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Diffstat (limited to 'contrib/isc-dhcp/client/dhclient-script.8')
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diff --git a/contrib/isc-dhcp/client/dhclient-script.8 b/contrib/isc-dhcp/client/dhclient-script.8 new file mode 100644 index 0000000..bae59b4 --- /dev/null +++ b/contrib/isc-dhcp/client/dhclient-script.8 @@ -0,0 +1,191 @@ +.\" dhclient-script.8 +.\" +.\" Copyright (c) 1997 The Internet Software Consortium. +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. Neither the name of The Internet Software Consortium nor the names +.\" of its contributors may be used to endorse or promote products derived +.\" from this software without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND +.\" CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, +.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF +.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE +.\" DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR +.\" CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF +.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND +.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, +.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT +.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" This software has been written for the Internet Software Consortium +.\" by Ted Lemon <mellon@fugue.com> in cooperation with Vixie +.\" Enterprises. To learn more about the Internet Software Consortium, +.\" see ``http://www.isc.org/isc''. To learn more about Vixie +.\" Enterprises, see ``http://www.vix.com''. +.TH dhclient 8 +.SH NAME +dhclient-script - DHCP client network configuration script +.SH DESCRIPTION +The DHCP client network configuration script is invoked from time to +time by \fBdhclient(8)\fR. This script is used by the dhcp client to +set each interface's initial configuration prior to requesting an +address, to test the address once it has been offered, and to set the +interface's final configuration once a lease has been acquired. If no +lease is acquired, the script is used to test predefined leases, if +any, and also called once if no valid lease can be identified. +.PP +This script is not meant to be customized by the end user. However, +the script may not work on particular versions of particular operating +systems (indeed, no standard script exists for some operating +systems), so a pioneering user may well need to create a new script or +modify an existing one. In general, customizations specific to a +particular computer should be done in the +.B ETCDIR/dhclient.conf +script. If you find that you can't make such a customization without +customizing dhclient.conf, please submit a bug report. +.SH OPERATION +When dhclient needs to invoke the client configuration script, it +writes a shell script into /tmp which defines a variety of variables. +In all cases, $reason is set to the name of the reason why the script +has been invoked. The following reasons are currently defined: +MEDIUM, PREINIT, ARPCHECK, ARPSEND, BOUND, RENEW, REBIND, REBOOT, +EXPIRE, FAIL and TIMEOUT. +.PP +.SH MEDIUM +The DHCP client is requesting that an interface's media type +be set. The interface name is passed in $interface, and the media +type is passed in $medium. +.SH PREINIT +The DHCP client is requesting that an interface be configured as +required in order to send packets prior to receiving an actual +address. For clients which use the BSD socket library, this means +configuring the interface with an IP address of 0.0.0.0 and a +broadcast address of 255.255.255.255. For other clients, it may be +possible to simply configure the interface up without actually giving +it an IP address at all. The interface name is passed in $interface, +and the media type in $medium. +.PP +If an IP alias has been declared in dhclient.conf, its address will be +passed in $alias_ip_address, and that ip alias should be deleted from +the interface, along with any routes to it. +.SH ARPSEND +The DHCP client is requesting that an address that has been offered to +it be checked to see if somebody else is using it, by sending an ARP +request for that address. It's not clear how to implement this, so +no examples exist yet. The IP address to check is passed in +$new_ip_address, and the interface name is passed in $interface. +.SH ARPCHECK +The DHCP client wants to know if a response to the ARP request send +using ARPCHECK has been received. If one has, the script should exit +with a nonzero status, indicating that the offered address has already +been requested and should be declined. $new_ip_address and +$interface are set as with ARPSEND. +.SH BOUND +The DHCP client has done an initial binding to a new address. The +new ip address is passed in $new_ip_address, and the interface name is +passed in $interface. The media type is passed in $medium. Any +options acquired from the server are passed using the option name +described in \fBdhcp-options\fR, except that dashes ('-') are replaced +by underscores ('_') in order to make valid shell variables, and the +variable names start with new_. So for example, the new subnet mask +would be passed in $new_subnet_mask. +.PP +When a binding has been completed, a lot of network parameters are +likely to need to be set up. A new /etc/resolv.conf needs to be +created, using the values of $new_domain_name and +$new_domain_name_servers (which may list more than one server, +seperated by spaces). A default route should be set using +$new_routers, and static routes may need to be set up using +$new_static_routes. +.PP +If an IP alias has been declared, it must be set up here. The alias +IP address will be written as $alias_ip_address, and other DHCP +options that are set for the alias (e.g., subnet mask) will be passed +in variables named as described previously except starting with +$alias_ instead of $new_. Care should be taken that the alias IP +address not be used if it is identical to the bound IP address +($new_ip_address), since the other alias parameters may be incorrect +in this case. +.SH RENEW +When a binding has been renewed, the script is called as in BOUND, +except that in addition to all the variables starting with $new_, +there is another set of variables starting with $old_. Persistent +settings that may have changed need to be deleted - for example, if a +local route to the bound address is being configured, the old local +route should be deleted. If the default route has changed, the old default +route should be deleted. If the static routes have changed, the old +ones should be deleted. Otherwise, processing can be done as with +BOUND. +.SH REBIND +The DHCP client has rebound to a new DHCP server. This can be handled +as with RENEW, except that if the IP address has changed, the ARP +table should be cleared. +.SH REBOOT +The DHCP client has successfully reacquired its old address after a +reboot. This can be processed as with BOUND. +.SH EXPIRE +The DHCP client has failed to renew its lease or acquire a new one, +and the lease has expired. The IP address must be relinquished, and +all related parameters should be deleted, as in RENEW and REBIND. +.SH FAIL +The DHCP client has been unable to contact any DHCP servers, and any +leases that have been tested have not proved to be valid. The +parameters from the last lease tested should be deconfigured. This +can be handled in the same way as EXPIRE. +.SH TIMEOUT +The DHCP client has been unable to contact any DHCP servers. +However, an old lease has been identified, and its parameters have +been passed in as with BOUND. The client configuration script should +test these parameters and, if it has reason to believe they are valid, +should exit with a value of zero. If not, it should exit with a +nonzero value. +.PP +The usual way to test a lease is to set up the network as with REBIND +(since this may be called to test more than one lease) and then ping +the first router defined in $routers. If a response is received, the +lease must be valid for the network to which the interface is +currently connected. It would be more complete to try to ping all of +the routers listed in $new_routers, as well as those listed in +$new_static_routes, but current scripts do not do this. +.SH FILES +Each operating system should generally have its own script file, +although the script files for similar operating systems may be similar +or even identical. The script files included in the Internet +Software Consortium DHCP distribution appear in the distribution tree +under client/scripts, and bear the names of the operating systems on +which they are intended to work. +.SH BUGS +If more than one interface is being used, there's no obvious way to +avoid clashes between server-supplied configuration parameters - for +example, the stock dhclient-script rewrites /etc/resolv.conf. If +more than one interface is being configured, /etc/resolv.conf will be +repeatedly initialized to the values provided by one server, and then +the other. Assuming the information provided by both servers is +valid, this shouldn't cause any real problems, but it could be +confusing. +.SH SEE ALSO +dhclient(8), dhcpd(8), dhcrelay(8), dhclient.conf(5) and +dhclient.leases(5). +.SH AUTHOR +.B dhclient-script(8) +has been written for the Internet Software Consortium +by Ted Lemon <mellon@fugue.com> in cooperation with Vixie +Enterprises. To learn more about the Internet Software Consortium, +see +.B http://www.vix.com/isc. +To learn more about Vixie +Enterprises, see +.B http://www.vix.com. |
