resolver(3)						     Library Functions Manual						       resolver(3)

Name
       res_mkquery, res_send, res_init, dn_comp, dn_expand - resolver routines

Syntax
       #include <sys/types.h>
       #include <netinet/in.h>
       #include <arpa/nameser.h>
       #include <resolv.h>

       res_mkquery(op, dname, class, type, data, datalen, newrr, buf, buflen)
       int op;
       char *dname;
       int class, type;
       char *data;
       int datalen;
       struct rrec *newrr;
       char *buf;
       int buflen;

       res_send(msg, msglen, answer, anslen)
       char *msg;
       int msglen;
       char *answer;
       int anslen;

       res_init()

       dn_comp(exp_dn, comp_dn, length, dnptrs, lastdnptr)
       char *exp_dn, *comp_dn;
       int length;
       char **dnptrs, **lastdnptr;

       dn_expand(msg, eomorig, comp_dn, exp_dn, length)
       char *msg, *eomorig, *comp_dn, exp_dn;
       int length;

Description
       The  resolver  routines	are  used  for	making, sending, and interpreting packets to BIND servers.  Global information that is used by the
       resolver routines is kept in the variable Most of the values have reasonable defaults and you need not be concerned with them.  The options
       are a simple bit mask and are or'ed in to enable.  The options stored in are defined in and are as follows:

       RES_INIT 	  True if the initial name server address and default domain name are initialized, for example if has been called.

       RES_DEBUG	  Print debugging messages.

       RES_AAONLY	  Accept authoritative answers only.

       RES_USEVC	  Use TCP connections for queries instead of UDP.

       RES_STAYOPEN	  This	is  used  with to keep the TCP connection open between queries.  This is useful only in programs that regularly do
			  many queries.  You should normally use UDP.

       RES_RECURSE	  Set the recursion desired bit in queries.  This is the default.  The routine does not do iterative queries  and  expects
			  the BIND server to handle recursion.

       RES_DEFNAMES	  Append the default domain name to single label queries.  This is the default.

       The following lists the routines found in

       res_init        This  routine  reads  the  initialization file to get the default domain name and the Internet address of the initial hosts
		       running the name server.  If this line does not exist, the host running the resolver is tried.

       res_mkquery     This routine makes a standard query message and places it in buf.  The res_mkquery routine returns the size of the query or
		       -1 if the query is larger than buflen.

		       op     The opcode is usually but can be any of the query types defined in nameser.h.

		       Dname  This  variable  is  the  domain  name.   If  dname  consists of a single label and the flag is enabled, which is the
			      default, dname is appended with the current domain name.	The current domain name is defined in a system	file,  but
			      you can override it by using the environment variable

       res_send        This  routine  sends  a	query  to the BIND servers and returns an answer.  It calls the routine.  If is not set, sends the
		       query to the local name server, and handle timeouts and retries.  The length of the message is returned or -1 if there were
		       errors.

       dn_comp	       This routine compresses the domain name exp_dn and stores it in comp_dn.  The size of the compressed name is returned or -1
		       if there were errors.  The length is the size of the array pointed to by comp_dn.

		       dnptrs This variable is a list of pointers to previously compressed names in the current message.  The first pointer points
			      to the beginning of the message and the list ends with

		       lastdnptr
			      This is a pointer to the end of the array pointed to by dnptrs.  A side effect is to update the list of pointers for
			      labels inserted into the message by dn_comp as the name is compressed.  If dnptr is NULL, the  names  are  not  com-
			      pressed.	If lastdnptr is NULL, the list is not updated.

       dn_expand       This routine expands the compressed domain name to a full BIND domain name.  Expanded names are converted to upper case.

		       msg    This variable is a pointer to the beginning of the message.

		       exp_dn This  variable  is a pointer to a buffer of size length for the result.  The size of the compressed name is returned
			      or -1 if there was an error.

Files
See Also
       named(8), resolv.conf(5)
       Guide to the BIND/Hesiod Service

																       resolver(3)