0. Introduction

This is an RFC2131 and RFC1541 compliant DHCP client daemon. RFC1541
was obsoleted by RFC2131, but there are still some RFC1541 compliant
DHCP servers. dhcpcd gets an IP address and other information from a
corresponding DHCP server, configures the network interface
automatically, and tries to renew the lease time according to RFC2131
or RFC1541 depending on the command line option.


1. Install

Do 'make' followed by 'make install'.


2. How to Use It

Invoke the client by typing 'dhcpcd' if you want it to run as a daemon
(i.e., background task).  Note that you do not have to explicitly put
it in the background with the '&' character - background processing is
automatic unless overridden by the '-d' option.  By default, it will
attach to 'eth0' unless you explicitly give an interface name on the
command line.


3. Supported DHCP Options

The current version of dhcpcd supports the following DHCP options:

  o lease time
  o renewal (T1) time
  o rebind (T2) time
  o netmask
  o broadcast address
  o router
  o time server
  o DNS
  o lpr server
  o host name
  o domain name
  o NTP server
  o NIS domain name

dhcpcd uses the netmask and broadcast address options if it gets these
options from the DHCP server. It uses the 'natural' netmask and
broadcast address if it does not get those options. dhcpcd configures
the host name by using the 'sethostname' system call if it gets the
host name option. It configures the NIS domain name by using the
'setdomainname' system call if it gets the NIS domain name option. It
creates the file '/etc/dhcpc/resolv.conf' if it gets DNS and domain
name options.  It also creates the file '/etc/dhcpc/ntp.conf' if it
gets NTP server option. The host name, NIS domain name, lpr server,
NTP server, and time server option values are written into the file 
'/etc/dhcpc/hostinfo-ifname' (ifname is actually replaced with the
network interface name like "eth0").


4. Command File

dhcpcd invokes the specified command file (specified with the '-c'
option) just after it gets an IP address from the DHCP server and
configures the network interface and host information. The following
options are passed to the command file as environmental variables (if
dhcpcd gets those options):

  o host name           HOSTNAME
  o NIS domainname      NISDOMAINNAME
  o lpr server          LPRSERVER, (LPRSERVER2, ...)
  o NTP server          NTPSERVER, (NTPSERVER2, ...)
  o time server         TIMESERVER, (TIMESERVER2, ...)
  o router              ROUTER, (ROUTER2, ...)


5. Cache File

dhcpcd saves the assigned IP address to the file
'/var/run/dhcpcd-cache.interface' (the word 'interface' is actually
replaced with the interface name like eht0, etc. to which dhcpcd is
attached) so that it can try to use that IP address when it is invoked
next time. Remove the file '/var/run/dhcpcd-cache.interface' before
you invoke dhcpcd unless you like using the previously assigned IP
address.


6. PCMCIA

dhcpcd can be automatically invoked when the PCMCIA card service gets
started. There is a sample 'network' shell script for pcmcia-cs in
the directory './pcmcia'. Read the file './pcmcia/README' for more
details.


7. Cable Modems and ADSL Modems

DHCP servers used in some cable modem servecices and ADSL services
require DHCP clients to include the hostname option having a specific
string provided by the service providers when the clients send the
DHCPDISCOVER and DHCPREQUEST messages. Try '-h' option in the case
you are using either cable modem service or ADSL service and dhcpcd
outputs the "no DHCPOFFER messages" error message.


8. Other Information

dhcpcd sends DHCPRELEASE message to the DHCP server and makes the
attached network interface down when it gets SIGINT or SIGTERM
signal.

dhcpcd currently does not support DHCPINFORM message.

dhcpcd does not work in the case that the same DHCP option
(e.g. domain name) appears multiple times in a message. dhcpcd simply
uses the option which appeared last. This happens only when options
have a long (more than 255 characters) value. This limitation will be
fixed in the next release. 


9. In case dhcpcd does not work

Some people send me emails stating just like:

  "Hey, Windows95 works, but dhcpcd does not work and it outputs
  the 'no DHCPOFFER messages' error message. Do you have any ideas?"

I have no idea only with such a comment. I cannot fix your problem
only from such kind of information either. I would appreciate it if
you could set up the following environment, log the output of
tcpdump, and send it to me in the case Win95 box works and dhcpcd
does not work:

                   Ethernet
    ------+---------------------+--------
       +--+--+               +--+--+
       |Win95|               |Linux|
       | box |               | box |
       +-----+               +-----+

  1. run tcpdump as:

	   tcpdump -s 500 -x udp port 67 or port 68 

	 on the Linux box

  2. boot the Win95 box
  3. log the output of tcpdump running on the Linux box





Enjoy,
Yoichi

$Id$