DNS: Retain stale entries in HostCache and return when requested

net/dns/dns_util.cc

 // Copyright (c) 2011 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/dns_util.h"
 
 #include <errno.h>
 #include <limits.h>
 
 #include <cstring>
 
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "build/build_config.h"
+#include "net/base/address_list.h"
 
 #if defined(OS_POSIX)
 #include <netinet/in.h>
 #if !defined(OS_NACL)
 #include <net/if.h>
 #if !defined(OS_ANDROID)
 #include <ifaddrs.h>
 #endif  // !defined(OS_ANDROID)
 #endif  // !defined(OS_NACL)
 #endif  // defined(OS_POSIX)
@@ skipping 159 matching lines @@
     const char* field_trial,
     base::TimeDelta default_delta,
     NetworkChangeNotifier::ConnectionType type) {
   base::TimeDelta out;
   if (!GetTimeDeltaForConnectionTypeFromFieldTrial(field_trial, type, &out))
     out = default_delta;
   return out;
 }
 #endif  // !defined(OS_NACL)
 
+AddressListDeltaType FindAddressListDeltaType(const AddressList& a,

[Randy Smith (Not in Mondays), 2016/04/28 16:24:16]

This is only used in host_cache.cc; any reason not to make it a static function
in that file, at least until it's actually needed elsewhere?  (Or is it needed
elsewhere in one of the follow-on CLs?  In which case, in an ideal world I'd
suggest starting in host_cache.cc and moving in that CL, and in this world, ok.
:-})

[Julia Tuttle, 2016/04/29 17:33:51]

Yeah, it's used in a follow-on CL.

+                                              const AddressList& b) {
+  bool pairwise_mismatch = false;
+  bool any_match = false;
+  bool any_missing = false;
+  bool same_size = a.size() == b.size();
+
+  for (size_t i = 0; i < a.size(); ++i) {
+    bool this_match = false;
+    for (size_t j = 0; j < b.size(); ++j) {
+      if (a[i] == b[j]) {
+        any_match = true;
+        this_match = true;
+      } else if (i == j) {
+        pairwise_mismatch = true;
+      }
+    }
+    if (!this_match)
+      any_missing = true;
+  }
+
+  if (same_size && !pairwise_mismatch)
+    return DELTA_IDENTICAL;
+  else if (same_size && !any_missing)
+    return DELTA_REORDERED;
+  else if (any_match)
+    return DELTA_OVERLAP;
+  else
+    return DELTA_DISJOINT;
+}
+
 }  // namespace net