Re: Sending short raw packets using sendmsg() broke

[David Miller <davem@davemloft.net>]

From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: Fri, 26 Feb 2016 12:33:13 -0500

> Right. The simplest, if hacky, fix is to add something along the lines of
> 
>   static unsigned short netdev_min_hard_header_len(struct net_device *dev)
>   {
>       if (unlikely(dev->type ==ARPHDR_AX25))
>         return AX25_KISS_HEADER_LEN;
>       else
>         return dev->hard_header_len;
>   }
> 
> Depending on how the variable encoding scheme works, a basic min
> length check may still produce buggy headers that confuse the stack or
> driver. I need to read up on AX25. If so, then extending header_ops
> with an optional validate() function is a more generic approach of
> checking header sanity.

I suspect we will need some kind of header ops for this.