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diff --git a/networking/udhcp/README b/networking/udhcp/README new file mode 100644 index 000000000..d3e5e3fbc --- /dev/null +++ b/networking/udhcp/README @@ -0,0 +1,197 @@ +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. |