From 87a713365925ff62b996d78b08e99cdd36695206 Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@yandex-team.ru>
Date: Fri, 21 May 2021 08:17:54 +0300
Subject: [PATCH] Add a test and fix the code

---
 src/Common/isLocalAddress.cpp            | 17 +++++++----------
 src/Common/tests/gtest_local_address.cpp | 23 ++++++++++++++++++++++-
 2 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/src/Common/isLocalAddress.cpp b/src/Common/isLocalAddress.cpp
index 2a76241300c..fba92f5d763 100644
--- a/src/Common/isLocalAddress.cpp
+++ b/src/Common/isLocalAddress.cpp
@@ -1,6 +1,7 @@
 #include <Common/isLocalAddress.h>
 
 #include <ifaddrs.h>
+#include <array>
 #include <cstring>
 #include <optional>
 #include <common/types.h>
@@ -95,17 +96,13 @@ bool isLocalAddress(const Poco::Net::IPAddress & address)
     {
         if (address.family() == Poco::Net::AddressFamily::IPv4)
         {
-            union
-            {
-                UInt32 word;
-                unsigned char digits[4];
-            } digits_union;
+            using Digits = std::array<UInt8, 4>;
+            Digits digits = unalignedLoad<Digits>(address.addr());  /// The address is located in memory in big endian form.
 
-            digits_union.word = ntohl(unalignedLoad<UInt32>(address.addr()));
-            if (digits_union.digits[0] == 127
-                && digits_union.digits[1] <= 1
-                && digits_union.digits[2] <= 1
-                && digits_union.digits[3] <= 1)
+            if (digits[0] == 127
+                && digits[1] <= 1
+                && digits[2] <= 1
+                && digits[3] <= 1)
             {
                 return true;
             }
diff --git a/src/Common/tests/gtest_local_address.cpp b/src/Common/tests/gtest_local_address.cpp
index 504fba19713..47824a7fa27 100644
--- a/src/Common/tests/gtest_local_address.cpp
+++ b/src/Common/tests/gtest_local_address.cpp
@@ -11,9 +11,30 @@ TEST(LocalAddress, SmokeTest)
     std::string address_str;
     DB::readString(address_str, cmd->out);
     cmd->wait();
-    std::cerr << "Got Address:" << address_str << std::endl;
+    std::cerr << "Got Address: " << address_str << std::endl;
 
     Poco::Net::IPAddress address(address_str);
 
     EXPECT_TRUE(DB::isLocalAddress(address));
 }
+
+TEST(LocalAddress, Localhost)
+{
+    EXPECT_TRUE(DB::isLocalAddress(Poco::Net::IPAddress{"127.0.0.1"}));
+    EXPECT_TRUE(DB::isLocalAddress(Poco::Net::IPAddress{"127.0.1.1"}));
+    EXPECT_TRUE(DB::isLocalAddress(Poco::Net::IPAddress{"127.1.1.1"}));
+    EXPECT_TRUE(DB::isLocalAddress(Poco::Net::IPAddress{"127.1.0.1"}));
+    EXPECT_TRUE(DB::isLocalAddress(Poco::Net::IPAddress{"127.1.0.0"}));
+    EXPECT_TRUE(DB::isLocalAddress(Poco::Net::IPAddress{"::1"}));
+
+    /// Make sure we don't mess with the byte order.
+    EXPECT_FALSE(DB::isLocalAddress(Poco::Net::IPAddress{"1.0.0.127"}));
+    EXPECT_FALSE(DB::isLocalAddress(Poco::Net::IPAddress{"1.1.1.127"}));
+
+    EXPECT_FALSE(DB::isLocalAddress(Poco::Net::IPAddress{"0.0.0.0"}));
+    EXPECT_FALSE(DB::isLocalAddress(Poco::Net::IPAddress{"::"}));
+    EXPECT_FALSE(DB::isLocalAddress(Poco::Net::IPAddress{"::2"}));
+
+    /// The the comment in the implementation of isLocalAddress.
+    EXPECT_FALSE(DB::isLocalAddress(Poco::Net::IPAddress{"127.0.0.2"}));
+}