[PATCH net-next mlxsw] mlxsw: spectrum_span: Support LAG under mirror-to-gretap

[Petr Machata]

When resolving a path that the packet will take after being encapsulated
in mirror-to-gretap scenarios, one of the devices en route could be a
LAG. In that case, mirror to first up slave that corresponds to a front
panel port.

Signed-off-by: Petr Machata <petrm at mellanox.com>
---

Notes:
    Unlike VLANs, we don't support LAG in SPAN and RSPAN situations, only
    ERSPAN ones. mlxsw can't actually support LAG well--since it needs to
    resolve the mirroring to a particular front panel port, there's no way
    to express the load balancing that the LAG is supposed to do.
    
    In SPAN and RSPAN scenarios, the decision to set up a certain mirror is
    purely an administrative one, and a given administrator can always
    resolve a particular front panel port themselves. For ERSPAN however,
    while the decision to mirror is administrative, routing of underlay
    packets is a matter of routing protocols that might just happen to put
    the remote tunnel end behind a LAG port. For these cases rather than
    dropping the mirroring altogether, and reinstating it again only when
    routes change, have mlxsw choose an arbitrary LAG member.

 drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c
index e5f4f76..da3f7f5 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c
@@ -245,6 +245,19 @@ mlxsw_sp_span_entry_vlan(const struct net_device *vlan_dev,
 	return vlan_dev_real_dev(vlan_dev);
 }
 
+static struct net_device *
+mlxsw_sp_span_entry_lag(struct net_device *lag_dev)
+{
+	struct net_device *dev;
+	struct list_head *iter;
+
+	netdev_for_each_lower_dev(lag_dev, dev, iter)
+		if ((dev->flags & IFF_UP) && mlxsw_sp_port_dev_check(dev))
+			return dev;
+
+	return NULL;
+}
+
 static __maybe_unused int
 mlxsw_sp_span_entry_tunnel_parms_common(struct net_device *edev,
 					union mlxsw_sp_l3addr saddr,
@@ -278,6 +291,14 @@ mlxsw_sp_span_entry_tunnel_parms_common(struct net_device *edev,
 		edev = mlxsw_sp_span_entry_vlan(edev, &vid);
 	}
 
+	if (netif_is_lag_master(edev)) {
+		if (!(edev->flags & IFF_UP))
+			goto unoffloadable;
+		edev = mlxsw_sp_span_entry_lag(edev);
+		if (!edev)
+			goto unoffloadable;
+	}
+
 	if (!mlxsw_sp_port_dev_check(edev))
 		goto unoffloadable;
 
-- 
2.4.11