373 lines
12 KiB
C
373 lines
12 KiB
C
/*
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* reply.c
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* - main handling and parsing routine for received datagrams
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*/
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/*
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* This file is
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* Copyright (C) 1997-2000 Ian Jackson <ian@davenant.greenend.org.uk>
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*
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* It is part of adns, which is
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* Copyright (C) 1997-2000 Ian Jackson <ian@davenant.greenend.org.uk>
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* Copyright (C) 1999-2000 Tony Finch <dot@dotat.at>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* $Id: reply.c,v 1.2 2002/08/13 14:44:59 fishwaldo Exp $
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*/
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#include "stdinc.h"
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#include "memory.h"
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#include "fileio.h"
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#include "internal.h"
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void adns__procdgram(adns_state ads, const byte *dgram, int dglen,
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int serv, int viatcp, struct timeval now) {
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int cbyte, rrstart, wantedrrs, rri, foundsoa, foundns, cname_here;
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int id, f1, f2, qdcount, ancount, nscount, arcount;
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int flg_ra, flg_rd, flg_tc, flg_qr, opcode;
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int rrtype, rrclass, rdlength, rdstart;
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int anstart, nsstart, arstart;
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int ownermatched, l, nrrs;
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unsigned long ttl, soattl;
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const typeinfo *typei;
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adns_query qu, nqu;
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dns_rcode rcode;
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adns_status st;
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vbuf tempvb;
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byte *newquery, *rrsdata;
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parseinfo pai;
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if (dglen<DNS_HDRSIZE) {
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adns__diag(ads,serv,0,"received datagram too short for message header (%d)",dglen);
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return;
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}
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cbyte= 0;
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GET_W(cbyte,id);
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GET_B(cbyte,f1);
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GET_B(cbyte,f2);
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GET_W(cbyte,qdcount);
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GET_W(cbyte,ancount);
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GET_W(cbyte,nscount);
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GET_W(cbyte,arcount);
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assert(cbyte == DNS_HDRSIZE);
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flg_qr= f1&0x80;
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opcode= (f1&0x78)>>3;
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flg_tc= f1&0x02;
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flg_rd= f1&0x01;
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flg_ra= f2&0x80;
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rcode= (f2&0x0f);
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cname_here= 0;
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if (!flg_qr) {
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adns__diag(ads,serv,0,"server sent us a query, not a response");
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return;
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}
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if (opcode) {
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adns__diag(ads,serv,0,"server sent us unknown opcode %d (wanted 0=QUERY)",opcode);
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return;
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}
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qu= 0;
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/* See if we can find the relevant query, or leave qu=0 otherwise ... */
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if (qdcount == 1) {
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for (qu= viatcp ? ads->tcpw.head : ads->udpw.head; qu; qu= nqu) {
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nqu= qu->next;
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if (qu->id != id) continue;
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if (dglen < qu->query_dglen) continue;
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if (memcmp(qu->query_dgram+DNS_HDRSIZE,
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dgram+DNS_HDRSIZE,
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qu->query_dglen-DNS_HDRSIZE))
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continue;
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if (viatcp) {
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assert(qu->state == query_tcpw);
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} else {
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assert(qu->state == query_tosend);
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if (!(qu->udpsent & (1<<serv))) continue;
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}
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break;
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}
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if (qu) {
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/* We're definitely going to do something with this query now */
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if (viatcp) LIST_UNLINK(ads->tcpw,qu);
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else LIST_UNLINK(ads->udpw,qu);
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}
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}
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/* If we're going to ignore the packet, we return as soon as we have
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* failed the query (if any) and printed the warning message (if
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* any).
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*/
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switch (rcode) {
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case rcode_noerror:
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case rcode_nxdomain:
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break;
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case rcode_formaterror:
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adns__warn(ads,serv,qu,"server cannot understand our query (Format Error)");
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if (qu) adns__query_fail(qu,adns_s_rcodeformaterror);
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return;
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case rcode_servfail:
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if (qu) adns__query_fail(qu,adns_s_rcodeservfail);
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else adns__debug(ads,serv,qu,"server failure on unidentifiable query");
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return;
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case rcode_notimp:
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adns__warn(ads,serv,qu,"server claims not to implement our query");
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if (qu) adns__query_fail(qu,adns_s_rcodenotimplemented);
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return;
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case rcode_refused:
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adns__debug(ads,serv,qu,"server refused our query");
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if (qu) adns__query_fail(qu,adns_s_rcoderefused);
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return;
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default:
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adns__warn(ads,serv,qu,"server gave unknown response code %d",rcode);
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if (qu) adns__query_fail(qu,adns_s_rcodeunknown);
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return;
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}
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if (!qu) {
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if (!qdcount) {
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adns__diag(ads,serv,0,"server sent reply without quoting our question");
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} else if (qdcount>1) {
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adns__diag(ads,serv,0,"server claimed to answer %d questions with one message",
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qdcount);
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} else if (ads->iflags & adns_if_debug) {
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adns__vbuf_init(&tempvb);
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adns__debug(ads,serv,0,"reply not found, id %02x, query owner %s",
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id, adns__diag_domain(ads,serv,0,&tempvb,dgram,dglen,DNS_HDRSIZE));
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adns__vbuf_free(&tempvb);
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}
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return;
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}
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/* We're definitely going to do something with this packet and this query now. */
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anstart= qu->query_dglen;
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arstart= -1;
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/* Now, take a look at the answer section, and see if it is complete.
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* If it has any CNAMEs we stuff them in the answer.
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*/
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wantedrrs= 0;
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cbyte= anstart;
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for (rri= 0; rri<ancount; rri++) {
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rrstart= cbyte;
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st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
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&rrtype,&rrclass,&ttl, &rdlength,&rdstart,
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&ownermatched);
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if (st) { adns__query_fail(qu,st); return; }
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if (rrtype == -1) goto x_truncated;
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if (rrclass != DNS_CLASS_IN) {
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adns__diag(ads,serv,qu,"ignoring answer RR with wrong class %d (expected IN=%d)",
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rrclass,DNS_CLASS_IN);
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continue;
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}
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if (!ownermatched) {
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if (ads->iflags & adns_if_debug) {
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adns__debug(ads,serv,qu,"ignoring RR with an unexpected owner %s",
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adns__diag_domain(ads,serv,qu, &qu->vb, dgram,dglen,rrstart));
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}
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continue;
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}
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if (rrtype == adns_r_cname &&
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(qu->typei->type & adns__rrt_typemask) != adns_r_cname) {
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if (qu->flags & adns_qf_cname_forbid) {
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adns__query_fail(qu,adns_s_prohibitedcname);
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return;
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} else if (qu->cname_dgram && ++qu->cname_count >= 2) {
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adns__debug(ads,serv,qu,"allegedly canonical name %s is actually alias for %s",
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qu->answer->cname,
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adns__diag_domain(ads,serv,qu, &qu->vb, dgram,dglen,rdstart));
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adns__query_fail(qu,adns_s_prohibitedcname);
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return;
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} else if (wantedrrs) { /* Ignore CNAME(s) after RR(s). */
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adns__debug(ads,serv,qu,"ignoring CNAME (to %s) coexisting with RR",
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adns__diag_domain(ads,serv,qu, &qu->vb, dgram,dglen,rdstart));
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} else {
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qu->cname_begin= rdstart;
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qu->cname_dglen= dglen;
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st= adns__parse_domain(ads,serv,qu, &qu->vb,
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qu->flags & adns_qf_quotefail_cname ? 0 : pdf_quoteok,
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dgram,dglen, &rdstart,rdstart+rdlength);
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if (!qu->vb.used) goto x_truncated;
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if (st) { adns__query_fail(qu,st); return; }
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l= strlen((char*)qu->vb.buf)+1;
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qu->answer->cname= adns__alloc_preserved(qu,l);
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if (!qu->answer->cname) { adns__query_fail(qu,adns_s_nomemory); return; }
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qu->cname_dgram= adns__alloc_mine(qu,dglen);
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memcpy(qu->cname_dgram,dgram,dglen);
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memcpy(qu->answer->cname,qu->vb.buf,l);
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cname_here= 1;
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adns__update_expires(qu,ttl,now);
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/* If we find the answer section truncated after this point we restart
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* the query at the CNAME; if beforehand then we obviously have to use
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* TCP. If there is no truncation we can use the whole answer if
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* it contains the relevant info.
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*/
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}
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} else if (rrtype == (qu->typei->type & adns__rrt_typemask)) {
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wantedrrs++;
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} else {
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adns__debug(ads,serv,qu,"ignoring answer RR with irrelevant type %d",rrtype);
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}
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}
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/* We defer handling truncated responses here, in case there was a CNAME
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* which we could use.
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*/
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if (flg_tc) goto x_truncated;
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nsstart= cbyte;
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if (!wantedrrs) {
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/* Oops, NODATA or NXDOMAIN or perhaps a referral (which would be a problem) */
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/* RFC2308: NODATA has _either_ a SOA _or_ _no_ NS records in authority section */
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foundsoa= 0; soattl= 0; foundns= 0;
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for (rri= 0; rri<nscount; rri++) {
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rrstart= cbyte;
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st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
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&rrtype,&rrclass,&ttl, &rdlength,&rdstart, 0);
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if (st) { adns__query_fail(qu,st); return; }
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if (rrtype==-1) goto x_truncated;
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if (rrclass != DNS_CLASS_IN) {
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adns__diag(ads,serv,qu,
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"ignoring authority RR with wrong class %d (expected IN=%d)",
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rrclass,DNS_CLASS_IN);
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continue;
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}
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if (rrtype == adns_r_soa_raw) { foundsoa= 1; soattl= ttl; break; }
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else if (rrtype == adns_r_ns_raw) { foundns= 1; }
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}
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if (rcode == rcode_nxdomain) {
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/* We still wanted to look for the SOA so we could find the TTL. */
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adns__update_expires(qu,soattl,now);
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if (qu->flags & adns_qf_search) {
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adns__search_next(ads,qu,now);
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} else {
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adns__query_fail(qu,adns_s_nxdomain);
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}
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return;
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}
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if (foundsoa || !foundns) {
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/* Aha ! A NODATA response, good. */
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adns__update_expires(qu,soattl,now);
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adns__query_fail(qu,adns_s_nodata);
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return;
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}
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/* Now what ? No relevant answers, no SOA, and at least some NS's.
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* Looks like a referral. Just one last chance ... if we came across
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* a CNAME in this datagram then we should probably do our own CNAME
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* lookup now in the hope that we won't get a referral again.
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*/
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if (cname_here) goto x_restartquery;
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/* Bloody hell, I thought we asked for recursion ? */
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if (!flg_ra) {
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adns__diag(ads,serv,qu,"server is not willing to do recursive lookups for us");
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adns__query_fail(qu,adns_s_norecurse);
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} else {
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if (!flg_rd)
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adns__diag(ads,serv,qu,"server thinks we didn't ask for recursive lookup");
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else
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adns__debug(ads,serv,qu,"server claims to do recursion, but gave us a referral");
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adns__query_fail(qu,adns_s_invalidresponse);
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}
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return;
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}
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/* Now, we have some RRs which we wanted. */
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qu->answer->rrs.untyped= adns__alloc_interim(qu,qu->typei->rrsz*wantedrrs);
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if (!qu->answer->rrs.untyped) { adns__query_fail(qu,adns_s_nomemory); return; }
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typei= qu->typei;
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cbyte= anstart;
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rrsdata= qu->answer->rrs.bytes;
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pai.ads= qu->ads;
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pai.qu= qu;
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pai.serv= serv;
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pai.dgram= dgram;
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pai.dglen= dglen;
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pai.nsstart= nsstart;
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pai.nscount= nscount;
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pai.arcount= arcount;
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pai.now= now;
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for (rri=0, nrrs=0; rri<ancount; rri++) {
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st= adns__findrr(qu,serv, dgram,dglen,&cbyte,
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&rrtype,&rrclass,&ttl, &rdlength,&rdstart,
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&ownermatched);
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assert(!st); assert(rrtype != -1);
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if (rrclass != DNS_CLASS_IN ||
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rrtype != (qu->typei->type & adns__rrt_typemask) ||
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!ownermatched)
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continue;
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adns__update_expires(qu,ttl,now);
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st= typei->parse(&pai, rdstart,rdstart+rdlength, rrsdata+nrrs*typei->rrsz);
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if (st) { adns__query_fail(qu,st); return; }
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if (rdstart==-1) goto x_truncated;
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nrrs++;
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}
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assert(nrrs==wantedrrs);
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qu->answer->nrrs= nrrs;
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/* This may have generated some child queries ... */
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if (qu->children.head) {
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qu->state= query_childw;
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LIST_LINK_TAIL(ads->childw,qu);
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return;
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}
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adns__query_done(qu);
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return;
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x_truncated:
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if (!flg_tc) {
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adns__diag(ads,serv,qu,"server sent datagram which points outside itself");
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adns__query_fail(qu,adns_s_invalidresponse);
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return;
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}
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qu->flags |= adns_qf_usevc;
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x_restartquery:
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if (qu->cname_dgram) {
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st= adns__mkquery_frdgram(qu->ads,&qu->vb,&qu->id,
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qu->cname_dgram, qu->cname_dglen, qu->cname_begin,
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qu->typei->type, qu->flags);
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if (st) { adns__query_fail(qu,st); return; }
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newquery= MyRealloc(qu->query_dgram,qu->vb.used);
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if (!newquery) { adns__query_fail(qu,adns_s_nomemory); return; }
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qu->query_dgram= newquery;
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qu->query_dglen= qu->vb.used;
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memcpy(newquery,qu->vb.buf,qu->vb.used);
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}
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if (qu->state == query_tcpw) qu->state= query_tosend;
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qu->retries= 0;
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adns__reset_preserved(qu);
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adns__query_send(qu,now);
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}
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