netdev - [PATCH 4/6] Better documentation of BDPU guard

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Date:   Mon, 13 Apr 2020 01:50:36 +0200
From:   roucaries.bastien@...il.com
To:     netdev@...r.kernel.org
Cc:     sergei.shtylyov@...entembedded.com,
        Stephen Hemminger <stephen@...workplumber.org>,
        Bastien Roucariès <rouca@...ian.org>
Subject: [PATCH 4/6] Better documentation of BDPU guard

From: Bastien Roucariès <rouca@...ian.org>

Document that guard disable the port and how to reenable it

Signed-off-by: Bastien Roucariès <rouca@...ian.org>
---
 man/man8/bridge.8 | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/man/man8/bridge.8 b/man/man8/bridge.8
index bd33635a..9bfd942f 100644
--- a/man/man8/bridge.8
+++ b/man/man8/bridge.8
@@ -340,7 +340,18 @@ STP BPDUs.
 .BR "guard on " or " guard off "
 Controls whether STP BPDUs will be processed by the bridge port. By default,
 the flag is turned off allowed BPDU processing. Turning this flag on will
-cause the port to stop processing STP BPDUs.
+disables
+the bridge port if a STP BPDU packet is received.
+
+If running Spanning Tree on bridge, hostile devices on the network
+may send BPDU on a port and cause network failure. Setting
+.B guard on
+will detect and stop this by disabling the port.
+The port will be restarted if link is brought down, or
+removed and reattached.  For example if guard is enable on
+eth0:
+
+.B ip link set dev eth0 down; ip link set dev eth0 up
 
 .TP
 .BR "hairpin on " or " hairpin off "
-- 
2.25.1