[lkml]   [2020]   [Jul]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] drivers/net/wan/lapbether: Use needed_headroom instead of hard_header_len
On Tue, Jul 28, 2020 at 6:42 PM Xie He <> wrote:
> On Tue, Jul 28, 2020 at 12:52 PM -0700
> Brian Norris <> wrote:
> > What is the intention with this X25 protocol? I guess the headers added
> > in lapbeth_data_transmit() are supposed to be "invisible", as with this
> > note in af_packet.c?
> This driver is not intended to be used with IPv4 or IPv6 protocols,
> but is intended to be used with a special "X.25" protocol. That's the
> reason the device type is ARPHRD_X25. I used "grep" in the X.25
> network layer code (net/x25) and I found there's nowhere
> "dev_hard_header" is called. I also used "grep" in all the X.25

That well could just be a bug in net/x25/. But from context, it does
appear that X.25 does not intend to expose its headers to higher

> drivers in the kernel (lapbether.c, x25_asy.c, hdlc_x25.c under
> drivers/net/wan) and I found no driver implemented "header_ops". So I
> think the X.25 networking code doesn't expect any header visible
> outside of the device driver, and X.25 drivers should make their
> headers invisible outside of them.
> So I think hard_header_len should be 0 for all X.25 drivers, so that
> they can be used correctly with af_packet.c.
> I don't know if this sounds plausible to you. If it does, could you
> please let me have your name in a "Reviewed_by" tag. It would be of
> great help to have your support. Thanks!

Sure, I can do that:

Reviewed-by: Brian Norris <>

I guess x25 is basically an abandoned project, if you're coming to me for this?

 \ /
  Last update: 2020-07-31 02:25    [W:0.088 / U:1.488 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site