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     dhcpctl_initialize - dhcpctl library initialization.


     #include <dhcpctl/dhcpctl.h>


     dhcpctl_connect(dhcpctl_handle *cxn, const char *host, int port,
             dhcpctl_handle auth);

     dhcpctl_wait_for_completion(dhcpctl_handle object,
             dhcpctl_status *status);

     dhcpctl_get_value(dhcpctl_data_string *value, dhcpctl_handle object,
             const char *name);

     dhcpctl_get_boolean(int *value, dhcpctl_handle object, const char *name);

     dhcpctl_set_value(dhcpctl_handle object, dhcpctl_data_string value,
             const char *name);

     dhcpctl_set_string_value(dhcpctl_handle object, const char *value,
             const char *name);

     dhcpctl_set_boolean_value(dhcpctl_handle object, int value,
             const char *name);

     dhcpctl_set_int_value(dhcpctl_handle object, int value,
             const char *name);

     dhcpctl_object_update(dhcpctl_handle connection, dhcpctl_handle object);

     dhcpctl_object_refresh(dhcpctl_handle connection, dhcpctl_handle object);

     dhcpctl_object_remove(dhcpctl_handle connection, dhcpctl_handle object);

     dhcpctl_set_callback(dhcpctl_handle object, void *data,
             void (*function) (dhcpctl_handle, dhcpctl_status, void *));

     dhcpctl_new_authenticator(dhcpctl_handle *object, const char *name,
             const char *algorithm, const char *secret, unsigned secret_len);

     dhcpctl_new_object(dhcpctl_handle *object, dhcpctl_handle connection,
             const char *object_type);

     dhcpctl_open_object(dhcpctl_handle object, dhcpctl_handle connection,
             int flags);

     omapi_data_string_new(dhcpctl_data_string, *data, unsigned, int, length,
             const, char, *filename,, int, lineno);

     dhcpctl_data_string_dereference(dhcpctl_data_string *, const char *,


     The dhcpctl set of functions provide an API that can be used to
     communicate with and manipulate a running ISC DHCP server. All functions
     return a value of isc_result_t.  The return values reflects the result of
     operations to local data structures. If an operation fails on the server
     for any reason, then the error result will be returned through the second
     parameter of the dhcpctl_wait_for_completion() call.

     dhcpctl_initialize() sets up the data structures the library needs to do
     its work. This function must be called once before any other.

     dhcpctl_connect() opens a connection to the DHCP server at the given host
     and port. If an authenticator has been created for the connection, then
     it is given as the 4th argument. On a successful return the address
     pointed at by the first argument will have a new connection object
     assigned to it.

     For example:

           s = dhcpctl_connect(&cxn, "", 7911, NULL);

     connects to the DHCP server on the localhost via port 7911 (the standard
     OMAPI port). No authentication is used for the connection.

     dhcpctl_wait_for_completion() flushes a pending message to the server and
     waits for the response. The result of the request as processed on the
     server is returned via the second parameter.

           s = dhcpctl_wait_for_completion(cxn, &wv);
           if (s != ISC_R_SUCCESS)
           else if (wv != ISC_R_SUCCESS)

     The call to dhcpctl_wait_for_completion() won't return until the remote
     message processing completes or the connection to the server is lost.

     dhcpctl_get_value() extracts a value of an attribute from the handle. The
     value can be of any length and is treated as a sequence of bytes.  The
     handle must have been created first with dhcpctl_new_object() and opened
     with dhcpctl_open_object().  The value is returned via the parameter
     named ``value''.  The last parameter is the name of attribute to

           dhcpctl_data_string value = NULL;
           dhcpctl_handle lease;
           time_t thetime;

           s = dhcpctl_get_value (&value, lease, "ends");
           assert(s == ISC_R_SUCCESS && value->len == sizeof(thetime));
           memcpy(&thetime, value->value, value->len);

     dhcpctl_get_boolean() extracts a boolean valued attribute from the object

     The dhcpctl_set_value(), dhcpctl_set_string_value(),
     dhcpctl_set_boolean_value(), and dhcpctl_set_int_value() functions all
     set a value on the object handle.

     dhcpctl_object_update() function queues a request for all the changes
     made to the object handle be be sent to the remote for processing. The
     changes made to the atributes on the handle will be applied to remote
     object if permitted.

     dhcpctl_object_refresh() queues up a request for a fresh copy of all the
     attribute values to be sent from the remote to refresh the values in the
     local object handle.

     dhcpctl_object_remove() queues a request for the removal on the server of
     the object referenced by the handle.

     The dhcpctl_set_callback() function sets up a user-defined function to be
     called when an event completes on the given object handle. This is needed
     for asynchronous handling of events, versus the synchronous handling
     given by dhcpctl_wait_for_completion().  When the function is called the
     first parameter is the object the event arrived for, the second is the
     status of the message that was processed, the third is the same value as
     the second parameter given to dhcpctl_set_callback().

     The dhcpctl_new_authenticator() creates a new authenticator object to be
     used for signing the messages that cross over the network. The ``name'',
     ``algorithm'', and ``secret'' values must all match what the server uses
     and are defined in its configuration file. The created object is returned
     through the first parameter and must be used as the 4th parameter to
     dhcpctl_connect().  Note that the 'secret' value must not be base64
     encoded, which is different from how the value appears in the dhcpd.conf

     dhcpctl_new_object() creates a local handle for an object on the the
     server. The ``object_type'' parameter is the ascii name of the type of
     object being accessed. e.g.  "lease".  This function only sets up local
     data structures, it does not queue any messages to be sent to the remote
     side, dhcpctl_open_object() does that.

     dhcpctl_open_object() builds and queues the request to the remote side.
     This function is used with handle created via dhcpctl_new_object().  The
     flags argument is a bit mask with the following values available for

               if the object does not exist then the remote will create it

               update the object on the remote side using the attributes
               already set in the handle.

               return and error if the object exists and DHCPCTL_CREATE was
               also specified

     The omapi_data_string_new() function allocates a new dhcpctl_data_string
     object. The data string will be large enough to hold ``length'' bytes of
     data. The ``file'' and ``lineno'' arguments are the source file location
     the call is made from, typically by using the __FILE__ and __LINE__
     macros or the MDL macro defined in

     dhcpctl_data_string_dereference() deallocates a data string created by
     omapi_data_string_new().  The memory for the object won't be freed until
     the last reference is released.


     The following program will connect to the DHCP server running on the
     local host and will get the details of the existing lease for IP address It will then print out the time the lease is due to expire.
     Note that most error checking has been ommitted for brevity.

           #include <stdarg.h>
           #include <sys/time.h>
           #include <sys/socket.h>
           #include <stdio.h>
           #include <netinet/in.h>

           #include <isc/result.h>
           #include <dhcpctl/dhcpctl.h>

           int main (int argc, char **argv) {
                   dhcpctl_data_string ipaddrstring = NULL;
                   dhcpctl_data_string value = NULL;
                   dhcpctl_handle connection = NULL;
                   dhcpctl_handle lease = NULL;
                   isc_result_t waitstatus;
                   struct in_addr convaddr;
                   time_t thetime;

                   dhcpctl_initialize ();

                   dhcpctl_connect (&connection, "",
                                    7911, 0);

                   dhcpctl_new_object (&lease, connection,

                   memset (&ipaddrstring, 0, sizeof

                   inet_pton(AF_INET, "",

                   omapi_data_string_new (&ipaddrstring,
                                          4, MDL);
                   memcpy(ipaddrstring->value, &convaddr.s_addr, 4);

                   dhcpctl_set_value (lease, ipaddrstring,

                   dhcpctl_open_object (lease, connection, 0);

                   dhcpctl_wait_for_completion (lease,
                   if (waitstatus != ISC_R_SUCCESS) {
                           /* server not authoritative */
                           exit (0);


                   dhcpctl_get_value (&value, lease, "ends");

                   memcpy(&thetime, value->value, value->len);

                   dhcpctl_data_string_dereference(&value, MDL);

                   fprintf (stdout, "ending time is %s",


     omapi(3), omshell(1), dhcpd(8), dhclient(8), dhcpd.conf(5),


     dhcpctl was written by Ted Lemon of Nominum, Inc.  This preliminary
     documentation was written by James Brister of Nominum, Inc.