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    Subject[PATCH 4.9 13/93] mlxsw: spectrum_router: Avoid potential packets loss
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Ido Schimmel <idosch@mellanox.com>


    [ Upstream commit f7df4923fa986247e93ec2cdff5ca168fff14dcf ]

    When the structure of the LPM tree changes (f.e., due to the addition of
    a new prefix), we unbind the old tree and then bind the new one. This
    may result in temporary packet loss.

    Instead, overwrite the old binding with the new one.

    Fixes: 6b75c4807db3 ("mlxsw: spectrum_router: Add virtual router management")
    Signed-off-by: Ido Schimmel <idosch@mellanox.com>
    Signed-off-by: Jiri Pirko <jiri@mellanox.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c | 30 ++++++++++++------
    1 file changed, 20 insertions(+), 10 deletions(-)

    --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
    +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
    @@ -500,30 +500,40 @@ static int
    mlxsw_sp_vr_lpm_tree_check(struct mlxsw_sp *mlxsw_sp, struct mlxsw_sp_vr *vr,
    struct mlxsw_sp_prefix_usage *req_prefix_usage)
    {
    - struct mlxsw_sp_lpm_tree *lpm_tree;
    + struct mlxsw_sp_lpm_tree *lpm_tree = vr->lpm_tree;
    + struct mlxsw_sp_lpm_tree *new_tree;
    + int err;

    - if (mlxsw_sp_prefix_usage_eq(req_prefix_usage,
    - &vr->lpm_tree->prefix_usage))
    + if (mlxsw_sp_prefix_usage_eq(req_prefix_usage, &lpm_tree->prefix_usage))
    return 0;

    - lpm_tree = mlxsw_sp_lpm_tree_get(mlxsw_sp, req_prefix_usage,
    + new_tree = mlxsw_sp_lpm_tree_get(mlxsw_sp, req_prefix_usage,
    vr->proto, false);
    - if (IS_ERR(lpm_tree)) {
    + if (IS_ERR(new_tree)) {
    /* We failed to get a tree according to the required
    * prefix usage. However, the current tree might be still good
    * for us if our requirement is subset of the prefixes used
    * in the tree.
    */
    if (mlxsw_sp_prefix_usage_subset(req_prefix_usage,
    - &vr->lpm_tree->prefix_usage))
    + &lpm_tree->prefix_usage))
    return 0;
    - return PTR_ERR(lpm_tree);
    + return PTR_ERR(new_tree);
    }

    - mlxsw_sp_vr_lpm_tree_unbind(mlxsw_sp, vr);
    - mlxsw_sp_lpm_tree_put(mlxsw_sp, vr->lpm_tree);
    + /* Prevent packet loss by overwriting existing binding */
    + vr->lpm_tree = new_tree;
    + err = mlxsw_sp_vr_lpm_tree_bind(mlxsw_sp, vr);
    + if (err)
    + goto err_tree_bind;
    + mlxsw_sp_lpm_tree_put(mlxsw_sp, lpm_tree);
    +
    + return 0;
    +
    +err_tree_bind:
    vr->lpm_tree = lpm_tree;
    - return mlxsw_sp_vr_lpm_tree_bind(mlxsw_sp, vr);
    + mlxsw_sp_lpm_tree_put(mlxsw_sp, new_tree);
    + return err;
    }

    static struct mlxsw_sp_vr *mlxsw_sp_vr_get(struct mlxsw_sp *mlxsw_sp,

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