net: sched: cls_api: handle generic cls errors

This patch adds extack support for generic cls handling. The extack
will be set deeper to each called function which is not part of netdev
core api.

Cc: David Ahern <dsahern@gmail.com>
Signed-off-by: Alexander Aring <aring@mojatatu.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_api.c

@@ -122,7 +122,8 @@ static inline u32 tcf_auto_prio(struct tcf_proto *tp)
 }
 
 static struct tcf_proto *tcf_proto_create(const char *kind, u32 protocol,
-					  u32 prio, struct tcf_chain *chain)
+					  u32 prio, struct tcf_chain *chain,
+					  struct netlink_ext_ack *extack)
 {
 	struct tcf_proto *tp;
 	int err;
@@ -148,6 +149,7 @@ static struct tcf_proto *tcf_proto_create(const char *kind, u32 protocol,
 			module_put(tp->ops->owner);
 			err = -EAGAIN;
 		} else {
+			NL_SET_ERR_MSG(extack, "TC classifier not found");
 			err = -ENOENT;
 		}
 		goto errout;
@@ -935,7 +937,8 @@ static int tfilter_notify(struct net *net, struct sk_buff *oskb,
 static int tfilter_del_notify(struct net *net, struct sk_buff *oskb,
 			      struct nlmsghdr *n, struct tcf_proto *tp,
 			      struct tcf_block *block, struct Qdisc *q,
-			      u32 parent, void *fh, bool unicast, bool *last)
+			      u32 parent, void *fh, bool unicast, bool *last,
+			      struct netlink_ext_ack *extack)
 {
 	struct sk_buff *skb;
 	u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;
@@ -947,6 +950,7 @@ static int tfilter_del_notify(struct net *net, struct sk_buff *oskb,
 
 	if (tcf_fill_node(net, skb, tp, block, q, parent, fh, portid,
 			  n->nlmsg_seq, n->nlmsg_flags, RTM_DELTFILTER) <= 0) {
+		NL_SET_ERR_MSG(extack, "Failed to build del event notification");
 		kfree_skb(skb);
 		return -EINVAL;
 	}
@@ -960,8 +964,11 @@ static int tfilter_del_notify(struct net *net, struct sk_buff *oskb,
 	if (unicast)
 		return netlink_unicast(net->rtnl, skb, portid, MSG_DONTWAIT);
 
-	return rtnetlink_send(skb, net, portid, RTNLGRP_TC,
-			      n->nlmsg_flags & NLM_F_ECHO);
+	err = rtnetlink_send(skb, net, portid, RTNLGRP_TC,
+			     n->nlmsg_flags & NLM_F_ECHO);
+	if (err < 0)
+		NL_SET_ERR_MSG(extack, "Failed to send filter delete notification");
+	return err;
 }
 
 static void tfilter_notify_chain(struct net *net, struct sk_buff *oskb,
@@ -1021,8 +1028,10 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 	if (prio == 0) {
 		switch (n->nlmsg_type) {
 		case RTM_DELTFILTER:
-			if (protocol || t->tcm_handle || tca[TCA_KIND])
+			if (protocol || t->tcm_handle || tca[TCA_KIND]) {
+				NL_SET_ERR_MSG(extack, "Cannot flush filters with protocol, handle or kind set");
 				return -ENOENT;
+			}
 			break;
 		case RTM_NEWTFILTER:
 			/* If no priority is provided by the user,
@@ -1035,6 +1044,7 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 			}
 			/* fall-through */
 		default:
+			NL_SET_ERR_MSG(extack, "Invalid filter command with priority of zero");
 			return -ENOENT;
 		}
 	}
@@ -1063,23 +1073,31 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 			parent = q->handle;
 		} else {
 			q = qdisc_lookup(dev, TC_H_MAJ(t->tcm_parent));
-			if (!q)
+			if (!q) {
+				NL_SET_ERR_MSG(extack, "Parent Qdisc doesn't exists");
 				return -EINVAL;
+			}
 		}
 
 		/* Is it classful? */
 		cops = q->ops->cl_ops;
-		if (!cops)
+		if (!cops) {
+			NL_SET_ERR_MSG(extack, "Qdisc not classful");
 			return -EINVAL;
+		}
 
-		if (!cops->tcf_block)
+		if (!cops->tcf_block) {
+			NL_SET_ERR_MSG(extack, "Class doesn't support blocks");
 			return -EOPNOTSUPP;
+		}
 
 		/* Do we search for filter, attached to class? */
 		if (TC_H_MIN(parent)) {
 			cl = cops->find(q, parent);
-			if (cl == 0)
+			if (cl == 0) {
+				NL_SET_ERR_MSG(extack, "Specified class doesn't exist");
 				return -ENOENT;
+			}
 		}
 
 		/* And the last stroke */
@@ -1097,12 +1115,14 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 
 	chain_index = tca[TCA_CHAIN] ? nla_get_u32(tca[TCA_CHAIN]) : 0;
 	if (chain_index > TC_ACT_EXT_VAL_MASK) {
+		NL_SET_ERR_MSG(extack, "Specified chain index exceeds upper limit");
 		err = -EINVAL;
 		goto errout;
 	}
 	chain = tcf_chain_get(block, chain_index,
 			      n->nlmsg_type == RTM_NEWTFILTER);
 	if (!chain) {
+		NL_SET_ERR_MSG(extack, "Cannot find specified filter chain");
 		err = n->nlmsg_type == RTM_NEWTFILTER ? -ENOMEM : -EINVAL;
 		goto errout;
 	}
@@ -1118,6 +1138,7 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 	tp = tcf_chain_tp_find(chain, &chain_info, protocol,
 			       prio, prio_allocate);
 	if (IS_ERR(tp)) {
+		NL_SET_ERR_MSG(extack, "Filter with specified priority/protocol not found");
 		err = PTR_ERR(tp);
 		goto errout;
 	}
@@ -1126,12 +1147,14 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 		/* Proto-tcf does not exist, create new one */
 
 		if (tca[TCA_KIND] == NULL || !protocol) {
+			NL_SET_ERR_MSG(extack, "Filter kind and protocol must be specified");
 			err = -EINVAL;
 			goto errout;
 		}
 
 		if (n->nlmsg_type != RTM_NEWTFILTER ||
 		    !(n->nlmsg_flags & NLM_F_CREATE)) {
+			NL_SET_ERR_MSG(extack, "Need both RTM_NEWTFILTER and NLM_F_CREATE to create a new filter");
 			err = -ENOENT;
 			goto errout;
 		}
@@ -1140,13 +1163,14 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 			prio = tcf_auto_prio(tcf_chain_tp_prev(&chain_info));
 
 		tp = tcf_proto_create(nla_data(tca[TCA_KIND]),
-				      protocol, prio, chain);
+				      protocol, prio, chain, extack);
 		if (IS_ERR(tp)) {
 			err = PTR_ERR(tp);
 			goto errout;
 		}
 		tp_created = 1;
 	} else if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], tp->ops->kind)) {
+		NL_SET_ERR_MSG(extack, "Specified filter kind does not match existing one");
 		err = -EINVAL;
 		goto errout;
 	}
@@ -1165,6 +1189,7 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 
 		if (n->nlmsg_type != RTM_NEWTFILTER ||
 		    !(n->nlmsg_flags & NLM_F_CREATE)) {
+			NL_SET_ERR_MSG(extack, "Need both RTM_NEWTFILTER and NLM_F_CREATE to create a new filter");
 			err = -ENOENT;
 			goto errout;
 		}
@@ -1176,13 +1201,15 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 			if (n->nlmsg_flags & NLM_F_EXCL) {
 				if (tp_created)
 					tcf_proto_destroy(tp);
+				NL_SET_ERR_MSG(extack, "Filter already exists");
 				err = -EEXIST;
 				goto errout;
 			}
 			break;
 		case RTM_DELTFILTER:
 			err = tfilter_del_notify(net, skb, n, tp, block,
-						 q, parent, fh, false, &last);
+						 q, parent, fh, false, &last,
+						 extack);
 			if (err)
 				goto errout;
 			if (last) {
@@ -1193,8 +1220,11 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 		case RTM_GETTFILTER:
 			err = tfilter_notify(net, skb, n, tp, block, q, parent,
 					     fh, RTM_NEWTFILTER, true);
+			if (err < 0)
+				NL_SET_ERR_MSG(extack, "Failed to send filter notify message");
 			goto errout;
 		default:
+			NL_SET_ERR_MSG(extack, "Invalid netlink message type");
 			err = -EINVAL;
 			goto errout;
 		}