blob: f7a3e8d6ff344994a489d29947f337533570341c [file] [log] [blame]
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/dns/dns_transaction.h"
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "base/base64url.h"
#include "base/big_endian.h"
#include "base/bind.h"
#include "base/callback_helpers.h"
#include "base/containers/circular_deque.h"
#include "base/location.h"
#include "base/macros.h"
#include "base/memory/ptr_util.h"
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "base/metrics/histogram_macros.h"
#include "base/rand_util.h"
#include "base/single_thread_task_runner.h"
#include "base/stl_util.h"
#include "base/strings/string_piece.h"
#include "base/threading/thread_checker.h"
#include "base/threading/thread_task_runner_handle.h"
#include "base/timer/timer.h"
#include "base/values.h"
#include "build/build_config.h"
#include "net/base/completion_callback.h"
#include "net/base/elements_upload_data_stream.h"
#include "net/base/io_buffer.h"
#include "net/base/ip_address.h"
#include "net/base/ip_endpoint.h"
#include "net/base/net_errors.h"
#include "net/base/upload_bytes_element_reader.h"
#include "net/dns/dns_protocol.h"
#include "net/dns/dns_query.h"
#include "net/dns/dns_response.h"
#include "net/dns/dns_session.h"
#include "net/dns/dns_util.h"
#include "net/log/net_log.h"
#include "net/log/net_log_capture_mode.h"
#include "net/log/net_log_event_type.h"
#include "net/log/net_log_source.h"
#include "net/log/net_log_with_source.h"
#include "net/socket/datagram_client_socket.h"
#include "net/socket/stream_socket.h"
#include "net/traffic_annotation/network_traffic_annotation.h"
#include "net/url_request/url_fetcher.h"
#include "net/url_request/url_fetcher_delegate.h"
#include "net/url_request/url_fetcher_response_writer.h"
#include "net/url_request/url_request_context.h"
#include "net/url_request/url_request_context_builder.h"
namespace net {
namespace {
constexpr net::NetworkTrafficAnnotationTag kTrafficAnnotation =
net::DefineNetworkTrafficAnnotation("dns_transaction", R"(
semantics {
sender: "DNS Transaction"
description:
"DNS Transaction implements a stub DNS resolver as defined in RFC "
"1034."
trigger:
"Any network request that may require DNS resolution, including "
"navigations, connecting to a proxy server, detecting proxy "
"settings, getting proxy config, certificate checking, and more."
data:
"Domain name that needs resolution."
destination: OTHER
destination_other:
"The connection is made to a DNS server based on user's network "
"settings."
}
policy {
cookies_allowed: NO
setting:
"This feature cannot be disabled. Without DNS Transactions Chrome "
"cannot resolve host names."
policy_exception_justification:
"Essential for Chrome's navigation."
})");
const char kDnsOverHttpResponseContentType[] = "application/dns-udpwireformat";
// Count labels in the fully-qualified name in DNS format.
int CountLabels(const std::string& name) {
size_t count = 0;
for (size_t i = 0; i < name.size() && name[i]; i += name[i] + 1)
++count;
return count;
}
bool IsIPLiteral(const std::string& hostname) {
IPAddress ip;
return ip.AssignFromIPLiteral(hostname);
}
std::unique_ptr<base::Value> NetLogStartCallback(
const std::string* hostname,
uint16_t qtype,
NetLogCaptureMode /* capture_mode */) {
std::unique_ptr<base::DictionaryValue> dict(new base::DictionaryValue());
dict->SetString("hostname", *hostname);
dict->SetInteger("query_type", qtype);
return std::move(dict);
}
// Values are used in UMA histograms. Do not change existing values.
enum MalformedResponseResult {
MALFORMED_OK = 0,
MALFORMED_MALFORMED = 1,
MALFORMED_FAILED = 2,
MALFORMED_MAX
};
void RecordMalformedResponseHistogram(int net_error) {
MalformedResponseResult error_type;
if (net_error == OK)
error_type = MALFORMED_OK;
else if (net_error == ERR_DNS_MALFORMED_RESPONSE)
error_type = MALFORMED_MALFORMED;
else
error_type = MALFORMED_FAILED;
UMA_HISTOGRAM_ENUMERATION("Net.DNS.ResultAfterMalformedResponse", error_type,
MALFORMED_MAX);
}
// ----------------------------------------------------------------------------
// A single asynchronous DNS exchange, which consists of sending out a
// DNS query, waiting for a response, and returning the response that it
// matches. Logging is done in the socket and in the outer DnsTransaction.
class DnsAttempt {
public:
explicit DnsAttempt(unsigned server_index)
: result_(ERR_FAILED), server_index_(server_index) {}
virtual ~DnsAttempt() = default;
// Starts the attempt. Returns ERR_IO_PENDING if cannot complete synchronously
// and calls |callback| upon completion.
virtual int Start(const CompletionCallback& callback) = 0;
// Returns the query of this attempt.
virtual const DnsQuery* GetQuery() const = 0;
// Returns the response or NULL if has not received a matching response from
// the server.
virtual const DnsResponse* GetResponse() const = 0;
// Returns the net log bound to the source of the socket.
virtual const NetLogWithSource& GetSocketNetLog() const = 0;
// Returns the index of the destination server within DnsConfig::nameservers.
unsigned server_index() const { return server_index_; }
// Returns a Value representing the received response, along with a reference
// to the NetLog source source of the UDP socket used. The request must have
// completed before this is called.
std::unique_ptr<base::Value> NetLogResponseCallback(
NetLogCaptureMode capture_mode) const {
DCHECK(GetResponse()->IsValid());
std::unique_ptr<base::DictionaryValue> dict(new base::DictionaryValue());
dict->SetInteger("rcode", GetResponse()->rcode());
dict->SetInteger("answer_count", GetResponse()->answer_count());
GetSocketNetLog().source().AddToEventParameters(dict.get());
return std::move(dict);
}
void set_result(int result) {
result_ = result;
}
// True if current attempt is pending (waiting for server response).
bool is_pending() const {
return result_ == ERR_IO_PENDING;
}
// True if attempt is completed (received server response).
bool is_completed() const {
return (result_ == OK) || (result_ == ERR_NAME_NOT_RESOLVED) ||
(result_ == ERR_DNS_SERVER_REQUIRES_TCP);
}
private:
// Result of last operation.
int result_;
const unsigned server_index_;
};
class DnsUDPAttempt : public DnsAttempt {
public:
DnsUDPAttempt(unsigned server_index,
std::unique_ptr<DnsSession::SocketLease> socket_lease,
std::unique_ptr<DnsQuery> query)
: DnsAttempt(server_index),
next_state_(STATE_NONE),
received_malformed_response_(false),
socket_lease_(std::move(socket_lease)),
query_(std::move(query)) {}
// DnsAttempt:
int Start(const CompletionCallback& callback) override {
DCHECK_EQ(STATE_NONE, next_state_);
callback_ = callback;
start_time_ = base::TimeTicks::Now();
next_state_ = STATE_SEND_QUERY;
return DoLoop(OK);
}
const DnsQuery* GetQuery() const override { return query_.get(); }
const DnsResponse* GetResponse() const override {
const DnsResponse* resp = response_.get();
return (resp != NULL && resp->IsValid()) ? resp : NULL;
}
const NetLogWithSource& GetSocketNetLog() const override {
return socket_lease_->socket()->NetLog();
}
private:
enum State {
STATE_SEND_QUERY,
STATE_SEND_QUERY_COMPLETE,
STATE_READ_RESPONSE,
STATE_READ_RESPONSE_COMPLETE,
STATE_NONE,
};
DatagramClientSocket* socket() {
return socket_lease_->socket();
}
int DoLoop(int result) {
CHECK_NE(STATE_NONE, next_state_);
int rv = result;
do {
State state = next_state_;
next_state_ = STATE_NONE;
switch (state) {
case STATE_SEND_QUERY:
rv = DoSendQuery();
break;
case STATE_SEND_QUERY_COMPLETE:
rv = DoSendQueryComplete(rv);
break;
case STATE_READ_RESPONSE:
rv = DoReadResponse();
break;
case STATE_READ_RESPONSE_COMPLETE:
rv = DoReadResponseComplete(rv);
break;
default:
NOTREACHED();
break;
}
} while (rv != ERR_IO_PENDING && next_state_ != STATE_NONE);
set_result(rv);
if (received_malformed_response_) {
// If we received a malformed response, and are now waiting for another
// one, indicate to the transaction that the server might be misbehaving.
if (rv == ERR_IO_PENDING)
return ERR_DNS_MALFORMED_RESPONSE;
// This is a new response after the original malformed one.
RecordMalformedResponseHistogram(rv);
}
if (rv == OK) {
DCHECK_EQ(STATE_NONE, next_state_);
UMA_HISTOGRAM_LONG_TIMES_100("AsyncDNS.UDPAttemptSuccess",
base::TimeTicks::Now() - start_time_);
} else if (rv != ERR_IO_PENDING) {
UMA_HISTOGRAM_LONG_TIMES_100("AsyncDNS.UDPAttemptFail",
base::TimeTicks::Now() - start_time_);
}
return rv;
}
int DoSendQuery() {
next_state_ = STATE_SEND_QUERY_COMPLETE;
return socket()->Write(
query_->io_buffer(), query_->io_buffer()->size(),
base::Bind(&DnsUDPAttempt::OnIOComplete, base::Unretained(this)),
kTrafficAnnotation);
}
int DoSendQueryComplete(int rv) {
DCHECK_NE(ERR_IO_PENDING, rv);
if (rv < 0)
return rv;
// Writing to UDP should not result in a partial datagram.
if (rv != query_->io_buffer()->size())
return ERR_MSG_TOO_BIG;
next_state_ = STATE_READ_RESPONSE;
return OK;
}
int DoReadResponse() {
next_state_ = STATE_READ_RESPONSE_COMPLETE;
response_ = std::make_unique<DnsResponse>();
return socket()->Read(
response_->io_buffer(), response_->io_buffer_size(),
base::Bind(&DnsUDPAttempt::OnIOComplete, base::Unretained(this)));
}
int DoReadResponseComplete(int rv) {
DCHECK_NE(ERR_IO_PENDING, rv);
if (rv < 0)
return rv;
DCHECK(rv);
if (!response_->InitParse(rv, *query_)) {
// Other implementations simply ignore mismatched responses. Since each
// DnsUDPAttempt binds to a different port, we might find that responses
// to previously timed out queries lead to failures in the future.
// Our solution is to make another attempt, in case the query truly
// failed, but keep this attempt alive, in case it was a false alarm.
received_malformed_response_ = true;
RecordMalformedResponseHistogram(ERR_DNS_MALFORMED_RESPONSE);
next_state_ = STATE_READ_RESPONSE;
return OK;
}
if (response_->flags() & dns_protocol::kFlagTC)
return ERR_DNS_SERVER_REQUIRES_TCP;
// TODO(szym): Extract TTL for NXDOMAIN results. http://crbug.com/115051
if (response_->rcode() == dns_protocol::kRcodeNXDOMAIN)
return ERR_NAME_NOT_RESOLVED;
if (response_->rcode() != dns_protocol::kRcodeNOERROR)
return ERR_DNS_SERVER_FAILED;
return OK;
}
void OnIOComplete(int rv) {
rv = DoLoop(rv);
if (rv != ERR_IO_PENDING)
callback_.Run(rv);
}
State next_state_;
bool received_malformed_response_;
base::TimeTicks start_time_;
std::unique_ptr<DnsSession::SocketLease> socket_lease_;
std::unique_ptr<DnsQuery> query_;
std::unique_ptr<DnsResponse> response_;
CompletionCallback callback_;
DISALLOW_COPY_AND_ASSIGN(DnsUDPAttempt);
};
class DnsHTTPAttempt : public DnsAttempt, public URLRequest::Delegate {
public:
DnsHTTPAttempt(unsigned server_index,
std::unique_ptr<DnsQuery> query,
const GURL& server,
bool use_post,
URLRequestContext* url_request_context,
RequestPriority request_priority_)
: DnsAttempt(server_index),
query_(std::move(query)),
weak_factory_(this) {
GURL url(server);
if (!use_post) {
std::string encoded_query;
base::Base64UrlEncode(base::StringPiece(query_->io_buffer()->data(),
query_->io_buffer()->size()),
base::Base64UrlEncodePolicy::INCLUDE_PADDING,
&encoded_query);
std::string query_str("content-type=application/dns-udpwireformat&body=" +
encoded_query);
GURL::Replacements replacements;
replacements.SetQuery(query_str.c_str(),
url::Component(0, query_str.length()));
url = server.ReplaceComponents(replacements);
}
HttpRequestHeaders extra_request_headers;
extra_request_headers.SetHeader("Accept", kDnsOverHttpResponseContentType);
request_ = url_request_context->CreateRequest(
url, request_priority_, this,
net::DefineNetworkTrafficAnnotation("dns_over_https", R"(
semantics {
sender: "DNS over HTTPS"
description: "Domain name resolution over HTTPS"
trigger: "User enters a navigates to a domain or Chrome otherwise "
"makes a connection to a domain whose IP address isn't cached"
data: "The domain name that is being requested"
destination: OTHER
destination_other: "The user configured DNS over HTTPS server, which"
"may be dns.google.com"
}
policy {
cookies_allowed: NO
setting:
"You can configure this feature via that 'dns_over_https_servers' and"
"'dns_over_https.method' prefs. Empty lists imply this feature is"
"disabled"
policy_exception_justification: "Experimental feature that"
"is disabled by default"
}
)"));
if (use_post) {
request_->set_method("POST");
std::unique_ptr<UploadElementReader> reader =
std::make_unique<UploadBytesElementReader>(
query_->io_buffer()->data(), query_->io_buffer()->size());
request_->set_upload(
ElementsUploadDataStream::CreateWithReader(std::move(reader), 0));
extra_request_headers.SetHeader(HttpRequestHeaders::kContentType,
kDnsOverHttpResponseContentType);
}
request_->SetExtraRequestHeaders(extra_request_headers);
request_->SetLoadFlags(request_->load_flags() | LOAD_DISABLE_CACHE |
LOAD_BYPASS_PROXY | LOAD_DO_NOT_SEND_COOKIES |
LOAD_DO_NOT_SAVE_COOKIES |
LOAD_DO_NOT_SEND_AUTH_DATA);
}
// DnsAttempt overrides.
int Start(const CompletionCallback& callback) override {
if (DNSDomainToString(query_->qname()).compare(request_->url().host()) ==
0) {
// Fast failing looking up a server with itself.
return ERR_DNS_HTTP_FAILED;
}
callback_ = callback;
request_->Start();
return ERR_IO_PENDING;
}
void Cancel() { request_.reset(); }
const DnsQuery* GetQuery() const override { return query_.get(); }
const DnsResponse* GetResponse() const override {
const DnsResponse* resp = response_.get();
return (resp != NULL && resp->IsValid()) ? resp : NULL;
}
const NetLogWithSource& GetSocketNetLog() const override {
return request_->net_log();
}
// URLRequest::Delegate overrides
void OnResponseStarted(net::URLRequest* request, int net_error) override {
DCHECK_NE(net::ERR_IO_PENDING, net_error);
std::string content_type;
if (net_error != OK) {
ResponseCompleted(net_error);
return;
}
if (request_->GetResponseCode() != 200 ||
!request->response_headers()->GetMimeType(&content_type) ||
0 != content_type.compare(kDnsOverHttpResponseContentType)) {
ResponseCompleted(ERR_DNS_MALFORMED_RESPONSE);
return;
}
buffer_ = new GrowableIOBuffer();
if (request->response_headers()->HasHeader(
HttpRequestHeaders::kContentLength)) {
buffer_->SetCapacity(request_->response_headers()->GetContentLength() +
1);
} else {
buffer_->SetCapacity(66560); // 64kb.
}
DCHECK(buffer_->data());
DCHECK_GT(buffer_->capacity(), 0);
int bytes_read =
request_->Read(buffer_.get(), buffer_->RemainingCapacity());
// If IO is pending, wait for the URLRequest to call OnReadCompleted.
if (bytes_read == net::ERR_IO_PENDING)
return;
OnReadCompleted(request_.get(), bytes_read);
}
void OnReadCompleted(net::URLRequest* request, int bytes_read) override {
// bytes_read can be an error.
if (bytes_read < 0) {
ResponseCompleted(bytes_read);
return;
}
DCHECK_GE(bytes_read, 0);
if (bytes_read > 0) {
buffer_->set_offset(buffer_->offset() + bytes_read);
if (buffer_->RemainingCapacity() == 0) {
buffer_->SetCapacity(buffer_->capacity() + 16384); // Grow by 16kb.
}
DCHECK(buffer_->data());
DCHECK_GT(buffer_->capacity(), 0);
int bytes_read =
request_->Read(buffer_.get(), buffer_->RemainingCapacity());
// If IO is pending, wait for the URLRequest to call OnReadCompleted.
if (bytes_read == net::ERR_IO_PENDING)
return;
if (bytes_read <= 0) {
OnReadCompleted(request_.get(), bytes_read);
} else {
// Else, trigger OnReadCompleted asynchronously to avoid starving the IO
// thread in case the URLRequest can provide data synchronously.
base::SequencedTaskRunnerHandle::Get()->PostTask(
FROM_HERE, base::BindOnce(&DnsHTTPAttempt::OnReadCompleted,
weak_factory_.GetWeakPtr(),
request_.get(), bytes_read));
}
} else {
// URLRequest reported an EOF. Call ResponseCompleted.
DCHECK_EQ(0, bytes_read);
ResponseCompleted(net::OK);
}
}
private:
void ResponseCompleted(int net_error) {
request_.reset();
callback_.Run(CompleteResponse(net_error));
}
int CompleteResponse(int net_error) {
DCHECK_NE(net::ERR_IO_PENDING, net_error);
if (net_error != OK) {
return net_error;
}
if (!buffer_.get() || 0 == buffer_->capacity())
return ERR_DNS_MALFORMED_RESPONSE;
size_t size = buffer_->offset();
buffer_->set_offset(0);
if (size == 0u)
return ERR_DNS_MALFORMED_RESPONSE;
response_ = std::make_unique<DnsResponse>(buffer_.get(), size + 1);
if (!response_->InitParse(size, *query_))
return ERR_DNS_MALFORMED_RESPONSE;
if (response_->rcode() == dns_protocol::kRcodeNXDOMAIN)
return ERR_NAME_NOT_RESOLVED;
if (response_->rcode() != dns_protocol::kRcodeNOERROR)
return ERR_DNS_SERVER_FAILED;
return OK;
}
scoped_refptr<GrowableIOBuffer> buffer_;
std::unique_ptr<DnsQuery> query_;
CompletionCallback callback_;
std::unique_ptr<DnsResponse> response_;
std::unique_ptr<URLRequest> request_;
base::WeakPtrFactory<DnsHTTPAttempt> weak_factory_;
DISALLOW_COPY_AND_ASSIGN(DnsHTTPAttempt);
};
class DnsTCPAttempt : public DnsAttempt {
public:
DnsTCPAttempt(unsigned server_index,
std::unique_ptr<StreamSocket> socket,
std::unique_ptr<DnsQuery> query)
: DnsAttempt(server_index),
next_state_(STATE_NONE),
socket_(std::move(socket)),
query_(std::move(query)),
length_buffer_(new IOBufferWithSize(sizeof(uint16_t))),
response_length_(0) {}
// DnsAttempt:
int Start(const CompletionCallback& callback) override {
DCHECK_EQ(STATE_NONE, next_state_);
callback_ = callback;
start_time_ = base::TimeTicks::Now();
next_state_ = STATE_CONNECT_COMPLETE;
int rv = socket_->Connect(
base::Bind(&DnsTCPAttempt::OnIOComplete, base::Unretained(this)));
if (rv == ERR_IO_PENDING) {
set_result(rv);
return rv;
}
return DoLoop(rv);
}
const DnsQuery* GetQuery() const override { return query_.get(); }
const DnsResponse* GetResponse() const override {
const DnsResponse* resp = response_.get();
return (resp != NULL && resp->IsValid()) ? resp : NULL;
}
const NetLogWithSource& GetSocketNetLog() const override {
return socket_->NetLog();
}
private:
enum State {
STATE_CONNECT_COMPLETE,
STATE_SEND_LENGTH,
STATE_SEND_QUERY,
STATE_READ_LENGTH,
STATE_READ_LENGTH_COMPLETE,
STATE_READ_RESPONSE,
STATE_READ_RESPONSE_COMPLETE,
STATE_NONE,
};
int DoLoop(int result) {
CHECK_NE(STATE_NONE, next_state_);
int rv = result;
do {
State state = next_state_;
next_state_ = STATE_NONE;
switch (state) {
case STATE_CONNECT_COMPLETE:
rv = DoConnectComplete(rv);
break;
case STATE_SEND_LENGTH:
rv = DoSendLength(rv);
break;
case STATE_SEND_QUERY:
rv = DoSendQuery(rv);
break;
case STATE_READ_LENGTH:
rv = DoReadLength(rv);
break;
case STATE_READ_LENGTH_COMPLETE:
rv = DoReadLengthComplete(rv);
break;
case STATE_READ_RESPONSE:
rv = DoReadResponse(rv);
break;
case STATE_READ_RESPONSE_COMPLETE:
rv = DoReadResponseComplete(rv);
break;
default:
NOTREACHED();
break;
}
} while (rv != ERR_IO_PENDING && next_state_ != STATE_NONE);
set_result(rv);
if (rv == OK) {
DCHECK_EQ(STATE_NONE, next_state_);
UMA_HISTOGRAM_LONG_TIMES_100("AsyncDNS.TCPAttemptSuccess",
base::TimeTicks::Now() - start_time_);
} else if (rv != ERR_IO_PENDING) {
UMA_HISTOGRAM_LONG_TIMES_100("AsyncDNS.TCPAttemptFail",
base::TimeTicks::Now() - start_time_);
}
return rv;
}
int DoConnectComplete(int rv) {
DCHECK_NE(ERR_IO_PENDING, rv);
if (rv < 0)
return rv;
uint16_t query_size = static_cast<uint16_t>(query_->io_buffer()->size());
if (static_cast<int>(query_size) != query_->io_buffer()->size())
return ERR_FAILED;
base::WriteBigEndian<uint16_t>(length_buffer_->data(), query_size);
buffer_ =
new DrainableIOBuffer(length_buffer_.get(), length_buffer_->size());
next_state_ = STATE_SEND_LENGTH;
return OK;
}
int DoSendLength(int rv) {
DCHECK_NE(ERR_IO_PENDING, rv);
if (rv < 0)
return rv;
buffer_->DidConsume(rv);
if (buffer_->BytesRemaining() > 0) {
next_state_ = STATE_SEND_LENGTH;
return socket_->Write(
buffer_.get(), buffer_->BytesRemaining(),
base::Bind(&DnsTCPAttempt::OnIOComplete, base::Unretained(this)),
kTrafficAnnotation);
}
buffer_ =
new DrainableIOBuffer(query_->io_buffer(), query_->io_buffer()->size());
next_state_ = STATE_SEND_QUERY;
return OK;
}
int DoSendQuery(int rv) {
DCHECK_NE(ERR_IO_PENDING, rv);
if (rv < 0)
return rv;
buffer_->DidConsume(rv);
if (buffer_->BytesRemaining() > 0) {
next_state_ = STATE_SEND_QUERY;
return socket_->Write(
buffer_.get(), buffer_->BytesRemaining(),
base::Bind(&DnsTCPAttempt::OnIOComplete, base::Unretained(this)),
kTrafficAnnotation);
}
buffer_ =
new DrainableIOBuffer(length_buffer_.get(), length_buffer_->size());
next_state_ = STATE_READ_LENGTH;
return OK;
}
int DoReadLength(int rv) {
DCHECK_EQ(OK, rv);
next_state_ = STATE_READ_LENGTH_COMPLETE;
return ReadIntoBuffer();
}
int DoReadLengthComplete(int rv) {
DCHECK_NE(ERR_IO_PENDING, rv);
if (rv < 0)
return rv;
if (rv == 0)
return ERR_CONNECTION_CLOSED;
buffer_->DidConsume(rv);
if (buffer_->BytesRemaining() > 0) {
next_state_ = STATE_READ_LENGTH;
return OK;
}
base::ReadBigEndian<uint16_t>(length_buffer_->data(), &response_length_);
// Check if advertised response is too short. (Optimization only.)
if (response_length_ < query_->io_buffer()->size())
return ERR_DNS_MALFORMED_RESPONSE;
// Allocate more space so that DnsResponse::InitParse sanity check passes.
response_.reset(new DnsResponse(response_length_ + 1));
buffer_ = new DrainableIOBuffer(response_->io_buffer(), response_length_);
next_state_ = STATE_READ_RESPONSE;
return OK;
}
int DoReadResponse(int rv) {
DCHECK_EQ(OK, rv);
next_state_ = STATE_READ_RESPONSE_COMPLETE;
return ReadIntoBuffer();
}
int DoReadResponseComplete(int rv) {
DCHECK_NE(ERR_IO_PENDING, rv);
if (rv < 0)
return rv;
if (rv == 0)
return ERR_CONNECTION_CLOSED;
buffer_->DidConsume(rv);
if (buffer_->BytesRemaining() > 0) {
next_state_ = STATE_READ_RESPONSE;
return OK;
}
DCHECK_GT(buffer_->BytesConsumed(), 0);
if (!response_->InitParse(buffer_->BytesConsumed(), *query_))
return ERR_DNS_MALFORMED_RESPONSE;
if (response_->flags() & dns_protocol::kFlagTC)
return ERR_UNEXPECTED;
// TODO(szym): Frankly, none of these are expected.
if (response_->rcode() == dns_protocol::kRcodeNXDOMAIN)
return ERR_NAME_NOT_RESOLVED;
if (response_->rcode() != dns_protocol::kRcodeNOERROR)
return ERR_DNS_SERVER_FAILED;
return OK;
}
void OnIOComplete(int rv) {
rv = DoLoop(rv);
if (rv != ERR_IO_PENDING)
callback_.Run(rv);
}
int ReadIntoBuffer() {
return socket_->Read(
buffer_.get(), buffer_->BytesRemaining(),
base::Bind(&DnsTCPAttempt::OnIOComplete, base::Unretained(this)));
}
State next_state_;
base::TimeTicks start_time_;
std::unique_ptr<StreamSocket> socket_;
std::unique_ptr<DnsQuery> query_;
scoped_refptr<IOBufferWithSize> length_buffer_;
scoped_refptr<DrainableIOBuffer> buffer_;
uint16_t response_length_;
std::unique_ptr<DnsResponse> response_;
CompletionCallback callback_;
DISALLOW_COPY_AND_ASSIGN(DnsTCPAttempt);
};
// ----------------------------------------------------------------------------
// Implements DnsTransaction. Configuration is supplied by DnsSession.
// The suffix list is built according to the DnsConfig from the session.
// The timeout for each DnsUDPAttempt is given by DnsSession::NextTimeout.
// The first server to attempt on each query is given by
// DnsSession::NextFirstServerIndex, and the order is round-robin afterwards.
// Each server is attempted DnsConfig::attempts times.
class DnsTransactionImpl : public DnsTransaction,
public base::SupportsWeakPtr<DnsTransactionImpl> {
public:
DnsTransactionImpl(DnsSession* session,
const std::string& hostname,
uint16_t qtype,
const DnsTransactionFactory::CallbackType& callback,
const NetLogWithSource& net_log,
const OptRecordRdata* opt_rdata)
: session_(session),
hostname_(hostname),
qtype_(qtype),
opt_rdata_(opt_rdata),
callback_(callback),
net_log_(net_log),
qnames_initial_size_(0),
attempts_count_(0),
doh_attempts_(0),
had_tcp_attempt_(false),
doh_attempt_(false),
first_server_index_(0),
request_priority_(DEFAULT_PRIORITY) {
DCHECK(session_.get());
DCHECK(!hostname_.empty());
DCHECK(!callback_.is_null());
DCHECK(!IsIPLiteral(hostname_));
}
~DnsTransactionImpl() override {
DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
if (!callback_.is_null()) {
net_log_.EndEventWithNetErrorCode(NetLogEventType::DNS_TRANSACTION,
ERR_ABORTED);
} // otherwise logged in DoCallback or Start
}
const std::string& GetHostname() const override {
DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
return hostname_;
}
uint16_t GetType() const override {
DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
return qtype_;
}
void Start() override {
DCHECK(!callback_.is_null());
DCHECK(attempts_.empty());
net_log_.BeginEvent(NetLogEventType::DNS_TRANSACTION,
base::Bind(&NetLogStartCallback, &hostname_, qtype_));
AttemptResult result(PrepareSearch(), NULL);
if (result.rv == OK) {
qnames_initial_size_ = qnames_.size();
if (qtype_ == dns_protocol::kTypeA)
UMA_HISTOGRAM_COUNTS_1M("AsyncDNS.SuffixSearchStart", qnames_.size());
result = ProcessAttemptResult(StartQuery());
}
// Must always return result asynchronously, to avoid reentrancy.
if (result.rv != ERR_IO_PENDING) {
base::ThreadTaskRunnerHandle::Get()->PostTask(
FROM_HERE,
base::Bind(&DnsTransactionImpl::DoCallback, AsWeakPtr(), result));
}
}
void SetRequestContext(URLRequestContext* context) override {
url_request_context_ = context;
}
void SetRequestPriority(RequestPriority priority) override {
request_priority_ = priority;
}
private:
// Wrapper for the result of a DnsUDPAttempt.
struct AttemptResult {
AttemptResult(int rv, const DnsAttempt* attempt)
: rv(rv), attempt(attempt) {}
int rv;
const DnsAttempt* attempt;
};
// Prepares |qnames_| according to the DnsConfig.
int PrepareSearch() {
const DnsConfig& config = session_->config();
std::string labeled_hostname;
if (!DNSDomainFromDot(hostname_, &labeled_hostname))
return ERR_INVALID_ARGUMENT;
if (hostname_.back() == '.') {
// It's a fully-qualified name, no suffix search.
qnames_.push_back(labeled_hostname);
return OK;
}
int ndots = CountLabels(labeled_hostname) - 1;
if (ndots > 0 && !config.append_to_multi_label_name) {
qnames_.push_back(labeled_hostname);
return OK;
}
// Set true when |labeled_hostname| is put on the list.
bool had_hostname = false;
if (ndots >= config.ndots) {
qnames_.push_back(labeled_hostname);
had_hostname = true;
}
std::string qname;
for (size_t i = 0; i < config.search.size(); ++i) {
// Ignore invalid (too long) combinations.
if (!DNSDomainFromDot(hostname_ + "." + config.search[i], &qname))
continue;
if (qname.size() == labeled_hostname.size()) {
if (had_hostname)
continue;
had_hostname = true;
}
qnames_.push_back(qname);
}
if (ndots > 0 && !had_hostname)
qnames_.push_back(labeled_hostname);
return qnames_.empty() ? ERR_DNS_SEARCH_EMPTY : OK;
}
void DoCallback(AttemptResult result) {
DCHECK_NE(ERR_IO_PENDING, result.rv);
// TODO(mgersh): consider changing back to a DCHECK once
// https://crbug.com/779589 is fixed.
if (callback_.is_null())
return;
const DnsResponse* response =
result.attempt ? result.attempt->GetResponse() : NULL;
CHECK(result.rv != OK || response != NULL);
timer_.Stop();
RecordLostPacketsIfAny();
if (result.rv == OK)
UMA_HISTOGRAM_COUNTS_1M("AsyncDNS.AttemptCountSuccess", attempts_count_);
else
UMA_HISTOGRAM_COUNTS_1M("AsyncDNS.AttemptCountFail", attempts_count_);
if (response && qtype_ == dns_protocol::kTypeA) {
UMA_HISTOGRAM_COUNTS_1M("AsyncDNS.SuffixSearchRemain", qnames_.size());
UMA_HISTOGRAM_COUNTS_1M("AsyncDNS.SuffixSearchDone",
qnames_initial_size_ - qnames_.size());
}
net_log_.EndEventWithNetErrorCode(NetLogEventType::DNS_TRANSACTION,
result.rv);
base::ResetAndReturn(&callback_).Run(this, result.rv, response);
}
bool IsHostInDnsOverHttpsServerList(const std::string& host) const {
for (const auto& server : session_->config().dns_over_https_servers) {
if (host == server.server.host_piece())
return true;
}
return false;
}
AttemptResult MakeAttempt() {
// Make an HTTP attempt unless we have already made more attempts
// than we have configured servers. Otherwise make a UDP attempt
// as long as we have configured nameservers.
DnsConfig config = session_->config();
if (doh_attempts_ < config.dns_over_https_servers.size())
return MakeHTTPAttempt(config.dns_over_https_servers);
DCHECK_GT(config.nameservers.size(), 0u);
return MakeUDPAttempt();
}
// Makes another attempt at the current name, |qnames_.front()|, using the
// next nameserver.
AttemptResult MakeUDPAttempt() {
doh_attempt_ = false;
unsigned attempt_number = attempts_.size();
uint16_t id = session_->NextQueryId();
std::unique_ptr<DnsQuery> query;
if (attempts_.empty()) {
query.reset(new DnsQuery(id, qnames_.front(), qtype_, opt_rdata_));
} else {
query = attempts_[0]->GetQuery()->CloneWithNewId(id);
}
const DnsConfig& config = session_->config();
unsigned non_doh_server_index =
(first_server_index_ + attempt_number - doh_attempts_) %
config.nameservers.size();
// Skip over known failed servers.
non_doh_server_index = session_->NextGoodServerIndex(non_doh_server_index);
std::unique_ptr<DnsSession::SocketLease> lease =
session_->AllocateSocket(non_doh_server_index, net_log_.source());
bool got_socket = !!lease.get();
DnsUDPAttempt* attempt = new DnsUDPAttempt(
non_doh_server_index, std::move(lease), std::move(query));
attempts_.push_back(base::WrapUnique(attempt));
++attempts_count_;
if (!got_socket)
return AttemptResult(ERR_CONNECTION_REFUSED, NULL);
net_log_.AddEvent(
NetLogEventType::DNS_TRANSACTION_ATTEMPT,
attempt->GetSocketNetLog().source().ToEventParametersCallback());
int rv = attempt->Start(base::Bind(
&DnsTransactionImpl::OnUdpAttemptComplete, base::Unretained(this),
attempt_number, base::TimeTicks::Now()));
if (rv == ERR_IO_PENDING) {
base::TimeDelta timeout =
session_->NextTimeout(non_doh_server_index, attempt_number);
timer_.Start(FROM_HERE, timeout, this, &DnsTransactionImpl::OnTimeout);
}
return AttemptResult(rv, attempt);
}
AttemptResult MakeHTTPAttempt(
const std::vector<DnsConfig::DnsOverHttpsServerConfig>& servers) {
doh_attempt_ = true;
unsigned attempt_number = attempts_.size();
uint16_t id = session_->NextQueryId();
std::unique_ptr<DnsQuery> query;
if (attempts_.empty()) {
query.reset(new DnsQuery(id, qnames_.front(), qtype_, opt_rdata_));
} else {
query = attempts_[0]->GetQuery()->CloneWithNewId(id);
}
// doh_attempts_ counts the number of attempts made via HTTPS. To
// get a server index cap that by the number of DoH servers we
// have configured and then offset it by the number of non-doh
// servers we have configured since they come first in the server
// stats list.
unsigned server_index = session_->NextGoodDnsOverHttpsServerIndex(
(doh_attempts_ % session_->config().dns_over_https_servers.size()) +
session_->config().nameservers.size());
attempts_.push_back(std::make_unique<DnsHTTPAttempt>(
server_index, std::move(query),
servers[server_index - session_->config().nameservers.size()].server,
servers[server_index - session_->config().nameservers.size()].use_post,
url_request_context_, request_priority_));
++doh_attempts_;
++attempts_count_;
// Check that we're not looking one of the DNS over HTTPS servers.
if (IsHostInDnsOverHttpsServerList(DNSDomainToString(qnames_.front()))) {
static_cast<DnsHTTPAttempt*>(attempts_.back().get())->Cancel();
return AttemptResult(ERR_CONNECTION_REFUSED, attempts_.back().get());
}
int rv = attempts_.back()->Start(
base::Bind(&DnsTransactionImpl::OnAttemptComplete,
base::Unretained(this), attempt_number));
return AttemptResult(rv, attempts_.back().get());
}
AttemptResult MakeTCPAttempt(const DnsAttempt* previous_attempt) {
DCHECK(previous_attempt);
DCHECK(!had_tcp_attempt_);
unsigned server_index = previous_attempt->server_index();
std::unique_ptr<StreamSocket> socket(
session_->CreateTCPSocket(server_index, net_log_.source()));
// TODO(szym): Reuse the same id to help the server?
uint16_t id = session_->NextQueryId();
std::unique_ptr<DnsQuery> query =
previous_attempt->GetQuery()->CloneWithNewId(id);
RecordLostPacketsIfAny();
// Cancel all other attempts that have not received a response, no point
// waiting on them.
for (auto it = attempts_.begin(); it != attempts_.end();) {
if (!(*it)->is_completed())
it = attempts_.erase(it);
else
++it;
}
unsigned attempt_number = attempts_.size();
DnsTCPAttempt* attempt =
new DnsTCPAttempt(server_index, std::move(socket), std::move(query));
attempts_.push_back(base::WrapUnique(attempt));
++attempts_count_;
had_tcp_attempt_ = true;
net_log_.AddEvent(
NetLogEventType::DNS_TRANSACTION_TCP_ATTEMPT,
attempt->GetSocketNetLog().source().ToEventParametersCallback());
int rv = attempt->Start(base::Bind(&DnsTransactionImpl::OnAttemptComplete,
base::Unretained(this), attempt_number));
if (rv == ERR_IO_PENDING) {
// Custom timeout for TCP attempt.
base::TimeDelta timeout = timer_.GetCurrentDelay() * 2;
timer_.Start(FROM_HERE, timeout, this, &DnsTransactionImpl::OnTimeout);
}
return AttemptResult(rv, attempt);
}
// Begins query for the current name. Makes the first attempt.
AttemptResult StartQuery() {
std::string dotted_qname = DNSDomainToString(qnames_.front());
net_log_.BeginEvent(NetLogEventType::DNS_TRANSACTION_QUERY,
NetLog::StringCallback("qname", &dotted_qname));
first_server_index_ = session_->config().nameservers.empty()
? 0
: session_->NextFirstServerIndex();
RecordLostPacketsIfAny();
attempts_.clear();
had_tcp_attempt_ = false;
return MakeAttempt();
}
void OnUdpAttemptComplete(unsigned attempt_number,
base::TimeTicks start,
int rv) {
DCHECK_LT(attempt_number, attempts_.size());
const DnsAttempt* attempt = attempts_[attempt_number].get();
if (attempt->GetResponse()) {
session_->RecordRTT(attempt->server_index(),
base::TimeTicks::Now() - start);
}
OnAttemptComplete(attempt_number, rv);
}
void OnAttemptComplete(unsigned attempt_number, int rv) {
if (callback_.is_null())
return;
DCHECK_LT(attempt_number, attempts_.size());
const DnsAttempt* attempt = attempts_[attempt_number].get();
AttemptResult result = ProcessAttemptResult(AttemptResult(rv, attempt));
if (result.rv != ERR_IO_PENDING)
DoCallback(result);
}
// Record packet loss for any incomplete attempts.
void RecordLostPacketsIfAny() {
// Loop through attempts until we find first that is completed
size_t first_completed = 0;
for (first_completed = 0; first_completed < attempts_.size();
++first_completed) {
if (attempts_[first_completed]->is_completed())
break;
}
// If there were no completed attempts, then we must be offline, so don't
// record any attempts as lost packets.
if (first_completed == attempts_.size())
return;
size_t num_servers = session_->config().nameservers.size() +
session_->config().dns_over_https_servers.size();
std::vector<int> server_attempts(num_servers);
for (size_t i = 0; i < first_completed; ++i) {
unsigned server_index = attempts_[i]->server_index();
int server_attempt = server_attempts[server_index]++;
// Don't record lost packet unless attempt is in pending state.
if (!attempts_[i]->is_pending())
continue;
session_->RecordLostPacket(server_index, server_attempt);
}
}
void LogResponse(const DnsAttempt* attempt) {
if (attempt && attempt->GetResponse()) {
net_log_.AddEvent(NetLogEventType::DNS_TRANSACTION_RESPONSE,
base::Bind(&DnsAttempt::NetLogResponseCallback,
base::Unretained(attempt)));
}
}
bool MoreAttemptsAllowed() const {
if (had_tcp_attempt_)
return false;
const DnsConfig& config = session_->config();
return attempts_.size() < config.attempts * config.nameservers.size() +
config.dns_over_https_servers.size();
}
// Resolves the result of a DnsAttempt until a terminal result is reached
// or it will complete asynchronously (ERR_IO_PENDING).
AttemptResult ProcessAttemptResult(AttemptResult result) {
while (result.rv != ERR_IO_PENDING) {
LogResponse(result.attempt);
switch (result.rv) {
case OK:
if (!doh_attempt_)
session_->RecordServerSuccess(result.attempt->server_index());
net_log_.EndEventWithNetErrorCode(
NetLogEventType::DNS_TRANSACTION_QUERY, result.rv);
DCHECK(result.attempt);
DCHECK(result.attempt->GetResponse());
return result;
case ERR_NAME_NOT_RESOLVED:
session_->RecordServerSuccess(result.attempt->server_index());
net_log_.EndEventWithNetErrorCode(
NetLogEventType::DNS_TRANSACTION_QUERY, result.rv);
// Try next suffix. Check that qnames_ isn't already empty first,
// which can happen when there are two attempts running at once.
// TODO(mgersh): remove this workaround for https://crbug.com/774846
// when https://crbug.com/779589 is fixed.
if (!qnames_.empty())
qnames_.pop_front();
if (qnames_.empty()) {
return AttemptResult(ERR_NAME_NOT_RESOLVED, NULL);
} else {
result = StartQuery();
}
break;
case ERR_CONNECTION_REFUSED:
case ERR_DNS_TIMED_OUT:
if (result.attempt)
session_->RecordServerFailure(result.attempt->server_index());
if (MoreAttemptsAllowed()) {
result = MakeAttempt();
} else {
return result;
}
break;
case ERR_DNS_SERVER_REQUIRES_TCP:
result = MakeTCPAttempt(result.attempt);
break;
default:
// Server failure.
DCHECK(result.attempt);
if (result.attempt != attempts_.back().get()) {
// This attempt already timed out. Ignore it.
session_->RecordServerFailure(result.attempt->server_index());
return AttemptResult(ERR_IO_PENDING, NULL);
}
if (MoreAttemptsAllowed()) {
result = MakeAttempt();
} else if (result.rv == ERR_DNS_MALFORMED_RESPONSE &&
!had_tcp_attempt_ && !doh_attempt_) {
// For UDP only, ignore the response and wait until the last
// attempt times out.
return AttemptResult(ERR_IO_PENDING, NULL);
} else {
return AttemptResult(result.rv, NULL);
}
break;
}
}
return result;
}
void OnTimeout() {
if (callback_.is_null())
return;
DCHECK(!attempts_.empty());
AttemptResult result = ProcessAttemptResult(
AttemptResult(ERR_DNS_TIMED_OUT, attempts_.back().get()));
if (result.rv != ERR_IO_PENDING)
DoCallback(result);
}
scoped_refptr<DnsSession> session_;
std::string hostname_;
uint16_t qtype_;
const OptRecordRdata* opt_rdata_;
// Cleared in DoCallback.
DnsTransactionFactory::CallbackType callback_;
NetLogWithSource net_log_;
// Search list of fully-qualified DNS names to query next (in DNS format).
base::circular_deque<std::string> qnames_;
size_t qnames_initial_size_;
// List of attempts for the current name.
std::vector<std::unique_ptr<DnsAttempt>> attempts_;
// Count of attempts, not reset when |attempts_| vector is cleared.
int attempts_count_;
uint16_t doh_attempts_;
bool had_tcp_attempt_;
bool doh_attempt_;
// Index of the first server to try on each search query.
int first_server_index_;
base::OneShotTimer timer_;
URLRequestContext* url_request_context_;
RequestPriority request_priority_;
THREAD_CHECKER(thread_checker_);
DISALLOW_COPY_AND_ASSIGN(DnsTransactionImpl);
};
// ----------------------------------------------------------------------------
// Implementation of DnsTransactionFactory that returns instances of
// DnsTransactionImpl.
class DnsTransactionFactoryImpl : public DnsTransactionFactory {
public:
explicit DnsTransactionFactoryImpl(DnsSession* session) {
session_ = session;
}
std::unique_ptr<DnsTransaction> CreateTransaction(
const std::string& hostname,
uint16_t qtype,
const CallbackType& callback,
const NetLogWithSource& net_log) override {
return std::unique_ptr<DnsTransaction>(new DnsTransactionImpl(
session_.get(), hostname, qtype, callback, net_log, opt_rdata_.get()));
}
void AddEDNSOption(const OptRecordRdata::Opt& opt) override {
if (opt_rdata_ == nullptr)
opt_rdata_ = std::make_unique<OptRecordRdata>();
opt_rdata_->AddOpt(opt);
}
private:
scoped_refptr<DnsSession> session_;
std::unique_ptr<OptRecordRdata> opt_rdata_;
};
} // namespace
// static
std::unique_ptr<DnsTransactionFactory> DnsTransactionFactory::CreateFactory(
DnsSession* session) {
return std::unique_ptr<DnsTransactionFactory>(
new DnsTransactionFactoryImpl(session));
}
} // namespace net