[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 "base/logging.h"
+#include "net/base/address_list.h"
+#include "net/base/ip_endpoint.h"
+
+namespace net {
+
+namespace {
+
+class AddressSorterWin : public AddressSorter {
+ public:
+  AddressSorterWin() {}
+
+  virtual ~AddressSorterWin() {}
+
+  virtual bool Sort(AddressList* list) const OVERRIDE {
+    // TODO(szym): Windows XP does not like V4MAPPED IPv6 addresses.
+    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;
+    }
+
+    SOCKET sock = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);

[mmenke, 2012/06/07 18:32:34]

I believe we technically need to call closesocket on this when done.  It's also
not clear how expensive this function call is.  We may want to cache the socket.

+    DCHECK_NE(INVALID_SOCKET, sock);
+    DWORD result_size = 0;
+    int result = WSAIoctl(sock, SIO_ADDRESS_LIST_SORT, sort_list, heap_size,
+                          sort_list, heap_size, &result_size, NULL, NULL);

[mmenke, 2012/06/07 18:32:34]

I do wonder about doing this on the IO thread.  Suspect there are a couple
registry reads involved.

+    if (result == SOCKET_ERROR) {
+      printf("FAILED %d\n", WSAGetLastError());

[mmenke, 2012/06/07 18:32:34]

You could make a NetLog entry or something here, if you want.  Regardless, get
rid of the printf.  :)

+      return false;  // Unsorted.
+    }
+    list->clear();
+    for (int i = 0; i < sort_list->iAddressCount; ++i) {
+      IPEndPoint endpoint;
+      endpoint.FromSockAddr(sort_list->Address[i].lpSockaddr,
+                            sort_list->Address[i].iSockaddrLength);
+      list->push_back(endpoint);
+    }
+    return true;
+  }
+
+  DISALLOW_COPY_AND_ASSIGN(AddressSorterWin);
+};
+
+}  // namespace
+
+// static
+scoped_ptr<AddressSorter> AddressSorter::CreateAddressSorter() {
+  return scoped_ptr<AddressSorter>(new AddressSorterWin());
+}
+
+}  // namespace net
+