Fix remaining RESP3 handshake snafus

Author: mgravell

tests/StackExchange.Redis.Tests/InProcessTestServer.cs

@@ -18,6 +18,7 @@ public class InProcessTestServer : MemoryCacheRedisServer
     private readonly ITestOutputHelper? _log;
     public InProcessTestServer(ITestOutputHelper? log = null)
     {
+        RedisVersion = RedisFeatures.v6_0_0; // for client to expect RESP3
         _log = log;
         // ReSharper disable once VirtualMemberCallInConstructor
         _log?.WriteLine($"Creating in-process server: {ToString()}");

toys/KestrelRedisServer/Program.cs

@@ -6,7 +6,9 @@
 
 var server = new MemoryCacheRedisServer
 {
-    RedisVersion = new(3, 0),
+    // note: we don't support many v6 features, but some clients
+    // want this before they'll try RESP3
+    RedisVersion = new(6, 0),
     // Password = "letmein",
 };
 

toys/StackExchange.Redis.Server/RedisServer.cs

@@ -209,7 +209,7 @@ protected virtual TypedRedisValue Hello(RedisClient client, in RedisRequest requ
 
                 for (int i = 2; i < request.Count && request.TryGetCommandBytes(i, out var key); i++)
                 {
-                    int remaining = request.Count - (i + 2);
+                    int remaining = request.Count - (i + 1);
                     TypedRedisValue ArgFail() => TypedRedisValue.Error($"ERR Syntax error in HELLO option '{key.ToString().ToLower()}'\"");
                     if (key.Equals(Literals.AUTH))
                     {
@@ -225,6 +225,10 @@ protected virtual TypedRedisValue Hello(RedisClient client, in RedisRequest requ
                         if (remaining < 1) return ArgFail();
                         name = request.GetString(++i);
                     }
+                    else
+                    {
+                        return ArgFail();
+                    }
                 }
             }