Re: [PATCH net] net: hdlc_x25: Use qdisc to queue outgoing LAPB frames

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]<

 



On 2021-01-28 23:06, Xie He wrote:
On Thu, Jan 28, 2021 at 11:47 AM Jakub Kicinski <kuba@xxxxxxxxxx> wrote:

Noob question - could you point at or provide a quick guide to layering
here? I take there is only one netdev, and something maintains an
internal queue which is not stopped when HW driver stops the qdisc?

Yes, there is only one netdev. The LAPB module (net/lapb/) (which is
used as a library by the netdev driver - hdlc_x25.c) is maintaining an
internal queue which is not stopped when the HW driver stops the
qdisc.

The queue is "write_queue" in "struct lapb_cb" in
"include/net/lapb.h". The code that takes skbs out of the queue and
feeds them to lower layers for transmission is at the "lapb_kick"
function in "net/lapb/lapb_out.c".

The layering is like this:

Upper layer (Layer 3) (net/x25/ or net/packet/)

^
| L3 packets (with control info)
v

The netdev driver (hdlc_x25.c)

^
| L3 packets
v

The LAPB Module (net/lapb/)

^
| LAPB (L2) frames
v

The netdev driver (hdlc_x25.c)

^
| LAPB (L2) frames
| (also called HDLC frames in the context of the HDLC subsystem)
v

HDLC core (hdlc.c)

^
| HDLC frames
v

HDLC Hardware Driver

@Xie: Thank you for the detailed presentation.


Sounds like we're optimizing to prevent drops, and this was not
reported from production, rather thru code inspection. Ergo I think
net-next will be more appropriate here, unless Martin disagrees.

Yes, I have no problem in targeting net-next instead. Thanks!

I agree.



[Index of Archives]     [Linux ACPI]     [Linux Kernel]     [Linux Laptop]     [Kernel Newbies]     [Security]     [Netfilter]     [Bugtraq]     [Photo]     [Yosemite Photos]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Video 4 Linux]     [Device Mapper]     [Linux Resources]

  Powered by Linux