/*
Technitium DNS Server
Copyright (C) 2021 Shreyas Zare (shreyas@technitium.com)
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 3 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 .
*/
using DnsApplicationCommon;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Net;
using System.Threading.Tasks;
using TechnitiumLibrary.Net;
using TechnitiumLibrary.Net.Dns;
using TechnitiumLibrary.Net.Dns.ResourceRecords;
namespace SplitHorizon
{
public class SimpleCNAME : IDnsApplicationRequestHandler
{
#region IDisposable
public void Dispose()
{
//do nothing
}
#endregion
#region public
public Task InitializeAsync(IDnsServer dnsServer, string config)
{
//no config needed
return Task.CompletedTask;
}
public Task ProcessRequestAsync(DnsDatagram request, IPEndPoint remoteEP, string zoneName, uint appRecordTtl, string appRecordData, bool isRecursionAllowed, IDnsServer dnsServer)
{
dynamic jsonAppRecordData = JsonConvert.DeserializeObject(appRecordData);
dynamic jsonCname;
if (NetUtilities.IsPrivateIP(remoteEP.Address))
jsonCname = jsonAppRecordData.@private;
else
jsonCname = jsonAppRecordData.@public;
if (jsonCname == null)
return Task.FromResult(null);
string cname = jsonCname.Value;
if (string.IsNullOrEmpty(cname))
return Task.FromResult(null);
IReadOnlyList answers;
if (request.Question[0].Name.Equals(zoneName, StringComparison.OrdinalIgnoreCase)) //check for zone apex
answers = new DnsResourceRecord[] { new DnsResourceRecord(request.Question[0].Name, DnsResourceRecordType.ANAME, DnsClass.IN, appRecordTtl, new DnsANAMERecord(cname)) }; //use ANAME
else
answers = new DnsResourceRecord[] { new DnsResourceRecord(request.Question[0].Name, DnsResourceRecordType.CNAME, DnsClass.IN, appRecordTtl, new DnsCNAMERecord(cname)) };
return Task.FromResult(new DnsDatagram(request.Identifier, true, request.OPCODE, true, false, request.RecursionDesired, isRecursionAllowed, false, false, DnsResponseCode.NoError, request.Question, answers));
}
#endregion
#region properties
public string Description
{ get { return "Returns different CNAME record for clients querying over public and private networks. Note that the app will return ANAME record for an APP record at zone apex."; } }
public string ApplicationRecordDataTemplate
{
get
{
return @"{
""public"": ""api.example.com"",
""private"": ""api.example.corp""
}";
}
}
#endregion
}
}