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From:   Peilin Ye <yepeilin.cs@gmail.com>
To:     Jamal Hadi Salim <jhs@mojatatu.com>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        Jiri Pirko <jiri@resnulli.us>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org,
        Daniel Borkmann <daniel@iogearbox.net>,
        Cong Wang <cong.wang@bytedance.com>,
        Peilin Ye <peilin.ye@bytedance.com>,
        Peilin Ye <yepeilin.cs@gmail.com>
Subject: [PATCH net-next 1/2] net/sched: sch_ingress: Support clsact egress mini-Qdisc option
Date:   Mon,  2 Aug 2021 13:49:47 -0700
Message-Id: <1931ca440b47344fe357d5438aeab4b439943d10.1627936393.git.peilin.ye@bytedance.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Peilin Ye <peilin.ye@bytedance.com>

If the ingress Qdisc is in use, currently it is not possible to add
another clsact egress mini-Qdisc to the same device without taking down
the ingress Qdisc, since both sch_ingress and sch_clsact use the same
handle (0xFFFF0000).

Add a "change" option for sch_ingress, so that users can enable or disable
a clsact egress mini-Qdisc, without suffering from downtime:

    $ tc qdisc add dev eth0 ingress
    $ tc qdisc change dev eth0 ingress clsact-on

Then users can add filters to the egress mini-Qdisc as usual:

    $ tc filter add dev eth0 egress protocol ip prio 10 \
	    matchall action skbmod swap mac

Deleting the ingress Qdisc removes the egress mini-Qdisc as well.  To
remove egress mini-Qdisc only, use:

    $ tc qdisc change dev eth0 ingress clsact-off

Finally, if the egress mini-Qdisc is enabled, the "show" command will
print out a "clsact" flag to indicate it:

    $ tc qdisc show ingress
    qdisc ingress ffff: dev eth0 parent ffff:fff1 ----------------
    $ tc qdisc change dev eth0 ingress clsact-on
    $ tc qdisc show ingress
    qdisc ingress ffff: dev eth0 parent ffff:fff1 ---------------- clsact

Reviewed-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
---
 include/uapi/linux/pkt_sched.h | 12 +++++
 net/sched/sch_ingress.c        | 92 ++++++++++++++++++++++++++++++++++
 2 files changed, 104 insertions(+)

diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 79a699f106b1..cb0eb5dd848a 100644
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h
@@ -586,6 +586,18 @@ enum {
 
 #define TCA_ATM_MAX	(__TCA_ATM_MAX - 1)
 
+/* INGRESS section */
+
+enum {
+	TCA_INGRESS_UNSPEC,
+	TCA_INGRESS_FLAGS,
+#define	TC_INGRESS_CLSACT	   _BITUL(0)	/* enable clsact egress mini-Qdisc */
+#define	TC_INGRESS_SUPPORTED_FLAGS TC_INGRESS_CLSACT
+	__TCA_INGRESS_MAX,
+};
+
+#define	TCA_INGRESS_MAX	(__TCA_INGRESS_MAX - 1)
+
 /* Network emulator */
 
 enum {
diff --git a/net/sched/sch_ingress.c b/net/sched/sch_ingress.c
index 84838128b9c5..96e00e9e727b 100644
--- a/net/sched/sch_ingress.c
+++ b/net/sched/sch_ingress.c
@@ -16,8 +16,12 @@
 
 struct ingress_sched_data {
 	struct tcf_block *block;
+	struct tcf_block *egress_block;
 	struct tcf_block_ext_info block_info;
+	struct tcf_block_ext_info egress_block_info;
 	struct mini_Qdisc_pair miniqp;
+	struct mini_Qdisc_pair miniqp_egress;
+	bool clsact;
 };
 
 static struct Qdisc *ingress_leaf(struct Qdisc *sch, unsigned long arg)
@@ -27,6 +31,11 @@ static struct Qdisc *ingress_leaf(struct Qdisc *sch, unsigned long arg)
 
 static unsigned long ingress_find(struct Qdisc *sch, u32 classid)
 {
+	struct ingress_sched_data *q = qdisc_priv(sch);
+
+	if (q->clsact && TC_H_MIN(classid) == TC_H_MIN(TC_H_MIN_EGRESS))
+		return TC_H_MIN(TC_H_MIN_EGRESS);
+
 	return TC_H_MIN(classid) + 1;
 }
 
@@ -49,6 +58,9 @@ static struct tcf_block *ingress_tcf_block(struct Qdisc *sch, unsigned long cl,
 {
 	struct ingress_sched_data *q = qdisc_priv(sch);
 
+	if (q->clsact && cl == TC_H_MIN(TC_H_MIN_EGRESS))
+		return q->egress_block;
+
 	return q->block;
 }
 
@@ -66,6 +78,14 @@ static void ingress_ingress_block_set(struct Qdisc *sch, u32 block_index)
 	q->block_info.block_index = block_index;
 }
 
+static void ingress_egress_block_set(struct Qdisc *sch, u32 block_index)
+{
+	struct ingress_sched_data *q = qdisc_priv(sch);
+
+	if (q->clsact)
+		q->egress_block_info.block_index = block_index;
+}
+
 static u32 ingress_ingress_block_get(struct Qdisc *sch)
 {
 	struct ingress_sched_data *q = qdisc_priv(sch);
@@ -73,6 +93,13 @@ static u32 ingress_ingress_block_get(struct Qdisc *sch)
 	return q->block_info.block_index;
 }
 
+static u32 ingress_egress_block_get(struct Qdisc *sch)
+{
+	struct ingress_sched_data *q = qdisc_priv(sch);
+
+	return q->clsact ? q->egress_block_info.block_index : 0;
+}
+
 static int ingress_init(struct Qdisc *sch, struct nlattr *opt,
 			struct netlink_ext_ack *extack)
 {
@@ -103,16 +130,78 @@ static void ingress_destroy(struct Qdisc *sch)
 
 	tcf_block_put_ext(q->block, sch, &q->block_info);
 	net_dec_ingress_queue();
+
+	if (q->clsact) {
+		tcf_block_put_ext(q->egress_block, sch, &q->egress_block_info);
+		net_dec_egress_queue();
+	}
+}
+
+static const struct nla_policy ingress_policy[TCA_INGRESS_MAX + 1] = {
+	[TCA_INGRESS_FLAGS] = NLA_POLICY_BITFIELD32(TC_INGRESS_SUPPORTED_FLAGS),
+};
+
+static int ingress_change(struct Qdisc *sch, struct nlattr *arg, struct netlink_ext_ack *extack)
+{
+	struct ingress_sched_data *q = qdisc_priv(sch);
+	struct net_device *dev = qdisc_dev(sch);
+	struct nlattr *tb[TCA_INGRESS_MAX + 1];
+	struct nla_bitfield32 flags;
+	int err;
+
+	err = nla_parse_nested_deprecated(tb, TCA_INGRESS_MAX, arg, ingress_policy, extack);
+	if (err < 0)
+		return err;
+
+	if (!tb[TCA_INGRESS_FLAGS])
+		return -EINVAL;
+
+	flags = nla_get_bitfield32(tb[TCA_INGRESS_FLAGS]);
+
+	if (flags.value & TC_INGRESS_CLSACT) {
+		if (q->clsact)
+			return -EEXIST;
+
+		/* enable clsact egress mini-Qdisc */
+		mini_qdisc_pair_init(&q->miniqp_egress, sch, &dev->miniq_egress);
+
+		q->egress_block_info.binder_type = FLOW_BLOCK_BINDER_TYPE_CLSACT_EGRESS;
+		q->egress_block_info.chain_head_change = clsact_chain_head_change;
+		q->egress_block_info.chain_head_change_priv = &q->miniqp_egress;
+
+		err = tcf_block_get_ext(&q->egress_block, sch, &q->egress_block_info, extack);
+		if (err)
+			return err;
+
+		net_inc_egress_queue();
+		q->clsact = true;
+	} else {
+		if (!q->clsact)
+			return -ENOENT;
+
+		/* disable clsact egress mini-Qdisc */
+		tcf_block_put_ext(q->egress_block, sch, &q->egress_block_info);
+
+		net_dec_egress_queue();
+		q->clsact = false;
+	}
+
+	return 0;
 }
 
 static int ingress_dump(struct Qdisc *sch, struct sk_buff *skb)
 {
+	struct ingress_sched_data *q = qdisc_priv(sch);
 	struct nlattr *nest;
 
 	nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
 	if (nest == NULL)
 		goto nla_put_failure;
 
+	if (nla_put_bitfield32(skb, TCA_INGRESS_FLAGS, q->clsact ? TC_INGRESS_CLSACT : 0,
+			       TC_INGRESS_SUPPORTED_FLAGS))
+		goto nla_put_failure;
+
 	return nla_nest_end(skb, nest);
 
 nla_put_failure:
@@ -137,9 +226,12 @@ static struct Qdisc_ops ingress_qdisc_ops __read_mostly = {
 	.static_flags		=	TCQ_F_CPUSTATS,
 	.init			=	ingress_init,
 	.destroy		=	ingress_destroy,
+	.change			=	ingress_change,
 	.dump			=	ingress_dump,
 	.ingress_block_set	=	ingress_ingress_block_set,
+	.egress_block_set	=	ingress_egress_block_set,
 	.ingress_block_get	=	ingress_ingress_block_get,
+	.egress_block_get	=	ingress_egress_block_get,
 	.owner			=	THIS_MODULE,
 };
 
-- 
2.20.1