Re: [PATCH net-next 0/1] Support for VLAN interface over HSR/PRP

From: Murali Karicheri
Date: Tue Sep 08 2020 - 12:55:32 EST

Hi Willem,

On 9/4/20 11:52 AM, Willem de Bruijn wrote:
On Thu, Sep 3, 2020 at 12:30 AM Murali Karicheri <m-karicheri2@xxxxxx> wrote:


On 9/2/20 12:14 PM, Murali Karicheri wrote:

On 9/1/20 3:54 PM, Murali Karicheri wrote:
This series add support for creating VLAN interface over HSR or
PRP interface. Typically industrial networks uses VLAN in
deployment and this capability is needed to support these

This is tested using two TI AM572x IDK boards connected back
to back over CPSW ports (eth0 and eth1).

Following is the setup

Physical Setup
_______________ (CPSW) _______________
| |----eth0-----| |
|TI AM572x IDK1| | TI AM572x IDK2|

Network Topolgy

TI AM571x IDK TI AM572x IDK CPSW ports
hsr0/prp0.100--| |--eth0--| |--hsr0/prp0.100
|----hsr0/prp0--| |---hsr0/prp0--|
hsr0/prp0.101--| |--eth1--| |--hsr0/prp0/101

Following tests:-
- create hsr or prp interface and ping the interface IP address
and verify ping is successful.
- Create 2 VLANs over hsr or prp interface on both IDKs (VID 100 and
101). Ping between the IP address of the VLAN interfaces
- Do iperf UDP traffic test with server on one IDK and client on the
other. Do this using 100 and 101 subnet IP addresses
- Dump /proc/net/vlan/{hsr|prp}0.100 and verify frames are transmitted
and received at these interfaces.
- Delete the vlan and hsr/prp interface and verify interfaces are
removed cleanly.

Logs for IDK-1 at
Logs for IDK-2 at

Murali Karicheri (1):
net: hsr/prp: add vlan support

net/hsr/hsr_device.c | 4 ----
net/hsr/hsr_forward.c | 16 +++++++++++++---
2 files changed, 13 insertions(+), 7 deletions(-)

I am not sure if the packet flow is right for this?

VLAN over HSR frame format is like this.

<Start of Frame><VLAN tag><HSR Tag><IP><CRC>

My ifconfig stats shows both hsr and hsr0.100 interfaces receiving

So I did a WARN_ON() in HSR driver before frame is forwarded to upper

a0868495local@uda0868495:~/Projects/upstream-kernel$ git diff
diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c
index de21df30b0d9..545a3cd8c71b 100644
--- a/net/hsr/hsr_forward.c
+++ b/net/hsr/hsr_forward.c
@@ -415,9 +415,11 @@ static void hsr_forward_do(struct hsr_frame_info

skb->dev = port->dev;
- if (port->type == HSR_PT_MASTER)
+ if (port->type == HSR_PT_MASTER) {
+ if (skb_vlan_tag_present(skb))
+ WARN_ON(1);
hsr_deliver_master(skb, port->dev,
- else
+ } else
hsr_xmit(skb, port, frame);

And I get the trace shown below.

[ 275.125431] WARNING: CPU: 0 PID: 0 at net/hsr/hsr_forward.c:420
[ 275.133822] Modules linked in: snd_soc_omap_hdmi snd_soc_ti_sdma
snd_soc_core snd_pcm_dmaengine snd_pcm snd_time4
[ 275.199705] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W
5.9.0-rc1-00658-g473e463812c2-dirty #8
[ 275.209573] Hardware name: Generic DRA74X (Flattened Device Tree)
[ 275.215703] [<c011177c>] (unwind_backtrace) from [<c010b6f0>]
[ 275.223487] [<c010b6f0>] (show_stack) from [<c055690c>]
[ 275.230747] [<c055690c>] (dump_stack) from [<c01386ac>]
[ 275.237656] [<c01386ac>] (__warn) from [<c0138a3c>]
[ 275.245177] [<c0138a3c>] (warn_slowpath_fmt) from [<c09564bc>]
[ 275.253657] [<c09564bc>] (hsr_forward_skb) from [<c0955534>]
[ 275.262047] [<c0955534>] (hsr_handle_frame) from [<c07c6704>]
[ 275.271223] [<c07c6704>] (__netif_receive_skb_core) from [<c07c7180>]
[ 275.281266] [<c07c7180>] (__netif_receive_skb_one_core) from
[<c07c72a4>] (netif_receive_skb+0x50/0x1c4)
[ 275.290793] [<c07c72a4>] (netif_receive_skb) from [<c071a55c>]
[ 275.299272] [<c071a55c>] (cpsw_rx_handler) from [<c0715ee8>]
[ 275.307925] [<c0715ee8>] (__cpdma_chan_process) from [<c0717294>]
[ 275.316754] [<c0717294>] (cpdma_chan_process) from [<c071dd14>]
[ 275.325145] [<c071dd14>] (cpsw_rx_mq_poll) from [<c07c8ae0>]
[ 275.333185] [<c07c8ae0>] (net_rx_action) from [<c0101370>]
[ 275.340965] [<c0101370>] (__do_softirq) from [<c013f5ec>]
[ 275.348224] [<c013f5ec>] (irq_exit) from [<c0199344>]
[ 275.356093] [<c0199344>] (__handle_domain_irq) from [<c056f8fc>]
[ 275.364481] [<c056f8fc>] (gic_handle_irq) from [<c0100b6c>]
[ 275.371996] Exception stack(0xc0e01f18 to 0xc0e01f60)

Shouldn't it show vlan_do_receive() ?

if (skb_vlan_tag_present(skb)) {
if (pt_prev) {
ret = deliver_skb(skb, pt_prev, orig_dev);
pt_prev = NULL;
if (vlan_do_receive(&skb))
goto another_round;
else if (unlikely(!skb))
goto out;


I did an ftrace today and I find vlan_do_receive() is called for the
incoming frames before passing SKB to hsr_handle_frame(). If someone
can review this, it will help. Thanks.

hsr_handle_frame is an rx_handler called after
__netif_receive_skb_core called vlan_do_receive and jumped back to

Yes. hsr_handle_frame() is a rx_handler() after the above code that
does vlan_do_receive(). The ftrace shows vlan_do_receive() is called
followed by call to hsr_handle_frame(). From ifconfig I can see both
hsr and vlan interface stats increments by same count. So I assume,
vlan_do_receive() is called initially and it removes the tag, update
stats and then return true and go for another round. Do you think that
is the case?

vlan_do_receive() calls vlan_find_dev(skb->dev, vlan_proto, vlan_id)
to retrieve the real netdevice (real device). However VLAN device is
attached to hsr device (real device), but SKB will have HSR slave Ethernet netdevice (in our case it is cpsw device) and vlan_find_dev()
would have failed since there is no vlan_info in cpsw netdev struct. So
below code in vlan_do_receive() should have failed and return false.

vlan_dev = vlan_find_dev(skb->dev, vlan_proto, vlan_id);
if (!vlan_dev)
return false;

So how does it goes for another_round ? May be vlan_find_dev is
finding the hsr netdevice?

I am not an expert and so the question. Probably I can put a
traceprintk() to confirm this, but if someone can clarify this
it will be great. But for that, I will spin v2 with the above comments
addressed as in my reply and post.


That's how it should work right?

Murali Karicheri
Texas Instruments