CSHARP-3191: driver tries to run getLastError on mongocryptd that does not exists.

src/MongoDB.Driver.Core/Core/Connections/ConnectionInitializer.cs

@@ -59,7 +59,7 @@ public ConnectionDescription Authenticate(IConnection connection, ConnectionDesc
             {
                 description = UpdateConnectionIdWithServerValue(description, connectionIdServerValue.Value);
             }
-            else
+            else if (!description.HelloResult.IsMongocryptd) // mongocryptd doesn't provide ConnectionId
             {
                 try
                 {
@@ -90,7 +90,7 @@ public async Task<ConnectionDescription> AuthenticateAsync(IConnection connectio
             {
                 description = UpdateConnectionIdWithServerValue(description, connectionIdServerValue.Value);
             }
-            else
+            else if (!description.HelloResult.IsMongocryptd) // mongocryptd doesn't provide ConnectionId
             {
                 try
                 {

src/MongoDB.Driver.Core/Core/Connections/HelloResult.cs

@@ -124,6 +124,14 @@ public bool IsArbiter
             get { return ServerType == ServerType.ReplicaSetArbiter; }
         }
 
+        /// <summary>
+        /// Gets a value indicating whether this instance is a mongocryptd.
+        /// </summary>
+        /// <value>
+        /// <c>true</c> if this instance is a mongocryptd; otherwise, <c>false</c>.
+        /// </value>
+        public bool IsMongocryptd => _wrapped.TryGetValue("iscryptd", out var isCryptd) && isCryptd.IsBoolean ? isCryptd.ToBoolean() : false;
+
         /// <summary>
         /// Gets a value indicating whether this instance is a replica set member.
         /// </summary>

tests/MongoDB.Driver.Core.Tests/Core/Connections/HelloResultTests.cs

@@ -17,6 +17,7 @@
 using System.Net;
 using FluentAssertions;
 using MongoDB.Bson;
+using MongoDB.Bson.TestHelpers.XunitExtensions;
 using MongoDB.Driver.Core.Clusters;
 using MongoDB.Driver.Core.Compression;
 using MongoDB.Driver.Core.Misc;
@@ -318,5 +319,19 @@ public void HelloOk_should_return_false_when_response_does_not_contain_helloOk()
             var subject = new HelloResult(doc);
             subject.HelloOk.Should().BeFalse();
         }
+
+        [Theory]
+        [ParameterAttributeData]
+        public void IsMongocryptd_should_return_expected_result([Values(false, true, null)] bool? isMongocryptd)
+        {
+            var helloResultDocument = new BsonDocument
+            {
+                { "iscryptd", () => isMongocryptd.Value, isMongocryptd.HasValue }
+            };
+
+            var subject = new HelloResult(helloResultDocument);
+
+            subject.IsMongocryptd.Should().Be(isMongocryptd.GetValueOrDefault());
+        }
     }
 }