From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: Fri,  4 Mar 2016 15:44:14 -0500

From: Willem de Bruijn <willemb@google.com>

Allow device-specific validation of link layer headers. Existing
checks drop all packets shorter than hard_header_len. For variable
length protocols, such packets can be valid.

patch 1 adds header_ops.validate and dev_validate_header
patch 2 replaces ll_header_truncated with dev_validate_header
patch 3 implements the protocol specific callback for AX25

Tested with a temporary eth_header_validate function. The AX25
code is compile-tested only at this point.

I'm not going to be able to send another pull request to Linus
before -final, so please respin this against net-next and I'll
queue it up for -stable.

You can add the missing Fixes: tags as well when you do this.

Thanks.