netdev - [PATCH] can: add a note that RECV_OWN_MSGS frames are subject to filtering

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Date:   Tue, 20 Apr 2021 21:12:00 +0200
From:   Erik Flodin <erik@...din.me>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Erik Flodin <erik@...din.me>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jonathan Corbet <corbet@....net>, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, linux-doc@...r.kernel.org
Subject: [PATCH] can: add a note that RECV_OWN_MSGS frames are subject to filtering

Some parts of the documentation may lead the reader to think that the
socket's own frames are always received when CAN_RAW_RECV_OWN_MSGS is
enabled, but all frames are subject to filtering.

As explained by Marc Kleine-Budde:

On TX complete of a CAN frame it's pushed into the RX path of the
networking stack, along with the information of the originating socket.

Then the CAN frame is delivered into AF_CAN, where it is passed on to
all registered receivers depending on filters. One receiver is the
sending socket in CAN_RAW. Then in CAN_RAW the it is checked if the
sending socket has RECV_OWN_MSGS enabled.

Signed-off-by: Erik Flodin <erik@...din.me>
---
 Documentation/networking/can.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/networking/can.rst b/Documentation/networking/can.rst
index f8dae662e454..f34cb0e4460e 100644
--- a/Documentation/networking/can.rst
+++ b/Documentation/networking/can.rst
@@ -608,6 +608,8 @@ demand:
     setsockopt(s, SOL_CAN_RAW, CAN_RAW_RECV_OWN_MSGS,
                &recv_own_msgs, sizeof(recv_own_msgs));

+Note that reception of a socket's own CAN frames are subject to the same
+filtering as other CAN frames (see :ref:`socketcan-rawfilter`).

 .. _socketcan-rawfd:

-- 
2.31.0