From: latten@austin.ibm.com
   Date: Fri, 18 Apr 2003 15:17:04 -0500

   I modified ah6_input() and esp6_input() to return zero instead of -EINVAL
   in the fix below. I tested it and it works.
   
   Please let me know if this is ok. 

I think it would be better if ipv6's upper-layer interface worked
like ipv4's.  ie. a < 0 return value means:

	next_proto =- ret;
	goto resubmit;

The less that is different between ipv4/ipv6 the better.