netdev - HSR/PRP sequence counter issue with Cisco Redbox

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Date:   Wed, 27 Jan 2021 12:15:34 +0000
From:   "Wenzel, Marco" <Marco.Wenzel@...berle.de>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: HSR/PRP sequence counter issue with Cisco Redbox

Hi,

we have figured out an issue with the current PRP driver when trying to communicate with Cisco IE 2000 industrial Ethernet switches in Redbox mode. The Cisco always resets the HSR/PRP sequence counter to "1" at low traffic (<= 1 frame in 400 ms). It can be reproduced by a simple ICMP echo request with 1 s interval between a Linux box running with PRP and a VDAN behind the Cisco Redbox. The Linux box then always receives frames with sequence counter "1" and drops them. The behavior is not configurable at the Cisco Redbox.

I fixed it by ignoring sequence counters with value "1" at the sequence counter check in hsr_register_frame_out ():

diff --git a/net/hsr/hsr_framereg.c b/net/hsr/hsr_framereg.c
index 5c97de459905..630c238e81f0 100644
--- a/net/hsr/hsr_framereg.c
+++ b/net/hsr/hsr_framereg.c
@@ -411,7 +411,7 @@ void hsr_register_frame_in(struct hsr_node *node, struct hsr_port *port,
 int hsr_register_frame_out(struct hsr_port *port, struct hsr_node *node,
                           u16 sequence_nr)
 {
-       if (seq_nr_before_or_eq(sequence_nr, node->seq_out[port->type]))
+       if (seq_nr_before_or_eq(sequence_nr, node->seq_out[port->type]) && (sequence_nr != 1))
                return 1;

        node->seq_out[port->type] = sequence_nr;

Do you think this could be a solution? Should this patch be officially applied in order to avoid other users running into these communication issues?

Thanks
Marco Wenzel