2.11BSD/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 __r_e_s.  Most of the values have reasonable
     defaults and can be ignored.  Options stored in __r_e_s._o_p_t_i_o_n_s
     are defined in _r_e_s_o_l_v._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., _r_e_s__i_n_i_t 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,
	  _r_e_s__s_e_n_d 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.  ( _r_e_s__s_e_n_d does not do iterative queries and
	  expects the name server to handle recursion.)

     RES_DEFNAMES
	  If set, _r_e_s__m_k_q_u_e_r_y 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
	  _g_e_t_h_o_s_t_b_y_n_a_m_e(3) will search for host names in the
	  current domain and in parent domains; see _h_o_s_t_n_a_m_e(7).

     _R_e_s__i_n_i_t

     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.  _R_e_s__m_k_q_u_e_r_y makes a standard query
     message and places it in _b_u_f.  _R_e_s__m_k_q_u_e_r_y will return the
     size of the query or -1 if the query is larger than _b_u_f_l_e_n.
     _O_p is usually QUERY but can be any of the query types
     defined in _n_a_m_e_s_e_r._h.  _D_n_a_m_e is the domain name.  If _d_n_a_m_e
     consists of a single label and the RES_DEFNAMES flag is
     enabled (the default), the current domain name will be
     appended to _d_n_a_m_e.  The current domain name is defined by
     the hostname or is specified in a system file; it can be



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



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

     _R_e_s__s_e_n_d sends a query to name servers and returns an
     answer.  It will call _r_e_s__i_n_i_t 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.

     _D_n__e_x_p_a_n_d expands the compressed domain name _c_o_m_p__d_n to a
     full domain name.	Expanded names are converted to upper
     case.  _M_s_g is a pointer to the beginning of the message,
     _e_x_p__d_n is a pointer to a buffer of size _l_e_n_g_t_h for the
     result.  The size of compressed name is returned or -1 if
     there was an error.

     _D_n__c_o_m_p compresses the domain name _e_x_p__d_n and stores it in
     _c_o_m_p__d_n.  The size of the compressed name is returned or -1
     if there were errors.  _l_e_n_g_t_h _i_s _t_h_e _s_i_z_e _o_f _t_h_e _c_o_m_p__d_n.
     _D_n_p_t_r_s 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.
     _l_a_s_t_d_n_p_t_r is a pointer to the end of the array pointed to
     _d_n_p_t_r_s.  A side effect is to update the list of pointers for
     labels inserted into the message by _d_n__c_o_m_p as the name is
     compressed.  If _d_n_p_t_r is NULL, names are not compressed.  If
     _l_a_s_t_d_n_p_t_r 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