[net/dns] When testing for IPv6, discard link local and Teredo addresses (measurement)

net/dns/host_resolver_impl.cc

 // 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/host_resolver_impl.h"
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
 #elif defined(OS_POSIX)
 #include <netdb.h>
@@ skipping 152 matching lines @@
   if (hostname[hostname.size() - 1] == '.') {
     return hostname.size() > kSuffixLen &&
         !hostname.compare(hostname.size() - kSuffixLen, kSuffixLen, kSuffix);
   }
   return hostname.size() > kSuffixLenTrimmed &&
       !hostname.compare(hostname.size() - kSuffixLenTrimmed, kSuffixLenTrimmed,
                         kSuffix, kSuffixLenTrimmed);
 }
 
 // Attempts to connect a UDP socket to |dest|:80.
-int AttemptRoute(const IPAddressNumber& dest) {
+bool AttemptRoute(const IPAddressNumber& dest) {
   scoped_ptr<DatagramClientSocket> socket(
       ClientSocketFactory::GetDefaultFactory()->CreateDatagramClientSocket(
           DatagramSocket::DEFAULT_BIND,
           RandIntCallback(),
           NULL,
           NetLog::Source()));
-  return socket->Connect(IPEndPoint(dest, 80));
+  int rv = socket->Connect(IPEndPoint(dest, 80));
+  if (rv != OK)
+    return false;
+  IPEndPoint endpoint;
+  rv = socket->GetLocalAddress(&endpoint);
+  if (rv != OK)
+    return false;
+  if (endpoint.GetFamily() == ADDRESS_FAMILY_IPV6) {

[mmenke, 2013/04/12 17:34:25]

Is there any case this won't be the case?  I wouldn't think so, so could also
add a DCHECK.

[szym, 2013/04/12 17:35:52]

I was considering calling AttemptRoute("8.8.8.8") to check if we need to fetch A
records.

For now I'll replace the |if| with a DCHECK.

+    const IPAddressNumber& address = endpoint.address();
+    bool is_link_local = (address[0] == 0xFE) && ((address[1] & 0xC0) == 0x80);
+    if (is_link_local)
+      return false;
+    const uint8 kTeredoPrefix[] = { 0x20, 0x01, 0, 0 };
+    bool is_teredo = std::equal(kTeredoPrefix,
+                                kTeredoPrefix + arraysize(kTeredoPrefix),
+                                address.begin());
+    if (is_teredo)
+      return false;
+  }
+  return true;
 }
 
 // Provide a common macro to simplify code and readability. We must use a
 // macro as the underlying HISTOGRAM macro creates static variables.
 #define DNS_HISTOGRAM(name, time) UMA_HISTOGRAM_CUSTOM_TIMES(name, time, \
     base::TimeDelta::FromMilliseconds(1), base::TimeDelta::FromHours(1), 100)
 
 // A macro to simplify code and readability.
 #define DNS_HISTOGRAM_BY_PRIORITY(basename, priority, time) \
   do { \
@@ skipping 1835 matching lines @@
   HostResolverFlags effective_flags =
       info.host_resolver_flags() | additional_resolver_flags_;
   AddressFamily effective_address_family = info.address_family();
 
   if (info.address_family() == ADDRESS_FAMILY_UNSPECIFIED) {
     base::TimeTicks start_time = base::TimeTicks::Now();
     // Google DNS address.
     const uint8 kIPv6Address[] =
         { 0x20, 0x01, 0x48, 0x60, 0x48, 0x60, 0x00, 0x00,
           0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x88, 0x88 };
-    int rv6 = AttemptRoute(
+    bool rv6 = AttemptRoute(
         IPAddressNumber(kIPv6Address, kIPv6Address + arraysize(kIPv6Address)));
 
     UMA_HISTOGRAM_TIMES("Net.IPv6ConnectDuration",
                         base::TimeTicks::Now() - start_time);
-    if (rv6 == OK) {
+    if (rv6) {
       UMA_HISTOGRAM_BOOLEAN("Net.IPv6ConnectSuccessMatch",
           default_address_family_ == ADDRESS_FAMILY_UNSPECIFIED);
     } else {
       UMA_HISTOGRAM_BOOLEAN("Net.IPv6ConnectFailureMatch",
           default_address_family_ != ADDRESS_FAMILY_UNSPECIFIED);
     }
   }
 
   if (effective_address_family == ADDRESS_FAMILY_UNSPECIFIED &&
       default_address_family_ != ADDRESS_FAMILY_UNSPECIFIED) {
@@ skipping 149 matching lines @@
   }
   DnsConfig dns_config;
   NetworkChangeNotifier::GetDnsConfig(&dns_config);
   dns_client_->SetConfig(dns_config);
   num_dns_failures_ = 0;
   if (dns_config.IsValid())
     UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", true);
 }
 
 }  // namespace net