net: sched: sch_red: Add qevents "early_drop" and "mark"

In order to allow acting on dropped and/or ECN-marked packets, add two new
qevents to the RED qdisc: "early_drop" and "mark". Filters attached at
"early_drop" block are executed as packets are early-dropped, those
attached at the "mark" block are executed as packets are ECN-marked.

Two new attributes are introduced: TCA_RED_EARLY_DROP_BLOCK with the block
index for the "early_drop" qevent, and TCA_RED_MARK_BLOCK for the "mark"
qevent. Absence of these attributes signifies "don't care": no block is
allocated in that case, or the existing blocks are left intact in case of
the change callback.

For purposes of offloading, blocks attached to these qevents appear with
newly-introduced binder types, FLOW_BLOCK_BINDER_TYPE_RED_EARLY_DROP and
FLOW_BLOCK_BINDER_TYPE_RED_MARK.

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

include/net/flow_offload.h

···
 	FLOW_BLOCK_BINDER_TYPE_UNSPEC,
 	FLOW_BLOCK_BINDER_TYPE_CLSACT_INGRESS,
 	FLOW_BLOCK_BINDER_TYPE_CLSACT_EGRESS,
+	FLOW_BLOCK_BINDER_TYPE_RED_EARLY_DROP,
+	FLOW_BLOCK_BINDER_TYPE_RED_MARK,
 };
 
 struct flow_block {

include/uapi/linux/pkt_sched.h

···
 	TCA_RED_STAB,
 	TCA_RED_MAX_P,
 	TCA_RED_FLAGS,		/* bitfield32 */
+	TCA_RED_EARLY_DROP_BLOCK, /* u32 */
+	TCA_RED_MARK_BLOCK,	/* u32 */
 	__TCA_RED_MAX,
 };
 

net/sched/sch_red.c

···
 	struct red_vars		vars;
 	struct red_stats	stats;
 	struct Qdisc		*qdisc;
+	struct tcf_qevent	qe_early_drop;
+	struct tcf_qevent	qe_mark;
 };
 
 #define TC_RED_SUPPORTED_FLAGS (TC_RED_HISTORIC_FLAGS | TC_RED_NODROP)
···
 
 		if (INET_ECN_set_ce(skb)) {
 			q->stats.prob_mark++;
+			skb = tcf_qevent_handle(&q->qe_mark, sch, skb, root_lock, to_free, &ret);
+			if (!skb)
+				return NET_XMIT_CN | ret;
 		} else if (!red_use_nodrop(q)) {
 			q->stats.prob_drop++;
 			goto congestion_drop;
···
 
 		if (INET_ECN_set_ce(skb)) {
 			q->stats.forced_mark++;
+			skb = tcf_qevent_handle(&q->qe_mark, sch, skb, root_lock, to_free, &ret);
+			if (!skb)
+				return NET_XMIT_CN | ret;
 		} else if (!red_use_nodrop(q)) {
 			q->stats.forced_drop++;
 			goto congestion_drop;
···
 	return ret;
 
 congestion_drop:
+	skb = tcf_qevent_handle(&q->qe_early_drop, sch, skb, root_lock, to_free, &ret);
+	if (!skb)
+		return NET_XMIT_CN | ret;
+
 	qdisc_drop(skb, sch, to_free);
 	return NET_XMIT_CN;
 }
···
 {
 	struct red_sched_data *q = qdisc_priv(sch);
 
+	tcf_qevent_destroy(&q->qe_mark, sch);
+	tcf_qevent_destroy(&q->qe_early_drop, sch);
 	del_timer_sync(&q->adapt_timer);
 	red_offload(sch, false);
 	qdisc_put(q->qdisc);
···
 	[TCA_RED_STAB]	= { .len = RED_STAB_SIZE },
 	[TCA_RED_MAX_P] = { .type = NLA_U32 },
 	[TCA_RED_FLAGS] = NLA_POLICY_BITFIELD32(TC_RED_SUPPORTED_FLAGS),
+	[TCA_RED_EARLY_DROP_BLOCK] = { .type = NLA_U32 },
+	[TCA_RED_MARK_BLOCK] = { .type = NLA_U32 },
 };
 
 static int __red_change(struct Qdisc *sch, struct nlattr **tb,
···
 	q->qdisc = &noop_qdisc;
 	q->sch = sch;
 	timer_setup(&q->adapt_timer, red_adaptative_timer, 0);
-	return __red_change(sch, tb, extack);
+
+	err = __red_change(sch, tb, extack);
+	if (err)
+		return err;
+
+	err = tcf_qevent_init(&q->qe_early_drop, sch,
+			      FLOW_BLOCK_BINDER_TYPE_RED_EARLY_DROP,
+			      tb[TCA_RED_EARLY_DROP_BLOCK], extack);
+	if (err)
+		goto err_early_drop_init;
+
+	err = tcf_qevent_init(&q->qe_mark, sch,
+			      FLOW_BLOCK_BINDER_TYPE_RED_MARK,
+			      tb[TCA_RED_MARK_BLOCK], extack);
+	if (err)
+		goto err_mark_init;
+
+	return 0;
+
+err_mark_init:
+	tcf_qevent_destroy(&q->qe_early_drop, sch);
+err_early_drop_init:
+	del_timer_sync(&q->adapt_timer);
+	red_offload(sch, false);
+	qdisc_put(q->qdisc);
+	return err;
 }
 
 static int red_change(struct Qdisc *sch, struct nlattr *opt,
 		      struct netlink_ext_ack *extack)
 {
+	struct red_sched_data *q = qdisc_priv(sch);
 	struct nlattr *tb[TCA_RED_MAX + 1];
 	int err;
 
···
 	err = nla_parse_nested_deprecated(tb, TCA_RED_MAX, opt, red_policy,
 					  extack);
 	if (err < 0)
+		return err;
+
+	err = tcf_qevent_validate_change(&q->qe_early_drop,
+					 tb[TCA_RED_EARLY_DROP_BLOCK], extack);
+	if (err)
+		return err;
+
+	err = tcf_qevent_validate_change(&q->qe_mark,
+					 tb[TCA_RED_MARK_BLOCK], extack);
+	if (err)
 		return err;
 
 	return __red_change(sch, tb, extack);
···
 	if (nla_put(skb, TCA_RED_PARMS, sizeof(opt), &opt) ||
 	    nla_put_u32(skb, TCA_RED_MAX_P, q->parms.max_P) ||
 	    nla_put_bitfield32(skb, TCA_RED_FLAGS,
-			       q->flags, TC_RED_SUPPORTED_FLAGS))
+			       q->flags, TC_RED_SUPPORTED_FLAGS) ||
+	    tcf_qevent_dump(skb, TCA_RED_MARK_BLOCK, &q->qe_mark) ||
+	    tcf_qevent_dump(skb, TCA_RED_EARLY_DROP_BLOCK, &q->qe_early_drop))
 		goto nla_put_failure;
 	return nla_nest_end(skb, opts);