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

NNAAMMEE
     rreess__qquueerryy, rreess__sseeaarrcchh, rreess__mmkkqquueerryy, rreess__sseenndd, rreess__iinniitt, ddnn__ccoommpp,
     ddnn__eexxppaanndd - resolver routines

SSYYNNOOPPSSIISS
     ##iinncclluuddee <<ssyyss//ttyyppeess..hh>>
     ##iinncclluuddee <<nneettiinneett//iinn..hh>>
     ##iinncclluuddee <<aarrppaa//nnaammeesseerr..hh>>
     ##iinncclluuddee <<rreessoollvv..hh>>

     rreess__qquueerryy(_c_h_a_r _*_d_n_a_m_e, _i_n_t _c_l_a_s_s, _i_n_t _t_y_p_e, _u___c_h_a_r _*_a_n_s_w_e_r, _i_n_t _a_n_s_l_e_n)

     rreess__sseeaarrcchh(_c_h_a_r _*_d_n_a_m_e, _i_n_t _c_l_a_s_s, _i_n_t _t_y_p_e, _u___c_h_a_r _*_a_n_s_w_e_r, _i_n_t _a_n_s_l_e_n)

     rreess__mmkkqquueerryy(_i_n_t _o_p, _c_h_a_r _*_d_n_a_m_e, _i_n_t _c_l_a_s_s, _i_n_t _t_y_p_e, _c_h_a_r _*_d_a_t_a,
             _i_n_t _d_a_t_a_l_e_n, _s_t_r_u_c_t _r_r_e_c _*_n_e_w_r_r, _c_h_a_r _*_b_u_f, _i_n_t _b_u_f_l_e_n)

     rreess__sseenndd(_c_h_a_r _*_m_s_g, _i_n_t _m_s_g_l_e_n, _c_h_a_r _*_a_n_s_w_e_r, _i_n_t _a_n_s_l_e_n)

     rreess__iinniitt()

     ddnn__ccoommpp(_c_h_a_r _*_e_x_p___d_n, _c_h_a_r _*_c_o_m_p___d_n, _i_n_t _l_e_n_g_t_h, _c_h_a_r _*_*_d_n_p_t_r_s,
             _c_h_a_r _*_*_l_a_s_t_d_n_p_t_r)

     ddnn__eexxppaanndd(_u___c_h_a_r _*_m_s_g, _u___c_h_a_r _*_e_o_m_o_r_i_g, _u___c_h_a_r _*_c_o_m_p___d_n, _u___c_h_a_r _*_e_x_p___d_n,
             _i_n_t _l_e_n_g_t_h)

DDEESSCCRRIIPPTTIIOONN
     These routines are used for making, sending and interpreting query and
     reply messages with Internet domain name servers.

     Global configuration and state information that is used by the resolver
     routines is kept in the structure ___r_e_s. Most of the values have reason-
     able defaults and can be ignored.  Options stored in ___r_e_s_._o_p_t_i_o_n_s are de-
     fined in _r_e_s_o_l_v_._h and are as follows.  Options are stored as 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., rreess__iinniitt() has been called).

     RES_DEBUG     Print debugging messages.

     RES_AAONLY    Accept authoritative answers only.  With this option,
                   rreess__sseenndd() should continue until it finds an authoritative
                   answer or finds an error.  Currently this is not implement-
                   ed.

     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 de-
                   fault.  (rreess__sseenndd() does not do iterative queries and ex-
                   pects the name server to handle recursion.)

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

                   This option is enabled by default.

     RES_DNSRCH    If this option is set, rreess__sseeaarrcchh() will search for host
                   names in the current domain and in parent domains; see
                   hostname(7).  This is used by the standard host lookup rou-
                   tine gethostbyname(3).  This option is enabled by default.

     The rreess__iinniitt() routine reads the configuration file (if any; see
     resolver(5))  to get the default domain name, search list and the Inter-
     net address of the local name server(s).  If no server is configured, the
     host running the resolver is tried.  The current domain name is defined
     by the hostname if not specified in the configuration file; it can be
     overridden by the environment variable LOCALDOMAIN. Initialization nor-
     mally occurs on the first call to one of the following routines.

     The rreess__qquueerryy() function provides an interface to the server query mecha-
     nism.  It constructs a query, sends it to the local server, awaits a re-
     sponse, and makes preliminary checks on the reply.  The query requests
     information of the specified _t_y_p_e and _c_l_a_s_s for the specified fully-
     qualified domain name _d_n_a_m_e. The reply message is left in the _a_n_s_w_e_r
     buffer with length _a_n_s_l_e_n supplied by the caller.

     The rreess__sseeaarrcchh() routine makes a query and awaits a response like
     rreess__qquueerryy(), but in addition, it implements the default and search rules
     controlled by the RES_DEFNAMES and RES_DNSRCH options.  It returns the
     first successful reply.

     The remaining routines are lower-level routines used by rreess__qquueerryy().  The
     rreess__mmkkqquueerryy() function constructs a standard query message and places it
     in _b_u_f. It returns the size of the query, or -1 if the query is larger
     than _b_u_f_l_e_n. The query type _o_p is usually QUERY, but can be any of the
     query types defined in <_a_r_p_a_/_n_a_m_e_s_e_r_._h>. The domain name for the query is
     given by _d_n_a_m_e. _N_e_w_r_r is currently unused but is intended for making up-
     date messages.

     The rreess__sseenndd() routine sends a pre-formatted query and returns an answer.
     It will call rreess__iinniitt() if RES_INIT is not set, send the query to the lo-
     cal name server, and handle timeouts and retries.  The length of the re-
     ply message is returned, or -1 if there were errors.

     The ddnn__ccoommpp() function 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.  The size of the array pointed to by _c_o_m_p___d_n is given by _l_e_n_g_t_h.
     The compression uses an array of pointers _d_n_p_t_r_s to previously-compressed
     names in the current message.  The first pointer points to to the begin-
     ning of the message and the list ends with NULL. The limit to the array
     is specified by _l_a_s_t_d_n_p_t_r. A side effect of ddnn__ccoommpp() is to update the
     list of pointers for labels inserted into the message as the name is com-
     pressed.  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.

     The ddnn__eexxppaanndd() entry expands the compressed domain name _c_o_m_p___d_n to a
     full domain name The compressed name is contained in a query or reply
     message; _m_s_g is a pointer to the beginning of the message.  The uncom-
     pressed name is placed in the buffer indicated by _e_x_p___d_n which is of size
     _l_e_n_g_t_h. The size of compressed name is returned or -1 if there was an er-
     ror.

FFIILLEESS
     /etc/resolv.conf The configuration file see resolver(5).

SSEEEE AALLSSOO
     gethostbyname(3),  named(8),  resolver(5),  hostname(7),


     _R_F_C_1_0_3_2, _R_F_C_1_0_3_3, _R_F_C_1_0_3_4, _R_F_C_1_0_3_5, _R_F_C_9_7_4

     _N_a_m_e _S_e_r_v_e_r _O_p_e_r_a_t_i_o_n_s _G_u_i_d_e _f_o_r _B_I_N_D.

HHIISSTTOORRYY
     The rreess__qquueerryy function appeared in 4.3BSD.

 MiNT-Net                        July 29, 1991                               3



























































