System Administration Commands dhcpagent(1M)
NAME
dhcpagent - Dynamic Host Configuration Protocol (DHCP)
client daemonSYNOPSIS
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. Forthis 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) daemonis controlled by telinit(1M). dhcpagent can be invoked as a
user process, albeit one requiring root privileges, but thisis not necessary, as ifconfig(1M) will start it automati-
cally.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 instructions 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 DHCPis 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 berenewed, dhcpagent will unconfigure the address, but the
interface will be left up and dhcpagent will attempt to
acquire a new address lease. dhcpagent monitors system
suspend/resume events and will validate any non-permanent
leases with the DHCP server upon resume. Similarly,SunOS 5.11 Last change: 21 Sep 2009 1
System Administration Commands dhcpagent(1M)
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 The lease validation mechanism will restart DHCP if the server indicates that the existing lease is no longer valid.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, thenthe existing lease will continue. This behavior can be modi-
fied with the VERIFIED_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 logi-
cal interfaces 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, itwill 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 param-
eters 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 defaultrouter, the agent does not directly configure the worksta-
tion, but instead acts as a database which may be interro-
gated 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 ondifferent 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 ofSunOS 5.11 Last change: 21 Sep 2009 2
System Administration Commands dhcpagent(1M)
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.For IPv4, the dhcpagent daemon can be configured to request
a particular 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; RFC 3315, option code 16). This identifier is the same as the platform namereturned 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. MessagesThe 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, 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 mostSunOS 5.11 Last change: 21 Sep 2009 3
System Administration Commands dhcpagent(1M)
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. Informational messages are generally controlledby the -v option. However, certain critical pieces of
information, such as the IP address obtained, are always provided. debugDebugging messages, which may be generated at two dif-
ferent levels of verbosity, are chiefly of benefit to persons having access to source code, but may be usefulas well in debugging difficult DHCP configuration prob-
lems. Debugging messages are only generated when usingthe -d option.
When dhcpagent is run without the -f option, all messages
are sent to the system logger syslog(3C) at the appropriatematching 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. Theevent program is invoked when dhcpagent receives the
DHCPv4 ACK or DHCPv6 Reply message from the DHCP serverfor the lease request of an address, indicating success-
ful initial configuration of the interface. (See alsothe INFORM and INFORM6 events, which occur when confi-
guration parameters are obtained without address leases.) EXTEND and EXTEND6 These events occur during lease extension. The eventSunOS 5.11 Last change: 21 Sep 2009 4
System Administration Commands dhcpagent(1M)
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 markedwith 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 interfacehas been abandoned due the user unplumbing the inter-
face, 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 configuration information from a DHCP server bymeans 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 theserver, and instead obtains only configuration parame-
ters. LOSS6SunOS 5.11 Last change: 21 Sep 2009 5
System Administration Commands dhcpagent(1M)
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. Thosebeing 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 justbefore dhcpagent relinquishes the address on an inter-
face 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 inter-
face 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 asdhcpagent itself, except that stdin, stdout, and stderr are
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.
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System Administration Commands dhcpagent(1M)
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 operating system image prior torunning dhcpagent. This option instructs the agent to
take over control of the interface. It is intended pri-
marily for use in boot scripts.The effect of this option depends on whether the inter-
face is being adopted.If the interface is being adopted, the following condi-
tions apply:dhcpagent uses the client id specified in
/chosen:
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, as published by the PROM or as error condition if the interface is an Infiniband inter-
face 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 Infini-
band and there is no value in /etc/default/dhcpagent, a
client id is generated as described by the draft docu-
ment on DHCP over Infiniband, available at: http://www.ietf.org-d n
Set debug level to n. Two levels of debugging arecurrently available, 1 and 2; the latter is more ver-
bose.-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).SunOS 5.11 Last change: 21 Sep 2009 7
System Administration Commands dhcpagent(1M)
-v
Provide verbose output useful for debugging site confi-
guration 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. FILESSunOS 5.11 Last change: 21 Sep 2009 8
System Administration Commands dhcpagent(1M)
/etc/dhcp/if.dhc /etc/dhcp/if.dh6 Contains the configuration for interface. The mereexistence of this file does not imply that the confi-
guration 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/iaidContains persistent storage for DUID (DHCP Unique Iden-
tifier) 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 interface 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 parameterrequest 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 theserver. If the server is unreachable for verifica-
tion, 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 toSunOS 5.11 Last change: 21 Sep 2009 9
System Administration Commands dhcpagent(1M)
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,llaType 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 systemtime. 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.SunOS 5.11 Last change: 21 Sep 2009 10
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3,hwtype,llaType 3, DUID-LL. This is the same as DUID-LLT
(type 1), except that a time stamp is not used. *,hexAny 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 for-
mat. 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 samemanner 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.SunOS 5.11 Last change: 21 Sep 2009 11
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This option works with DHCPv4 only. /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 | SUNWcs ||_____________________________|_____________________________|
| Interface Stability | Committed ||_____________________________|_____________________________|
SEE ALSO
dhcpinfo(1), ifconfig(1M), init(1M), in.mpathd(1M), in.ndpd(1M), syslog(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 Working 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. NOTESThe 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 RFC4361. The /etc/default/dhcpagent CLIENT_ID value, if any,
overrides this automatic identifier.SunOS 5.11 Last change: 21 Sep 2009 12
System Administration Commands dhcpagent(1M)
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 physical 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. Additionally, 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) torevert 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 areplumbed by dhcpagent automatically.
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