RESOLVER(3N-SVR4)   RISC/os Reference Manual    RESOLVER(3N-SVR4)



NAME
     resolver, 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>

     vresmkquery(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, msglen, compdn, expdn, length)
     char *msg, *compdn, expdn;
     int  msglen, 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 vari-
     able _res.  Most of the values have reasonable defaults and
     can be ignored.  Options are a simple bit mask and are OR'ed
     in to enable.  Options stored in _res.options are defined in
     /usr/include/resolv.h and are as follows.

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

     RES_DEBUG           Print debugging messages.




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     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 con-
                         nection open between queries.  This is
                         useful only in programs that regularly
                         do many queries.  UDP should be the nor-
                         mal mode used.

     RES_IGNTC           Unused currently (ignore truncation
                         errors, that is, do not 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 recur-
                         sion.

     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 /usr/include/arpa/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 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



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     there was an error.

     dncomp 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 array
     pointed to by comp_dn.  dnptrs is a list of pointers to pre-
     viously 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, do not
     try to compress names.  If lastdnptr is NULL, do not update
     the list.

FILES
     /usr/include/arpa/nameserv.h
     /usr/include/netinet/in.h
     /usr/include/resolv.h
     /usr/include/sys/types.h
     /etc/resolv.conf
     /usr/lib/libresolv.a

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

NOTES
     /usr/lib/libresolv.a is necessary for compiling programs.

     Programs must be loaded with the option -lresolv.

























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