.\" Copyright (c) 1985 Regents of the University of California. .\" All rights reserved. The Berkeley software License Agreement .\" specifies the terms and conditions for redistribution. .\" .\" @(#)resolver.3 1.7 (Berkeley) 5/27/86 .\" .TH RESOLVER 3 "15 November 1985" .UC 4 .SH NAME res_mkquery, res_send, res_init, dn_comp, dn_expand \- resolver routines .SH SYNOPSIS .B #include .br .B #include .br .B #include .br .B #include .PP .B "res_mkquery(op, dname, class, type, data, datalen, newrr, buf, buflen)" .br .B int op; .br .B char *dname; .br .B int class, type; .br .B char *data; .br .B int datalen; .br .B struct rrec *newrr; .br .B char *buf; .br .B int buflen; .PP .B res_send(msg, msglen, answer, anslen) .br .B char *msg; .br .B int msglen; .br .B char *answer; .br .B int anslen; .PP .B res_init() .PP .B dn_comp(exp_dn, comp_dn, length, dnptrs, lastdnptr) .br .B char *exp_dn, *comp_dn; .br .B int length; .br .B char **dnptrs, **lastdnptr; .PP .B dn_expand(msg, eomorig, comp_dn, exp_dn, length) .br .B char *msg, *eomorig, *comp_dn, exp_dn; .br .B int length; .SH 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 .IR _res . Most of the values have reasonable defaults and can be ignored. Options stored in .I _res.options are defined in .I resolv.h and are as follows. Options are a simple bit mask and are or'ed in to enable. .IP RES_INIT True if the initial name server address and default domain name are initialized (i.e., .I res_init has been called). .IP RES_DEBUG Print debugging messages. .IP RES_AAONLY Accept authoritative answers only. .I Res_send will continue until it finds an authoritative answer or finds an error. Currently this is not implemented. .IP RES_USEVC Use TCP connections for queries instead of UDP. .IP 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. .IP RES_IGNTC Unused currently (ignore truncation errors, i.e., don't retry with TCP). .IP RES_RECURSE Set the recursion desired bit in queries. This is the default. ( .I res_send does not do iterative queries and expects the name server to handle recursion.) .IP RES_DEFNAMES Append the default domain name to single label queries. This is the default. .PP .I Res_init .PP 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. .I Res_mkquery makes a standard query message and places it in .IR buf . .I Res_mkquery will return the size of the query or \-1 if the query is larger than .IR buflen . .I Op is usually QUERY but can be any of the query types defined in .IR nameser.h . .I Dname is the domain name. If .I dname consists of a single label and the RES_DEFNAMES flag is enabled (the default), .I 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. .I Newrr is currently unused but is intended for making update messages. .PP .I Res_send sends a query to name servers and returns an answer. It will call .I res_init 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. .PP .I Dn_expand expands the compressed domain name .I comp_dn to a full domain name. Expanded names are converted to upper case. .I Msg is a pointer to the beginning of the message, .I exp_dn is a pointer to a buffer of size .I length for the result. The size of compressed name is returned or -1 if there was an error. .PP .I Dn_comp compresses the domain name .I exp_dn and stores it in .IR comp_dn . The size of the compressed name is returned or -1 if there were errors. .I length is the size of the array pointed to by .IR comp_dn . .I 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. .I lastdnptr is a pointer to the end of the array pointed to .IR dnptrs . A side effect is to update the list of pointers for labels inserted into the message by .I dn_comp as the name is compressed. If .I dnptr is NULL, we don't try to compress names. If .I lastdnptr is NULL, we don't update the list. .SH FILES /etc/resolv.conf see resolver(5) .SH "SEE ALSO" named(8), resolver(5), RFC882, RFC883, RFC973, RFC974, SMM:11 Name Server Operations Guide for BIND