RESOLVER(3) RESOLVER(3) NAME res_mkquery, res_send, res_init, dn_comp, dn_expand - resolver routines SYNOPSIS #include #include #include #include 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 to 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 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., _r_e_s__i_n_i_t has been called). RES_DEBUG Print debugging messages. RES_AAONLY Accept authoritative answers only. _R_e_s__s_e_n_d 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. ( _r_e_s__s_e_n_d 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. _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 con‐ sists of a single label and the RES_DEFNAMES flag is enabled (the default), _d_n_a_m_e will be appended with the current domain name. The cur‐ rent domain name is defined in a system file and can be overridden by the environment variable LOCALDOMAIN. _N_e_w_r_r is currently unused but is intended for making update messages. _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 _a_r_r_a_y _p_o_i_n_t_e_d _t_o _b_y _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, we don’t try to compress names. If _l_a_s_t_d_n_p_t_r is NULL, we don’t update the list. FILES /etc/resolv.conf see resolver(5) SEE ALSO named(8), resolver(5), RFC882, RFC883, RFC973, RFC974, SMM:11 Name Server Operations Guide for BIND 4th Berkeley Distribution 15 November 1985 RESOLVER(3)