fclose the pointer if chmod fails, fixes [b434b7f79e]

[thirdparty/dhcpcd.git] / dhcpcd.conf.5.in

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.Dd February 5, 2016
.Dt DHCPCD.CONF 5
.Os
.Sh NAME
.Nm dhcpcd.conf
.Nd dhcpcd configuration file
.Sh DESCRIPTION
Although
.Nm dhcpcd
can do everything from the command line, there are cases where it's just easier
to do it once in a configuration file.
Most of the options found in
.Xr dhcpcd 8
can be used here.
The first word on the line is the option and the rest of the line is the value.
Leading and trailing whitespace for the option and value are trimmed.
You can escape characters in the value using the \\ character.
Comments can be prefixed with the # character.
String values should be quoted with the " character.
.Pp
Here's a list of available options:
.Bl -tag -width indent
.It Ic allowinterfaces Ar pattern
When discovering interfaces, the interface name must match
.Ar pattern
which is a space or comma separated list of patterns passed to
.Xr fnmatch 3 .
If the same interface is matched in
.Ic denyinterfaces
then it is still denied.
.It Ic denyinterfaces Ar pattern
When discovering interfaces, the interface name must not match
.Ar pattern
which is a space or comma separated list of patterns passed to
.Xr fnmatch 3 .
.It Ic arping Ar address Op address
.Nm dhcpcd
will arping each address in order before attempting DHCP.
If an address is found, we will select the replying hardware address as the
profile, otherwise the ip address.
Example:
.Pp
.D1 interface bge0
.D1 arping 192.168.0.1
.Pp
.D1 profile 192.168.0.1
.D1 static ip_address=192.168.0.10/24
.It Ic authprotocol Ar protocol Ar algorithm Ar rdm
Authenticate DHCP messages.
See the Supported Authentication Protocols section.
.It Ic authtoken Ar secretid Ar realm Ar expire Ar key
Define a shared key for use in authentication.
.Ar realm can be "" to for use with the
.Ar delayed
prptocol.
.Ar expire
is the date the token expires and should be formatted "yyy-mm-dd HH:MM".
You can use the keyword
.Ar forever
or
.Ar 0
which means the token never expires.
For the token protocol,
.Ar secretid
needs to be 0 and
.Ar realm
needs to be "".
If
.Nm dhcpcd
has the error
.D1 dhcp_auth_encode: Invalid argument
then it means that
.Nm dhcpcd
could not find the correct authentication token in your configuration.
.It Ic background
Background immediately.
This is useful for startup scripts which don't disable link messages for
carrier status.
.It Ic blacklist Ar address Ns Op /cidr
Ignores all packets from
.Ar address Ns Op /cidr .
.It Ic whitelist Ar address Ns Op /cidr
Only accept packets from
.Ar address Ns Op /cidr .
.Ic blacklist
is ignored if
.Ic whitelist
is set.
.It Ic bootp
Be a BOOTP client.
Basically, this just doesn't send a DHCP Message Type option and will only
interact with a BOOTP server.
All other DHCP options still work.
.It Ic broadcast
Instructs the DHCP server to broadcast replies back to the client.
Normally this is only set for non Ethernet interfaces,
such as FireWire and InfiniBand.
In most cases,
.Nm dhcpcd
will set this automatically.
.It Ic controlgroup Ar group
Sets the group ownership of
.Pa @RUNDIR@/dhcpcd.sock
so that users other than root can connect to
.Nm dhcpcd .
.It Ic debug
Echo debug messages to the stderr and syslog.
.It Ic dev Ar value
Load the
.Ar value
.Pa /dev
management module.
.Nm dhcpcd
will load the first one found to work, if any.
.It Ic env Ar value
Push
.Ar value
to the environment for use in
.Xr dhcpcd-run-hooks 8 .
For example, you can force the hostname hook to always set the hostname with
.Ic env
.Va force_hostname=YES .
Or set which driver
.Xr wpa_supplicant 8
should use with
.Ic env
.Va wpa_supplicant_driver=nl80211
.Pp
If the hostname is set, will be will set to the FQDN if possible as per
RFC 4702 section 3.1.
If the FQDN option is missing,
.Nm dhcpcd
will still try and set a FQDN from the hostname and domain options for
consistency.
To override this, set
.Ic env
.Va hostname_fqdn=[YES|NO|SERVER] .
A value of server means just what the server says, don't manipulate it.
This could lead to an inconsistent hostname on a DHCPv4 and DHCPv6 network
where the DHCPv4 hostname is short and the DHCPv6 has an FQDN.
DHCPv6 has no hostname option.
.It Ic clientid Ar string
Send the
.Ar clientid .
If the string is of the format 01:02:03 then it is encoded as hex.
For interfaces whose hardware address is longer than 8 bytes, or if the
.Ar clientid
is an empty string then
.Nm dhcpcd
sends a default
.Ar clientid
of the hardware family and the hardware address.
.It Ic duid
Generate an
.Rs
.%T "RFC 4361"
.Re
compliant DHCP Unique Identifier.
If persistent storage is available then a DUID-LLT (link local address + time)
is generated, otherwise DUID-LL is generated (link local address).
This, plus the IAID will be used as the
.Ic clientid .
The DUID-LLT generated will be held in
.Pa @SYSCONFDIR@/dhcpcd.duid
and should not be copied to other hosts.
.It Ic iaid Ar iaid
Set the Interface Association Identifier to
.Ar iaid .
This option must be used in an
.Ic interface
block.
This defaults to the last 4 bytes of the hardware address assigned to the
interface.
Each instance of this should be unique within the scope of the client and
.Nm dhcpcd
warns if a conflict is detected.
If there is a conflict, it is only a problem if the conflicted IAIDs are
used on the same network.
.It Ic dhcp
Enable DHCP on the interface, on by default.
.It Ic dhcp6
Enable DHCPv6 on the interface, on by default.
.It Ic ipv4
Enable IPv4 on the interface, on by default.
.It Ic ipv6
Enable IPv6 on the interface, on by default.
.It Ic persistent
.Nm dhcpcd
normally de-configures the interface and configuration when it exits.
Sometimes, this isn't desirable if, for example, you have root mounted over
NFS or SSH clients connect to this host and they need to be notified of
the host shutting down.
You can use this option to stop this from happening.
.It Ic fallback Ar profile
Fallback to using this profile if DHCP fails.
This allows you to configure a static profile instead of using ZeroConf.
.It Ic hostname Ar name
Sends
.Ar hostname
to the DHCP server so it can be registered in DNS.
If
.Ar hostname
is an empty string then the current system hostname is sent.
If
.Ar hostname
is a FQDN (ie, contains a .) then it will be encoded as such.
.It Ic hostname_short
Sends the short hostname to the DHCP server instead of the FQDN.
This is useful because DHCP servers will not register the FQDN in their
DNS if the domain part does not match theirs.
.Pp
Also, see the
.Ic env
option above to control how the hostname is set on the host.
.It Ic ia_na Op Ar iaid Op / address
Request a DHCPv6 Normal Address for
.Ar iaid .
.Ar iaid
defaults to the
.Ic iaid
option as described above.
You can request more than one ia_na by specifying a unique
.Ar iaid
for each one.
.It Ic ia_ta Op Ar iaid
Request a DHCPv6 Temporary Address for
.Ar iaid .
You can request more than one ia_ta by specifying a unique
.Ar iaid
for each one.
.It Ic ia_pd Op Ar iaid Oo / Ar prefix / Ar prefix_len Oc Op Ar interface Op / Ar sla_id Op / Ar prefix_len Op / Ar suffix
Request a DHCPv6 Delegated Prefix for
.Ar iaid .
This option must be used in an
.Ic interface
block.
Unless a
.Ar sla_id
of 0 is assigned, a reject route is installed for the Delegated Prefix to
stop unallocated addresses being resolved upstream.
This reject route is in essence SLA 0, thus you need space within the prefix
to assign a SLA per interface.
If no
.Ar interface
is given then we will assign a prefix to every other interface with a
.Ar sla_id
equivalent to the interface index assigned by the OS.
Otherwise addresses are only assigned for each
.Ar interface
and
.Ar sla_id .
Each assigned address will have a
.Ar suffix ,
defaulting to 1.
If the
.Ar suffix
is 0 then a slaac address is assigned.
You cannot assign a prefix to the requesting interface unless the
DHCPv6 server supports
.Li RFC6603
Prefix Exclude Option.
.Nm dhcpcd
has to be running for all the interfaces it is delegating to.
A default
.Ar prefix_len
of 64 is assumed, unless the maximum
.Ar sla_id
does not fit.
In this case
.Ar prefix_len
is increased to the highest multiple of 8 that can accommodate the
.Ar sla_id .
.Ar sla_id
is an integer and is added to the prefix which must fit inside
.Ar prefix_len
less the length of the delegated prefix.
.Ar sla_id can be 0 only if the Delegated Prefix is assigned to one interface.
You can specify multiple
.Ar interface /
.Ar sla_id /
.Ar prefix_len
per
.Ic ia_pd ,
space separated.
IPv6RS should be disabled globally when requesting a Prefix Delegation.
.Pp
In the following example eth0 is the externally facing interface to be
configured for both IPv4 and IPv6.
The DHCPv4 server will provide us with an IPv4 address and a default route.
The DHCPv6 server is going to provide us with an IPv6 address, a default
route and a /64 subnet to be delegated to the internal interface.
The eth1 interface will be automatically configured
for IPv6 using the first address (::1) from the delegated prefix.
A second prefix is requested and assigned to two other interfaces.
.Xr rtadvd 8
can be used with an empty configuration file on eth1, eth2 and eth3,
to provide automatic
IPv6 address configuration for the internal network.
.Bd -literal
noipv6rs                 # disable routing solicitation
denyinterfaces eth2      # Don't touch eth2 at all
interface eth0
  ipv6rs                 # enable routing solicitation get the
                         # default IPv6 route
  ia_na 1                # request an IPv6 address
  ia_pd 2 eth1/0         # request a PD and assign it to eth1
  ia_pd 3 eth2/1 eth3/2  # req a PD and assign it to eth2 and eth3
                         # we cannot use SLA 0 above because we are
                         # assinging the PD to more than one interface
.Ed
.It Ic ipv4only
Only configure IPv4.
.It Ic ipv6only
Only confgiure IPv6.
.It Ic fqdn Op disable | ptr | both
ptr just asks the DHCP server to update the PTR
record of the host in DNS whereas both also updates the A record.
disable will disable the FQDN option.
The default is both.
.Nm dhcpcd
itself never does any DNS updates.
.Nm dhcpcd
encodes the FQDN hostname as specified in
.Li RFC1035 .
.It Ic interface Ar interface
Subsequent options are only parsed for this
.Ar interface .
.It Ic ipv6ra_autoconf
Generate SLAAC addresses for each Prefix advertised by a
Router Advertisement message with the Auto flag set.
On by default.
.It Ic ipv6ra_noautoconf
Disables the above option.
.It Ic ipv6ra_fork
By default, when
.Nm dhcpcd
receives an IPv6 RA,
.Nm dhcpcd
will only fork to the background if the RA contains at least one unexpired
RDNSS option and a valid prefix or no DHCPv6 instruction.
Set this option so to make
.Nm dhcpcd
always fork on an RA.
.It Ic ipv6ra_own
Disables kernel IPv6 Router Advertisment processing so dhcpcd can manage
addresses and routes.
.It Ic ipv6ra_own_default
Each time dhcpcd receives an IPv6 Router Adveristment, dhcpcd will manage
the default route only.
This allows dhcpcd to prefer an interface for outbound traffic based on metric
and/or user selection rather than the kernel.
.It Ic ipv6ra_accept_nopublic
Some IPv6 routers advertise themselves as a default router without any
public prefixes or managed addresses.
Generally, this is incorrect behaviour and
.Nm dhcpcd
will ignore the advertisement unless this option is turned on.
.It Ic ipv6rs
Enables IPv6 Router Advertisment solicitation.
This is on by default, but is documented here in the case where it is disabled
globally but needs to be enabled for one interface.
.It Ic leasetime Ar seconds
Request a leasetime of
.Ar seconds .
.It Ic logfile Ar logfile
Writes to the specified
.Ar logfile
rather than
.Xr syslog 3 .
The
.Ar logfile
is truncated when opened and is reopened when
.Nm dhcpcd
receives the
.Dv SIGUSR2
signal.
.It Ic metric Ar metric
Metrics are used to prefer an interface over another one, lowest wins.
.Nm dhcpcd
will supply a default metric of 200 +
.Xr if_nametoindex 3 .
An extra 100 will be added for wireless interfaces.
.It Ic noalias
Any pre-existing IPv4 addresses existing address will be removed from the
interface when adding a new IPv4 address.
.It Ic noarp
Don't send any ARP requests.
This also disables IPv4LL.
.It Ic noauthrequired
Don't require authentication even though we requested it.
Also allows FORCERENEW and RECONFIGURE messages without authentication.
.It Ic nodelay
Don't delay for an initial randomised time when starting protocols.
.It Ic nodev
Don't load
.Pa /dev
management modules.
.It Ic nodhcp
Don't start DHCP or listen to DHCP messages.
This is only useful when allowing IPv4LL.
.It Ic nodhcp6
Don't start DHCPv6 or listen to DHCPv6 messages.
Normally DHCPv6 is started by a RA instruction or configuration.
.It Ic nogateway
Don't install any default routes.
.It Ic gateway
Install a default route if available (default).
.It Ic nohook Ar script
Don't run this hook script.
Matches full name, or prefixed with 2 numbers optionally ending with
.Pa .sh .
.Pp
So to stop
.Nm dhcpcd
from touching your DNS settings or starting wpa_supplicant you would do:-
.D1 nohook resolv.conf, wpa_supplicant
.It Ic noipv4
Don't attempt to configure an IPv4 address.
.It Ic noipv4ll
Don't attempt to obtain an IPv4LL address if we failed to get one via DHCP.
See
.Rs
.%T "RFC 3927"
.Re
.It Ic noipv6
Don't attmept to configure an IPv6 address.
.It Ic noipv6rs
Disable solicitation and receipt of IPv6 Router Advertisements.
.It Ic nolink
Don't receive link messages about carrier status.
You should only set this for buggy interface drivers.
.It Ic noup
Don't bring the interface up when in master mode.
If
.Nm
cannot determine the carrier state,
.Nm
will enter a tight polling loop until the interface is marked up and running
or a valid carrier state is reported.
.It Ic option Ar option
Requests the
.Ar option
from the server.
It can be a variable to be used in
.Xr dhcpcd-run-hooks 8
or the numerical value.
You can specify more
.Ar option Ns s
separated by commas, spaces or more
.Ic option
lines.
.Ar option
Prepend dhcp6_ to
.Ar option
to request a DHCPv6 option.
If no DHCPv6 options are configured,
then DHCPv4 options are mapped to equivalent DHCPv6 options.
.Pp
Prepend nd_ to
.Ar option
to handle ND options, but this only works for the
.Ic nooption ,
.Ic reject
and
.Ic require
options.
.It Ic nooption Ar option
Remove the option from the message before it's processed.
.It Ic require Ar option
Requires the
.Ar option
to be present in all messages, otherwise the message is ignored.
To enforce that
.Nm dhcpcd
only responds to DHCP servers and not BOOTP servers, you can
.Ic require
.Ar dhcp_message_type .
This isn't an exact science though because a BOOTP server can send DHCP like
options.
.It Ic reject Ar option
Reject a message that contains the
.Ar option .
This is useful when you cannot use
.Ic require
to select / de-select BOOTP messages.
.It Ic destination Ar option
If
.Nm
detects an address added to a point to point interface (PPP, TUN, etc) then
it will set the listed DHCP options to the destination address of the
interface.
.It Ic profile Ar name
Subsequent options are only parsed for this profile
.Ar name .
.It Ic quiet
Suppress any dhcpcd output to the console, except for errors.
.It Ic reboot Ar seconds
Allow
.Ar reboot
seconds before moving to the DISCOVER phase if we have an old lease to use
and moving from DISCOVER to IPv4LL if no reply.
The default is 5 seconds.
A setting of 0 seconds causes
.Nm dhcpcd
to skip the REBOOT phase and go straight into DISCOVER.
This is desirable for mobile users because if you change from network A to
network B and they use the same subnet and the address from network A isn't
in use on network B, then the DHCP server will remain silent even if authorative
which means
.Nm dhcpcd
will timeout before moving back to the DISCOVER phase.
.It Ic release
.Nm dhcpcd
will release the lease prior to stopping the interface.
.It Ic script Ar script
Use
.Ar script
instead of the default
.Pa @SCRIPT@ .
.It Ic ssid Ar ssid
Subsequent options are only parsed for this wireless
.Ar ssid .
.It Ic slaac Op Ar hwaddr | Ar private
Selects the interface identifier used for SLAAC generated IPv6 addresses.
If
.Ar private
is used, a RFC7217 address is generated.
.It Ic static Ar value
Configures a static
.Ar value .
If you set
.Ic ip_address
then
.Nm dhcpcd
will not attempt to obtain a lease and just use the value for the address with
an infinite lease time.
.Pp
Here is an example which configures a static address, routes and dns.
.D1 interface eth0
.D1 static ip_address=192.168.0.10/24
.D1 static routers=192.168.0.1
.D1 static domain_name_servers=192.168.0.1
.Pp
Here is an example for PPP which gives the destination a default route.
It uses the special destination keyword to insert the destination address
into the value.
.D1 interface ppp0
.D1 static ip_address=
.D1 destination routers
.It Ic timeout Ar seconds
Timeout after
.Ar seconds ,
instead of the default 30.
A setting of 0
.Ar seconds
causes
.Nm dhcpcd
to wait forever to get a lease.
If
.Nm dhcpcd
is working on a single interface then
.Nm dhcpcd
will exit when a timeout occurs, otherwise
.Nm dhcpcd
will fork into the background.
If using IPv4LL then
.Nm dhcpcd
start the IPv4LL process after the timeout and then wait a little longer
before really timing out.
.It Ic userclass Ar string
Tag the DHCPv4 messages with the userclass.
You can specify more than one.
.It Ic vendor Ar code , Ns Ar value
Add an encapsulated vendor option.
.Ar code
should be between 1 and 254 inclusive.
To add a raw vendor string, omit
.Ar code
but keep the comma.
Examples.
.Pp
Set the vendor option 01 with an IP address.
.D1 vendor 01,192.168.0.2
Set the vendor option 02 with a hex code.
.D1 vendor 02,01:02:03:04:05
Set the vendor option 03 with an IP address as a string.
.D1 vendor 03,\e"192.168.0.2\e"
Set un-encapsulated vendor option to hello world.
.D1 vendor ,"hello world"
.It Ic vendorclassid Ar string
Set the DHCP Vendor Class.
DHCPv6 has it's own option as shown below.
The default is
dhcpcd-<version>:<os>:<machine>:<platform>.
For example
.D1 dhcpcd-5.5.6:NetBSD-6.99.5:i386:i386
If not set then none is sent.
Some badly configured DHCP servers reject unknown vendorclassids.
To work around it, try and impersonate Windows by using the MSFT vendorclassid.
.It Ic vendclass Ar en Ar data
Add the DHCPv6 Vendor Indetifying Vendor Class with the IANA assigned Enterprise
Number
.Ar en
with the
.Ar data .
This option can be set more than once to add more data, but the behaviour,
as per
.Xr RFC 3925
is undefined if the Enterprise Number differs.
.It Ic waitip Op 4 | 6
Wait for an address to be assigned before forking to the background.
4 means wait for an IPv4 address to be assigned.
6 means wait for an IPv6 address to be assigned.
If no argument is given,
.Nm
will wait for any address protocol to be assigned.
It is possible to wait for more than one address protocol and
.Nm
will only fork to the background when all waiting conditions are satisfied.
.It Ic xidhwaddr
Use the last four bytes of the hardware address as the DHCP xid instead
of a randomly generated number.
.El
.Ss Defining new options
DHCP, ND and DHCPv6 allow for the use of custom options.
Each option needs to be started with the
.Ic define ,
.If definend
or
.Ic define6
directive.
This can optionally be followed by both
.Ic embed
or
.Ic encap
options.
Both can be specified more than once and
.Ic embed
must come before
.Ic encap .
.Bl -tag -width indent
.It Ic define Ar code Ar type Ar variable
Defines the DHCP option
.Ar code
of
.Ar type
with a name of
.Ar variable
exported to
.Xr dhcpcd-run-hooks 8 .
.It Ic definend Ar code Ar type Ar variable
Defines the ND option
.Ar code
of
.Ar type
with a name of
.Ar variable
exported to
.Xr dhcpcd-run-hooks 8 ,
with a prefix of
.Va _nd .
.It Ic define6 Ar code Ar type Ar variable
Defines the DHCPv6 option
.Ar code
of
.Ar type
with a name of
.Ar variable
exported to
.Xr dhcpcd-run-hooks 8 ,
with a prefix of
.Va _dhcp6 .
.It Ic vendopt Ar code Ar type Ar variable
Defines the Vendor-Identifying Vendor Options.
The
.Ar code
is the IANA Enterprise Number which will unqiuely describe the encapsulated
options.
.Ar type
is normally
.Ar encap .
.Ar variable
names the Vendor option to be exported.
.It Ic embed Ar type Ar variable
Defines an embedded variable within the defined option.
The length is determined by the
.Ar type .
If the
.Ar variable
is not the same as defined in the parent option,
it is prefixed with the parent
.Ar variable
first with an underscore.
If the
.Ar variable
has the name of
.Ar reserved
then it is not processed.
.It Ic encap Ar code Ar type Ar variable
Defines an encapsulated variable within the defined option.
The length is determined by the
.Ar type .
If the
.Ar variable
is not the same as defined in the parent option,
it is prefixed with the parent
.Ar variable
first with an underscore.
.El
.Ss Type prefix
These keywords come before the type itself, to describe it more fully.
You can use more than one, but they must appear in the order listed below.
.Bl -tag -width -indent
.It Ic request
Requests the option by default without having to be specified in user
configuration
.It Ic norequest
This option cannot be requested, regardless of user configuration
.It Ic optional
This option is optional.
Only makes sense for embedded options where like the client FQDN option where
the FQDN string itself is optional.
.It Ic index
The option can appear more than once and will be indexed.
.It Ic array
The option data is split into a space separated array, each element being
the same type.
.El
.Ss Types to define
The type directly affects the length of data consumed inside the option.
Any remaining data is normally discarded.
Lengths can be specified for string and binhex types, but this is generally
with other data embedded afterwards in the same option.
.Bl -tag -width indent
.It Ic ipaddress
An IPv4 address, 4 bytes.
.It Ic ip6address
An IPv6 address, 16 bytes.
.It Ic string Op : Ic length
A NVT ASCII string of printable characters.
.It Ic byte
A byte.
.It Ic bitflags : Ic flags
A byte represented as a string of flags, most significant bit first.
For example, using ABCDEFGH then A would equal 10000000, B 01000000,
C 00100000, etc.
If the bit is not set, the flag is not printed.
A flag of 0 is not printed even if the bit postition is set.
This is to allow reservation of the first bits while assinging the last bits.
.It Ic int16
A signed 16bit integer, 2 bytes.
.It Ic uint16
An unsigned 16bit integer, 2 bytes.
.It Ic int32
A signed 32bit integer, 4 bytes.
.It Ic uint32
An unsigned 32bit integer, 4 bytes.
.It Ic flag
A fixed value (1) to indicate that the option is present, 0 bytes.
.It Ic domain
A RFC 3397 encoded string.
.It Ic dname
A RFC 1035 validated string.
.It Ic binhex Op : Ic length
Binary data expressed as hexadecimal.
.It Ic embed
Contains embedded options (implies encap as well).
.It Ic encap
Contains encapsulated options (implies embed as well).
.It Ic option
References an option from the global definition.
.El
.Ss Example definition
.D1 # DHCP option 81, Fully Qualified Domain Name, RFC4702
.D1 define 81 embed fqdn
.D1 embed byte flags
.D1 embed byte rcode1
.D1 embed byte rcode2
.D1 embed domain fqdn
.Pp
.D1 # DHCP option 125, Vendor Specific Information Option, RFC3925
.D1 define 125 encap vsio
.D1 embed uint32 enterprise_number
.D1 # Options defined for the enterprise number
.D1 encap 1 ipaddress ipaddress
.Ss Supported Authentication Protocols
.Bl -tag -width -indent
.It Ic token
Sends and expects the token with the secretid 0 and realm of "" in each message.
.It Ic delayedrealm
Delayed Authentication.
.Nm dhcpcd
will send an authentication option with no key or MAC.
The server will see this option, and select a key for
.Nm , writing the
.Ar realm
and
.Ar secretid
in it.
.Nm dhcpcd
will then look for a non-expired token with a matching realm and secretid.
This token is used to authenicate all other messages.
.It Ic delayed
Same as above, but without a realm.
.El
.Ss Supported Authentication Algorithms
If none specified,
.Ic hmac-md5
is the default.
.Bl -tag -width -indent
.It Ic hmac-md5
.El
.Ss Supported Replay Detection Mechanisms
If none specified,
.Ic monotonic
is the default.
If this is changed from what was previously used,
or the means of calculating or storing it is broken then the DHCP server
will probably have to have its notion of the clients Replay Detection Value
reset.
.Bl -tag -width -indent
.It Ic monocounter
Read the number in the file
.Pa @DBDIR@/dhcpcd-rdm.monotonic
and add one to it.
.It Ic monotime
Create a NTP timestamp from the system time.
.It Ic monotonic
Same as
.Ic monotime .
.El
.Sh SEE ALSO
.Xr fnmatch 3 ,
.Xr if_nametoindex 3 ,
.Xr dhcpcd 8 ,
.Xr dhcpcd-run-hooks 8
.Sh AUTHORS
.An Roy Marples Aq Mt roy@marples.name
.Sh BUGS
Please report them to
.Lk http://roy.marples.name/projects/dhcpcd