diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 8e9581bc9..497c55571 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,10 @@
+2012-02-27  Corinna Vinschen  <corinna@vinschen.de>
+
+	* cygtls.cc (dll_cmp): New comparison function for bsearch.
+	(well_known_dlls): New array containing well-known DLLs.
+	(_cygtls::call2): Add code for BLODA detection.
+	* net.cc (fdsock): Ditto.
+
 2012-02-26  Corinna Vinschen  <corinna@vinschen.de>
 
 	* environ.cc (enum settings): Add setbool.  Rename justset to setdword
diff --git a/winsup/cygwin/cygtls.cc b/winsup/cygwin/cygtls.cc
index f45cfaa52..7b9c2a827 100644
--- a/winsup/cygwin/cygtls.cc
+++ b/winsup/cygwin/cygtls.cc
@@ -1,6 +1,7 @@
 /* cygtls.cc
 
-   Copyright 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Red Hat, Inc.
+   Copyright 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011,
+   2012 Red Hat, Inc.
 
 This software is a copyrighted work licensed under the terms of the
 Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
@@ -62,10 +63,68 @@ _cygtls::call (DWORD (*func) (void *, void *), void *arg)
   _my_tls.call2 (func, arg, buf);
 }
 
+static int
+dll_cmp (const void *a, const void *b)
+{
+  return wcscasecmp ((const wchar_t *) a, *(const wchar_t **) b);
+}
+
+/* Keep sorted!
+   This is a list of well-known core system DLLs which contain code
+   whiuch is started in its own thread by the system.  Kernel32.dll,
+   for instance, contains the thread called on every Ctrl-C keypress
+   in a console window.  The DLLs in this list are not recognized as
+   BLODAs. */
+const wchar_t *well_known_dlls[] =
+{
+  L"kernel32.dll",
+  L"mswsock.dll",
+  L"ntdll.dll",
+  L"ws2_32.dll",
+};
+
 void
 _cygtls::call2 (DWORD (*func) (void *, void *), void *arg, void *buf)
 {
   init_thread (buf, func);
+
+  /* Optional BLODA detection.  The idea is that the function address is
+     supposed to be within Cygwin itself.  This is also true for pthreads,
+     since pthreads are always calling thread_wrapper in miscfuncs.cc. 
+     Therefore, every function call to a function outside of the Cygwin DLL
+     is potentially a thread injected into the Cygwin process by some BLODA.
+
+     But that's a bit too simple.  Assuming the application itself calls
+     CreateThread, then this is a bad idea, but not really invalid.  So we
+     shouldn't print a BLODA message if the address is within the loaded
+     image of the application.  Also, ntdll.dll starts threads into the
+     application which */
+  if (detect_bloda)
+    {
+      PIMAGE_DOS_HEADER img_start = (PIMAGE_DOS_HEADER) GetModuleHandle (NULL);
+      PIMAGE_NT_HEADERS32 ntheader = (PIMAGE_NT_HEADERS32)
+			       ((PBYTE) img_start + img_start->e_lfanew);
+      void *img_end = (void *) ((PBYTE) img_start
+				+ ntheader->OptionalHeader.SizeOfImage);
+      if (((void *) func < (void *) cygwin_hmodule
+	   || (void *) func > (void *) cygheap)
+	  && ((void *) func < (void *) img_start || (void *) func >= img_end))
+	{
+	  MEMORY_BASIC_INFORMATION mbi;
+	  wchar_t modname[PATH_MAX];
+
+	  VirtualQuery ((PVOID) func, &mbi, sizeof mbi);
+	  GetModuleFileNameW ((HMODULE) mbi.AllocationBase, modname, PATH_MAX);
+	  /* Fetch basename and check against list of above system DLLs. */
+	  const wchar_t *modbasename = wcsrchr (modname, L'\\') + 1;
+	  if (!bsearch (modbasename, well_known_dlls,
+			sizeof well_known_dlls / sizeof well_known_dlls[0],
+			sizeof well_known_dlls[0], dll_cmp))
+	    small_printf ("\n\nPotential BLODA detected!  Thread function "
+			  "called outside of Cygwin DLL:\n  %W\n\n", modname);
+	}
+    }
+
   DWORD res = func (arg, buf);
   remove (INFINITE);
   /* Don't call ExitThread on the main thread since we may have been
diff --git a/winsup/cygwin/net.cc b/winsup/cygwin/net.cc
index 2115debab..40ab47bf3 100644
--- a/winsup/cygwin/net.cc
+++ b/winsup/cygwin/net.cc
@@ -1,7 +1,7 @@
 /* net.cc: network-related routines.
 
    Copyright 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
-   2005, 2006, 2007, 2008, 2009, 2010, 2011 Red Hat, Inc.
+   2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Red Hat, Inc.
 
 This file is part of Cygwin.
 
@@ -532,19 +532,33 @@ fdsock (cygheap_fdmanip& fd, const device *dev, SOCKET soc)
 		      sizeof (base_soc), &bret, NULL, NULL);
       if (ret)
 	debug_printf ("WSAIoctl: %lu", WSAGetLastError ());
-      else if (base_soc != soc
-	       && GetHandleInformation ((HANDLE) base_soc, &flags)
-	       && (flags & HANDLE_FLAG_INHERIT))
+      else if (base_soc != soc)
 	{
-	  if (!DuplicateHandle (GetCurrentProcess (), (HANDLE) base_soc,
-				GetCurrentProcess (), (PHANDLE) &base_soc,
-				0, TRUE, DUPLICATE_SAME_ACCESS))
-	    debug_printf ("DuplicateHandle failed, %E");
-	  else
+	  /* LSPs are often BLODAs as well.  So we print an info about
+	     detecting an LSP if BLODA detection is desired. */
+	  if (detect_bloda)
 	    {
-	      closesocket (soc);
-	      soc = base_soc;
-	      fixup = false;
+	      WSAPROTOCOL_INFO prot;
+
+	      memset (&prot, 0, sizeof prot);
+	      ::getsockopt (soc, SOL_SOCKET, SO_PROTOCOL_INFO, (char *) &prot,
+			    (size = sizeof prot, &size));
+	      small_printf ("\n\nPotential BLODA detected!  Layered Socket "
+			    "Service Provider:\n  %s\n\n", prot.szProtocol);
+	    }
+	  if (GetHandleInformation ((HANDLE) base_soc, &flags)
+	      && (flags & HANDLE_FLAG_INHERIT))
+	    {
+	      if (!DuplicateHandle (GetCurrentProcess (), (HANDLE) base_soc,
+				    GetCurrentProcess (), (PHANDLE) &base_soc,
+				    0, TRUE, DUPLICATE_SAME_ACCESS))
+		debug_printf ("DuplicateHandle failed, %E");
+	      else
+		{
+		  closesocket (soc);
+		  soc = base_soc;
+		  fixup = false;
+		}
 	    }
 	}
     }