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

net/base/net_util.cc

Index: net/base/net_util.cc
diff --git a/net/base/net_util.cc b/net/base/net_util.cc
index 56e779a6ae87dc2ee3095b6af6340b9042568ee3..d39d7abf7ff4889cd3518c092c968d1d43562c1a 100644
--- a/net/base/net_util.cc
+++ b/net/base/net_util.cc
@@ -2216,6 +2216,12 @@ bool ParseIPLiteralToNumber(const std::string& ip_literal,
   return family == url_canon::CanonHostInfo::IPV4;
 }
 
+namespace {
+
+const unsigned char kIPv4MappedPrefix[] =
+    { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF };
+}
+
 IPAddressNumber ConvertIPv4NumberToIPv6Number(
     const IPAddressNumber& ipv4_number) {
   DCHECK(ipv4_number.size() == 4);
@@ -2224,13 +2230,27 @@ IPAddressNumber ConvertIPv4NumberToIPv6Number(
   // <80 bits of zeros>  + <16 bits of ones> + <32-bit IPv4 address>.
   IPAddressNumber ipv6_number;
   ipv6_number.reserve(16);
-  ipv6_number.insert(ipv6_number.end(), 10, 0);
-  ipv6_number.push_back(0xFF);
-  ipv6_number.push_back(0xFF);
+  ipv6_number.insert(ipv6_number.end(),
+                     kIPv4MappedPrefix,
+                     kIPv4MappedPrefix + arraysize(kIPv4MappedPrefix));
   ipv6_number.insert(ipv6_number.end(), ipv4_number.begin(), ipv4_number.end());
   return ipv6_number;
 }
 
+bool IsIPv4Mapped(const IPAddressNumber& address) {
+  if (address.size() != kIPv6AddressSize)
+    return false;
+  return std::equal(address.begin(),
+                    address.begin() + arraysize(kIPv4MappedPrefix),
+                    kIPv4MappedPrefix);
+}
+
+IPAddressNumber ConvertIPv4MappedToIPv4(const IPAddressNumber& address) {
+  DCHECK(IsIPv4Mapped(address));
+  return IPAddressNumber(address.begin() + arraysize(kIPv4MappedPrefix),
+                         address.end());
+}
+
 bool ParseCIDRBlock(const std::string& cidr_literal,
                     IPAddressNumber* ip_number,
                     size_t* prefix_length_in_bits) {