[net/dns] Resolve AF_UNSPEC on dual-stacked systems. Sort addresses according to RFC3484.

net/dns/address_sorter_win.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/address_sorter.h"
+
+#include <winsock2.h>
+
+#include <algorithm>
+
+#include "base/logging.h"
+#include "base/win/windows_version.h"
+#include "net/base/address_list.h"
+#include "net/base/ip_endpoint.h"
+#include "net/base/winsock_init.h"
+
+namespace net {
+
+namespace {
+
+// If |ipe| has IPv4-mapped IPv6 address, converts it to IPv4.

[mmenke, 2012/07/30 15:37:00]

nit:  "and leaves all other addresses unmodified."

+void ConvertIPv4MappedToIPv4(IPEndPoint* ipe) {

[mmenke, 2012/07/30 15:37:00]

May want to put this in net_util.cc.  I don't see it being needed elsewhere, but
if it is, nice to have it easy to find.

+  DCHECK_EQ(AF_INET6, ipe->GetFamily());
+  const IPAddressNumber& address = ipe->address();
+  const unsigned char prefix[] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF };
+  if (std::equal(address.begin(), address.begin() + arraysize(prefix),
+                 prefix)) {
+    *ipe = IPEndPoint(
+        IPAddressNumber(address.begin() + arraysize(prefix), address.end()),
+        ipe->port());
+  }
+}
+
+class AddressSorterWin : public AddressSorter {
+ public:
+  AddressSorterWin() : socket_(INVALID_SOCKET) {
+    EnsureWinsockInit();
+    socket_ = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+    DCHECK_NE(INVALID_SOCKET, socket_);
+  }
+
+  virtual ~AddressSorterWin() {
+    closesocket(socket_);
+  }
+
+  virtual bool Sort(AddressList* list) const OVERRIDE {
+    size_t heap_size = sizeof(SOCKET_ADDRESS_LIST) +
+        list->size() * (sizeof(SOCKET_ADDRESS) + sizeof(SOCKADDR_STORAGE));
+    scoped_ptr_malloc<SOCKET_ADDRESS_LIST> heap_in(
+        reinterpret_cast<SOCKET_ADDRESS_LIST*>(malloc(heap_size)));
+
+    SOCKET_ADDRESS_LIST* sort_list = heap_in.get();
+    sort_list->iAddressCount = list->size();
+    SOCKADDR_STORAGE* storage = reinterpret_cast<SOCKADDR_STORAGE*>(
+        sort_list->Address + sort_list->iAddressCount);
+
+    for (size_t i = 0; i < list->size(); ++i) {
+      IPEndPoint& ipe = (*list)[i];
+      // Addresses must be sockaddr_in6.
+      if (ipe.GetFamily() == AF_INET) {
+        ipe = IPEndPoint(ConvertIPv4NumberToIPv6Number(ipe.address()),
+                         ipe.port());
+      }
+
+      struct sockaddr* addr = reinterpret_cast<struct sockaddr*>(storage + i);
+      socklen_t addr_len = sizeof(SOCKADDR_STORAGE);
+      bool result = ipe.ToSockAddr(addr, &addr_len);
+      DCHECK(result);
+      sort_list->Address[i].lpSockaddr = addr;
+      sort_list->Address[i].iSockaddrLength = addr_len;
+    }
+
+    DWORD result_size = 0;
+    int result = WSAIoctl(socket_, SIO_ADDRESS_LIST_SORT, sort_list, heap_size,

[cbentzel, 2012/07/30 15:53:43]

Could this be blocking the IO thread? 

[szym, 2012/07/30 16:28:45]

Yes, but no more than GetAdaptersAddresses. The work that this ioctl performs is
comparable to the work performed in AddressSorterPosix with the additional
requirement to enumerate the source addresses.

In my experiments so far, AddressSorterWin::Sort mostly measures at 0ms, and
never breaks 1ms. I'll try to test it on a slow XP machine, and I'm prepared to
move it over to a WorkerPool.

[mmenke1, 2012/07/30 17:19:06]

If I recall correctly, eroman has said previously that GetAdaptersAddresses has
been a cause of jank.

+                          sort_list, heap_size, &result_size, NULL, NULL);

[mmenke, 2012/07/30 15:37:00]

Wonder if this ever eats addresses depending on local connectivity state. 
Mostly concerned about it breaking unit tests.

[szym, 2012/07/30 16:28:45]

I'll need to test it, but either way I wouldn't test the the contents of the
resulting AddressList, just that the WSAIoctl (and AddressSorterWin*::Sort)
succeeds.

+    if (result == SOCKET_ERROR) {
+      LOG(ERROR) << "SIO_ADDRESS_LIST_SORT failed" << WSAGetLastError();
+      return false;  // Unsorted.
+    }
+    list->clear();
+    for (int i = 0; i < sort_list->iAddressCount; ++i) {
+      IPEndPoint ipe;
+      ipe.FromSockAddr(sort_list->Address[i].lpSockaddr,
+                       sort_list->Address[i].iSockaddrLength);
+      // Unmap V4MAPPED IPv6 addresses so that Happy Eyeballs works properly.
+      ConvertIPv4MappedToIPv4(&ipe);
+      list->push_back(ipe);
+    }
+    return true;
+  }
+
+ private:
+  // The socket to run WSAIoctl on.
+  SOCKET socket_;
+
+  DISALLOW_COPY_AND_ASSIGN(AddressSorterWin);
+};
+
+// Wrapper for AddressSorterWin which does not sort IPv4 or IPv4-mapped
+// addresses but always puts them at the end of the list. Needed because the
+// SIO_ADDRESS_LIST_SORT does not support IPv4 addresses on Windows XP.
+class AddressSorterWinXP : public AddressSorter {
+ public:
+  AddressSorterWinXP() {}
+  virtual ~AddressSorterWinXP() {}
+
+  virtual bool Sort(AddressList* list) const OVERRIDE {
+    AddressList list_ipv4;
+    AddressList list_ipv6;
+    for (size_t i = 0; i < list->size(); ++i) {
+      IPEndPoint ipe = (*list)[i];
+      if (ipe.GetFamily() == AF_INET6)
+        ConvertIPv4MappedToIPv4(&ipe);
+      if (ipe.GetFamily() == AF_INET) {
+        list_ipv4.push_back(ipe);
+      } else {
+        list_ipv6.push_back(ipe);
+      }
+    }
+    if (!list_ipv6.empty() && !sorter_.Sort(&list_ipv6))
+      return false;
+    list->clear();
+    list->insert(list->end(), list_ipv6.begin(), list_ipv6.end());
+    list->insert(list->end(), list_ipv4.begin(), list_ipv4.end());
+    return true;
+  }
+
+ private:
+  AddressSorterWin sorter_;
+
+  DISALLOW_COPY_AND_ASSIGN(AddressSorterWinXP);
+};
+
+}  // namespace
+
+// static
+scoped_ptr<AddressSorter> AddressSorter::CreateAddressSorter() {
+  if (base::win::GetVersion() < base::win::VERSION_VISTA)
+    return scoped_ptr<AddressSorter>(new AddressSorterWinXP());
+  return scoped_ptr<AddressSorter>(new AddressSorterWin());
+}
+
+}  // namespace net
+