In this first form, the format of data...
depends on the decimal value. The following formats are defined
for this first form:
1,hwtype,time,lla
Type 1, DUID-LLT. The hwtype value is an integer in the
range 0-65535, and indicates the type of hardware. The time
value is the number of seconds since midnight, January 1st,
2000 UTC, and can be omitted to use the current system
time. The lla value is either a colon-separated MAC address
or the name of a physical interface. If the name of an
interface is used, the hwtype value can be omitted. For
example: 1,,,hme0
2,enterprise,hex...
Type 2, DUID-EN. The enterprise value is an integer in the
range 0-4294967295 and represents the SMI Enterprise number
for an organization. The hex string is an even-length
sequence of hexadecimal digits.
3,hwtype,lla
Type 3, DUID-LL. This is the same as DUID-LLT (type 1),
except that a time stamp is not used.
*,hex
Any other type value (0 or 4-65535) can be used with an
even-length hexadecimal string.
The second and third forms of CLIENT_ID are legal for IPv4
only. These both represent raw Client ID (without RFC 4361), in
hex, or NVT ASCII string format. Thus, "Sun" and 0x53756E are
equivalent.
PARAM_REQUEST_LIST
Specifies a list of comma-separated integer values of options
for which the client would like values, or symbolic Site or
Option option names. Symbolic option names for IPv4 are
resolved through /etc/dhcp/inittab. Option names for IPv6 are
resolved by means of /etc/dhcp/inittab6.
PARAM_IGNORE_LIST
Specifies a list of options (constructed in the same manner as
PARAM_REQUEST_LIST) that the DHCP client will ignore. Ignored
options are treated as though the server did not return the
options specified. Ignored options are not visible using
dhcpinfo(1) or acted on by the client. This parameter can be
used, for example, to disable an unwanted client name or
default router.
REQUEST_HOSTNAME
Indicates the client requests the DHCP server to map the
client's leased IPv4 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.
This option works with DHCPv4 only.
/etc/dhcp/eventhook
Location of a DHCP event program.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWcs │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Committed │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOdhcpinfo(1), ifconfig(1M), init(1M), in.mpathd(1M), in.ndpd(1M), sys‐
log(3C), attributes(5), dhcp(5)
Croft, B. and Gilmore, J.,Bootstrap Protocol (BOOTP)RFC 951, Network
Working Group, September 1985.
Droms, R., Dynamic Host Configuration Protocol, RFC 2131, Network Work‐
ing Group, March 1997.
Lemon, T. and B. Sommerfeld. RFC 4361, Node-specific Client Identifiers
for Dynamic Host Configuration Protocol Version Four (DHCPv4). Nominum
and Sun Microsystems. February 2006.
Droms, R. RFC 3315, Dynamic Host Configuration Protocol for IPv6
(DHCPv6). Cisco Systems. July 2003.
NOTES
The dhcpagent daemon can be used on IPv4 logical interfaces, just as
with physical interfaces. When used on a logical interface, the daemon
automatically constructs a Client ID value based on the DUID and IAID
values, according to RFC 4361. The /etc/default/dhcpagent CLIENT_ID
value, if any, overrides this automatic identifier.
As with physical IPv4 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 phys‐
ical IPv4 interfaces, dhcpagent does not add or remove default routes
associated with logical interfaces.
DHCP can be performed on IPMP IP interfaces to acquire and maintain
IPMP data addresses. Because an IPMP IP interface has no hardware
address, the daemon automatically constructs a Client ID using the same
approach described above for IPv4 logical interfaces. In addition, the
lack of a hardware address means the daemon must set the "broadcast"
flag in all DISCOVER and REQUEST messages on IPMP IP interfaces. Some
DHCP servers may refuse such requests.
DHCP can be performed on IP interfaces that are part of an IPMP group
(to acquire and maintain test addresses). The daemon will automatically
set the NOFAILOVER and DEPRECATED flags on each test address. Addition‐
ally, the daemon will not add or remove default routes in this case.
Note that the actual DHCP packet exchange may be performed over any
active IP interface in the IPMP group. It is strongly recommended that
test addresses have infinite leases. Otherwise, an extended network
outage detectable only by probes may cause test address leases to
expire, causing in.mpathd(1M) to revert to link-based failure detection
and trigger an erroneous repair.
With DHCPv6, the link-local interface must be configured using
/etc/hostname6.hme0 in order for DHCPv6 to run on hme0 at boot time.
The logical interfaces for each address are plumbed by dhcpagent auto‐
matically.
SunOS 5.11 21 Sep 2009 dhcpagent(1M)
