net: sch_tbf: Add a graft command

As another qdisc is linked to the TBF, the latter should issue an event to
give drivers a chance to react to the grafting. In other qdiscs, this event
is called GRAFT, so follow suit with TBF as well.

Signed-off-by: Petr Machata <[e-mail]>
Signed-off-by: Ido Schimmel <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/pkt_cls.h

···
 	TC_TBF_REPLACE,
 	TC_TBF_DESTROY,
 	TC_TBF_STATS,
+	TC_TBF_GRAFT,
 };
 
 struct tc_tbf_qopt_offload_replace_params {
···
 	union {
 		struct tc_tbf_qopt_offload_replace_params replace_params;
 		struct tc_qopt_offload_stats stats;
+		u32 child_handle;
 	};
 };
 

net/sched/sch_tbf.c

···
 	return qdisc_offload_dump_helper(sch, TC_SETUP_QDISC_TBF, &qopt);
 }
 
+static void tbf_offload_graft(struct Qdisc *sch, struct Qdisc *new,
+			      struct Qdisc *old, struct netlink_ext_ack *extack)
+{
+	struct tc_tbf_qopt_offload graft_offload = {
+		.handle		= sch->handle,
+		.parent		= sch->parent,
+		.child_handle	= new->handle,
+		.command	= TC_TBF_GRAFT,
+	};
+
+	qdisc_offload_graft_helper(qdisc_dev(sch), sch, new, old,
+				   TC_SETUP_QDISC_TBF, &graft_offload, extack);
+}
+
 /* GSO packet is too big, segment it so that tbf can transmit
  * each segment in time
  */
···
 		new = &noop_qdisc;
 
 	*old = qdisc_replace(sch, new, &q->qdisc);
+
+	tbf_offload_graft(sch, new, *old, extack);
 	return 0;
 }