at encap, copy the ECN bit of the payload into the tunnel header
at encap, compute flow hash on the inner packet for more entropy
at decap, copy the ECN bit of the tunnel header into the payload
at encap, copy the DSCP bits of the payload into the tunnel header
at encap, set the DF bit in the tunnel header
tunnel_encap_decap_flags
Flags controlling tunnel behaviour.
at encap, copy the DF bit of the payload into the tunnel header