Test that a write reply with the wrong magic will force a retry

tests/acceptance/fakes/dest/write_wrong_magic.rb

@@ -0,0 +1,24 @@
+#!/usr/bin/env ruby
+# encoding: utf-8
+
+# Accept a connection, write hello, wait for a write request, read the
+# data, then write back a reply with a bad magic field.  We then
+# expect a reconnect.
+
+require 'flexnbd/fake_dest'
+include FlexNBD
+
+addr, port = *ARGV
+server = FakeDest.new( addr, port )
+
+client = server.accept
+client.write_hello
+req = client.read_request
+client.read_data( req[:len] )
+client.write_reply( req[:handle], 0, :magic => :wrong )
+
+client2 = server.accept
+client.close
+client2.close
+
+exit(0)