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diff --git a/networking/udhcp/README.udhcpc b/networking/udhcp/README.udhcpc new file mode 100644 index 0000000..3591605 --- /dev/null +++ b/networking/udhcp/README.udhcpc @@ -0,0 +1,139 @@ +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 + |