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authorRuss Dill2002-10-31 19:21:27 +0000
committerRuss Dill2002-10-31 19:21:27 +0000
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+udhcp client (udhcpc)
+--------------------
+
+The udhcp client negotiates a lease with the DHCP server and notifies
+a set of scripts when a leases is obtained or lost.
+
+
+command line options
+-------------------
+
+The command line options for the udhcp client are:
+
+-c, --clientid=CLIENTID Client identifier
+-H, --hostname=HOSTNAME Client hostname
+-h, Alias for -H
+-f, --foreground Do not fork after getting lease
+-b, --background Fork to background if lease cannot be
+ immediately negotiated.
+-i, --interface=INTERFACE Interface to use (default: eth0)
+-n, --now Exit with failure if lease cannot be
+ immediately negotiated.
+-p, --pidfile=file Store process ID of daemon in file
+-q, --quit Quit after obtaining lease
+-r, --request=IP IP address to request (default: none)
+-s, --script=file Run file at dhcp events (default:
+ /usr/share/udhcpc/default.script)
+-v, --version Display version
+
+
+If the requested IP address cannot be obtained, the client accepts the
+address that the server offers.
+
+
+udhcp client scripts
+-------------------
+
+When an event occurs, udhcpc calls the action script. The script by
+default is /usr/share/udhcpc/default.script but this can be changed via
+the command line arguments. The three possible arguments to the script
+are:
+
+ deconfig: This argument is used when udhcpc starts, and
+ when a leases is lost. The script should put the interface in an
+ up, but deconfigured state, ie: ifconfig $interface 0.0.0.0.
+
+ bound: This argument is used when udhcpc moves from an
+ unbound, to a bound state. All of the paramaters are set in
+ enviromental variables, The script should configure the interface,
+ and set any other relavent parameters (default gateway, dns server,
+ etc).
+
+ renew: This argument is used when a DHCP lease is renewed. All of
+ the paramaters are set in enviromental variables. This argument is
+ used when the interface is already configured, so the IP address,
+ will not change, however, the other DHCP paramaters, such as the
+ default gateway, subnet mask, and dns server may change.
+
+ nak: This argument is used with udhcpc receives a NAK message.
+ The script with the deconfig argument will be called directly
+ afterwards, so no changes to the network interface are neccessary.
+ This hook is provided for purely informational purposes (the
+ message option may contain a reason for the NAK).
+
+The paramaters for enviromental variables are as follows:
+
+ $HOME - The set $HOME env or "/"
+ $PATH - the set $PATH env or "/bin:/usr/bin:/sbin:/usr/sbin"
+ $1 - What action the script should perform
+ interface - The interface this was obtained on
+ ip - The obtained IP
+ siaddr - The bootp next server option
+ sname - The bootp server name option
+ boot_file - The bootp boot file option
+ subnet - The assigend subnet mask
+ timezone - Offset in seconds from UTC
+ router - A list of routers
+ timesvr - A list of time servers
+ namesvr - A list of IEN 116 name servers
+ dns - A list of DNS server
+ logsvr - A list of MIT-LCS UDP log servers
+ cookiesvr - A list of RFC 865 cookie servers
+ lprsvr - A list of LPR servers
+ hostname - The assigned hostname
+ bootsize - The length in 512 octect blocks of the bootfile
+ domain - The domain name of the network
+ swapsvr - The IP address of the client's swap server
+ rootpath - The path name of the client's root disk
+ ipttl - The TTL to use for this network
+ mtu - The MTU to use for this network
+ broadcast - The broadcast address for this network
+ ntpsrv - A list of NTP servers
+ wins - A list of WINS servers
+ lease - The lease time, in seconds
+ dhcptype - DHCP message type (safely ignored)
+ serverid - The IP of the server
+ message - Reason for a DHCPNAK
+ tftp - The TFTP server name
+ bootfile - The bootfile name
+
+additional options are easily added in options.c.
+
+
+note on udhcpc's random seed
+---------------------------
+
+udhcpc will seed its random number generator (used for generating xid's)
+by reading /dev/urandom. If you have a lot of embedded systems on the same
+network, with no entropy, you can either seed /dev/urandom by a method of
+your own, or doing the following on startup:
+
+ifconfig eth0 > /dev/urandom
+
+in order to seed /dev/urandom with some data (mac address) unique to your
+system. If reading /dev/urandom fails, udhcpc will fall back to its old
+behavior of seeding with time(0).
+
+
+signals accepted by udhcpc
+-------------------------
+
+udhcpc also responds to SIGUSR1 and SIGUSR2. SIGUSR1 will force a renew state,
+and SIGUSR2 will force a release of the current lease, and cause udhcpc to
+go into an inactive state (until it is killed, or receives a SIGUSR1). You do
+not need to sleep between sending signals, as signals received are processed
+sequencially in the order they are received.
+
+
+compile time options
+-------------------
+
+options.c contains a set of dhcp options for the client:
+
+ name[10]: The name of the option as it will appear in scripts
+
+ flags: The type of option, as well as if it will be requested
+ by the client (OPTION_REQ)
+
+ code: The DHCP code for this option
+