From 4845b2185f9829a018354543f14672691abcb107 Mon Sep 17 00:00:00 2001
From: RvdH <ruud.vd.hout@hotmail.com>
Date: Mon, 4 Oct 2021 15:01:13 +0200
Subject: [PATCH] 5.7.0-DNSServer INI Setting(s)

Boolean UseDNSCache
String DNSServer
---
 .../Common/Application/IniFileSettings.cpp    |  6 ++-
 .../Common/Application/IniFileSettings.h      |  4 ++
 .../Server/Common/TCPIP/DNSResolverWinApi.cpp | 49 ++++++++++++++++++-
 3 files changed, 56 insertions(+), 3 deletions(-)

diff --git a/hmailserver/source/Server/Common/Application/IniFileSettings.cpp b/hmailserver/source/Server/Common/Application/IniFileSettings.cpp
index e4a2b1cea..92962fd91 100644
--- a/hmailserver/source/Server/Common/Application/IniFileSettings.cpp
+++ b/hmailserver/source/Server/Common/Application/IniFileSettings.cpp
@@ -59,7 +59,8 @@ namespace HM
       blocked_iphold_seconds_(0),
       smtpdmax_size_drop_(0),
       backup_messages_dbonly_(false),
-      add_xauth_user_ip_(false)
+      add_xauth_user_ip_(false),
+      use_dns_cache_(true)
       
    {
 
@@ -194,7 +195,8 @@ namespace HM
       smtpdmax_size_drop_ =  ReadIniSettingInteger_("Settings", "SMTPDMaxSizeDrop",0);
       backup_messages_dbonly_ =  ReadIniSettingInteger_("Settings", "BackupMessagesDBOnly",0) == 1;
       add_xauth_user_ip_ =  ReadIniSettingInteger_("Settings", "AddXAuthUserIP",1) == 1;
-
+      use_dns_cache_ = ReadIniSettingInteger_("Settings", "UseDNSCache", 1) == 1;
+      dns_server_ = ReadIniSettingString_("Settings", "DNSServer", "");
       rewrite_envelope_from_when_forwarding_ = ReadIniSettingInteger_("Settings", "RewriteEnvelopeFromWhenForwarding", 0) == 1;
       m_sDisableAUTHList = ReadIniSettingString_("Settings", "DisableAUTHList", "");
    }
diff --git a/hmailserver/source/Server/Common/Application/IniFileSettings.h b/hmailserver/source/Server/Common/Application/IniFileSettings.h
index 00f368a74..daac8f4e1 100644
--- a/hmailserver/source/Server/Common/Application/IniFileSettings.h
+++ b/hmailserver/source/Server/Common/Application/IniFileSettings.h
@@ -110,6 +110,8 @@ namespace HM
       bool GetBackupMessagesDBOnly () const { return backup_messages_dbonly_; }
       bool GetAddXAuthUserIP () const { return add_xauth_user_ip_; }
       bool GetRewriteEnvelopeFromWhenForwarding() const { return rewrite_envelope_from_when_forwarding_; }
+      bool GetUseDNSCache() const { return use_dns_cache_; }
+      String GetDNSServer() const { return dns_server_; }
       std::set<int> GetAuthDisabledOnPorts();
 
    private:   
@@ -188,6 +190,8 @@ namespace HM
       bool backup_messages_dbonly_;
       bool add_xauth_user_ip_;
       bool rewrite_envelope_from_when_forwarding_;
+      bool use_dns_cache_;
+      String dns_server_;
       String database_provider_;
 
       String m_sDisableAUTHList;
diff --git a/hmailserver/source/Server/Common/TCPIP/DNSResolverWinApi.cpp b/hmailserver/source/Server/Common/TCPIP/DNSResolverWinApi.cpp
index 24670bfe2..57eed19c3 100644
--- a/hmailserver/source/Server/Common/TCPIP/DNSResolverWinApi.cpp
+++ b/hmailserver/source/Server/Common/TCPIP/DNSResolverWinApi.cpp
@@ -65,7 +65,51 @@ namespace HM
    {
       PDNS_RECORD pDnsRecord = NULL;
       
-      DNS_STATUS nDnsStatus = DnsQuery(query, resourceType, DNS_QUERY_STANDARD, NULL, &pDnsRecord, NULL);
+      PIP4_ARRAY pSrvList = NULL;
+
+      DWORD fOptions;
+      fOptions = DNS_QUERY_STANDARD;
+
+      if (!IniFileSettings::Instance()->GetUseDNSCache())
+      {
+         fOptions += DNS_QUERY_BYPASS_CACHE;
+      }
+
+      AnsiString sCustomDNS;
+      sCustomDNS = IniFileSettings::Instance()->GetDNSServer().Trim();
+      if (!sCustomDNS.IsEmpty())
+      {
+         pSrvList = (PIP4_ARRAY)malloc(sizeof(IP4_ARRAY));
+         if (!pSrvList) {
+
+            String sMessage;
+            sMessage.Format(_T("Unable to allocate memory for DNS server list. Query: %s, Type: %d."), query, resourceType);
+            ErrorManager::Instance()->ReportError(ErrorManager::Low, 4401, "DNSResolver::_Resolve", sMessage);
+
+            return false;
+         }
+
+         // Custom DNSServer IPv4 address
+         pSrvList->AddrCount = 1;
+         pSrvList->AddrArray[0] = inet_addr(sCustomDNS.c_str()); //Custom DNS server IP address
+         if (pSrvList->AddrArray[0] == INADDR_NONE) {
+
+            String sMessage;
+            sMessage.Format(_T("Invalid DNSServer IP address. DNSServer IP: %hs."), sCustomDNS.c_str());
+            ErrorManager::Instance()->ReportError(ErrorManager::Low, 4401, "DNSResolver::_Resolve", sMessage);
+
+            // fallback to the system dns servers
+            pSrvList = NULL;
+         }
+         else
+         {
+            // We need this if not using system dns servers
+            if (fOptions != DNS_QUERY_BYPASS_CACHE)
+               fOptions += DNS_QUERY_BYPASS_CACHE;
+         }
+      }
+
+      DNS_STATUS nDnsStatus = DnsQuery(query, resourceType, fOptions, pSrvList, &pDnsRecord, NULL);
 
       PDNS_RECORD pDnsRecordsToDelete = pDnsRecord;
 
@@ -186,6 +230,9 @@ namespace HM
       _FreeDNSRecord(pDnsRecordsToDelete);
       pDnsRecordsToDelete = 0;
 
+      if (pSrvList != NULL)
+         free(pSrvList);
+
       std::sort(foundRecords.begin(), foundRecords.end(), SortDnsRecordsByPreference);