resolver(3C)                      SDK R4.11                     resolver(3C)


NAME
       resolver: resmkquery, ressend, resinit, dncomp, dnexpand - make,
       send, and interpret packets to Internet domain name servers

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

       resmkquery(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;

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

       resinit()

       dncomp(expdn, compdn, length, dnptrs, lastdnptr)
       char *expdn, *compdn;
       int length;
       char **dnptrs, **lastdnptr;

       dnexpand(msg, eomorig, compdn, expdn, length)
       char *msg, *eomorig, *compdn, expdn;
       int  length;

DESCRIPTION
       These routines are used for making, sending and interpreting packets
       to 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 a simple bit mask and are or'ed in to enable.

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

       RES_DEBUG
              Print debugging messages.

       RES_AAONLY
              Accept authoritative answers only.  Ressend will continue
              until it finds an authoritative answer or finds an error.
              Currently this is not implemented.

       RES_USEVC
              Use TCP connections for queries instead of UDP.

       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.
              (ressend does not do iterative queries and expects the name
              server to handle recursion.)

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

       Resinit

       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.
       Resmkquery makes a standard query message and places it in buf.
       Resmkquery 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), dname will be appended with the current domain name. The
       current domain name is defined in a system file and can be overridden
       by the environment variable LOCALDOMAIN.  Newrr is currently unused
       but is intended for making update messages.

       Ressend sends a query to name servers and returns an answer.  It
       will call resinit 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.

       Dnexpand expands the compressed domain name compdn to a full domain
       name.  Expanded names are converted to upper case.  Msg is a pointer
       to the beginning of the message, expdn 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.

       Dncomp compresses the domain name expdn and stores it in compdn.
       The size of the compressed name is returned or -1 if there were
       errors.  length is the size of the array pointed to by compdn.
       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 dncomp as
       the name is compressed.  If dnptr is NULL, we don't try to compress
       names. If lastdnptr is NULL, we don't update the list.

FILES
       /etc/resolv.conf

SEE ALSO
       named(1M), resolv.conf(4M).


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