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res_send.cpp
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res_send.cpp
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/* $NetBSD: res_send.c,v 1.9 2006/01/24 17:41:25 christos Exp $ */
/*
* Copyright (c) 1985, 1989, 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.
*/
/*
* Send query to name server and wait for reply.
*/
#define LOG_TAG "resolv"
#include <chrono>
#include <sys/param.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/uio.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <poll.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <span>
#include <android-base/logging.h>
#include <android-base/result.h>
#include <android/multinetwork.h> // ResNsendFlags
#include <netdutils/Slice.h>
#include <netdutils/Stopwatch.h>
#include "DnsTlsDispatcher.h"
#include "DnsTlsTransport.h"
#include "Experiments.h"
#include "PrivateDnsConfiguration.h"
#include "netd_resolv/resolv.h"
#include "private/android_filesystem_config.h"
#include "doh.h"
#include "res_comp.h"
#include "res_debug.h"
#include "resolv_cache.h"
#include "stats.h"
#include "stats.pb.h"
#include "util.h"
using namespace std::chrono_literals;
// TODO: use the namespace something like android::netd_resolv for libnetd_resolv
using android::base::ErrnoError;
using android::base::Result;
using android::base::unique_fd;
using android::net::CacheStatus;
using android::net::DnsQueryEvent;
using android::net::DnsTlsDispatcher;
using android::net::DnsTlsServer;
using android::net::DnsTlsTransport;
using android::net::Experiments;
using android::net::IpVersion;
using android::net::IV_IPV4;
using android::net::IV_IPV6;
using android::net::IV_UNKNOWN;
using android::net::LinuxErrno;
using android::net::NetworkDnsEventReported;
using android::net::NS_T_AAAA;
using android::net::NS_T_INVALID;
using android::net::NsRcode;
using android::net::NsType;
using android::net::PrivateDnsConfiguration;
using android::net::PrivateDnsMode;
using android::net::PrivateDnsModes;
using android::net::PrivateDnsStatus;
using android::net::PROTO_DOH;
using android::net::PROTO_MDNS;
using android::net::PROTO_TCP;
using android::net::PROTO_UDP;
using android::netdutils::IPSockAddr;
using android::netdutils::Slice;
using android::netdutils::Stopwatch;
using std::span;
const std::vector<IPSockAddr> mdns_addrs = {IPSockAddr::toIPSockAddr("ff02::fb", 5353),
IPSockAddr::toIPSockAddr("224.0.0.251", 5353)};
static int setupUdpSocket(ResState* statp, const sockaddr* sockap, unique_fd* fd_out, int* terrno);
static int send_dg(ResState* statp, res_params* params, span<const uint8_t> msg, span<uint8_t> ans,
int* terrno, size_t* ns, int* v_circuit, int* gotsomewhere, time_t* at,
int* rcode, int* delay);
static int send_vc(ResState* statp, res_params* params, span<const uint8_t> msg, span<uint8_t> ans,
int* terrno, size_t ns, time_t* at, int* rcode, int* delay);
static int send_mdns(ResState* statp, span<const uint8_t> msg, span<uint8_t> ans, int* terrno,
int* rcode);
static void dump_error(const char*, const struct sockaddr*);
static int sock_eq(struct sockaddr*, struct sockaddr*);
static int connect_with_timeout(int sock, const struct sockaddr* nsap, socklen_t salen,
const struct timespec timeout);
static int retrying_poll(const int sock, short events, const struct timespec* finish);
static int res_private_dns_send(ResState*, const Slice query, const Slice answer, int* rcode,
bool* fallback);
static int res_tls_send(const std::list<DnsTlsServer>& tlsServers, ResState*, const Slice query,
const Slice answer, int* rcode, PrivateDnsMode mode);
static ssize_t res_doh_send(ResState*, const Slice query, const Slice answer, int* rcode);
NsType getQueryType(span<const uint8_t> msg) {
ns_msg handle;
ns_rr rr;
if (ns_initparse(msg.data(), msg.size(), &handle) < 0 ||
ns_parserr(&handle, ns_s_qd, 0, &rr) < 0) {
return NS_T_INVALID;
}
return static_cast<NsType>(ns_rr_type(rr));
}
IpVersion ipFamilyToIPVersion(const int ipFamily) {
switch (ipFamily) {
case AF_INET:
return IV_IPV4;
case AF_INET6:
return IV_IPV6;
default:
return IV_UNKNOWN;
}
}
// BEGIN: Code copied from ISC eventlib
// TODO: move away from this code
#define BILLION 1000000000
static struct timespec evConsTime(time_t sec, long nsec) {
struct timespec x;
x.tv_sec = sec;
x.tv_nsec = nsec;
return (x);
}
static struct timespec evAddTime(struct timespec addend1, struct timespec addend2) {
struct timespec x;
x.tv_sec = addend1.tv_sec + addend2.tv_sec;
x.tv_nsec = addend1.tv_nsec + addend2.tv_nsec;
if (x.tv_nsec >= BILLION) {
x.tv_sec++;
x.tv_nsec -= BILLION;
}
return (x);
}
static struct timespec evSubTime(struct timespec minuend, struct timespec subtrahend) {
struct timespec x;
x.tv_sec = minuend.tv_sec - subtrahend.tv_sec;
if (minuend.tv_nsec >= subtrahend.tv_nsec)
x.tv_nsec = minuend.tv_nsec - subtrahend.tv_nsec;
else {
x.tv_nsec = BILLION - subtrahend.tv_nsec + minuend.tv_nsec;
x.tv_sec--;
}
return (x);
}
static int evCmpTime(struct timespec a, struct timespec b) {
#define SGN(x) ((x) < 0 ? (-1) : (x) > 0 ? (1) : (0));
time_t s = a.tv_sec - b.tv_sec;
long n;
if (s != 0) return SGN(s);
n = a.tv_nsec - b.tv_nsec;
return SGN(n);
}
static struct timespec evNowTime(void) {
struct timespec tsnow;
clock_gettime(CLOCK_REALTIME, &tsnow);
return tsnow;
}
// END: Code copied from ISC eventlib
/* BIONIC-BEGIN: implement source port randomization */
static int random_bind(int s, int family, bool isMdns) {
sockaddr_union u;
int j;
socklen_t slen;
/* clear all, this also sets the IP4/6 address to 'any' */
memset(&u, 0, sizeof u);
switch (family) {
case AF_INET:
u.sin.sin_family = family;
slen = sizeof u.sin;
break;
case AF_INET6:
u.sin6.sin6_family = family;
slen = sizeof u.sin6;
break;
default:
errno = EPROTO;
return -1;
}
/* first try to bind to a random source port a few times */
for (j = 0; j < 10; j++) {
/* find a random port between 1025 .. 65534 */
int port = 1025 + (arc4random_uniform(65535 - 1025));
// RFC 6762 section 5.1: Don't use 5353 source port on one-shot Multicast DNS queries. DNS
// resolver does not fully compliant mDNS.
if (isMdns && port == 5353) continue;
if (family == AF_INET)
u.sin.sin_port = htons(port);
else
u.sin6.sin6_port = htons(port);
if (!bind(s, &u.sa, slen)) return 0;
}
// nothing after 10 attempts, our network table is probably busy
// let the system decide which port is best
if (family == AF_INET)
u.sin.sin_port = 0;
else
u.sin6.sin6_port = 0;
return bind(s, &u.sa, slen);
}
/* BIONIC-END */
// Disables all nameservers other than selectedServer
static void res_set_usable_server(int selectedServer, int nscount, bool usable_servers[]) {
int usableIndex = 0;
for (int ns = 0; ns < nscount; ns++) {
if (usable_servers[ns]) ++usableIndex;
if (usableIndex != selectedServer) usable_servers[ns] = false;
}
}
// Looks up the nameserver address in res.nsaddrs[], returns the ns number if found, otherwise -1.
static int res_ourserver_p(ResState* statp, const sockaddr* sa) {
const sockaddr_in *inp, *srv;
const sockaddr_in6 *in6p, *srv6;
int ns = 0;
switch (sa->sa_family) {
case AF_INET:
inp = (const struct sockaddr_in*) (const void*) sa;
for (const IPSockAddr& ipsa : statp->nsaddrs) {
sockaddr_storage ss = ipsa;
srv = reinterpret_cast<sockaddr_in*>(&ss);
if (srv->sin_family == inp->sin_family && srv->sin_port == inp->sin_port &&
(srv->sin_addr.s_addr == INADDR_ANY ||
srv->sin_addr.s_addr == inp->sin_addr.s_addr))
return ns;
++ns;
}
break;
case AF_INET6:
in6p = (const struct sockaddr_in6*) (const void*) sa;
for (const IPSockAddr& ipsa : statp->nsaddrs) {
sockaddr_storage ss = ipsa;
srv6 = reinterpret_cast<sockaddr_in6*>(&ss);
if (srv6->sin6_family == in6p->sin6_family && srv6->sin6_port == in6p->sin6_port &&
#ifdef HAVE_SIN6_SCOPE_ID
(srv6->sin6_scope_id == 0 || srv6->sin6_scope_id == in6p->sin6_scope_id) &&
#endif
(IN6_IS_ADDR_UNSPECIFIED(&srv6->sin6_addr) ||
IN6_ARE_ADDR_EQUAL(&srv6->sin6_addr, &in6p->sin6_addr)))
return ns;
++ns;
}
break;
default:
break;
}
return -1;
}
/* int
* res_nameinquery(name, type, cl, msg, eom)
* look for (name, type, cl) in the query section of packet (msg, eom)
* requires:
* msg + HFIXEDSZ <= eom
* returns:
* -1 : format error
* 0 : not found
* >0 : found
* author:
* paul vixie, 29may94
*/
int res_nameinquery(const char* name, int type, int cl, const uint8_t* msg, const uint8_t* eom) {
const uint8_t* cp = msg + HFIXEDSZ;
int qdcount = ntohs(((const HEADER*)(const void*)msg)->qdcount);
while (qdcount-- > 0) {
char tname[MAXDNAME + 1];
int n = dn_expand(msg, eom, cp, tname, sizeof tname);
if (n < 0) return (-1);
cp += n;
if (cp + 2 * INT16SZ > eom) return (-1);
int ttype = ntohs(*reinterpret_cast<const uint16_t*>(cp));
cp += INT16SZ;
int tclass = ntohs(*reinterpret_cast<const uint16_t*>(cp));
cp += INT16SZ;
if (ttype == type && tclass == cl && ns_samename(tname, name) == 1) return (1);
}
return (0);
}
/* int
* res_queriesmatch(buf1, eom1, buf2, eom2)
* is there a 1:1 mapping of (name,type,class)
* in (buf1,eom1) and (buf2,eom2)?
* returns:
* -1 : format error
* 0 : not a 1:1 mapping
* >0 : is a 1:1 mapping
* author:
* paul vixie, 29may94
*/
int res_queriesmatch(const uint8_t* buf1, const uint8_t* eom1, const uint8_t* buf2,
const uint8_t* eom2) {
const uint8_t* cp = buf1 + HFIXEDSZ;
int qdcount = ntohs(((const HEADER*) (const void*) buf1)->qdcount);
if (buf1 + HFIXEDSZ > eom1 || buf2 + HFIXEDSZ > eom2) return (-1);
/*
* Only header section present in replies to
* dynamic update packets.
*/
if ((((const HEADER*) (const void*) buf1)->opcode == ns_o_update) &&
(((const HEADER*) (const void*) buf2)->opcode == ns_o_update))
return (1);
if (qdcount != ntohs(((const HEADER*) (const void*) buf2)->qdcount)) return (0);
while (qdcount-- > 0) {
char tname[MAXDNAME + 1];
int n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
if (n < 0) return (-1);
cp += n;
if (cp + 2 * INT16SZ > eom1) return (-1);
int ttype = ntohs(*reinterpret_cast<const uint16_t*>(cp));
cp += INT16SZ;
int tclass = ntohs(*reinterpret_cast<const uint16_t*>(cp));
cp += INT16SZ;
if (!res_nameinquery(tname, ttype, tclass, buf2, eom2)) return (0);
}
return (1);
}
static DnsQueryEvent* addDnsQueryEvent(NetworkDnsEventReported* event) {
return event->mutable_dns_query_events()->add_dns_query_event();
}
static bool isNetworkRestricted(int terrno) {
// It's possible that system was in some network restricted mode, which blocked
// the operation of sending packet and resulted in EPERM errno.
// It would be no reason to keep retrying on that case.
// TODO: Check the system status to know if network restricted mode is
// enabled.
return (terrno == EPERM);
}
int res_nsend(ResState* statp, span<const uint8_t> msg, span<uint8_t> ans, int* rcode,
uint32_t flags, std::chrono::milliseconds sleepTimeMs) {
LOG(DEBUG) << __func__;
// Should not happen
if (ans.size() < HFIXEDSZ) {
// TODO: Remove errno once callers stop using it
errno = EINVAL;
return -EINVAL;
}
res_pquery(msg);
int anslen = 0;
Stopwatch cacheStopwatch;
ResolvCacheStatus cache_status = resolv_cache_lookup(statp->netid, msg, ans, &anslen, flags);
const int32_t cacheLatencyUs = saturate_cast<int32_t>(cacheStopwatch.timeTakenUs());
if (cache_status == RESOLV_CACHE_FOUND) {
HEADER* hp = (HEADER*)(void*)ans.data();
*rcode = hp->rcode;
DnsQueryEvent* dnsQueryEvent = addDnsQueryEvent(statp->event);
dnsQueryEvent->set_latency_micros(cacheLatencyUs);
dnsQueryEvent->set_cache_hit(static_cast<CacheStatus>(cache_status));
dnsQueryEvent->set_type(getQueryType(msg));
return anslen;
} else if (cache_status != RESOLV_CACHE_UNSUPPORTED) {
// had a cache miss for a known network, so populate the thread private
// data so the normal resolve path can do its thing
resolv_populate_res_for_net(statp);
}
// MDNS
if (isMdnsResolution(statp->flags)) {
// Use an impossible error code as default value.
int terrno = ETIME;
int resplen = 0;
*rcode = RCODE_INTERNAL_ERROR;
Stopwatch queryStopwatch;
resplen = send_mdns(statp, msg, ans, &terrno, rcode);
const IPSockAddr& receivedMdnsAddr =
(getQueryType(msg) == NS_T_AAAA) ? mdns_addrs[0] : mdns_addrs[1];
DnsQueryEvent* mDnsQueryEvent = addDnsQueryEvent(statp->event);
mDnsQueryEvent->set_cache_hit(static_cast<CacheStatus>(cache_status));
mDnsQueryEvent->set_latency_micros(saturate_cast<int32_t>(queryStopwatch.timeTakenUs()));
mDnsQueryEvent->set_ip_version(ipFamilyToIPVersion(receivedMdnsAddr.family()));
mDnsQueryEvent->set_rcode(static_cast<NsRcode>(*rcode));
mDnsQueryEvent->set_protocol(PROTO_MDNS);
mDnsQueryEvent->set_type(getQueryType(msg));
mDnsQueryEvent->set_linux_errno(static_cast<LinuxErrno>(terrno));
resolv_stats_add(statp->netid, receivedMdnsAddr, mDnsQueryEvent);
if (resplen <= 0) {
_resolv_cache_query_failed(statp->netid, msg, flags);
return -terrno;
}
LOG(DEBUG) << __func__ << ": got answer:";
res_pquery(ans.first(resplen));
if (cache_status == RESOLV_CACHE_NOTFOUND) {
resolv_cache_add(statp->netid, msg, {ans.data(), resplen});
}
return resplen;
}
if (statp->nameserverCount() == 0) {
// We have no nameservers configured and it's not a MDNS resolution, so there's no
// point trying. Tell the cache the query failed, or any retries and anyone else
// asking the same question will block for PENDING_REQUEST_TIMEOUT seconds instead
// of failing fast.
_resolv_cache_query_failed(statp->netid, msg, flags);
// TODO: Remove errno once callers stop using it
errno = ESRCH;
return -ESRCH;
}
// Private DNS
if (!(statp->netcontext_flags & NET_CONTEXT_FLAG_USE_LOCAL_NAMESERVERS)) {
bool fallback = false;
int resplen =
res_private_dns_send(statp, Slice(const_cast<uint8_t*>(msg.data()), msg.size()),
Slice(ans.data(), ans.size()), rcode, &fallback);
if (resplen > 0) {
LOG(DEBUG) << __func__ << ": got answer from Private DNS";
res_pquery(ans.first(resplen));
if (cache_status == RESOLV_CACHE_NOTFOUND) {
resolv_cache_add(statp->netid, msg, ans.first(resplen));
}
return resplen;
}
if (!fallback) {
_resolv_cache_query_failed(statp->netid, msg, flags);
return -ETIMEDOUT;
}
}
// If parallel_lookup is enabled, it might be required to wait some time to avoid
// gateways from dropping packets if queries are sent too close together.
if (sleepTimeMs != 0ms) {
std::this_thread::sleep_for(sleepTimeMs);
}
res_stats stats[MAXNS]{};
res_params params;
int revision_id = resolv_cache_get_resolver_stats(statp->netid, ¶ms, stats, statp->nsaddrs);
if (revision_id < 0) {
// TODO: Remove errno once callers stop using it
errno = ESRCH;
return -ESRCH;
}
bool usable_servers[MAXNS];
int usableServersCount = android_net_res_stats_get_usable_servers(
¶ms, stats, statp->nameserverCount(), usable_servers);
if (statp->sort_nameservers) {
// It's unnecessary to mark a DNS server as unusable since broken servers will be less
// likely to be chosen.
for (int i = 0; i < statp->nameserverCount(); i++) {
usable_servers[i] = true;
}
}
// TODO: Let it always choose the first nameserver when sort_nameservers is enabled.
if ((flags & ANDROID_RESOLV_NO_RETRY) && usableServersCount > 1) {
auto hp = reinterpret_cast<const HEADER*>(msg.data());
// Select a random server based on the query id
int selectedServer = (hp->id % usableServersCount) + 1;
res_set_usable_server(selectedServer, statp->nameserverCount(), usable_servers);
}
// Send request, RETRY times, or until successful.
int retryTimes = (flags & ANDROID_RESOLV_NO_RETRY) ? 1 : params.retry_count;
int useTcp = msg.size() > PACKETSZ;
int gotsomewhere = 0;
// Use an impossible error code as default value
int terrno = ETIME;
// plaintext DNS
for (int attempt = 0; attempt < retryTimes; ++attempt) {
for (size_t ns = 0; ns < statp->nsaddrs.size(); ++ns) {
if (!usable_servers[ns]) continue;
*rcode = RCODE_INTERNAL_ERROR;
// Get server addr
const IPSockAddr& serverSockAddr = statp->nsaddrs[ns];
LOG(DEBUG) << __func__ << ": Querying server (# " << ns + 1
<< ") address = " << serverSockAddr.toString();
::android::net::Protocol query_proto = useTcp ? PROTO_TCP : PROTO_UDP;
time_t query_time = 0;
int delay = 0;
bool fallbackTCP = false;
const bool shouldRecordStats = (attempt == 0);
int resplen;
Stopwatch queryStopwatch;
int retry_count_for_event = 0;
size_t actualNs = ns;
// Use an impossible error code as default value
terrno = ETIME;
if (useTcp) {
// TCP; at most one attempt per server.
attempt = retryTimes;
resplen =
send_vc(statp, ¶ms, msg, ans, &terrno, ns, &query_time, rcode, &delay);
if (msg.size() <= PACKETSZ && resplen <= 0 &&
statp->tc_mode == aidl::android::net::IDnsResolver::TC_MODE_UDP_TCP) {
// reset to UDP for next query on next DNS server if resolver is currently doing
// TCP fallback retry and current server does not support TCP connectin
useTcp = false;
}
LOG(INFO) << __func__ << ": used send_vc " << resplen << " terrno: " << terrno;
} else {
// UDP
resplen = send_dg(statp, ¶ms, msg, ans, &terrno, &actualNs, &useTcp,
&gotsomewhere, &query_time, rcode, &delay);
fallbackTCP = useTcp ? true : false;
retry_count_for_event = attempt;
LOG(INFO) << __func__ << ": used send_dg " << resplen << " terrno: " << terrno;
}
const IPSockAddr& receivedServerAddr = statp->nsaddrs[actualNs];
DnsQueryEvent* dnsQueryEvent = addDnsQueryEvent(statp->event);
dnsQueryEvent->set_cache_hit(static_cast<CacheStatus>(cache_status));
// When |retryTimes| > 1, we cannot actually know the correct latency value if we
// received the answer from the previous server. So temporarily set the latency as -1 if
// that condition happened.
// TODO: make the latency value accurate.
dnsQueryEvent->set_latency_micros(
(actualNs == ns) ? saturate_cast<int32_t>(queryStopwatch.timeTakenUs()) : -1);
dnsQueryEvent->set_dns_server_index(actualNs);
dnsQueryEvent->set_ip_version(ipFamilyToIPVersion(receivedServerAddr.family()));
dnsQueryEvent->set_retry_times(retry_count_for_event);
dnsQueryEvent->set_rcode(static_cast<NsRcode>(*rcode));
dnsQueryEvent->set_protocol(query_proto);
dnsQueryEvent->set_type(getQueryType(msg));
dnsQueryEvent->set_linux_errno(static_cast<LinuxErrno>(terrno));
// Only record stats the first time we try a query. This ensures that
// queries that deterministically fail (e.g., a name that always returns
// SERVFAIL or times out) do not unduly affect the stats.
if (shouldRecordStats) {
// (b/151166599): This is a workaround to prevent that DnsResolver calculates the
// reliability of DNS servers from being broken when network restricted mode is
// enabled.
// TODO: Introduce the new server selection instead of skipping stats recording.
if (!isNetworkRestricted(terrno)) {
res_sample sample;
res_stats_set_sample(&sample, query_time, *rcode, delay);
// KeepListening UDP mechanism is incompatible with usable_servers of legacy
// stats, so keep the old logic for now.
// TODO: Replace usable_servers of legacy stats with new one.
resolv_cache_add_resolver_stats_sample(
statp->netid, revision_id, serverSockAddr, sample, params.max_samples);
resolv_stats_add(statp->netid, receivedServerAddr, dnsQueryEvent);
}
}
if (resplen == 0) continue;
if (fallbackTCP) {
ns--;
continue;
}
if (resplen < 0) {
_resolv_cache_query_failed(statp->netid, msg, flags);
statp->closeSockets();
return -terrno;
}
LOG(DEBUG) << __func__ << ": got answer:";
res_pquery(ans.first(resplen));
if (cache_status == RESOLV_CACHE_NOTFOUND) {
resolv_cache_add(statp->netid, msg, {ans.data(), resplen});
}
statp->closeSockets();
return (resplen);
} // for each ns
} // for each retry
statp->closeSockets();
terrno = useTcp ? terrno : gotsomewhere ? ETIMEDOUT : ECONNREFUSED;
// TODO: Remove errno once callers stop using it
errno = useTcp ? terrno
: gotsomewhere ? ETIMEDOUT /* no answer obtained */
: ECONNREFUSED /* no nameservers found */;
_resolv_cache_query_failed(statp->netid, msg, flags);
return -terrno;
}
static struct timespec get_timeout(ResState* statp, const res_params* params, const int addrIndex) {
int msec;
msec = params->base_timeout_msec << addrIndex;
// Legacy algorithm which scales the timeout by nameserver number.
// For instance, with 4 nameservers: 5s, 2.5s, 5s, 10s
// This has no effect with 1 or 2 nameservers
if (addrIndex > 0) {
msec /= statp->nameserverCount();
}
// For safety, don't allow OEMs and experiments to configure a timeout shorter than 1s.
if (msec < 1000) {
msec = 1000; // Use at least 1000ms
}
LOG(INFO) << __func__ << ": using timeout of " << msec << " msec";
struct timespec result;
result.tv_sec = msec / 1000;
result.tv_nsec = (msec % 1000) * 1000000;
return result;
}
static int send_vc(ResState* statp, res_params* params, span<const uint8_t> msg, span<uint8_t> ans,
int* terrno, size_t ns, time_t* at, int* rcode, int* delay) {
*at = time(NULL);
*delay = 0;
const HEADER* hp = (const HEADER*)(const void*)msg.data();
HEADER* anhp = (HEADER*)(void*)ans.data();
struct sockaddr* nsap;
int nsaplen;
int truncating, connreset, n;
uint8_t* cp;
LOG(INFO) << __func__ << ": using send_vc";
// It should never happen, but just in case.
if (ns >= statp->nsaddrs.size()) {
LOG(ERROR) << __func__ << ": Out-of-bound indexing: " << ns;
*terrno = EINVAL;
return -1;
}
sockaddr_storage ss = statp->nsaddrs[ns];
nsap = reinterpret_cast<sockaddr*>(&ss);
nsaplen = sockaddrSize(nsap);
connreset = 0;
same_ns:
truncating = 0;
struct timespec start_time = evNowTime();
/* Are we still talking to whom we want to talk to? */
if (statp->tcp_nssock >= 0 && (statp->flags & RES_F_VC) != 0) {
struct sockaddr_storage peer;
socklen_t size = sizeof peer;
unsigned old_mark;
socklen_t mark_size = sizeof(old_mark);
if (getpeername(statp->tcp_nssock, (struct sockaddr*)(void*)&peer, &size) < 0 ||
!sock_eq((struct sockaddr*)(void*)&peer, nsap) ||
getsockopt(statp->tcp_nssock, SOL_SOCKET, SO_MARK, &old_mark, &mark_size) < 0 ||
old_mark != statp->mark) {
statp->closeSockets();
}
}
if (statp->tcp_nssock < 0 || (statp->flags & RES_F_VC) == 0) {
if (statp->tcp_nssock >= 0) statp->closeSockets();
statp->tcp_nssock.reset(socket(nsap->sa_family, SOCK_STREAM | SOCK_CLOEXEC, 0));
if (statp->tcp_nssock < 0) {
*terrno = errno;
PLOG(DEBUG) << __func__ << ": socket(vc): ";
switch (errno) {
case EPROTONOSUPPORT:
case EPFNOSUPPORT:
case EAFNOSUPPORT:
return 0;
default:
return -1;
}
}
const uid_t uid = statp->enforce_dns_uid ? AID_DNS : statp->uid;
resolv_tag_socket(statp->tcp_nssock, uid, statp->pid);
if (statp->mark != MARK_UNSET) {
if (setsockopt(statp->tcp_nssock, SOL_SOCKET, SO_MARK, &statp->mark,
sizeof(statp->mark)) < 0) {
*terrno = errno;
PLOG(DEBUG) << __func__ << ": setsockopt: ";
return -1;
}
}
errno = 0;
if (random_bind(statp->tcp_nssock, nsap->sa_family, false /* isMdns */) < 0) {
*terrno = errno;
dump_error("bind/vc", nsap);
statp->closeSockets();
return (0);
}
if (connect_with_timeout(statp->tcp_nssock, nsap, (socklen_t)nsaplen,
get_timeout(statp, params, ns)) < 0) {
*terrno = errno;
dump_error("connect/vc", nsap);
statp->closeSockets();
/*
* The way connect_with_timeout() is implemented prevents us from reliably
* determining whether this was really a timeout or e.g. ECONNREFUSED. Since
* currently both cases are handled in the same way, there is no need to
* change this (yet). If we ever need to reliably distinguish between these
* cases, both connect_with_timeout() and retrying_poll() need to be
* modified, though.
*/
*rcode = RCODE_TIMEOUT;
return (0);
}
statp->flags |= RES_F_VC;
}
/*
* Send length & message
*/
uint16_t len = htons(static_cast<uint16_t>(msg.size()));
const iovec iov[] = {
{.iov_base = &len, .iov_len = INT16SZ},
{.iov_base = const_cast<uint8_t*>(msg.data()),
.iov_len = static_cast<size_t>(msg.size())},
};
if (writev(statp->tcp_nssock, iov, 2) != (INT16SZ + msg.size())) {
*terrno = errno;
PLOG(DEBUG) << __func__ << ": write failed: ";
statp->closeSockets();
return (0);
}
/*
* Receive length & response
*/
read_len:
cp = ans.data();
len = INT16SZ;
while ((n = read(statp->tcp_nssock, (char*)cp, (size_t)len)) > 0) {
cp += n;
if ((len -= n) == 0) break;
}
if (n <= 0) {
*terrno = errno;
PLOG(DEBUG) << __func__ << ": read failed: ";
statp->closeSockets();
/*
* A long running process might get its TCP
* connection reset if the remote server was
* restarted. Requery the server instead of
* trying a new one. When there is only one
* server, this means that a query might work
* instead of failing. We only allow one reset
* per query to prevent looping.
*/
if (*terrno == ECONNRESET && !connreset) {
connreset = 1;
goto same_ns;
}
return (0);
}
uint16_t resplen = ntohs(*reinterpret_cast<const uint16_t*>(ans.data()));
if (resplen > ans.size()) {
LOG(DEBUG) << __func__ << ": response truncated";
truncating = 1;
len = ans.size();
} else
len = resplen;
if (len < HFIXEDSZ) {
/*
* Undersized message.
*/
LOG(DEBUG) << __func__ << ": undersized: " << len;
*terrno = EMSGSIZE;
statp->closeSockets();
return (0);
}
cp = ans.data();
while (len != 0 && (n = read(statp->tcp_nssock, (char*)cp, (size_t)len)) > 0) {
cp += n;
len -= n;
}
if (n <= 0) {
*terrno = errno;
PLOG(DEBUG) << __func__ << ": read(vc): ";
statp->closeSockets();
return (0);
}
if (truncating) {
/*
* Flush rest of answer so connection stays in synch.
*/
anhp->tc = 1;
len = resplen - ans.size();
while (len != 0) {
char junk[PACKETSZ];
n = read(statp->tcp_nssock, junk, (len > sizeof junk) ? sizeof junk : len);
if (n > 0)
len -= n;
else
break;
}
LOG(WARNING) << __func__ << ": resplen " << resplen << " exceeds buf size " << ans.size();
// return size should never exceed container size
resplen = ans.size();
}
/*
* If the calling application has bailed out of
* a previous call and failed to arrange to have
* the circuit closed or the server has got
* itself confused, then drop the packet and
* wait for the correct one.
*/
if (hp->id != anhp->id) {
LOG(DEBUG) << __func__ << ": ld answer (unexpected):";
res_pquery({ans.data(), resplen});
goto read_len;
}
/*
* All is well, or the error is fatal. Signal that the
* next nameserver ought not be tried.
*/
if (resplen > 0) {
struct timespec done = evNowTime();
*delay = res_stats_calculate_rtt(&done, &start_time);
*rcode = anhp->rcode;
}
*terrno = 0;
return (resplen);
}
/* return -1 on error (errno set), 0 on success */
static int connect_with_timeout(int sock, const sockaddr* nsap, socklen_t salen,
const timespec timeout) {
int res, origflags;
origflags = fcntl(sock, F_GETFL, 0);
fcntl(sock, F_SETFL, origflags | O_NONBLOCK);
res = connect(sock, nsap, salen);
if (res < 0 && errno != EINPROGRESS) {
res = -1;
goto done;
}
if (res != 0) {
timespec now = evNowTime();
timespec finish = evAddTime(now, timeout);
LOG(INFO) << __func__ << ": " << sock << " send_vc";
res = retrying_poll(sock, POLLIN | POLLOUT, &finish);
if (res <= 0) {
res = -1;
}
}
done:
fcntl(sock, F_SETFL, origflags);
LOG(INFO) << __func__ << ": " << sock << " connect_with_const timeout returning " << res;
return res;
}
static int retrying_poll(const int sock, const short events, const struct timespec* finish) {
struct timespec now, timeout;
retry:
LOG(INFO) << __func__ << ": " << sock << " retrying_poll";
now = evNowTime();
if (evCmpTime(*finish, now) > 0)
timeout = evSubTime(*finish, now);
else
timeout = evConsTime(0L, 0L);
struct pollfd fds = {.fd = sock, .events = events};
int n = ppoll(&fds, 1, &timeout, /*__mask=*/NULL);
if (n == 0) {
LOG(INFO) << __func__ << ": " << sock << " retrying_poll timeout";
errno = ETIMEDOUT;
return 0;
}
if (n < 0) {
if (errno == EINTR) goto retry;
PLOG(INFO) << __func__ << ": " << sock << " retrying_poll failed";
return n;
}
if (fds.revents & (POLLIN | POLLOUT | POLLERR)) {
int error;
socklen_t len = sizeof(error);
if (getsockopt(sock, SOL_SOCKET, SO_ERROR, &error, &len) < 0 || error) {
errno = error;
PLOG(INFO) << __func__ << ": " << sock << " retrying_poll getsockopt failed";
return -1;
}
}
LOG(INFO) << __func__ << ": " << sock << " retrying_poll returning " << n;
return n;
}
static std::vector<pollfd> extractUdpFdset(ResState* statp, const short events = POLLIN) {
std::vector<pollfd> fdset(statp->nsaddrs.size());
for (size_t i = 0; i < statp->nsaddrs.size(); ++i) {
fdset[i] = {.fd = statp->udpsocks[i], .events = events};
}
return fdset;
}
static Result<std::vector<int>> udpRetryingPoll(ResState* statp, const timespec* finish) {
for (;;) {
LOG(DEBUG) << __func__ << ": poll";