[net/dns] Add test DualFamilyLocalhost and fix it when DnsClient enabled.

On some platforms, listening on "localhost" binds to the IPv6 loopback
(::1), even if there's no global IPv6 connectivity. In such situations,
HostResolverImpl restricts lookups to IPv4 (AF_INET) for performance
reasons, but then navigating to http://localhost results in "connection
refused".

HostResolverProc has a workaround for this situation. This CL adds a
test for this behavior and replicates the workaround in
HostResolverImpl::ServeFromHosts (for the built-in asynchronous DNS).

BUG=224215

Review URL: https://codereview.chromium.org/14208010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@194663 0039d316-1c4b-4281-b951-d872f2087c98

net/dns/host_resolver_impl.cc

@@ -250,6 +250,25 @@ AddressList EnsurePortOnAddressList(const AddressList& list, uint16 port) {
   return AddressList::CopyWithPort(list, port);
 }
 
+// Returns true if |addresses| contains only IPv4 loopback addresses.
+bool IsAllIPv4Loopback(const AddressList& addresses) {
+  for (unsigned i = 0; i < addresses.size(); ++i) {
+    const IPAddressNumber& address = addresses[i].address();
+    switch (addresses[i].GetFamily()) {
+      case ADDRESS_FAMILY_IPV4:
+        if (address[0] != 127)
+          return false;
+        break;
+      case ADDRESS_FAMILY_IPV6:
+        return false;
+      default:
+        NOTREACHED();
+        return false;
+    }
+  }
+  return true;
+}
+
 // Creates NetLog parameters when the resolve failed.
 base::Value* NetLogProcTaskFailedCallback(uint32 attempt_number,
                                           int net_error,
@@ -1950,7 +1969,6 @@ bool HostResolverImpl::ServeFromHosts(const Key& key,
   DCHECK(addresses);
   if (!HaveDnsConfig())
     return false;
-
   addresses->clear();
 
   // HOSTS lookups are case-insensitive.
@@ -1979,6 +1997,17 @@ bool HostResolverImpl::ServeFromHosts(const Key& key,
       addresses->push_back(IPEndPoint(it->second, info.port()));
   }
 
+  // If got only loopback addresses and the family was restricted, resolve
+  // again, without restrictions. See SystemHostResolverCall for rationale.
+  if ((key.host_resolver_flags &
+          HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6) &&
+      IsAllIPv4Loopback(*addresses)) {
+    Key new_key(key);
+    new_key.address_family = ADDRESS_FAMILY_UNSPECIFIED;
+    new_key.host_resolver_flags &=
+        ~HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6;
+    return ServeFromHosts(new_key, info, addresses);
+  }
   return !addresses->empty();
 }
 
@@ -2118,6 +2147,7 @@ void HostResolverImpl::OnIPAddressChanged() {
 void HostResolverImpl::OnDNSChanged() {
   DnsConfig dns_config;
   NetworkChangeNotifier::GetDnsConfig(&dns_config);
+
   if (net_log_) {
     net_log_->AddGlobalEntry(
         NetLog::TYPE_DNS_CONFIG_CHANGED,

net/dns/host_resolver_impl_unittest.cc

@@ -177,6 +177,16 @@ class MockHostResolverProc : public HostResolverProc {
   DISALLOW_COPY_AND_ASSIGN(MockHostResolverProc);
 };
 
+bool AddressListContains(const AddressList& list, const std::string& address,
+                         int port) {
+  IPAddressNumber ip;
+  bool rv = ParseIPLiteralToNumber(address, &ip);
+  DCHECK(rv);
+  return std::find(list.begin(),
+                   list.end(),
+                   IPEndPoint(ip, port)) != list.end();
+}
+
 // A wrapper for requests to a HostResolver.
 class Request {
  public:
@@ -231,12 +241,7 @@ class Request {
   bool pending() const { return handle_ != NULL; }
 
   bool HasAddress(const std::string& address, int port) const {
-    IPAddressNumber ip;
-    bool rv = ParseIPLiteralToNumber(address, &ip);
-    DCHECK(rv);
-    return std::find(list_.begin(),
-                     list_.end(),
-                     IPEndPoint(ip, port)) != list_.end();
+    return AddressListContains(list_, address, port);
   }
 
   // Returns the number of addresses in |list_|.
@@ -1482,4 +1487,67 @@ TEST_F(HostResolverImplDnsTest, DontDisableDnsClientOnSporadicFailure) {
   EXPECT_EQ(OK, req->WaitForResult());
 }
 
+// Confirm that resolving "localhost" is unrestricted even if there are no
+// global IPv6 address. See SystemHostResolverCall for rationale.
+// Test both the DnsClient and system host resolver paths.
+TEST_F(HostResolverImplDnsTest, DualFamilyLocalhost) {
+  // Use regular SystemHostResolverCall!
+  scoped_refptr<HostResolverProc> proc(new SystemHostResolverProc());
+  resolver_.reset(new HostResolverImpl(HostCache::CreateDefaultCache(),
+                                       DefaultLimits(),
+                                       DefaultParams(proc),
+                                       NULL));
+  resolver_->SetDnsClient(CreateMockDnsClient(DnsConfig(), dns_rules_));
+  resolver_->SetDefaultAddressFamily(ADDRESS_FAMILY_IPV4);
+
+  // Get the expected output.
+  AddressList addrlist;
+  int rv = proc->Resolve("localhost", ADDRESS_FAMILY_UNSPECIFIED, 0, &addrlist,
+                         NULL);
+  if (rv != OK)
+    return;
+
+  for (unsigned i = 0; i < addrlist.size(); ++i)
+    LOG(WARNING) << addrlist[i].ToString();
+
+  bool saw_ipv4 = AddressListContains(addrlist, "127.0.0.1", 0);
+  bool saw_ipv6 = AddressListContains(addrlist, "::1", 0);
+  if (!saw_ipv4 && !saw_ipv6)
+    return;
+
+  HostResolver::RequestInfo info(HostPortPair("localhost", 80));
+  info.set_address_family(ADDRESS_FAMILY_UNSPECIFIED);
+  info.set_host_resolver_flags(HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6);
+
+  // Try without DnsClient.
+  ChangeDnsConfig(DnsConfig());
+  Request* req = CreateRequest(info);
+  // It is resolved via getaddrinfo, so expect asynchronous result.
+  EXPECT_EQ(ERR_IO_PENDING, req->Resolve());
+  EXPECT_EQ(OK, req->WaitForResult());
+
+  EXPECT_EQ(saw_ipv4, req->HasAddress("127.0.0.1", 80));
+  EXPECT_EQ(saw_ipv6, req->HasAddress("::1", 80));
+
+  // Configure DnsClient with dual-host HOSTS file.
+  DnsConfig config = CreateValidDnsConfig();
+  DnsHosts hosts;
+  IPAddressNumber local_ipv4, local_ipv6;
+  ASSERT_TRUE(ParseIPLiteralToNumber("127.0.0.1", &local_ipv4));
+  ASSERT_TRUE(ParseIPLiteralToNumber("::1", &local_ipv6));
+  if (saw_ipv4)
+    hosts[DnsHostsKey("localhost", ADDRESS_FAMILY_IPV4)] = local_ipv4;
+  if (saw_ipv6)
+    hosts[DnsHostsKey("localhost", ADDRESS_FAMILY_IPV6)] = local_ipv6;
+  config.hosts = hosts;
+
+  ChangeDnsConfig(config);
+  req = CreateRequest(info);
+  // Expect synchronous resolution from DnsHosts.
+  EXPECT_EQ(OK, req->Resolve());
+
+  EXPECT_EQ(saw_ipv4, req->HasAddress("127.0.0.1", 80));
+  EXPECT_EQ(saw_ipv6, req->HasAddress("::1", 80));
+}
+
 }  // namespace net

net/dns/host_resolver_proc.h

@@ -92,7 +92,7 @@ NET_EXPORT_PRIVATE int SystemHostResolverCall(
     int* os_error);
 
 // Wraps call to SystemHostResolverCall as an instance of HostResolverProc.
-class SystemHostResolverProc : public HostResolverProc {
+class NET_EXPORT_PRIVATE SystemHostResolverProc : public HostResolverProc {
  public:
   SystemHostResolverProc();
   virtual int Resolve(const std::string& hostname,