Core/Network: Refactor local/remote ip address selection code and allow using hostnames in LoginREST bnetserver config options

13 files changed, 386 insertions, 93 deletions

diff --git a/src/common/Asio/AsioHacksFwd.h b/src/common/Asio/AsioHacksFwd.h
index 6030436d39d..a8f04b16d81 100644
--- a/src/common/Asio/AsioHacksFwd.h
+++ b/src/common/Asio/AsioHacksFwd.h
@@ -38,6 +38,11 @@ namespace boost
         namespace ip
         {
             class address;
+            class address_v4;
+            class address_v6;
+
+            class network_v4;
+            class network_v6;
 
             class tcp;
 
diff --git a/src/common/Asio/IpAddress.h b/src/common/Asio/IpAddress.h
index 30500d662c6..22af8bbfd41 100644
--- a/src/common/Asio/IpAddress.h
+++ b/src/common/Asio/IpAddress.h
@@ -27,6 +27,7 @@ namespace Trinity
     {
         using boost::asio::ip::make_address;
         using boost::asio::ip::make_address_v4;
+        using boost::asio::ip::make_address_v6;
         inline uint32 address_to_uint(boost::asio::ip::address_v4 const& address) { return address.to_uint(); }
     }
 }
diff --git a/src/common/Asio/IpNetwork.cpp b/src/common/Asio/IpNetwork.cpp
new file mode 100644
index 00000000000..5e5dcb9ac22
--- /dev/null
+++ b/src/common/Asio/IpNetwork.cpp
@@ -0,0 +1,284 @@
+/*
+ * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "IpNetwork.h"
+#include "IpAddress.h"
+#include <boost/asio/ip/network_v4.hpp>
+#include <boost/asio/ip/network_v6.hpp>
+
+namespace
+{
+std::vector<boost::asio::ip::network_v4> LocalV4Networks;
+std::vector<boost::asio::ip::network_v6> LocalV6Networks;
+}
+
+namespace Trinity::Net
+{
+bool IsInLocalNetwork(boost::asio::ip::address const& clientAddress)
+{
+    if (clientAddress.is_v4())
+    {
+        return std::any_of(LocalV4Networks.begin(), LocalV4Networks.end(), [clientAddressV4 = clientAddress.to_v4()](boost::asio::ip::network_v4 const& network)
+        {
+            return IsInNetwork(network, clientAddressV4);
+        });
+    }
+
+    if (clientAddress.is_v6())
+    {
+        return std::any_of(LocalV6Networks.begin(), LocalV6Networks.end(), [clientAddressV6 = clientAddress.to_v6()](boost::asio::ip::network_v6 const& network)
+        {
+            return IsInNetwork(network, clientAddressV6);
+        });
+    }
+
+    return false;
+};
+
+bool IsInNetwork(boost::asio::ip::network_v4 const& network, boost::asio::ip::address_v4 const& clientAddress)
+{
+    if (clientAddress == network.address())
+        return true;
+
+    boost::asio::ip::network_v4 endpointAsNetwork = boost::asio::ip::make_network_v4(clientAddress, 32);
+    return endpointAsNetwork.is_subnet_of(network);
+}
+
+bool IsInNetwork(boost::asio::ip::network_v6 const& network, boost::asio::ip::address_v6 const& clientAddress)
+{
+    if (clientAddress == network.address())
+        return true;
+
+    boost::asio::ip::network_v6 endpointAsNetwork = boost::asio::ip::make_network_v6(clientAddress, 128);
+    return endpointAsNetwork.is_subnet_of(network);
+}
+
+Optional<std::size_t> SelectAddressForClient(boost::asio::ip::address const& clientAddress, std::span<boost::asio::ip::address> const& addresses)
+{
+    Optional<std::size_t> localIpv6Index;
+    Optional<std::size_t> externalIpv6Index;
+    Optional<std::size_t> loopbackIpv6Index;
+    Optional<std::size_t> localIpv4Index;
+    Optional<std::size_t> externalIpv4Index;
+    Optional<std::size_t> loopbackIpv4Index;
+
+    for (std::size_t i = 0; i < addresses.size(); ++i)
+    {
+        boost::asio::ip::address const& address = addresses[i];
+
+        if (IsInLocalNetwork(address))
+        {
+            if (address.is_v6() && !localIpv6Index)
+                localIpv6Index = i;
+
+            if (address.is_v4() && !localIpv4Index)
+                localIpv4Index = i;
+        }
+        else
+        {
+            if (address.is_v6() && !externalIpv6Index)
+                externalIpv6Index = i;
+
+            if (address.is_v4() && !externalIpv4Index)
+                externalIpv4Index = i;
+        }
+
+        if (address.is_loopback())
+        {
+            if (address.is_v6() && !loopbackIpv6Index)
+                loopbackIpv6Index = i;
+
+            if (address.is_v4() && !loopbackIpv4Index)
+                loopbackIpv4Index = i;
+        }
+    }
+
+    if (IsInLocalNetwork(clientAddress) || clientAddress.is_loopback())
+    {
+        // client is in the same network as this process, prefer local addresses
+
+        // first, try finding a local ipv6 address
+        if (clientAddress.is_v6() && localIpv6Index)
+        {
+            // we have a usable ipv6 local address
+            return localIpv6Index;
+        }
+
+        // we dont have a local v6, return local v4
+        if (localIpv4Index)
+            return localIpv4Index;
+    }
+
+    if (clientAddress.is_loopback())
+    {
+        // fallback, search for a loopback address in configuration
+        if (clientAddress.is_v6() && loopbackIpv6Index)
+            return loopbackIpv6Index;
+
+        if (loopbackIpv4Index)
+            return loopbackIpv4Index;
+    }
+
+    // client is NOT in the same network as this process
+    if (clientAddress.is_v6() && externalIpv6Index)
+        return externalIpv6Index;
+
+    return externalIpv4Index;
+}
+}
+
+#if TRINITY_PLATFORM == TRINITY_PLATFORM_WINDOWS
+
+#include <boost/dll/shared_library.hpp>
+#include <iphlpapi.h>
+
+void Trinity::Net::ScanLocalNetworks()
+{
+    LocalV4Networks.clear();
+    LocalV6Networks.clear();
+
+    boost::system::error_code dllError;
+    boost::dll::shared_library iphlp("Iphlpapi.dll", dllError, boost::dll::load_mode::search_system_folders);
+    if (dllError || !iphlp.is_loaded())
+        return;
+
+    auto getAdaptersAddresses = iphlp.get<decltype(GetAdaptersAddresses)>("GetAdaptersAddresses");
+    if (!getAdaptersAddresses)
+        return;
+
+    ULONG queryFlags = GAA_FLAG_SKIP_UNICAST | GAA_FLAG_SKIP_ANYCAST | GAA_FLAG_SKIP_MULTICAST | GAA_FLAG_SKIP_DNS_SERVER | GAA_FLAG_INCLUDE_PREFIX | GAA_FLAG_SKIP_FRIENDLY_NAME;
+    ULONG bufferSize = 0;
+
+    if (getAdaptersAddresses(AF_UNSPEC, queryFlags, nullptr, nullptr, &bufferSize) != ERROR_BUFFER_OVERFLOW)
+        return;
+
+    std::unique_ptr<std::byte[]> addressesBuffer = std::make_unique<std::byte[]>(bufferSize);
+    if (getAdaptersAddresses(AF_UNSPEC, queryFlags, nullptr, reinterpret_cast<IP_ADAPTER_ADDRESSES*>(addressesBuffer.get()), &bufferSize) != ERROR_SUCCESS)
+        return;
+
+    for (IP_ADAPTER_ADDRESSES* itr = reinterpret_cast<IP_ADAPTER_ADDRESSES*>(addressesBuffer.get()); itr; itr = itr->Next)
+    {
+        if (itr->IfType == IF_TYPE_SOFTWARE_LOOPBACK)
+            continue;
+
+        if (itr->OperStatus != IfOperStatusUp)
+            continue;
+
+        for (IP_ADAPTER_PREFIX_XP* prefix = itr->FirstPrefix; prefix; prefix = prefix->Next)
+        {
+            switch (prefix->Address.lpSockaddr->sa_family)
+            {
+                case AF_INET:
+                {
+                    SOCKADDR_IN* ipv4raw = reinterpret_cast<SOCKADDR_IN*>(prefix->Address.lpSockaddr);
+                    boost::asio::ip::address_v4::bytes_type addressBytes;
+                    std::memcpy(addressBytes.data(), &ipv4raw->sin_addr.s_addr, addressBytes.size());
+                    boost::asio::ip::address_v4 address = make_address_v4(addressBytes);
+                    if (address.is_unspecified() || address.is_multicast() || address == boost::asio::ip::address_v4::broadcast())
+                        continue;
+
+                    LocalV4Networks.push_back(boost::asio::ip::make_network_v4(address, prefix->PrefixLength));
+                    break;
+                }
+                case AF_INET6:
+                {
+                    SOCKADDR_IN6* ipv6raw = reinterpret_cast<SOCKADDR_IN6*>(prefix->Address.lpSockaddr);
+                    boost::asio::ip::address_v6::bytes_type addressBytes;
+                    std::memcpy(addressBytes.data(), ipv6raw->sin6_addr.s6_addr, addressBytes.size());
+                    boost::asio::ip::address_v6 address = make_address_v6(addressBytes, ipv6raw->sin6_scope_id);
+                    if (address.is_unspecified() || address.is_multicast())
+                        continue;
+
+                    LocalV6Networks.push_back(boost::asio::ip::make_network_v6(address, prefix->PrefixLength));
+                    break;
+                }
+                default:
+                    break;
+            }
+        }
+    }
+}
+
+#else
+
+#include <numeric>
+#include <ifaddrs.h>
+
+void Trinity::Net::ScanLocalNetworks()
+{
+    LocalV4Networks.clear();
+    LocalV6Networks.clear();
+
+    ifaddrs* addressesLinkedList = nullptr;
+    if (getifaddrs(&addressesLinkedList) == -1)
+        return;
+
+    for (ifaddrs* itr = addressesLinkedList; itr; itr = itr->ifa_next)
+    {
+        if (!itr->ifa_addr)
+            continue;
+
+        switch (itr->ifa_addr->sa_family)
+        {
+            case AF_INET:
+            {
+                sockaddr_in* ipv4raw = reinterpret_cast<sockaddr_in*>(itr->ifa_addr);
+                boost::asio::ip::address_v4::bytes_type addressBytes;
+                std::memcpy(addressBytes.data(), &ipv4raw->sin_addr.s_addr, addressBytes.size());
+                boost::asio::ip::address_v4 address = make_address_v4(addressBytes);
+                if (address.is_unspecified() || address.is_loopback() || address.is_multicast() || address == boost::asio::ip::address_v4::broadcast())
+                    continue;
+
+                if (sockaddr_in* netmask4raw = reinterpret_cast<sockaddr_in*>(itr->ifa_netmask))
+                {
+                    boost::asio::ip::address_v4::bytes_type netmaskBytes;
+                    std::memcpy(netmaskBytes.data(), &netmask4raw->sin_addr.s_addr, netmaskBytes.size());
+                    boost::asio::ip::address_v4 netmask = make_address_v4(netmaskBytes);
+                    LocalV4Networks.push_back(boost::asio::ip::make_network_v4(address, netmask));
+                }
+                else
+                    LocalV4Networks.push_back(boost::asio::ip::make_network_v4(address, 32));
+                break;
+            }
+            case AF_INET6:
+            {
+                sockaddr_in6* ipv6raw = reinterpret_cast<sockaddr_in6*>(itr->ifa_addr);
+                boost::asio::ip::address_v6::bytes_type addressBytes;
+                std::memcpy(addressBytes.data(), ipv6raw->sin6_addr.s6_addr, addressBytes.size());
+                boost::asio::ip::address_v6 address = make_address_v6(addressBytes, ipv6raw->sin6_scope_id);
+                if (address.is_unspecified() || address.is_loopback() || address.is_multicast())
+                    continue;
+
+                if (sockaddr_in6* netmask6raw = reinterpret_cast<sockaddr_in6*>(itr->ifa_netmask))
+                {
+                    int32 prefixLength = 0;
+                    for (uint8 addressByte : netmask6raw->sin6_addr.s6_addr)
+                        prefixLength += std::countl_one(addressByte);
+
+                    LocalV6Networks.push_back(boost::asio::ip::make_network_v6(address, prefixLength));
+                }
+                else
+                    LocalV6Networks.push_back(boost::asio::ip::make_network_v6(address, 128));
+                break;
+            }
+        }
+    }
+
+    freeifaddrs(addressesLinkedList);
+}
+
+#endif
diff --git a/src/common/Asio/IpNetwork.h b/src/common/Asio/IpNetwork.h
index 294532c5c78..242c344fc15 100644
--- a/src/common/Asio/IpNetwork.h
+++ b/src/common/Asio/IpNetwork.h
@@ -18,40 +18,22 @@
 #ifndef IpNetwork_h__
 #define IpNetwork_h__
 
+#include "AsioHacksFwd.h"
 #include "Define.h"
-#include "IpAddress.h"
-#include <boost/asio/ip/network_v4.hpp>
-#include <boost/asio/ip/network_v6.hpp>
+#include "Optional.h"
+#include <span>
 
-namespace Trinity
+namespace Trinity::Net
 {
-    namespace Net
-    {
-        inline bool IsInNetwork(boost::asio::ip::address_v4 const& networkAddress, boost::asio::ip::address_v4 const& mask, boost::asio::ip::address_v4 const& clientAddress)
-        {
-            boost::asio::ip::network_v4 network = boost::asio::ip::make_network_v4(networkAddress, mask);
-            boost::asio::ip::address_v4_range hosts = network.hosts();
-            return hosts.find(clientAddress) != hosts.end();
-        }
-
-        inline boost::asio::ip::address_v4 GetDefaultNetmaskV4(boost::asio::ip::address_v4 const& networkAddress)
-        {
-            if ((address_to_uint(networkAddress) & 0x80000000) == 0)
-                return boost::asio::ip::address_v4(0xFF000000);
-            if ((address_to_uint(networkAddress) & 0xC0000000) == 0x80000000)
-                return boost::asio::ip::address_v4(0xFFFF0000);
-            if ((address_to_uint(networkAddress) & 0xE0000000) == 0xC0000000)
-                return boost::asio::ip::address_v4(0xFFFFFF00);
-            return boost::asio::ip::address_v4(0xFFFFFFFF);
-        }
-
-        inline bool IsInNetwork(boost::asio::ip::address_v6 const& networkAddress, uint16 prefixLength, boost::asio::ip::address_v6 const& clientAddress)
-        {
-            boost::asio::ip::network_v6 network = boost::asio::ip::make_network_v6(networkAddress, prefixLength);
-            boost::asio::ip::address_v6_range hosts = network.hosts();
-            return hosts.find(clientAddress) != hosts.end();
-        }
-    }
+TC_COMMON_API bool IsInLocalNetwork(boost::asio::ip::address const& clientAddress);
+
+TC_COMMON_API bool IsInNetwork(boost::asio::ip::network_v4 const& network, boost::asio::ip::address_v4 const& clientAddress);
+
+TC_COMMON_API bool IsInNetwork(boost::asio::ip::network_v6 const& network, boost::asio::ip::address_v6 const& clientAddress);
+
+TC_COMMON_API Optional<std::size_t> SelectAddressForClient(boost::asio::ip::address const& clientAddress, std::span<boost::asio::ip::address> const& addresses);
+
+TC_COMMON_API void ScanLocalNetworks();
 }
 
 #endif // IpNetwork_h__
diff --git a/src/server/bnetserver/Main.cpp b/src/server/bnetserver/Main.cpp
index a1b93920489..6b2e058262e 100644
--- a/src/server/bnetserver/Main.cpp
+++ b/src/server/bnetserver/Main.cpp
@@ -32,6 +32,7 @@
 #include "DeadlineTimer.h"
 #include "GitRevision.h"
 #include "IPLocation.h"
+#include "IpNetwork.h"
 #include "LoginRESTService.h"
 #include "MySQLThreading.h"
 #include "OpenSSLCrypto.h"
@@ -192,6 +193,8 @@ int main(int argc, char** argv)
 
     std::shared_ptr<Trinity::Asio::IoContext> ioContext = std::make_shared<Trinity::Asio::IoContext>();
 
+    Trinity::Net::ScanLocalNetworks();
+
     // Start the listening port (acceptor) for auth connections
     int32 bnport = sConfigMgr->GetIntDefault("BattlenetPort", 1119);
     if (bnport < 0 || bnport > 0xFFFF)
diff --git a/src/server/bnetserver/REST/LoginRESTService.cpp b/src/server/bnetserver/REST/LoginRESTService.cpp
index 5267b2bd761..6e260b4df56 100644
--- a/src/server/bnetserver/REST/LoginRESTService.cpp
+++ b/src/server/bnetserver/REST/LoginRESTService.cpp
@@ -90,7 +90,8 @@ bool LoginRESTService::Start(Trinity::Asio::IoContext* ioContext)
         return false;
     }
 
-    _externalAddress = *externalAddress;
+    _externalEndpoint = *externalAddress;
+    _externalHostname = Trinity::StringFormat("{}:{}", configuredAddress, _port);
 
     configuredAddress = sConfigMgr->GetStringDefault("LoginREST.LocalAddress", "127.0.0.1");
     Optional<boost::asio::ip::tcp::endpoint> localAddress = resolver.Resolve(boost::asio::ip::tcp::v4(), configuredAddress, std::to_string(_port));
@@ -100,8 +101,8 @@ bool LoginRESTService::Start(Trinity::Asio::IoContext* ioContext)
         return false;
     }
 
-    _localAddress = *localAddress;
-    _localNetmask = Trinity::Net::GetDefaultNetmaskV4(_localAddress.address().to_v4());
+    _localEndpoint = *localAddress;
+    _localHostname = Trinity::StringFormat("{}:{}", configuredAddress, _port);
 
     // set up form inputs
     Battlenet::JSON::Login::FormInput* input;
@@ -135,17 +136,48 @@ void LoginRESTService::Stop()
     _thread.join();
 }
 
-boost::asio::ip::tcp::endpoint const& LoginRESTService::GetAddressForClient(boost::asio::ip::address const& address) const
+boost::asio::ip::tcp::endpoint const& LoginRESTService::GetEndpointForClient(boost::asio::ip::address const& address) const
 {
+    std::array<boost::asio::ip::address, 2> addresses = std::array{ _externalEndpoint.address(), _localEndpoint.address() };
+    if (auto addressIndex = Trinity::Net::SelectAddressForClient(address, addresses))
+    {
+        switch (*addressIndex)
+        {
+            case 0:
+                return _externalEndpoint;
+            case 1:
+                return _localEndpoint;
+            default:
+                break;
+        }
+    }
+
     if (address.is_loopback())
-        return _localAddress;
-    else if (_localAddress.address().is_loopback())
-        return _externalAddress;
+        return _localEndpoint;
+
+    return _externalEndpoint;
+}
 
-    if (Trinity::Net::IsInNetwork(_localAddress.address().to_v4(), _localNetmask, address.to_v4()))
-        return _localAddress;
+std::string const& LoginRESTService::GetHostnameForClient(boost::asio::ip::address const& address) const
+{
+    std::array<boost::asio::ip::address, 2> addresses = std::array{ _externalEndpoint.address(), _localEndpoint.address() };
+    if (auto addressIndex = Trinity::Net::SelectAddressForClient(address, addresses))
+    {
+        switch (*addressIndex)
+        {
+            case 0:
+                return _externalHostname;
+            case 1:
+                return _localHostname;
+            default:
+                break;
+        }
+    }
+
+    if (address.is_loopback())
+        return _localHostname;
 
-    return _externalAddress;
+    return _externalHostname;
 }
 
 void LoginRESTService::Run()
@@ -298,7 +330,7 @@ int32 LoginRESTService::HandleGetGameAccounts(std::shared_ptr<AsyncRequest> requ
 
 int32 LoginRESTService::HandleGetPortal(std::shared_ptr<AsyncRequest> request)
 {
-    boost::asio::ip::tcp::endpoint const& endpoint = GetAddressForClient(boost::asio::ip::address_v4(request->GetClient()->ip));
+    boost::asio::ip::tcp::endpoint const& endpoint = GetEndpointForClient(boost::asio::ip::address_v4(request->GetClient()->ip));
     std::string response = Trinity::StringFormat("{}:{}", endpoint.address().to_string(), sConfigMgr->GetIntDefault("BattlenetPort", 1119));
 
     soap_response(request->GetClient(), SOAP_FILE);
diff --git a/src/server/bnetserver/REST/LoginRESTService.h b/src/server/bnetserver/REST/LoginRESTService.h
index e4d22dd9661..5c549fbf589 100644
--- a/src/server/bnetserver/REST/LoginRESTService.h
+++ b/src/server/bnetserver/REST/LoginRESTService.h
@@ -46,7 +46,8 @@ public:
     bool Start(Trinity::Asio::IoContext* ioContext);
     void Stop();
 
-    boost::asio::ip::tcp::endpoint const& GetAddressForClient(boost::asio::ip::address const& address) const;
+    boost::asio::ip::tcp::endpoint const& GetEndpointForClient(boost::asio::ip::address const& address) const;
+    std::string const& GetHostnameForClient(boost::asio::ip::address const& address) const;
 
 private:
     void Run();
@@ -101,9 +102,10 @@ private:
     Battlenet::JSON::Login::FormInputs _formInputs;
     std::string _bindIP;
     int32 _port;
-    boost::asio::ip::tcp::endpoint _externalAddress;
-    boost::asio::ip::tcp::endpoint _localAddress;
-    boost::asio::ip::address_v4 _localNetmask;
+    std::string _externalHostname;
+    boost::asio::ip::tcp::endpoint _externalEndpoint;
+    std::string _localHostname;
+    boost::asio::ip::tcp::endpoint _localEndpoint;
     uint32 _loginTicketDuration;
 
     HttpMethodHandlerMap _getHandlers;
diff --git a/src/server/bnetserver/Server/Session.cpp b/src/server/bnetserver/Server/Session.cpp
index 806b371f79d..f98c429acf8 100644
--- a/src/server/bnetserver/Server/Session.cpp
+++ b/src/server/bnetserver/Server/Session.cpp
@@ -232,11 +232,11 @@ uint32 Battlenet::Session::HandleLogon(authentication::v1::LogonRequest const* l
     if (logonRequest->has_cached_web_credentials())
         return VerifyWebCredentials(logonRequest->cached_web_credentials(), continuation);
 
-    boost::asio::ip::tcp::endpoint const& endpoint = sLoginService.GetAddressForClient(GetRemoteIpAddress());
+    std::string const& hostname = sLoginService.GetHostnameForClient(GetRemoteIpAddress());
 
     challenge::v1::ChallengeExternalRequest externalChallenge;
     externalChallenge.set_payload_type("web_auth_url");
-    externalChallenge.set_payload(Trinity::StringFormat("https://{}:{}/bnetserver/login/", endpoint.address().to_string(), endpoint.port()));
+    externalChallenge.set_payload(Trinity::StringFormat("https://{}/bnetserver/login/", hostname));
     Service<challenge::v1::ChallengeListener>(this).OnExternalChallenge(&externalChallenge);
     return ERROR_OK;
 }
diff --git a/src/server/database/Database/Implementation/LoginDatabase.cpp b/src/server/database/Database/Implementation/LoginDatabase.cpp
index 21b0b7534f1..0b9fd4e8f89 100644
--- a/src/server/database/Database/Implementation/LoginDatabase.cpp
+++ b/src/server/database/Database/Implementation/LoginDatabase.cpp
@@ -23,7 +23,7 @@ void LoginDatabaseConnection::DoPrepareStatements()
     if (!m_reconnecting)
         m_stmts.resize(MAX_LOGINDATABASE_STATEMENTS);
 
-    PrepareStatement(LOGIN_SEL_REALMLIST, "SELECT id, name, address, localAddress, localSubnetMask, port, icon, flag, timezone, allowedSecurityLevel, population, gamebuild, Region, Battlegroup FROM realmlist WHERE flag <> 3 ORDER BY name", CONNECTION_SYNCH);
+    PrepareStatement(LOGIN_SEL_REALMLIST, "SELECT id, name, address, localAddress, port, icon, flag, timezone, allowedSecurityLevel, population, gamebuild, Region, Battlegroup FROM realmlist WHERE flag <> 3 ORDER BY name", CONNECTION_SYNCH);
     PrepareStatement(LOGIN_DEL_EXPIRED_IP_BANS, "DELETE FROM ip_banned WHERE unbandate<>bandate AND unbandate<=UNIX_TIMESTAMP()", CONNECTION_ASYNC);
     PrepareStatement(LOGIN_UPD_EXPIRED_ACCOUNT_BANS, "UPDATE account_banned SET active = 0 WHERE active = 1 AND unbandate<>bandate AND unbandate<=UNIX_TIMESTAMP()", CONNECTION_ASYNC);
     PrepareStatement(LOGIN_SEL_IP_INFO, "SELECT unbandate > UNIX_TIMESTAMP() OR unbandate = bandate AS banned, NULL as country FROM ip_banned WHERE ip = ?", CONNECTION_ASYNC);
diff --git a/src/server/shared/Realm/Realm.cpp b/src/server/shared/Realm/Realm.cpp
index 0648de535a3..87b7114111d 100644
--- a/src/server/shared/Realm/Realm.cpp
+++ b/src/server/shared/Realm/Realm.cpp
@@ -31,31 +31,24 @@ void Realm::SetName(std::string name)
 
 boost::asio::ip::address Realm::GetAddressForClient(boost::asio::ip::address const& clientAddr) const
 {
-    boost::asio::ip::address realmIp;
-
-    // Attempt to send best address for client
-    if (clientAddr.is_loopback())
+    std::array<boost::asio::ip::address, 2> addresses = std::array{ *ExternalAddress, * LocalAddress };
+    if (auto addressIndex = Trinity::Net::SelectAddressForClient(clientAddr, addresses))
     {
-        // Try guessing if realm is also connected locally
-        if (LocalAddress->is_loopback() || ExternalAddress->is_loopback())
-            realmIp = clientAddr;
-        else
+        switch (*addressIndex)
         {
-            // Assume that user connecting from the machine that bnetserver is located on
-            // has all realms available in his local network
-            realmIp = *LocalAddress;
+            case 0:
+                return *ExternalAddress;
+            case 1:
+                return *LocalAddress;
+            default:
+                break;
         }
     }
-    else
-    {
-        if (clientAddr.is_v4() && Trinity::Net::IsInNetwork(LocalAddress->to_v4(), LocalSubnetMask->to_v4(), clientAddr.to_v4()))
-            realmIp = *LocalAddress;
-        else
-            realmIp = *ExternalAddress;
-    }
 
-    // Return external IP
-    return realmIp;
+    if (clientAddr.is_loopback())
+        return *LocalAddress;
+
+    return *ExternalAddress;
 }
 
 uint32 Realm::GetConfigId() const
diff --git a/src/server/shared/Realm/RealmList.cpp b/src/server/shared/Realm/RealmList.cpp
index c43b12ae241..ff152276c12 100644
--- a/src/server/shared/Realm/RealmList.cpp
+++ b/src/server/shared/Realm/RealmList.cpp
@@ -94,7 +94,7 @@ void RealmList::LoadBuildInfo()
 }
 
 void RealmList::UpdateRealm(Realm& realm, Battlenet::RealmHandle const& id, uint32 build, std::string const& name,
-    boost::asio::ip::address&& address, boost::asio::ip::address&& localAddr, boost::asio::ip::address&& localSubmask,
+    boost::asio::ip::address&& address, boost::asio::ip::address&& localAddr,
     uint16 port, uint8 icon, RealmFlags flag, uint8 timezone, AccountTypes allowedSecurityLevel,
     float population)
 {
@@ -111,8 +111,6 @@ void RealmList::UpdateRealm(Realm& realm, Battlenet::RealmHandle const& id, uint
         realm.ExternalAddress = std::make_unique<boost::asio::ip::address>(std::move(address));
     if (!realm.LocalAddress || *realm.LocalAddress != localAddr)
         realm.LocalAddress = std::make_unique<boost::asio::ip::address>(std::move(localAddr));
-    if (!realm.LocalSubnetMask || *realm.LocalSubnetMask != localSubmask)
-        realm.LocalSubnetMask = std::make_unique<boost::asio::ip::address>(std::move(localSubmask));
     realm.Port = port;
 }
 
@@ -145,7 +143,6 @@ void RealmList::UpdateRealms(boost::system::error_code const& error)
                 std::string name = fields[1].GetString();
                 std::string externalAddressString = fields[2].GetString();
                 std::string localAddressString = fields[3].GetString();
-                std::string localSubmaskString = fields[4].GetString();
 
                 Optional<boost::asio::ip::tcp::endpoint> externalAddress = _resolver->Resolve(boost::asio::ip::tcp::v4(), externalAddressString, "");
                 if (!externalAddress)
@@ -161,30 +158,23 @@ void RealmList::UpdateRealms(boost::system::error_code const& error)
                     continue;
                 }
 
-                Optional<boost::asio::ip::tcp::endpoint> localSubmask = _resolver->Resolve(boost::asio::ip::tcp::v4(), localSubmaskString, "");
-                if (!localSubmask)
-                {
-                    TC_LOG_ERROR("realmlist", "Could not resolve localSubnetMask {} for realm \"{}\" id {}", localSubmaskString, name, realmId);
-                    continue;
-                }
-
-                uint16 port = fields[5].GetUInt16();
-                uint8 icon = fields[6].GetUInt8();
+                uint16 port = fields[4].GetUInt16();
+                uint8 icon = fields[5].GetUInt8();
                 if (icon == REALM_TYPE_FFA_PVP)
                     icon = REALM_TYPE_PVP;
                 if (icon >= MAX_CLIENT_REALM_TYPE)
                     icon = REALM_TYPE_NORMAL;
-                RealmFlags flag = RealmFlags(fields[7].GetUInt8());
-                uint8 timezone = fields[8].GetUInt8();
-                uint8 allowedSecurityLevel = fields[9].GetUInt8();
-                float pop = fields[10].GetFloat();
-                uint32 build = fields[11].GetUInt32();
-                uint8 region = fields[12].GetUInt8();
-                uint8 battlegroup = fields[13].GetUInt8();
+                RealmFlags flag = RealmFlags(fields[6].GetUInt8());
+                uint8 timezone = fields[7].GetUInt8();
+                uint8 allowedSecurityLevel = fields[8].GetUInt8();
+                float pop = fields[9].GetFloat();
+                uint32 build = fields[10].GetUInt32();
+                uint8 region = fields[11].GetUInt8();
+                uint8 battlegroup = fields[12].GetUInt8();
 
                 Battlenet::RealmHandle id{ region, battlegroup, realmId };
 
-                UpdateRealm(newRealms[id], id, build, name, externalAddress->address(), localAddress->address(), localSubmask->address(), port, icon,
+                UpdateRealm(newRealms[id], id, build, name, externalAddress->address(), localAddress->address(), port, icon,
                     flag, timezone, (allowedSecurityLevel <= SEC_ADMINISTRATOR ? AccountTypes(allowedSecurityLevel) : SEC_ADMINISTRATOR), pop);
 
                 newSubRegions.insert(Battlenet::RealmHandle{ region, battlegroup, 0 }.GetAddressString());
diff --git a/src/server/shared/Realm/RealmList.h b/src/server/shared/Realm/RealmList.h
index 3d820120c37..3032b9975cb 100644
--- a/src/server/shared/Realm/RealmList.h
+++ b/src/server/shared/Realm/RealmList.h
@@ -98,7 +98,7 @@ private:
     void LoadBuildInfo();
     void UpdateRealms(boost::system::error_code const& error);
     void UpdateRealm(Realm& realm, Battlenet::RealmHandle const& id, uint32 build, std::string const& name,
-        boost::asio::ip::address&& address, boost::asio::ip::address&& localAddr, boost::asio::ip::address&& localSubmask,
+        boost::asio::ip::address&& address, boost::asio::ip::address&& localAddr,
         uint16 port, uint8 icon, RealmFlags flag, uint8 timezone, AccountTypes allowedSecurityLevel, float population);
 
     std::vector<RealmBuildInfo> _builds;
diff --git a/src/server/worldserver/Main.cpp b/src/server/worldserver/Main.cpp
index d56fa0156da..013b4b0f977 100644
--- a/src/server/worldserver/Main.cpp
+++ b/src/server/worldserver/Main.cpp
@@ -34,10 +34,10 @@
 #include "GitRevision.h"
 #include "InstanceLockMgr.h"
 #include "IoContext.h"
+#include "IpNetwork.h"
 #include "MapManager.h"
 #include "Metric.h"
 #include "MySQLThreading.h"
-#include "ObjectAccessor.h"
 #include "OpenSSLCrypto.h"
 #include "OutdoorPvP/OutdoorPvPMgr.h"
 #include "ProcessPriority.h"
@@ -290,6 +290,8 @@ extern int main(int argc, char** argv)
     if (vm.count("update-databases-only"))
         return 0;
 
+    Trinity::Net::ScanLocalNetworks();
+
     // Set server offline (not connectable)
     LoginDatabase.DirectPExecute("UPDATE realmlist SET flag = flag | {} WHERE id = '{}'", REALM_FLAG_OFFLINE, realm.Id.Realm);
 
@@ -619,7 +621,6 @@ bool LoadRealmInfo()
         realm.Build = realmListRealm->Build;
         realm.ExternalAddress = std::make_unique<boost::asio::ip::address>(*realmListRealm->ExternalAddress);
         realm.LocalAddress = std::make_unique<boost::asio::ip::address>(*realmListRealm->LocalAddress);
-        realm.LocalSubnetMask = std::make_unique<boost::asio::ip::address>(*realmListRealm->LocalSubnetMask);
         realm.Port = realmListRealm->Port;
         realm.Name = realmListRealm->Name;
         realm.NormalizedName = realmListRealm->NormalizedName;