/* $NetBSD: res_query.c,v 1.7 2006/01/24 17:41:25 christos Exp $ */
/*
* Copyright (c) 1988, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* Portions Copyright (c) 1993 by Digital Equipment Corporation.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies, and that
* the name of Digital Equipment Corporation not be used in advertising or
* publicity pertaining to distribution of the document or software without
* specific, written prior permission.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
* WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT
* CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
* DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
* PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
* ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
* SOFTWARE.
*/
/*
* Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
* Portions Copyright (c) 1996-1999 by Internet Software Consortium.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
* OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#define LOG_TAG "res_query"
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <ctype.h>
#include <errno.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/param.h>
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <android-base/logging.h>
#include "resolv_cache.h"
#include "resolv_private.h"
#if PACKETSZ > 1024
#define MAXPACKET PACKETSZ
#else
#define MAXPACKET 1024
#endif
/*
* Formulate a normal query, send, and await answer.
* Returned answer is placed in supplied buffer "answer".
* Perform preliminary check of answer, returning success only
* if no error is indicated and the answer count is nonzero.
* Return the size of the response on success, -1 on error.
* Error number is left in *herrno.
*
* Caller must parse answer and determine whether it answers the question.
*/
int res_nquery(res_state statp, const char* name, // domain name
int cl, int type, // class and type of query
u_char* answer, // buffer to put answer
int anslen, // size of answer buffer
int* herrno) // legacy and extended h_errno
// NETD_RESOLV_H_ERRNO_EXT_*
{
u_char buf[MAXPACKET];
HEADER* hp = (HEADER*) (void*) answer;
int n;
int rcode = NOERROR;
bool retried = false;
again:
hp->rcode = NOERROR; /* default */
LOG(DEBUG) << __func__ << ": (" << cl << ", " << type << ")";
n = res_nmkquery(statp, QUERY, name, cl, type, NULL, 0, NULL, buf, sizeof(buf));
if (n > 0 && (statp->options & (RES_USE_EDNS0 | RES_USE_DNSSEC)) != 0U && !retried)
n = res_nopt(statp, n, buf, sizeof(buf), anslen);
if (n <= 0) {
LOG(DEBUG) << __func__ << ": mkquery failed";
*herrno = NO_RECOVERY;
return n;
}
n = res_nsend(statp, buf, n, answer, anslen, &rcode, 0);
if (n < 0) {
/* if the query choked with EDNS0, retry without EDNS0 */
if ((statp->options & (RES_USE_EDNS0 | RES_USE_DNSSEC)) != 0U &&
(statp->_flags & RES_F_EDNS0ERR) && !retried) {
LOG(DEBUG) << __func__ << ": retry without EDNS0";
retried = true;
goto again;
}
LOG(DEBUG) << __func__ << ": send error";
// Note that rcodes SERVFAIL, NOTIMP, REFUSED may cause res_nquery() to return a general
// error code EAI_AGAIN, but mapping the error code from rcode as res_queryN() does for
// getaddrinfo(). Different rcodes trigger different behaviors:
//
// - SERVFAIL, NOTIMP, REFUSED
// These result in send_dg() returning 0, causing res_nsend() to try the next
// nameserver. After all nameservers failed, res_nsend() returns -ETIMEDOUT, causing
// res_nquery() to return EAI_AGAIN here regardless of the rcode from the DNS response.
//
// - NXDOMAIN, FORMERR
// These rcodes may cause res_nsend() to return successfully (i.e. the result is a
// positive integer). In this case, res_nquery() returns error number by referring
// the rcode from the DNS response.
switch (rcode) {
case RCODE_TIMEOUT: // Not defined in RFC.
// DNS metrics monitors DNS query timeout.
*herrno = NETD_RESOLV_H_ERRNO_EXT_TIMEOUT; // extended h_errno.
break;
default:
*herrno = TRY_AGAIN;
break;
}
return n;
}
if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
LOG(DEBUG) << __func__ << ": rcode = (" << p_rcode(hp->rcode)
<< "), counts = an:" << ntohs(hp->ancount) << " ns:" << ntohs(hp->nscount)
<< " ar:" << ntohs(hp->arcount);
switch (hp->rcode) {
case NXDOMAIN:
*herrno = HOST_NOT_FOUND;
break;
case SERVFAIL:
*herrno = TRY_AGAIN;
break;
case NOERROR:
*herrno = NO_DATA;
break;
case FORMERR:
case NOTIMP:
case REFUSED:
default:
*herrno = NO_RECOVERY;
break;
}
return -1;
}
return n;
}
/*
* Formulate a normal query, send, and retrieve answer in supplied buffer.
* Return the size of the response on success, -1 on error.
* If enabled, implement search rules until answer or unrecoverable failure
* is detected. Error code, if any, is left in *herrno.
*/
int res_nsearch(res_state statp, const char* name, /* domain name */
int cl, int type, /* class and type of query */
u_char* answer, /* buffer to put answer */
int anslen, /* size of answer */
int* herrno) /* legacy and extended
h_errno NETD_RESOLV_H_ERRNO_EXT_* */
{
const char *cp, *const *domain;
HEADER* hp = (HEADER*) (void*) answer;
u_int dots;
int trailing_dot, ret, saved_herrno;
int got_nodata = 0, got_servfail = 0, root_on_list = 0;
int tried_as_is = 0;
int searched = 0;
errno = 0;
*herrno = HOST_NOT_FOUND; /* True if we never query. */
dots = 0;
for (cp = name; *cp != '\0'; cp++) dots += (*cp == '.');
trailing_dot = 0;
if (cp > name && *--cp == '.') trailing_dot++;
/*
* If there are enough dots in the name, let's just give it a
* try 'as is'. The threshold can be set with the "ndots" option.
* Also, query 'as is', if there is a trailing dot in the name.
*/
saved_herrno = -1;
if (dots >= statp->ndots || trailing_dot) {
ret = res_nquerydomain(statp, name, NULL, cl, type, answer, anslen, herrno);
if (ret > 0 || trailing_dot) return ret;
saved_herrno = *herrno;
tried_as_is++;
}
/*
* We do at least one level of search if
* - there is no dot and RES_DEFNAME is set, or
* - there is at least one dot, there is no trailing dot,
* and RES_DNSRCH is set.
*/
if ((!dots && (statp->options & RES_DEFNAMES) != 0U) ||
(dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) {
int done = 0;
/* Unfortunately we need to load network-specific info
* (dns servers, search domains) before
* the domain stuff is tried. Will have a better
* fix after thread pools are used as this will
* be loaded once for the thread instead of each
* time a query is tried.
*/
_resolv_populate_res_for_net(statp);
for (domain = (const char* const*) statp->dnsrch; *domain && !done; domain++) {
searched = 1;
if (domain[0][0] == '\0' || (domain[0][0] == '.' && domain[0][1] == '\0'))
root_on_list++;
ret = res_nquerydomain(statp, name, *domain, cl, type, answer, anslen, herrno);
if (ret > 0) return ret;
/*
* If no server present, give up.
* If name isn't found in this domain,
* keep trying higher domains in the search list
* (if that's enabled).
* On a NO_DATA error, keep trying, otherwise
* a wildcard entry of another type could keep us
* from finding this entry higher in the domain.
* If we get some other error (negative answer or
* server failure), then stop searching up,
* but try the input name below in case it's
* fully-qualified.
*/
if (errno == ECONNREFUSED) {
*herrno = TRY_AGAIN;
return -1;
}
switch (*herrno) {
case NO_DATA:
got_nodata++;
break;
case HOST_NOT_FOUND:
/* keep trying */
break;
case TRY_AGAIN:
if (hp->rcode == SERVFAIL) {
/* try next search element, if any */
got_servfail++;
break;
}
[[fallthrough]];
default:
/* anything else implies that we're done */
done++;
}
/* if we got here for some reason other than DNSRCH,
* we only wanted one iteration of the loop, so stop.
*/
if ((statp->options & RES_DNSRCH) == 0U) done++;
}
}
/*
* If the query has not already been tried as is then try it
* unless RES_NOTLDQUERY is set and there were no dots.
*/
if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) &&
!(tried_as_is || root_on_list)) {
ret = res_nquerydomain(statp, name, NULL, cl, type, answer, anslen, herrno);
if (ret > 0) return ret;
}
/* if we got here, we didn't satisfy the search.
* if we did an initial full query, return that query's H_ERRNO
* (note that we wouldn't be here if that query had succeeded).
* else if we ever got a nodata, send that back as the reason.
* else send back meaningless H_ERRNO, that being the one from
* the last DNSRCH we did.
*/
if (saved_herrno != -1)
*herrno = saved_herrno;
else if (got_nodata)
*herrno = NO_DATA;
else if (got_servfail)
*herrno = TRY_AGAIN;
return -1;
}
/*
* Perform a call on res_query on the concatenation of name and domain,
* removing a trailing dot from name if domain is NULL.
*/
int res_nquerydomain(res_state statp, const char* name, const char* domain, int cl,
int type, /* class and type of query */
u_char* answer, /* buffer to put answer */
int anslen, /* size of answer */
int* herrno) /* legacy and extended h_errno NETD_RESOLV_H_ERRNO_EXT_* */
{
char nbuf[MAXDNAME];
const char* longname = nbuf;
int n, d;
if (domain == NULL) {
LOG(DEBUG) << __func__ << ": (null, " << cl << ", " << type << ")";
/*
* Check for trailing '.';
* copy without '.' if present.
*/
n = strlen(name);
if (n >= MAXDNAME) {
*herrno = NO_RECOVERY;
return -1;
}
n--;
if (n >= 0 && name[n] == '.') {
strncpy(nbuf, name, (size_t) n);
nbuf[n] = '\0';
} else
longname = name;
} else {
LOG(DEBUG) << __func__ << ": (" << cl << ", " << type << ")";
n = strlen(name);
d = strlen(domain);
if (n + d + 1 >= MAXDNAME) {
*herrno = NO_RECOVERY;
return -1;
}
snprintf(nbuf, sizeof(nbuf), "%s.%s", name, domain);
}
return res_nquery(statp, longname, cl, type, answer, anslen, herrno);
}