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android/platform/packages/modules/DnsResolver/refs/heads/android17-security-release/./res_send.cpp
blob: 4a479ed05509947ee6c0b8cee2f7ef52e7441916 [file] [edit]
/* $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 <numeric>
#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::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;
// Order matters: we put IPv6 first to prioritize that.
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, int* rcode);
static int send_vc(ResState* statp, res_params* params, span<const uint8_t> msg, span<uint8_t> ans,
int* terrno, size_t ns, int* rcode);
static int send_mdns(ResState* statp, span<const uint8_t> msg, span<uint8_t> ans, int* terrno,
int* rcode, IPSockAddr* receivedMdnsAddr);
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);
static int elapsedTimeInMs(const timespec& from);
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) {
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 (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);
}
static bool isClientStreamSocketClosed(std::optional<int> fd) {
if (!fd.has_value()) return false;
if (!android::net::Experiments::getInstance()->getFlag("no_retry_after_cancel", 0)) {
return false;
}
struct pollfd fds{
// POLLHUP is always included in events but is specified explicitly here
.fd = fd.value(),
.events = POLLHUP,
};
return (poll(&fds, 1, /* timeout=*/0) > 0) && (fds.revents & POLLHUP);
}
static bool isErrorOrNoDataAnswer(int rcode, span<uint8_t> ans) {
if (rcode != NOERROR) {
return true;
}
// NODATA responses have NOERROR rcode but no answer record (NODATA is not a rcode).
return reinterpret_cast<const HEADER*>(ans.data())->ancount == 0;
}
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);
// TODO(b/394031336): Implement caching for mDNS.
// The DNS cache keys by netid, ignoring the interface queries get routed towards. This is fine
// for unicast DNS requests, where:
// 1. We always send a single query per type (i.e., even if a network has multiple interfaces,
// we will send a single A and AAAA query).
// 2. Results cannot be IPv6 link-local addresses
// It is not fine for mDNS, where both things can happen.
if (isMdnsResolution(statp->flags)) {
// Use an impossible error code as default value.
int terrno = ETIME;
int resplen = 0;
*rcode = RCODE_INTERNAL_ERROR;
Stopwatch queryStopwatch;
IPSockAddr receivedMdnsAddr;
resplen = send_mdns(statp, msg, ans, &terrno, rcode, &receivedMdnsAddr);
DnsQueryEvent* mDnsQueryEvent = addDnsQueryEvent(statp->event);
mDnsQueryEvent->set_cache_hit(static_cast<CacheStatus>(RESOLV_CACHE_UNSUPPORTED));
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) {
LOG(DEBUG) << __func__ << ": got answer from mDNS:";
res_pquery(ans.first(resplen));
return resplen;
}
}
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);
}
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);
LOG(DEBUG) << __func__ << ": no nameserver";
// 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);
LOG(DEBUG) << __func__ << ": private DNS failed";
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, &params, stats, statp->nsaddrs);
if (revision_id < 0) {
LOG(ERROR) << __func__ << ": 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(
&params, 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;
bool tryAllServers = (flags & RESOLV_TRY_ALL_USABLE_SERVERS);
int useTcp = msg.size() > PACKETSZ;
int gotsomewhere = 0;
int firstErrorRcode = NOERROR;
std::vector<uint8_t> firstErrorAns;
// Use an impossible error code as default value
int terrno = ETIME;
// plaintext DNS
for (int attempt = 0; attempt < retryTimes; ++attempt) {
if (attempt > 0 && isClientStreamSocketClosed(statp->app_socket)) {
// Stop retrying if the remote end is not listening for answers anymore. Only do that
// for retries and not the initial query to minimize latency (although the check is very
// cheap) in the vast majority of cases where queries are not immediately cancelled, and
// to make testing easier so tests can cancel immediately and reliably expect one query.
// This could also cancel before the first attempt if private DNS was already tried and
// this is a fallback, but this is not done here for simplicity.
break;
}
for (size_t ns = 0; ns < statp->nsaddrs.size(); ++ns) {
if (!usable_servers[ns]) continue;
*rcode = RCODE_INTERNAL_ERROR;
LOG(DEBUG) << __func__ << ": Querying server (# " << ns + 1
<< ") address = " << statp->nsaddrs[ns].toString();
::android::net::Protocol query_proto = useTcp ? PROTO_TCP : PROTO_UDP;
const time_t query_time = time(nullptr);
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, &params, msg, ans, &terrno, ns, rcode);
delay = elapsedTimeInMs(statp->tcp_nssock_ts);
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, &params, msg, ans, &terrno, &actualNs, &useTcp,
&gotsomewhere, rcode);
delay = elapsedTimeInMs(statp->udpsocks_ts[actualNs]);
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);
resolv_cache_add_resolver_stats_sample(statp->netid, revision_id,
receivedServerAddr, 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;
}
if (tryAllServers && isErrorOrNoDataAnswer(*rcode, ans)) {
// Do not query this server again, but continue querying
usable_servers[ns] = false;
if (firstErrorAns.empty()) {
firstErrorRcode = *rcode;
firstErrorAns.assign(ans.data(), ans.data() + resplen);
}
continue;
}
LOG(DEBUG) << __func__ << ": got answer:";
res_pquery(ans.first(resplen));
if (cache_status == RESOLV_CACHE_NOTFOUND) {
resolv_cache_add(statp->netid, msg, std::span(ans.data(), resplen));
}
statp->closeSockets();
return (resplen);
} // for each ns
} // for each retry
bool tryAllServersGotError =
firstErrorAns.size() &&
std::accumulate(usable_servers, usable_servers + statp->nsaddrs.size(), 0) == 0;
if (tryAllServersGotError) {
std::copy(firstErrorAns.begin(), firstErrorAns.end(), ans.data());
int resplen = firstErrorAns.size();
*rcode = firstErrorRcode;
LOG(DEBUG) << __func__ << ": returning first error after trying all servers:";
res_pquery(ans.first(resplen));
return resplen;
}
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(DEBUG) << __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, int* rcode) {
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(DEBUG) << __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;
/* 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;
}
}
statp->tcp_nssock_ts = evNowTime();
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) < 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) != static_cast<ptrdiff_t>(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) {
*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(DEBUG) << __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(DEBUG) << __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(DEBUG) << __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(DEBUG) << __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";
timespec start_time = evNowTime();
timespec timeout = (evCmpTime(*finish, start_time) > 0) ? evSubTime(*finish, start_time)
: evConsTime(0L, 0L);
std::vector<pollfd> fdset = extractUdpFdset(statp);
const int n = ppoll(fdset.data(), fdset.size(), &timeout, /*__mask=*/nullptr);
if (n <= 0) {
if (errno == EINTR && n < 0) continue;
if (n == 0) errno = ETIMEDOUT;
PLOG(INFO) << __func__ << ": failed";
return ErrnoError();
}
std::vector<int> fdsToRead;
for (const auto& pollfd : fdset) {
if (pollfd.revents & (POLLIN | POLLERR)) {
fdsToRead.push_back(pollfd.fd);
}
}
LOG(DEBUG) << __func__ << ": "
<< " returning fd size: " << fdsToRead.size();
return fdsToRead;
}
}
static Result<std::vector<int>> udpRetryingPollWrapper(ResState* statp, int addrInfo,
const timespec* finish) {
const bool keepListeningUdp =
android::net::Experiments::getInstance()->getFlag("keep_listening_udp", 0);
if (keepListeningUdp) return udpRetryingPoll(statp, finish);
if (int n = retrying_poll(statp->udpsocks[addrInfo], POLLIN, finish); n <= 0) {
return ErrnoError();
}
return std::vector<int>{statp->udpsocks[addrInfo]};
}
bool ignoreInvalidAnswer(ResState* statp, const sockaddr_storage& from, span<const uint8_t> msg,
span<uint8_t> ans, int* receivedFromNs) {
const HEADER* hp = (const HEADER*)(const void*)msg.data();
HEADER* anhp = (HEADER*)(void*)ans.data();
if (hp->id != anhp->id) {
// response from old query, ignore it.
LOG(DEBUG) << __func__ << ": old answer:";
return true;
}
if (*receivedFromNs = res_ourserver_p(statp, (sockaddr*)(void*)&from); *receivedFromNs < 0) {
// response from wrong server? ignore it.
LOG(DEBUG) << __func__ << ": not our server:";
return true;
}
if (!res_queriesmatch(msg.data(), msg.data() + msg.size(), ans.data(),
ans.data() + ans.size())) {
// response contains wrong query? ignore it.
LOG(DEBUG) << __func__ << ": wrong query name:";
return true;
}
return false;
}
// return 1 - setup udp socket success.
// return 0 - bind error, protocol error.
// return -1 - create socket fail, except |EPROTONOSUPPORT| EPFNOSUPPORT |EAFNOSUPPORT|.
// set socket option fail.
static int setupUdpSocket(ResState* statp, const sockaddr* sockap, unique_fd* fd_out, int* terrno) {
fd_out->reset(socket(sockap->sa_family, SOCK_DGRAM | SOCK_CLOEXEC, 0));
if (*fd_out < 0) {
*terrno = errno;
PLOG(ERROR) << __func__ << ": socket: ";
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(*fd_out, uid, statp->pid);
if (statp->mark != MARK_UNSET) {
if (setsockopt(*fd_out, SOL_SOCKET, SO_MARK, &(statp->mark), sizeof(statp->mark)) < 0) {
*terrno = errno;
return -1;
}
}
if (random_bind(*fd_out, sockap->sa_family) < 0) {
*terrno = errno;
dump_error("bind", sockap);
return 0;
}
return 1;
}
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, int* rcode) {
// 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;
}
const sockaddr_storage ss = statp->nsaddrs[*ns];
const sockaddr* nsap = reinterpret_cast<const sockaddr*>(&ss);
if (statp->udpsocks[*ns] == -1) {
int result = setupUdpSocket(statp, nsap, &statp->udpsocks[*ns], terrno);
if (result <= 0) return result;
statp->udpsocks_ts[*ns] = evNowTime();
// Use a "connected" datagram socket to receive an ECONNREFUSED error
// on the next socket operation when the server responds with an
// ICMP port-unreachable error. This way we can detect the absence of
// a nameserver without timing out.
if (connect(statp->udpsocks[*ns], nsap, sockaddrSize(nsap)) < 0) {
*terrno = errno;
dump_error("connect(dg)", nsap);
statp->closeSockets();
return 0;
}
LOG(DEBUG) << __func__ << ": new DG socket";
}
if (send(statp->udpsocks[*ns], msg.data(), msg.size(), 0) !=
static_cast<ptrdiff_t>(msg.size())) {
*terrno = errno;
PLOG(DEBUG) << __func__ << ": send: ";
statp->closeSockets();
return 0;
}
timespec timeout = get_timeout(statp, params, *ns);
timespec start_time = evNowTime();
timespec finish = evAddTime(start_time, timeout);
for (;;) {
// Wait for reply.
auto result = udpRetryingPollWrapper(statp, *ns, &finish);
if (!result.has_value()) {
const bool isTimeout = (result.error().code() == ETIMEDOUT);
*rcode = (isTimeout) ? RCODE_TIMEOUT : *rcode;
*terrno = (isTimeout) ? ETIMEDOUT : errno;
*gotsomewhere = (isTimeout) ? 1 : *gotsomewhere;
// Leave the UDP sockets open on timeout so we can keep listening for
// a late response from this server while retrying on the next server.
if (!isTimeout) statp->closeSockets();
LOG(DEBUG) << __func__ << ": " << (isTimeout ? "timeout" : "poll");
return 0;
}
bool needRetry = false;
for (int fd : result.value()) {
needRetry = false;
sockaddr_storage from;
socklen_t fromlen = sizeof(from);
int resplen =
recvfrom(fd, ans.data(), ans.size(), 0, (sockaddr*)(void*)&from, &fromlen);
if (resplen <= 0) {
*terrno = errno;
PLOG(DEBUG) << __func__ << ": recvfrom: ";
continue;
}
*gotsomewhere = 1;
if (resplen < HFIXEDSZ) {
// Undersized message.
LOG(DEBUG) << __func__ << ": undersized: " << resplen;
*terrno = EMSGSIZE;
continue;
}
if (resplen > static_cast<ptrdiff_t>(ans.size())) {
LOG(FATAL) << __func__ << ": invalid resplen (too large): " << resplen;
}
int receivedFromNs = *ns;
if (needRetry = ignoreInvalidAnswer(statp, from, msg, ans, &receivedFromNs);
needRetry) {
res_pquery(ans.first(resplen));
continue;
}
HEADER* anhp = (HEADER*)(void*)ans.data();
if (anhp->rcode == FORMERR && (statp->netcontext_flags & NET_CONTEXT_FLAG_USE_EDNS)) {
// Do not retry if the server do not understand EDNS0.
// The case has to be captured here, as FORMERR packet do not
// carry query section, hence res_queriesmatch() returns 0.
LOG(DEBUG) << __func__ << ": server rejected query with EDNS0:";
res_pquery(ans.first(resplen));
// record the error
statp->flags |= RES_F_EDNS0ERR;
*terrno = EREMOTEIO;
continue;
}
if (anhp->rcode == SERVFAIL || anhp->rcode == NOTIMP || anhp->rcode == REFUSED) {
LOG(DEBUG) << __func__ << ": server rejected query:";
res_pquery(ans.first(resplen));
*rcode = anhp->rcode;
continue;
}
if (anhp->tc) {
// To get the rest of answer,
// use TCP with same server.
LOG(DEBUG) << __func__ << ": truncated answer";
*terrno = E2BIG;
*v_circuit = 1;
return 1;
}
// All is well, or the error is fatal. Signal that the
// next nameserver ought not be tried.
*rcode = anhp->rcode;
*ns = receivedFromNs;
*terrno = 0;
return resplen;
}
if (!needRetry) return 0;
}
}
// return length - when receiving valid packets.
// return 0 - when mdns packets transfer error.
static int send_mdns(ResState* statp, span<const uint8_t> msg, span<uint8_t> ans, int* terrno,
int* rcode, IPSockAddr* receivedMdnsAddr) {
// Always query the IPv6 multicast address for mDNS first, regardless of
// the state of IPv4/IPv6 connectivity.
// This works for IPv4 only networks since we won't receive a "successful"
// mDNS answer (either sendto will fail, or we won't receive a response),
// in which case we will fallback onto IPv4.
// This won't always lead to the best performance, but it was deemed
// preferable due to the much simpler code.
for (const auto& mdns_addr : mdns_addrs) {
const sockaddr_storage ss = mdns_addr;
*receivedMdnsAddr = mdns_addr;
const sockaddr* mdnsap = reinterpret_cast<const sockaddr*>(&ss);
unique_fd fd;
if (setupUdpSocket(statp, mdnsap, &fd, terrno) <= 0) return 0;
if (statp->target_interface_index_for_mdns != 0) {
if (mdnsap->sa_family == AF_INET) {
struct ip_mreqn mreqn = {};
mreqn.imr_ifindex = statp->target_interface_index_for_mdns;
if (setsockopt(fd, IPPROTO_IP, IP_MULTICAST_IF, &mreqn, sizeof(mreqn)) < 0) {
*terrno = errno;
continue;
}
} else if (mdnsap->sa_family == AF_INET6) {
if (setsockopt(fd, IPPROTO_IPV6, IPV6_MULTICAST_IF,
&statp->target_interface_index_for_mdns,
sizeof(statp->target_interface_index_for_mdns)) < 0) {
*terrno = errno;
continue;
}
}
}
if (sendto(fd, msg.data(), msg.size(), 0, mdnsap, sockaddrSize(mdnsap)) !=
static_cast<ptrdiff_t>(msg.size())) {
*terrno = errno;
continue;
}
// Wait for 702ms. Justification: 99.99% of networks use a DTIM period <= 5, so a device
// connected to a WiFi network should receive the query within 500ms. This gives an
// additional 202ms to receive a unicast reply.
const struct timespec finish = evAddTime(evNowTime(), {0, 702000000});
// Wait for reply.
if (retrying_poll(fd, POLLIN, &finish) <= 0) {
*terrno = errno;
if (*terrno == ETIMEDOUT) *rcode = RCODE_TIMEOUT;
LOG(ERROR) << __func__ << ": " << ((*terrno == ETIMEDOUT) ? "timeout" : "poll failed");
continue;
}
sockaddr_storage from;
socklen_t fromlen = sizeof(from);
int resplen = recvfrom(fd, ans.data(), ans.size(), 0, (sockaddr*)(void*)&from, &fromlen);
if (resplen <= 0) {
*terrno = errno;
continue;
}
if (resplen < HFIXEDSZ) {
// Undersized message.
LOG(ERROR) << __func__ << ": undersized: " << resplen;
*terrno = EMSGSIZE;
continue;
}
HEADER* anhp = (HEADER*)(void*)ans.data();
if (anhp->tc) {
LOG(DEBUG) << __func__ << ": truncated answer";
*terrno = E2BIG;
continue;
}
*rcode = anhp->rcode;
*terrno = 0;
return resplen;
}
return 0;
}
static void dump_error(const char* str, const struct sockaddr* address) {
char hbuf[NI_MAXHOST];
char sbuf[NI_MAXSERV];
constexpr int niflags = NI_NUMERICHOST | NI_NUMERICSERV;
const int err = errno;
if (!WOULD_LOG(DEBUG)) return;
if (getnameinfo(address, sockaddrSize(address), hbuf, sizeof(hbuf), sbuf, sizeof(sbuf),
niflags)) {
strncpy(hbuf, "?", sizeof(hbuf) - 1);
hbuf[sizeof(hbuf) - 1] = '\0';
strncpy(sbuf, "?", sizeof(sbuf) - 1);
sbuf[sizeof(sbuf) - 1] = '\0';
}
errno = err;
PLOG(DEBUG) << __func__ << ": " << str << " ([" << hbuf << "]." << sbuf << "): ";
}
static int sock_eq(struct sockaddr* a, struct sockaddr* b) {
struct sockaddr_in *a4, *b4;
struct sockaddr_in6 *a6, *b6;
if (a->sa_family != b->sa_family) return 0;
switch (a->sa_family) {
case AF_INET:
a4 = (struct sockaddr_in*) (void*) a;
b4 = (struct sockaddr_in*) (void*) b;
return a4->sin_port == b4->sin_port && a4->sin_addr.s_addr == b4->sin_addr.s_addr;
case AF_INET6:
a6 = (struct sockaddr_in6*) (void*) a;
b6 = (struct sockaddr_in6*) (void*) b;
return a6->sin6_port == b6->sin6_port &&
#ifdef HAVE_SIN6_SCOPE_ID
a6->sin6_scope_id == b6->sin6_scope_id &&
#endif
IN6_ARE_ADDR_EQUAL(&a6->sin6_addr, &b6->sin6_addr);
default:
return 0;
}
}
static int res_private_dns_send(ResState* statp, const Slice query, const Slice answer, int* rcode,
bool* fallback) {
const unsigned netId = statp->netid;
auto& privateDnsConfiguration = PrivateDnsConfiguration::getInstance();
PrivateDnsStatus privateDnsStatus = privateDnsConfiguration.getStatus(netId);
statp->event->set_private_dns_modes(convertEnumType(privateDnsStatus.mode));
ssize_t result = -1;
switch (privateDnsStatus.mode) {
case PrivateDnsMode::OFF: {
*fallback = true;
return -1;
}
case PrivateDnsMode::OPPORTUNISTIC: {
*fallback = true;
if (privateDnsStatus.hasValidatedDohServers()) {
result = res_doh_send(statp, query, answer, rcode);
if (result != DOH_RESULT_CAN_NOT_SEND) return result;
}
return res_tls_send(privateDnsStatus.validatedServers(), statp, query, answer, rcode,
privateDnsStatus.mode);
}
case PrivateDnsMode::STRICT: {
*fallback = false;
if (privateDnsStatus.hasValidatedDohServers()) {
result = res_doh_send(statp, query, answer, rcode);
if (result != DOH_RESULT_CAN_NOT_SEND) return result;
}
if (privateDnsStatus.validatedServers().empty()) {
// Sleep and iterate some small number of times checking for the
// arrival of resolved and validated server IP addresses, instead
// of returning an immediate error.
// This is needed because as soon as a network becomes the default network, apps
// will send DNS queries on that network. If no servers have yet validated, and we
// do not block those queries, they would immediately fail, causing
// application-visible errors. Note that this can happen even before the network
// validates, since an unvalidated network can become the default network if no
// validated networks are available.
//
// TODO: see if there is a better way to address this problem, such as buffering the
// queries in a queue or only blocking queries for the first few seconds after a
// default network change.
for (int i = 0; i < 42; i++) {
std::this_thread::sleep_for(std::chrono::milliseconds(100));
// Calling getStatus() to merely check if there's any validated server seems
// wasteful. Consider adding a new method in PrivateDnsConfiguration for speed
// ups.
privateDnsStatus = privateDnsConfiguration.getStatus(netId);
if (privateDnsStatus.hasValidatedDohServers()) {
result = res_doh_send(statp, query, answer, rcode);
if (result != DOH_RESULT_CAN_NOT_SEND) return result;
}
// Switch to use the DoT servers if they are validated.
if (!privateDnsStatus.validatedServers().empty()) {
break;
}
}
}
return res_tls_send(privateDnsStatus.validatedServers(), statp, query, answer, rcode,
privateDnsStatus.mode);
}
}
LOG(ERROR) << __func__ << ": unknown private DNS mode";
return -1;
}
ssize_t res_doh_send(ResState* statp, const Slice query, const Slice answer, int* rcode) {
auto& privateDnsConfiguration = PrivateDnsConfiguration::getInstance();
const unsigned netId = statp->netid;
LOG(DEBUG) << __func__ << ": performing query over Https";
Stopwatch queryStopwatch;
int queryTimeout = Experiments::getInstance()->getFlag(
"doh_query_timeout_ms", PrivateDnsConfiguration::kDohQueryDefaultTimeoutMs);
if (queryTimeout < 1000) {
queryTimeout = 1000;
}
ssize_t result = privateDnsConfiguration.dohQuery(netId, query, answer, queryTimeout);
LOG(INFO) << __func__ << ": Https query result: " << result << ", netid=" << netId;
if (result == DOH_RESULT_CAN_NOT_SEND) return DOH_RESULT_CAN_NOT_SEND;
DnsQueryEvent* dnsQueryEvent = statp->event->mutable_dns_query_events()->add_dns_query_event();
dnsQueryEvent->set_latency_micros(saturate_cast<int32_t>(queryStopwatch.timeTakenUs()));
// TODO: Make this information available.
// dnsQueryEvent->set_ip_version(ipFamilyToIPVersion(?));
if (result > 0) {
*rcode = reinterpret_cast<HEADER*>(answer.base())->rcode;
} else {
*rcode = -result;
}
dnsQueryEvent->set_rcode(static_cast<NsRcode>(*rcode));
dnsQueryEvent->set_protocol(PROTO_DOH);
span<const uint8_t> msg(query.base(), query.size());
dnsQueryEvent->set_type(getQueryType(msg));
auto dohServerAddr = privateDnsConfiguration.getDohServer(netId);
if (dohServerAddr.ok()) {
resolv_stats_add(netId, dohServerAddr.value(), dnsQueryEvent);
}
return result;
}
int res_tls_send(const std::list<DnsTlsServer>& tlsServers, ResState* statp, const Slice query,
const Slice answer, int* rcode, PrivateDnsMode mode) {
if (tlsServers.empty()) return -1;
LOG(DEBUG) << __func__ << ": performing query over TLS";
const bool dotQuickFallback =
(mode == PrivateDnsMode::STRICT)
? 0
: Experiments::getInstance()->getFlag("dot_quick_fallback", 1);
int resplen = 0;
const auto response = DnsTlsDispatcher::getInstance().query(tlsServers, statp, query, answer,
&resplen, dotQuickFallback);
LOG(INFO) << __func__ << ": TLS query result: " << static_cast<int>(response);
if (mode == PrivateDnsMode::OPPORTUNISTIC) {
// In opportunistic mode, handle falling back to cleartext in some
// cases (DNS shouldn't fail if a validated opportunistic mode server
// becomes unreachable for some reason).
switch (response) {
case DnsTlsTransport::Response::success:
*rcode = reinterpret_cast<HEADER*>(answer.base())->rcode;
return resplen;
// It's OPPORTUNISTIC mode,
// hence it's not required to do anything because it'll fallback to UDP.
case DnsTlsTransport::Response::network_error:
case DnsTlsTransport::Response::internal_error:
default:
return -1;
}
} else {
// Strict mode
switch (response) {
case DnsTlsTransport::Response::success:
*rcode = reinterpret_cast<HEADER*>(answer.base())->rcode;
return resplen;
case DnsTlsTransport::Response::network_error:
// This case happens when the query stored in DnsTlsTransport is expired since
// either 1) the query has been tried for 3 times but no response or 2) fail to
// establish the connection with the server.
*rcode = RCODE_TIMEOUT;
[[fallthrough]];
default:
return -1;
}
}
}
int resolv_res_nsend(const android_net_context* netContext, std::optional<int> app_socket,
span<const uint8_t> msg, span<uint8_t> ans, int* rcode, uint32_t flags,
NetworkDnsEventReported* event) {
assert(event != nullptr);
ResState res(netContext, app_socket, event);
resolv_populate_res_for_net(&res);
*rcode = NOERROR;
return res_nsend(&res, msg, ans, rcode, flags);
}
// Returns the elapsed time in milliseconds since the given time `from`.
int elapsedTimeInMs(const timespec& from) {
const timespec now = evNowTime();
return res_stats_calculate_rtt(&now, &from);
}