sched: add new attr TCA_EXT_WARN_MSG to report tc extact message

We will report extack message if there is an error via netlink_ack(). But
if the rule is not to be exclusively executed by the hardware, extack is not
passed along and offloading failures don't get logged.

In commit 81c7288b170a ("sched: cls: enable verbose logging") Marcelo
made cls could log verbose info for offloading failures, which helps
improving Open vSwitch debuggability when using flower offloading.

It would also be helpful if userspace monitor tools, like "tc monitor",
could log this kind of message, as it doesn't require vswitchd log level
adjusment. Let's add a new tc attributes to report the extack message so
the monitor program could receive the failures. e.g.

  # tc monitor
  added chain dev enp3s0f1np1 parent ffff: chain 0
  added filter dev enp3s0f1np1 ingress protocol all pref 49152 flower chain 0 handle 0x1
    ct_state +trk+new
    not_in_hw
          action order 1: gact action drop
           random type none pass val 0
           index 1 ref 1 bind 1

  Warning: mlx5_core: matching on ct_state +new isn't supported.

In this patch I only report the extack message on add/del operations.
It doesn't look like we need to report the extack message on get/dump
operations.

Note this message not only reporte to multicast groups, it could also
be reported unicast, which may affect the current usersapce tool's behaivor.

Suggested-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://lore.kernel.org/r/20230113034353.2766735-1-liuhangbin@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 34 insertions, 21 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 72d2c204d5f3..c14018a8052c 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -902,7 +902,8 @@ static void qdisc_offload_graft_root(struct net_device *dev,
 }
 
 static int tc_fill_qdisc(struct sk_buff *skb, struct Qdisc *q, u32 clid,
-			 u32 portid, u32 seq, u16 flags, int event)
+			 u32 portid, u32 seq, u16 flags, int event,
+			 struct netlink_ext_ack *extack)
 {
 	struct gnet_stats_basic_sync __percpu *cpu_bstats = NULL;
 	struct gnet_stats_queue __percpu *cpu_qstats = NULL;
@@ -970,7 +971,12 @@ static int tc_fill_qdisc(struct sk_buff *skb, struct Qdisc *q, u32 clid,
 	if (gnet_stats_finish_copy(&d) < 0)
 		goto nla_put_failure;
 
+	if (extack && extack->_msg &&
+	    nla_put_string(skb, TCA_EXT_WARN_MSG, extack->_msg))
+		goto out_nlmsg_trim;
+
 	nlh->nlmsg_len = skb_tail_pointer(skb) - b;
+
 	return skb->len;
 
 out_nlmsg_trim:
@@ -991,7 +997,8 @@ static bool tc_qdisc_dump_ignore(struct Qdisc *q, bool dump_invisible)
 
 static int qdisc_notify(struct net *net, struct sk_buff *oskb,
 			struct nlmsghdr *n, u32 clid,
-			struct Qdisc *old, struct Qdisc *new)
+			struct Qdisc *old, struct Qdisc *new,
+			struct netlink_ext_ack *extack)
 {
 	struct sk_buff *skb;
 	u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;
@@ -1002,12 +1009,12 @@ static int qdisc_notify(struct net *net, struct sk_buff *oskb,
 
 	if (old && !tc_qdisc_dump_ignore(old, false)) {
 		if (tc_fill_qdisc(skb, old, clid, portid, n->nlmsg_seq,
-				  0, RTM_DELQDISC) < 0)
+				  0, RTM_DELQDISC, extack) < 0)
 			goto err_out;
 	}
 	if (new && !tc_qdisc_dump_ignore(new, false)) {
 		if (tc_fill_qdisc(skb, new, clid, portid, n->nlmsg_seq,
-				  old ? NLM_F_REPLACE : 0, RTM_NEWQDISC) < 0)
+				  old ? NLM_F_REPLACE : 0, RTM_NEWQDISC, extack) < 0)
 			goto err_out;
 	}
 
@@ -1022,10 +1029,11 @@ err_out:
 
 static void notify_and_destroy(struct net *net, struct sk_buff *skb,
 			       struct nlmsghdr *n, u32 clid,
-			       struct Qdisc *old, struct Qdisc *new)
+			       struct Qdisc *old, struct Qdisc *new,
+			       struct netlink_ext_ack *extack)
 {
 	if (new || old)
-		qdisc_notify(net, skb, n, clid, old, new);
+		qdisc_notify(net, skb, n, clid, old, new, extack);
 
 	if (old)
 		qdisc_put(old);
@@ -1105,12 +1113,12 @@ skip:
 				qdisc_refcount_inc(new);
 			rcu_assign_pointer(dev->qdisc, new ? : &noop_qdisc);
 
-			notify_and_destroy(net, skb, n, classid, old, new);
+			notify_and_destroy(net, skb, n, classid, old, new, extack);
 
 			if (new && new->ops->attach)
 				new->ops->attach(new);
 		} else {
-			notify_and_destroy(net, skb, n, classid, old, new);
+			notify_and_destroy(net, skb, n, classid, old, new, extack);
 		}
 
 		if (dev->flags & IFF_UP)
@@ -1141,7 +1149,7 @@ skip:
 		err = cops->graft(parent, cl, new, &old, extack);
 		if (err)
 			return err;
-		notify_and_destroy(net, skb, n, classid, old, new);
+		notify_and_destroy(net, skb, n, classid, old, new, extack);
 	}
 	return 0;
 }
@@ -1509,7 +1517,7 @@ static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
 		if (err != 0)
 			return err;
 	} else {
-		qdisc_notify(net, skb, n, clid, NULL, q);
+		qdisc_notify(net, skb, n, clid, NULL, q, NULL);
 	}
 	return 0;
 }
@@ -1648,7 +1656,7 @@ replay:
 	}
 	err = qdisc_change(q, tca, extack);
 	if (err == 0)
-		qdisc_notify(net, skb, n, clid, NULL, q);
+		qdisc_notify(net, skb, n, clid, NULL, q, extack);
 	return err;
 
 create_n_graft:
@@ -1715,7 +1723,7 @@ static int tc_dump_qdisc_root(struct Qdisc *root, struct sk_buff *skb,
 		if (!tc_qdisc_dump_ignore(q, dump_invisible) &&
 		    tc_fill_qdisc(skb, q, q->parent, NETLINK_CB(cb->skb).portid,
 				  cb->nlh->nlmsg_seq, NLM_F_MULTI,
-				  RTM_NEWQDISC) <= 0)
+				  RTM_NEWQDISC, NULL) <= 0)
 			goto done;
 		q_idx++;
 	}
@@ -1737,7 +1745,7 @@ static int tc_dump_qdisc_root(struct Qdisc *root, struct sk_buff *skb,
 		if (!tc_qdisc_dump_ignore(q, dump_invisible) &&
 		    tc_fill_qdisc(skb, q, q->parent, NETLINK_CB(cb->skb).portid,
 				  cb->nlh->nlmsg_seq, NLM_F_MULTI,
-				  RTM_NEWQDISC) <= 0)
+				  RTM_NEWQDISC, NULL) <= 0)
 			goto done;
 		q_idx++;
 	}
@@ -1810,8 +1818,8 @@ done:
  ************************************************/
 
 static int tc_fill_tclass(struct sk_buff *skb, struct Qdisc *q,
-			  unsigned long cl,
-			  u32 portid, u32 seq, u16 flags, int event)
+			  unsigned long cl, u32 portid, u32 seq, u16 flags,
+			  int event, struct netlink_ext_ack *extack)
 {
 	struct tcmsg *tcm;
 	struct nlmsghdr  *nlh;
@@ -1846,7 +1854,12 @@ static int tc_fill_tclass(struct sk_buff *skb, struct Qdisc *q,
 	if (gnet_stats_finish_copy(&d) < 0)
 		goto nla_put_failure;
 
+	if (extack && extack->_msg &&
+	    nla_put_string(skb, TCA_EXT_WARN_MSG, extack->_msg))
+		goto out_nlmsg_trim;
+
 	nlh->nlmsg_len = skb_tail_pointer(skb) - b;
+
 	return skb->len;
 
 out_nlmsg_trim:
@@ -1857,7 +1870,7 @@ nla_put_failure:
 
 static int tclass_notify(struct net *net, struct sk_buff *oskb,
 			 struct nlmsghdr *n, struct Qdisc *q,
-			 unsigned long cl, int event)
+			 unsigned long cl, int event, struct netlink_ext_ack *extack)
 {
 	struct sk_buff *skb;
 	u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;
@@ -1866,7 +1879,7 @@ static int tclass_notify(struct net *net, struct sk_buff *oskb,
 	if (!skb)
 		return -ENOBUFS;
 
-	if (tc_fill_tclass(skb, q, cl, portid, n->nlmsg_seq, 0, event) < 0) {
+	if (tc_fill_tclass(skb, q, cl, portid, n->nlmsg_seq, 0, event, extack) < 0) {
 		kfree_skb(skb);
 		return -EINVAL;
 	}
@@ -1893,7 +1906,7 @@ static int tclass_del_notify(struct net *net,
 		return -ENOBUFS;
 
 	if (tc_fill_tclass(skb, q, cl, portid, n->nlmsg_seq, 0,
-			   RTM_DELTCLASS) < 0) {
+			   RTM_DELTCLASS, extack) < 0) {
 		kfree_skb(skb);
 		return -EINVAL;
 	}
@@ -2100,7 +2113,7 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n,
 			tc_bind_tclass(q, portid, clid, 0);
 			goto out;
 		case RTM_GETTCLASS:
-			err = tclass_notify(net, skb, n, q, cl, RTM_NEWTCLASS);
+			err = tclass_notify(net, skb, n, q, cl, RTM_NEWTCLASS, extack);
 			goto out;
 		default:
 			err = -EINVAL;
@@ -2118,7 +2131,7 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n,
 	if (cops->change)
 		err = cops->change(q, clid, portid, tca, &new_cl, extack);
 	if (err == 0) {
-		tclass_notify(net, skb, n, q, new_cl, RTM_NEWTCLASS);
+		tclass_notify(net, skb, n, q, new_cl, RTM_NEWTCLASS, extack);
 		/* We just create a new class, need to do reverse binding. */
 		if (cl != new_cl)
 			tc_bind_tclass(q, portid, clid, new_cl);
@@ -2140,7 +2153,7 @@ static int qdisc_class_dump(struct Qdisc *q, unsigned long cl,
 
 	return tc_fill_tclass(a->skb, q, cl, NETLINK_CB(a->cb->skb).portid,
 			      a->cb->nlh->nlmsg_seq, NLM_F_MULTI,
-			      RTM_NEWTCLASS);
+			      RTM_NEWTCLASS, NULL);
 }
 
 static int tc_dump_tclass_qdisc(struct Qdisc *q, struct sk_buff *skb,