RESOLVER(3-BSD)     RISC/os Reference Manual      RESOLVER(3-BSD)



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

SYNOPSIS
   Headers
     For -systype svr3:

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

     For -systype bsd43:

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

   Declarations
     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



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     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 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 con-
          tinue 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



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     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
     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 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 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(8) in the System Administrator's Reference Manual.
     Name Server Operations Guide for BIND, Chapter 15 in the
     System Administrator's Guide.

NOTE
     When these routines are used in a program which is compiled
     in -systype svr3, they are not resolved by libc.a.  See
     intro(3) for more information.














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