mlxsw: spectrum_router: Avoid potential packets loss

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>

1 files changed, 20 insertions, 10 deletions

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
index d7ac22d7f940..bd8de6b9be71 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
@@ -441,30 +441,40 @@ 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,