Filter additional records from DNS SRV response (#4463)

Author: vha-schleupen

src/Microsoft.Extensions.ServiceDiscovery.Dns/DnsSrvServiceEndpointProvider.cs

@@ -42,7 +42,7 @@ protected override async Task ResolveAsyncCore()
         }
 
         var lookupMapping = new Dictionary<string, DnsResourceRecord>();
-        foreach (var record in result.Additionals)
+        foreach (var record in result.Additionals.Where(x => x is AddressRecord or CNameRecord))
         {
             ttl = MinTtl(record, ttl);
             lookupMapping[record.DomainName] = record;

tests/Microsoft.Extensions.ServiceDiscovery.Dns.Tests/DnsSrvServiceEndpointResolverTests.cs

@@ -91,7 +91,8 @@ public async Task ResolveServiceEndpoint_DnsSrv()
                     {
                         new ARecord(new ResourceRecordInfo("srv-a", ResourceRecordType.A, queryClass, 64, 0), IPAddress.Parse("10.10.10.10")),
                         new ARecord(new ResourceRecordInfo("srv-b", ResourceRecordType.AAAA, queryClass, 64, 0), IPAddress.IPv6Loopback),
-                        new CNameRecord(new ResourceRecordInfo("srv-c", ResourceRecordType.AAAA, queryClass, 64, 0), DnsString.Parse("remotehost"))
+                        new CNameRecord(new ResourceRecordInfo("srv-c", ResourceRecordType.AAAA, queryClass, 64, 0), DnsString.Parse("remotehost")),
+                        new TxtRecord(new ResourceRecordInfo("srv-a", ResourceRecordType.TXT, queryClass, 64, 0), ["some txt values"], ["some txt utf8 values"])
                     }
                 };
 
@@ -152,7 +153,8 @@ public async Task ResolveServiceEndpoint_DnsSrv_MultipleProviders_PreventMixing(
                     {
                         new ARecord(new ResourceRecordInfo("srv-a", ResourceRecordType.A, queryClass, 64, 0), IPAddress.Parse("10.10.10.10")),
                         new ARecord(new ResourceRecordInfo("srv-b", ResourceRecordType.AAAA, queryClass, 64, 0), IPAddress.IPv6Loopback),
-                        new CNameRecord(new ResourceRecordInfo("srv-c", ResourceRecordType.AAAA, queryClass, 64, 0), DnsString.Parse("remotehost"))
+                        new CNameRecord(new ResourceRecordInfo("srv-c", ResourceRecordType.AAAA, queryClass, 64, 0), DnsString.Parse("remotehost")),
+                        new TxtRecord(new ResourceRecordInfo("srv-a", ResourceRecordType.TXT, queryClass, 64, 0), ["some txt values"], ["some txt utf8 values"])
                     }
                 };