PROTO_HDR_FIELD_MASK
BIT((proto_hdr_field) & PROTO_HDR_FIELD_MASK)
((hdr)->field_selector |= BIT((field) & PROTO_HDR_FIELD_MASK))
((hdr)->field_selector &= ~BIT((field) & PROTO_HDR_FIELD_MASK))
((hdr)->field_selector & BIT((val) & PROTO_HDR_FIELD_MASK))