3 files changed, 70 insertions, 0 deletions
diff --git a/net/base/net_util.cc b/net/base/net_util.cc
index a850eb8..959ee29 100644
--- a/net/base/net_util.cc
+++ b/net/base/net_util.cc
@@ -2111,6 +2111,40 @@ int GetPortFromSockaddr(const struct sockaddr* address, socklen_t address_len) {
   return ntohs(*port_field);
 }
 
+bool IsLocalhost(const std::string& host) {
+  if (host == "localhost" ||
+      host == "localhost.localdomain" ||
+      host == "localhost6" ||
+      host == "localhost6.localdomain6")
+    return true;
+
+  IPAddressNumber ip_number;
+  if (ParseIPLiteralToNumber(host, &ip_number)) {
+    size_t size = ip_number.size();
+    switch (size) {
+      case kIPv4AddressSize: {
+        IPAddressNumber localhost_prefix;
+        localhost_prefix.push_back(127);
+        for (int i = 0; i < 3; ++i) {
+          localhost_prefix.push_back(0);
+        }
+        return IPNumberMatchesPrefix(ip_number, localhost_prefix, 8);
+      }
+
+      case kIPv6AddressSize: {
+        struct in6_addr sin6_addr;
+        memcpy(&sin6_addr, &ip_number[0], kIPv6AddressSize);
+        return IN6_IS_ADDR_LOOPBACK(&sin6_addr) != FALSE;
+      }
+
+      default:
+        NOTREACHED();
+    }
+  }
+
+  return false;
+}
+
 NetworkInterface::NetworkInterface() {
 }
 
diff --git a/net/base/net_util.h b/net/base/net_util.h
index 4e1d07e..bae27c3 100644
--- a/net/base/net_util.h
+++ b/net/base/net_util.h
@@ -427,6 +427,14 @@ const uint16* GetPortFieldFromSockaddr(const struct sockaddr* address,
 int GetPortFromSockaddr(const struct sockaddr* address,
                         socklen_t address_len);
 
+// Returns true if |host| is one of the names (e.g. "localhost") or IP
+// addresses (IPv4 127.0.0.0/8 or IPv6 ::1) that indicate a loopback.
+//
+// Note that this function does not check for IP addresses other than
+// the above, although other IP addresses may point to the local
+// machine.
+bool IsLocalhost(const std::string& host);
+
 // struct that is used by GetNetworkList() to represent a network
 // interface.
 struct NetworkInterface {
diff --git a/net/base/net_util_unittest.cc b/net/base/net_util_unittest.cc
index 9f15bc5..292d416 100644
--- a/net/base/net_util_unittest.cc
+++ b/net/base/net_util_unittest.cc
@@ -2166,6 +2166,34 @@ TEST(NetUtilTest, IPNumberMatchesPrefix) {
   }
 }
 
+TEST(NetUtilTest, IsLocalhost) {
+  EXPECT_TRUE(net::IsLocalhost("localhost"));
+  EXPECT_TRUE(net::IsLocalhost("localhost.localdomain"));
+  EXPECT_TRUE(net::IsLocalhost("localhost6"));
+  EXPECT_TRUE(net::IsLocalhost("localhost6.localdomain6"));
+  EXPECT_TRUE(net::IsLocalhost("127.0.0.1"));
+  EXPECT_TRUE(net::IsLocalhost("127.0.1.0"));
+  EXPECT_TRUE(net::IsLocalhost("127.1.0.0"));
+  EXPECT_TRUE(net::IsLocalhost("127.0.0.255"));
+  EXPECT_TRUE(net::IsLocalhost("127.0.255.0"));
+  EXPECT_TRUE(net::IsLocalhost("127.255.0.0"));
+  EXPECT_TRUE(net::IsLocalhost("::1"));
+  EXPECT_TRUE(net::IsLocalhost("0:0:0:0:0:0:0:1"));
+
+  EXPECT_FALSE(net::IsLocalhost("localhostx"));
+  EXPECT_FALSE(net::IsLocalhost("foo.localdomain"));
+  EXPECT_FALSE(net::IsLocalhost("localhost6x"));
+  EXPECT_FALSE(net::IsLocalhost("localhost.localdomain6"));
+  EXPECT_FALSE(net::IsLocalhost("localhost6.localdomain"));
+  EXPECT_FALSE(net::IsLocalhost("127.0.0.1.1"));
+  EXPECT_FALSE(net::IsLocalhost(".127.0.0.255"));
+  EXPECT_FALSE(net::IsLocalhost("::2"));
+  EXPECT_FALSE(net::IsLocalhost("::1:1"));
+  EXPECT_FALSE(net::IsLocalhost("0:0:0:0:1:0:0:1"));
+  EXPECT_FALSE(net::IsLocalhost("::1:1"));
+  EXPECT_FALSE(net::IsLocalhost("0:0:0:0:0:0:0:0:1"));
+}
+
 // Verify GetNetworkList().
 TEST(NetUtilTest, GetNetworkList) {
   NetworkInterfaceList list;