datapath: backport: allow output of MPLS packets on tunnel vports

Upstream commit:
    commit fe3a5f6c795810edb1646a840fec3c8c350c2a4e
    Author: Simon Horman <[email protected]>

    openvswitch: allow output of MPLS packets on tunnel vports

    Currently output of MPLS packets on tunnel vports is not allowed by Open
    vSwitch. This is because historically encapsulation was done in such a way
    that the inner_protocol field of the skb needed to hold the inner protocol
    for both MPLS and tunnel encapsulation in order for GSO segmentation to be
    performed correctly.

    Since b2acd1dc3949 ("openvswitch: Use regular GRE net_device instead of
    vport") Open vSwitch makes use of lwt to output to tunnel netdevs which
    perform encapsulation. As no drivers expose support for MPLS offloads this
    means that GSO packets are segmented in software by validate_xmit_skb(),
    which is called from __dev_queue_xmit(), before tunnel encapsulation occurs.
    This means that the inner protocol of MPLS is no longer needed by the time
    encapsulation occurs and the contention on the inner_protocol field of the
    skb no longer occurs.

    Thus it is now safe to output MPLS to tunnel vports.

    Signed-off-by: Simon Horman <[email protected]>
    Reviewed-by: Jesse Gross <[email protected]>
    Signed-off-by: David S. Miller <[email protected]>

Signed-off-by: Pravin B Shelar <[email protected]>
Acked-by: Jesse Gross <[email protected]>

datapath/flow_netlink.c

@@ -2046,9 +2046,10 @@ static int validate_set(const struct nlattr *a,
 		break;
 
 	case OVS_KEY_ATTR_TUNNEL:
+#ifndef USE_UPSTREAM_TUNNEL
 		if (eth_p_mpls(eth_type))
 			return -EINVAL;
-
+#endif
 		if (masked)
 			return -EINVAL; /* Masked tunnel set not supported. */