Add a test for a second client connecting during a mirror

tests/fakes/source/connect_during_hello.rb

@@ -0,0 +1,36 @@
+#!/usr/bin/env ruby
+
+# Connect to the destination, then hang.  Connect a second time to the
+# destinatioin.  This will trigger the destination's thread clearer.
+
+require 'socket'
+require 'timeout'
+
+addr, port = *ARGV
+
+# client_sock1 is a connection the destination is expecting.
+client_sock1 = nil
+begin
+  Timeout.timeout(2) do
+    client_sock1 = TCPSocket.open( addr, port )
+  end
+rescue Timeout::Error
+  $stderr.puts "Timed out connecting."
+  exit 1
+end
+
+#client_sock2 is the interloper.
+client_sock2 = nil
+begin
+  Timeout.timeout(2) do
+    client_sock2 = TCPSocket.open( addr, port )
+  end
+rescue Timeout::Error
+  $stderr.puts "Timed out connecting a second time."
+  exit 1
+end
+
+# This is the expected source crashing after connect
+client_sock1.close
+# And this is just a tidy-up.
+client_sock2.close

tests/flexnbd.rb

@@ -313,7 +313,9 @@ class FlexNBD
   end
 
   def kill
-    can_die(2)
+    # At this point, to a certain degree we don't care what the exit
+    # status is
+    can_die(1)
     if @pid
       begin
         Process.kill("INT", @pid)

tests/nbd_scenarios

@@ -263,6 +263,8 @@ class NBDConnectSourceFailureScenarios < Test::Unit::TestCase
 
     assert @env.fake_reports_success
   end
+
+
 end
 
 
@@ -280,26 +282,28 @@ class NBDConnectDestFailureScenarios < Test::Unit::TestCase
 
 
   def test_hello_blocked_by_disconnect_causes_error_not_fatal
-    @env.nbd1.can_die(1)
     run_fake( "source/close_after_connect" )
     assert_no_control
   end
 
 
   def test_hello_goes_astray_causes_timeout_error
-    @env.nbd1.can_die(1)
     run_fake( "source/hang_after_hello" )
     assert_no_control
   end
 
 
   def test_disconnect_after_hello_causes_error_not_fatal
-    @env.nbd1.can_die(1)
     run_fake( "source/close_after_hello" )
     assert_no_control
   end
 
 
+  def test_double_connect_during_hello
+    run_fake( "source/connect_during_hello" )
+  end
+
+
   private
   def run_fake( name )
     @env.run_fake( name, @env.ip, @env.port1 )