Russ Dill | f5ecd43 | 2002-10-31 19:21:27 +0000 | [diff] [blame] | 1 | udhcp client (udhcpc) |
| 2 | -------------------- |
| 3 | |
| 4 | The udhcp client negotiates a lease with the DHCP server and notifies |
| 5 | a set of scripts when a leases is obtained or lost. |
| 6 | |
| 7 | |
| 8 | command line options |
| 9 | ------------------- |
| 10 | |
| 11 | The command line options for the udhcp client are: |
| 12 | |
| 13 | -c, --clientid=CLIENTID Client identifier |
| 14 | -H, --hostname=HOSTNAME Client hostname |
| 15 | -h, Alias for -H |
| 16 | -f, --foreground Do not fork after getting lease |
| 17 | -b, --background Fork to background if lease cannot be |
| 18 | immediately negotiated. |
| 19 | -i, --interface=INTERFACE Interface to use (default: eth0) |
| 20 | -n, --now Exit with failure if lease cannot be |
| 21 | immediately negotiated. |
| 22 | -p, --pidfile=file Store process ID of daemon in file |
| 23 | -q, --quit Quit after obtaining lease |
| 24 | -r, --request=IP IP address to request (default: none) |
| 25 | -s, --script=file Run file at dhcp events (default: |
| 26 | /usr/share/udhcpc/default.script) |
| 27 | -v, --version Display version |
| 28 | |
| 29 | |
| 30 | If the requested IP address cannot be obtained, the client accepts the |
| 31 | address that the server offers. |
| 32 | |
| 33 | |
| 34 | udhcp client scripts |
| 35 | ------------------- |
| 36 | |
Russ Dill | ae01fa9 | 2002-11-19 00:41:09 +0000 | [diff] [blame] | 37 | When an event occurs, udhcpc calls the action script. udhcpc never does |
| 38 | any configuration of the network interface itself, but instead relies on |
Eric Andersen | c7bda1c | 2004-03-15 08:29:22 +0000 | [diff] [blame] | 39 | a set of scripts. The script by default is |
Russ Dill | ae01fa9 | 2002-11-19 00:41:09 +0000 | [diff] [blame] | 40 | /usr/share/udhcpc/default.script but this can be changed via the command |
| 41 | line arguments. The three possible arguments to the script are: |
Russ Dill | f5ecd43 | 2002-10-31 19:21:27 +0000 | [diff] [blame] | 42 | |
| 43 | deconfig: This argument is used when udhcpc starts, and |
Russ Dill | ae01fa9 | 2002-11-19 00:41:09 +0000 | [diff] [blame] | 44 | when a leases is lost. The script must put the interface in an |
Russ Dill | f5ecd43 | 2002-10-31 19:21:27 +0000 | [diff] [blame] | 45 | up, but deconfigured state, ie: ifconfig $interface 0.0.0.0. |
Eric Andersen | c7bda1c | 2004-03-15 08:29:22 +0000 | [diff] [blame] | 46 | |
Russ Dill | f5ecd43 | 2002-10-31 19:21:27 +0000 | [diff] [blame] | 47 | bound: This argument is used when udhcpc moves from an |
| 48 | unbound, to a bound state. All of the paramaters are set in |
| 49 | enviromental variables, The script should configure the interface, |
Eric Andersen | c7bda1c | 2004-03-15 08:29:22 +0000 | [diff] [blame] | 50 | and set any other relavent parameters (default gateway, dns server, |
Russ Dill | f5ecd43 | 2002-10-31 19:21:27 +0000 | [diff] [blame] | 51 | etc). |
Eric Andersen | c7bda1c | 2004-03-15 08:29:22 +0000 | [diff] [blame] | 52 | |
Russ Dill | f5ecd43 | 2002-10-31 19:21:27 +0000 | [diff] [blame] | 53 | renew: This argument is used when a DHCP lease is renewed. All of |
| 54 | the paramaters are set in enviromental variables. This argument is |
| 55 | used when the interface is already configured, so the IP address, |
| 56 | will not change, however, the other DHCP paramaters, such as the |
| 57 | default gateway, subnet mask, and dns server may change. |
| 58 | |
| 59 | nak: This argument is used with udhcpc receives a NAK message. |
| 60 | The script with the deconfig argument will be called directly |
| 61 | afterwards, so no changes to the network interface are neccessary. |
| 62 | This hook is provided for purely informational purposes (the |
| 63 | message option may contain a reason for the NAK). |
| 64 | |
| 65 | The paramaters for enviromental variables are as follows: |
| 66 | |
| 67 | $HOME - The set $HOME env or "/" |
| 68 | $PATH - the set $PATH env or "/bin:/usr/bin:/sbin:/usr/sbin" |
| 69 | $1 - What action the script should perform |
| 70 | interface - The interface this was obtained on |
| 71 | ip - The obtained IP |
Russ Dill | 1eb7a17 | 2002-12-11 21:12:45 +0000 | [diff] [blame] | 72 | mask - The number of bits in the netmask (ie: 24) |
Russ Dill | f5ecd43 | 2002-10-31 19:21:27 +0000 | [diff] [blame] | 73 | siaddr - The bootp next server option |
| 74 | sname - The bootp server name option |
| 75 | boot_file - The bootp boot file option |
| 76 | subnet - The assigend subnet mask |
| 77 | timezone - Offset in seconds from UTC |
| 78 | router - A list of routers |
| 79 | timesvr - A list of time servers |
| 80 | namesvr - A list of IEN 116 name servers |
| 81 | dns - A list of DNS server |
| 82 | logsvr - A list of MIT-LCS UDP log servers |
| 83 | cookiesvr - A list of RFC 865 cookie servers |
| 84 | lprsvr - A list of LPR servers |
| 85 | hostname - The assigned hostname |
| 86 | bootsize - The length in 512 octect blocks of the bootfile |
| 87 | domain - The domain name of the network |
| 88 | swapsvr - The IP address of the client's swap server |
| 89 | rootpath - The path name of the client's root disk |
| 90 | ipttl - The TTL to use for this network |
| 91 | mtu - The MTU to use for this network |
| 92 | broadcast - The broadcast address for this network |
| 93 | ntpsrv - A list of NTP servers |
| 94 | wins - A list of WINS servers |
| 95 | lease - The lease time, in seconds |
| 96 | dhcptype - DHCP message type (safely ignored) |
| 97 | serverid - The IP of the server |
| 98 | message - Reason for a DHCPNAK |
| 99 | tftp - The TFTP server name |
| 100 | bootfile - The bootfile name |
| 101 | |
| 102 | additional options are easily added in options.c. |
| 103 | |
| 104 | |
| 105 | note on udhcpc's random seed |
| 106 | --------------------------- |
| 107 | |
| 108 | udhcpc will seed its random number generator (used for generating xid's) |
| 109 | by reading /dev/urandom. If you have a lot of embedded systems on the same |
| 110 | network, with no entropy, you can either seed /dev/urandom by a method of |
| 111 | your own, or doing the following on startup: |
| 112 | |
| 113 | ifconfig eth0 > /dev/urandom |
| 114 | |
| 115 | in order to seed /dev/urandom with some data (mac address) unique to your |
| 116 | system. If reading /dev/urandom fails, udhcpc will fall back to its old |
| 117 | behavior of seeding with time(0). |
| 118 | |
| 119 | |
| 120 | signals accepted by udhcpc |
| 121 | ------------------------- |
| 122 | |
| 123 | udhcpc also responds to SIGUSR1 and SIGUSR2. SIGUSR1 will force a renew state, |
| 124 | and SIGUSR2 will force a release of the current lease, and cause udhcpc to |
| 125 | go into an inactive state (until it is killed, or receives a SIGUSR1). You do |
| 126 | not need to sleep between sending signals, as signals received are processed |
| 127 | sequencially in the order they are received. |
| 128 | |
| 129 | |
| 130 | compile time options |
| 131 | ------------------- |
| 132 | |
| 133 | options.c contains a set of dhcp options for the client: |
| 134 | |
| 135 | name[10]: The name of the option as it will appear in scripts |
Eric Andersen | c7bda1c | 2004-03-15 08:29:22 +0000 | [diff] [blame] | 136 | |
Russ Dill | f5ecd43 | 2002-10-31 19:21:27 +0000 | [diff] [blame] | 137 | flags: The type of option, as well as if it will be requested |
| 138 | by the client (OPTION_REQ) |
| 139 | |
| 140 | code: The DHCP code for this option |
| 141 | |