network_diagnostics: Add fake host resolver

Introduce the fake host resolver class, used by unit tests, to avoid
duplication across multiple routines.

BUG=chromium:956783
TEST=none

Change-Id: I4a5e9b6f07de4b55a07e54cd46c8e879c3df080e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2434555Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Kartik Hegde <khegde@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811918}

chrome/browser/chromeos/BUILD.gn

@@ -3413,6 +3413,8 @@ source_set("unit_tests") {
     "net/network_diagnostics/dns_latency_routine_unittest.cc",
     "net/network_diagnostics/dns_resolution_routine_unittest.cc",
     "net/network_diagnostics/dns_resolver_present_routine_unittest.cc",
+    "net/network_diagnostics/fake_host_resolver.cc",
+    "net/network_diagnostics/fake_host_resolver.h",
     "net/network_diagnostics/gateway_can_be_pinged_routine_unittest.cc",
     "net/network_diagnostics/has_secure_wifi_connection_routine_unittest.cc",
     "net/network_diagnostics/http_firewall_routine_unittest.cc",

chrome/browser/chromeos/net/network_diagnostics/fake_host_resolver.cc

+// Copyright 2020 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 "chrome/browser/chromeos/net/network_diagnostics/fake_host_resolver.h"
+
+#include <cstdint>
+#include <utility>
+
+#include "base/logging.h"
+#include "base/notreached.h"
+#include "base/optional.h"
+#include "mojo/public/cpp/bindings/remote.h"
+#include "net/base/address_list.h"
+#include "net/dns/public/resolve_error_info.h"
+
+namespace chromeos {
+namespace network_diagnostics {
+
+FakeHostResolver::DnsResult::DnsResult(
+    int32_t result,
+    net::ResolveErrorInfo resolve_error_info,
+    base::Optional<net::AddressList> resolved_addresses)
+    : result_(result),
+      resolve_error_info_(resolve_error_info),
+      resolved_addresses_(resolved_addresses) {}
+
+FakeHostResolver::DnsResult::~DnsResult() = default;
+
+FakeHostResolver::FakeHostResolver(
+    mojo::PendingReceiver<network::mojom::HostResolver> receiver)
+    : receiver_(this, std::move(receiver)) {}
+
+FakeHostResolver::~FakeHostResolver() = default;
+
+void FakeHostResolver::ResolveHost(
+    const net::HostPortPair& host,
+    const net::NetworkIsolationKey& network_isolation_key,
+    network::mojom::ResolveHostParametersPtr optional_parameters,
+    mojo::PendingRemote<network::mojom::ResolveHostClient>
+        pending_response_client) {
+  mojo::Remote<network::mojom::ResolveHostClient> response_client(
+      std::move(pending_response_client));
+  DnsResult* result = fake_dns_results_.front();
+  DCHECK(result);
+  fake_dns_results_.pop_front();
+  response_client->OnComplete(result->result_, result->resolve_error_info_,
+                              result->resolved_addresses_);
+}
+
+void FakeHostResolver::MdnsListen(
+    const net::HostPortPair& host,
+    net::DnsQueryType query_type,
+    mojo::PendingRemote<network::mojom::MdnsListenClient> response_client,
+    MdnsListenCallback callback) {
+  NOTIMPLEMENTED();
+}
+
+}  // namespace network_diagnostics
+}  // namespace chromeos

chrome/browser/chromeos/net/network_diagnostics/fake_host_resolver.h

+// Copyright 2020 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_NET_NETWORK_DIAGNOSTICS_FAKE_HOST_RESOLVER_H_
+#define CHROME_BROWSER_CHROMEOS_NET_NETWORK_DIAGNOSTICS_FAKE_HOST_RESOLVER_H_
+
+#include <deque>
+
+#include "base/optional.h"
+#include "mojo/public/cpp/bindings/pending_receiver.h"
+#include "mojo/public/cpp/bindings/receiver.h"
+#include "net/base/address_list.h"
+#include "net/dns/public/resolve_error_info.h"
+#include "services/network/public/mojom/host_resolver.mojom.h"
+
+namespace chromeos {
+namespace network_diagnostics {
+
+// Used in unit tests, the FakeHostResolver class simulates the behavior of a
+// host resolver.
+class FakeHostResolver : public network::mojom::HostResolver {
+ public:
+  struct DnsResult {
+   public:
+    DnsResult(int32_t result,
+              net::ResolveErrorInfo resolve_error_info,
+              base::Optional<net::AddressList> resolved_addresses);
+    ~DnsResult();
+
+    int result_;
+    net::ResolveErrorInfo resolve_error_info_;
+    base::Optional<net::AddressList> resolved_addresses_;
+  };
+
+  FakeHostResolver(
+      mojo::PendingReceiver<network::mojom::HostResolver> receiver);
+  ~FakeHostResolver() override;
+
+  // network::mojom::HostResolver
+  void ResolveHost(const net::HostPortPair& host,
+                   const net::NetworkIsolationKey& network_isolation_key,
+                   network::mojom::ResolveHostParametersPtr optional_parameters,
+                   mojo::PendingRemote<network::mojom::ResolveHostClient>
+                       pending_response_client) override;
+  void MdnsListen(
+      const net::HostPortPair& host,
+      net::DnsQueryType query_type,
+      mojo::PendingRemote<network::mojom::MdnsListenClient> response_client,
+      MdnsListenCallback callback) override;
+
+  // Sets the fake dns results.
+  void set_fake_dns_results(std::deque<DnsResult*> fake_dns_results) {
+    fake_dns_results_ = std::move(fake_dns_results);
+  }
+
+ private:
+  mojo::Receiver<network::mojom::HostResolver> receiver_;
+  // Use the list of fake dns results to fake different responses for multiple
+  // calls to the host_resolver's ResolveHost().
+  std::deque<DnsResult*> fake_dns_results_;
+};
+
+}  // namespace network_diagnostics
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_NET_NETWORK_DIAGNOSTICS_FAKE_HOST_RESOLVER_H_