# 2.11BSD#431 - /usr/man/cat3/resolver.0

    RESOLVER(3)	    UNIX Programmer's Manual	      RESOLVER(3)

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

    SYNOPSIS
         #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
         These routines are used for making, sending and interpreting
         packets for use with Internet domain name servers.  Global
         information that is used by the resolver routines is kept in
         the variable _res.  Most of the values have reasonable
         defaults and can be ignored.  Options stored in _res.options
         are defined in resolv.h and are as follows.  Options are
         stored a simple bit mask containing the bitwise ``or'' of
         the options enabled.

         RES_INIT
    	  True if the initial name server address and default
    	  domain name are initialized (i.e., res_init has been
    	  called).

    Printed 11/26/99	November 21, 1987			1

    RESOLVER(3)	    UNIX Programmer's Manual	      RESOLVER(3)

         RES_DEBUG
    	  Print debugging messages.

         RES_AAONLY
    	  Accept authoritative answers only.  With this option,
    	  res_send should continue until it finds an authorita-
    	  tive answer or finds an error.  Currently this is not
    	  implemented.

         RES_USEVC
    	  Use TCP connections for queries instead of UDP
    	  datagrams.

         RES_STAYOPEN
    	  Used with RES_USEVC to keep the TCP connection open
    	  between queries.  This is useful only in programs that
    	  regularly do many queries.  UDP should be the normal
    	  mode used.

         RES_IGNTC
    	  Unused currently (ignore truncation errors, i.e., don't
    	  retry with TCP).

         RES_RECURSE
    	  Set the recursion-desired bit in queries.  This is the
    	  default.  ( res_send does not do iterative queries and
    	  expects the name server to handle recursion.)

         RES_DEFNAMES
    	  If set, res_mkquery will append the default domain name
    	  to single-component names (those that do not contain a
    	  dot).  This is the default.

         RES_DNSRCH
    	  If this option is set, the standard host lookup routine
    	  gethostbyname(3) will search for host names in the
    	  current domain and in parent domains; see hostname(7).

         Res_init

         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 makes a standard query
         message and places it in buf.  Res_mkquery will return the
         size of the query or -1 if the query is larger than buflen.
         Op is usually QUERY but can be any of the query types
         defined in nameser.h.  Dname is the domain name.  If dname
         consists of a single label and the RES_DEFNAMES flag is
         enabled (the default), the current domain name will be
         appended to dname.  The current domain name is defined by
         the hostname or is specified in a system file; it can be

    Printed 11/26/99	November 21, 1987			2

    RESOLVER(3)	    UNIX Programmer's Manual	      RESOLVER(3)

         overridden by the environment variable LOCALDOMAIN.  Newrr
         is currently unused but is intended for making update mes-
         sages.

         Res_send sends a query to name servers and returns an
         answer.  It will call res_init if RES_INIT is not set, send
         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_expand expands the compressed domain name comp_dn to a
         full domain name.	Expanded names are converted to upper
         case.  Msg is a pointer to the beginning of the message,
         exp_dn is a pointer to a buffer of size length for the
         result.  The size of compressed name is returned or -1 if
         there was an error.

         Dn_comp 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.  length is the size of the comp_dn.
         Dnptrs is a list of pointers to previously compressed names
         in the current message.  The first pointer points to to the
         beginning of the message and the list ends with NULL.
         lastdnptr is a pointer to the end of the array pointed to
         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, names are not compressed.  If
         lastdnptr is NULL, the list of labels is not updated.

    FILES
         /etc/resolv.conf	 see resolver(5)

    SEE ALSO
         gethostbyname(3), named(8), resolver(5), hostname(7),
         RFC882, RFC883, RFC973, RFC974,
         SMM:11 Name Server Operations Guide for BIND

    Printed 11/26/99	November 21, 1987			3

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