Disable async DNS if VPN is present on L and earlier

The DnsConfigService can't get a correct DNS config for a VPN until
Android M. On earlier versions, check for a VPN and treat it as a config
read failure.

Bug: 805020
Change-Id: I696c52a2e012460ddd70381e5278c3abca9ca665
Reviewed-on: https://chromium-review.googlesource.com/894149Reviewed-by: Paul Jensen <pauljensen@chromium.org>
Commit-Queue: Miriam Gershenson <mgersh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533287}

net/base/address_tracker_linux.cc

@@ -437,9 +437,14 @@ void AddressTrackerLinux::CloseSocket() {
 }
 
 bool AddressTrackerLinux::IsTunnelInterface(int interface_index) const {
-  // Linux kernel drivers/net/tun.c uses "tun" name prefix.
   char buf[IFNAMSIZ] = {0};
-  return strncmp(get_interface_name_(interface_index, buf), "tun", 3) == 0;
+  return IsTunnelInterfaceName(get_interface_name_(interface_index, buf));
+}
+
+// static
+bool AddressTrackerLinux::IsTunnelInterfaceName(const char* name) {
+  // Linux kernel drivers/net/tun.c uses "tun" name prefix.
+  return strncmp(name, "tun", 3) == 0;
 }
 
 void AddressTrackerLinux::UpdateCurrentConnectionType() {

net/base/address_tracker_linux.h

@@ -82,6 +82,9 @@ class NET_EXPORT_PRIVATE AddressTrackerLinux :
   // with exclusively talking to the kernel and not the C library.
   static char* GetInterfaceName(int interface_index, char* buf);
 
+  // Does |name| refer to a tunnel interface?
+  static bool IsTunnelInterfaceName(const char* name);
+
  private:
   friend class AddressTrackerLinuxTest;
 

net/base/address_tracker_linux_unittest.cc

@@ -736,6 +736,11 @@ TEST_F(AddressTrackerLinuxTest, BroadcastInit) {
   runner2.VerifyCompletes();
 }
 
+TEST_F(AddressTrackerLinuxTest, TunnelInterfaceName) {
+  EXPECT_TRUE(AddressTrackerLinux::IsTunnelInterfaceName("tun0"));
+  EXPECT_FALSE(AddressTrackerLinux::IsTunnelInterfaceName("wlan0"));
+}
+
 }  // namespace
 
 }  // namespace internal

net/dns/dns_config_service_posix.cc

@@ -35,7 +35,9 @@
 #include <sys/system_properties.h>
 #include "base/android/build_info.h"
 #include "net/android/network_library.h"
+#include "net/base/address_tracker_linux.h"
 #include "net/base/network_change_notifier.h"
+#include "net/base/network_interfaces.h"
 #endif
 
 namespace net {
@@ -118,6 +120,20 @@ class DnsConfigWatcher {
 };
 #endif  // defined(OS_IOS)
 
+#if defined(OS_ANDROID)
+bool IsVpnPresent() {
+  NetworkInterfaceList networks;
+  if (!GetNetworkList(&networks, INCLUDE_HOST_SCOPE_VIRTUAL_INTERFACES))
+    return false;
+
+  for (NetworkInterface network : networks) {
+    if (AddressTrackerLinux::IsTunnelInterfaceName(network.name.c_str()))
+      return true;
+  }
+  return false;
+}
+#endif  // defined(OS_ANDROID)
+
 ConfigParsePosixResult ReadDnsConfig(DnsConfig* dns_config) {
   base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
 #if !defined(OS_ANDROID)
@@ -184,6 +200,11 @@ ConfigParsePosixResult ReadDnsConfig(DnsConfig* dns_config) {
     return CONFIG_PARSE_POSIX_OK;
   }
 
+  if (IsVpnPresent()) {
+    dns_config->unhandled_options = true;
+    return CONFIG_PARSE_POSIX_UNHANDLED_OPTIONS;
+  }
+
   char property_value[PROP_VALUE_MAX];
   __system_property_get("net.dns1", property_value);
   std::string dns1_string = property_value;