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udhcp server/client package readme ------------------------- The udhcp server/client package is primarily geared towards embedded systems. It does however, strive to be fully functional, and RFC compliant. udhcp server (udhcpd) -------------------- The only command line argument to udhcpd is an optional specifed config file. If no config file is specified, udhcpd uses the default config file, /etc/udhcpd.conf. Ex: udhcpd /etc/udhcpd.eth1.conf The udhcp server employs a number of simple config files: udhcpd.leases ------------ The udhcpd.leases behavior is designed for an embedded system. The file is written either every auto_time seconds, or when a SIGUSR1 is received (the auto_time timer restarts if a SIGUSR1 is received). If you send a SIGTERM to udhcpd directly after a SIGUSR1, udhcpd will finish writing the leases file and wait for the aftermentioned script to be executed and finish before quiting, so you do not need to sleep between sending signals. When the file is written, a script can be optionally called to commit the file to flash. Lease times are stored in the file by time remaining in lease (for systems without clock that works when there is no power), or by the absolute time that it expires in seconds from epoch. In the remainig format, expired leases are stored as zero. The file is of the format: 16 byte MAC 4 byte ip address u32 expire time 16 byte MAC 4 byte ip address u32 expire time . etc. example: hexdump udhcpd.leases 0000000 1000 c95a 27d9 0000 0000 0000 0000 0000 0000010 a8c0 150a 0d00 2d29 5000 23fc 8566 0000 0000020 0000 0000 0000 0000 a8c0 140a 0d00 4e29 0000030 udhcpd.conf ---------- The format is fairly simple, there is a sample file with all the available options and comments describing them in samples/udhcpd.conf 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. 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. 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. 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 ------------------- The Makefile contains three of the compile time options: DEBUG: If DEBUG is defined, udhcpd will output extra debugging output, compile with -g, and not fork to the background when run. SYSLOG: If SYSLOG is defined, udhcpd will log all its messages syslog, otherwise, it will attempt to log them to stdout. COMBINED_BINARY: If COMBINED_BINARY is define, one binary, udhcpd, is created. If called as udhcpd, the dhcp server will be started. If called as udhcpc, the dhcp client will be started. dhcpd.h contains the other two compile time options: LEASE_TIME: The default lease time if not specified in the config file. DHCPD_CONFIG_FILE: The defualt config file to use. 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 busybox drop-in -------------- udhcp is now a drop-in component for busybox (http://busybox.net). To update busybox to the latest revision, simply do a: cp *.[ch] README AUTHORS COPYING ChangeLog TODO \ <busybox_source>/networking/udhcp The only two files udhcp does not provide are config.in and Makefile.in, so these may need to be updated from time to time.