Formerly sysdeps/mach/hurd/__ioctl.c.~28~

diff --git a/sysdeps/mach/hurd/ioctl.c b/sysdeps/mach/hurd/ioctl.c
index 6e552b2..10f3d19 100644 (file)
--- a/sysdeps/mach/hurd/ioctl.c
+++ b/sysdeps/mach/hurd/ioctl.c
@@ -152,8 +152,17 @@ DEFUN(__ioctl, (fd, request),
 
   /* Compute the Mach message ID for the RPC from the group and command
      parts of the ioctl request.  */
-  msgid = (100000 +
-          ((_IOC_GROUP (request) - 'f') * 4000) + _IOC_COMMAND (request));
+  msgid = 100000 + ((_IOC_GROUP (request) - 'f') * 4000); /* Base subsystem */
+  /* Because of MiG's poorly chosen algorithm of adding 100 to a request
+     msgid to produce the reply msgid, we cannot just add the command part
+     of the ioctl request to the subsystem base msgid.  For ioctl requests
+     past 99, we must skip blocks of 100 msgids to allow for the reply
+     msgids corresponding to the earlier requests.  */
+  if (_IOC_COMMAND (request) >= 100)
+    msgid += 100;
+  if (_IOC_COMMAND (request) >= 200)
+    msgid += 100;
+  msgid += _IOC_COMMAND (request);
 
   if (_IOC_INOUT (request) & IOC_IN)
     {