Connect EmbeddedChannel when FuzzTesting

FuzzTesting/Sources/ServerFuzzerLib/ServerFuzzer.swift

@@ -22,6 +22,8 @@ public func test(_ start: UnsafeRawPointer, _ count: Int) -> CInt {
   let bytes = UnsafeRawBufferPointer(start: start, count: count)
 
   let channel = EmbeddedChannel()
+  try! channel.connect(to: try! SocketAddress(ipAddress: "127.0.0.1", port: 0)).wait()
+
   defer {
     _ = try? channel.finish()
   }

Sources/GRPC/ConnectionManager.swift

@@ -514,9 +514,14 @@ internal final class ConnectionManager {
       state.candidate.whenComplete {
         switch $0 {
         case let .success(channel):
-          // In case we do successfully connect, close immediately.
-          channel.close(mode: .all, promise: nil)
-          promise.completeWith(channel.closeFuture.recoveringFromUncleanShutdown())
+          // In case we do successfully connect, close on the next loop tick. When connecting a
+          // channel NIO will complete the promise for the channel before firing channel active.
+          // That means we may close and fire inactive before active which HTTP/2 will be unhappy
+          // about.
+          self.eventLoop.execute {
+            channel.close(mode: .all, promise: nil)
+            promise.completeWith(channel.closeFuture.recoveringFromUncleanShutdown())
+          }
 
         case .failure:
           // We failed to connect, that's fine we still shutdown successfully.

Tests/GRPCTests/ServerFuzzingRegressionTests.swift

@@ -31,6 +31,7 @@ final class ServerFuzzingRegressionTests: GRPCTestCase {
 
   private func runTest(withInput buffer: ByteBuffer) {
     let channel = EmbeddedChannel()
+    try! channel.connect(to: try! SocketAddress(ipAddress: "127.0.0.1", port: 0)).wait()
     defer {
       _ = try? channel.finish()
     }