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    Subject[PATCH 5.17 121/158] net: bridge: Clear offload_fwd_mark when passing frame up bridge interface.
    Date
    From: Andrew Lunn <andrew@lunn.ch>

    [ Upstream commit fbb3abdf2223cd0dfc07de85fe5a43ba7f435bdf ]

    It is possible to stack bridges on top of each other. Consider the
    following which makes use of an Ethernet switch:

    br1
    / \
    / \
    / \
    br0.11 wlan0
    |
    br0
    / | \
    p1 p2 p3

    br0 is offloaded to the switch. Above br0 is a vlan interface, for
    vlan 11. This vlan interface is then a slave of br1. br1 also has a
    wireless interface as a slave. This setup trunks wireless lan traffic
    over the copper network inside a VLAN.

    A frame received on p1 which is passed up to the bridge has the
    skb->offload_fwd_mark flag set to true, indicating that the switch has
    dealt with forwarding the frame out ports p2 and p3 as needed. This
    flag instructs the software bridge it does not need to pass the frame
    back down again. However, the flag is not getting reset when the frame
    is passed upwards. As a result br1 sees the flag, wrongly interprets
    it, and fails to forward the frame to wlan0.

    When passing a frame upwards, clear the flag. This is the Rx
    equivalent of br_switchdev_frame_unmark() in br_dev_xmit().

    Fixes: f1c2eddf4cb6 ("bridge: switchdev: Use an helper to clear forward mark")
    Signed-off-by: Andrew Lunn <andrew@lunn.ch>
    Reviewed-by: Ido Schimmel <idosch@nvidia.com>
    Tested-by: Ido Schimmel <idosch@nvidia.com>
    Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
    Link: https://lore.kernel.org/r/20220518005840.771575-1-andrew@lunn.ch
    Signed-off-by: Paolo Abeni <pabeni@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/bridge/br_input.c | 7 +++++++
    1 file changed, 7 insertions(+)

    diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
    index b50382f957c1..6743c8a0fe8e 100644
    --- a/net/bridge/br_input.c
    +++ b/net/bridge/br_input.c
    @@ -39,6 +39,13 @@ static int br_pass_frame_up(struct sk_buff *skb)
    dev_sw_netstats_rx_add(brdev, skb->len);

    vg = br_vlan_group_rcu(br);
    +
    + /* Reset the offload_fwd_mark because there could be a stacked
    + * bridge above, and it should not think this bridge it doing
    + * that bridge's work forwarding out its ports.
    + */
    + br_switchdev_frame_unmark(skb);
    +
    /* Bridge is just like any other port. Make sure the
    * packet is allowed except in promisc mode when someone
    * may be running packet capture.
    --
    2.35.1


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