[PATCH v2 net-next 0/3] net: Allow non-fatal messages to be passed in extack

[PATCH v2 net-next 0/3] net: Allow non-fatal messages to be passed in extack

[David Ahern]

There are many cases where networking subsystems throw non-fatal warning
messages that end up in dmesg / kernel log to which a user making the
change is completely oblivious. This set makes the extack facility
usable for returning such messages.

The case in point here is spectrum and adding FIB rules which causes an
offload abort. Make the use case more user friendly by letting the user
know that offload is no longer happening because of the rule change.

v2
- kept the offload abort in a work queue entry per Ido's comment

David Ahern (3):
  netlink: Allow ext_ack to carry non-error messages
  net: Add extack to fib_notifier_info
  mlxsw: spectrum_router: Return extack message on abort due to fib
    rules

 .../net/ethernet/mellanox/mlxsw/spectrum_router.c  | 108 +++++++++++++--------
 include/net/fib_notifier.h                         |   1 +
 net/core/fib_rules.c                               |   9 +-
 net/ipv4/fib_trie.c                                |  13 ++-
 net/ipv6/ip6_fib.c                                 |  15 +--
 net/netlink/af_netlink.c                           |  18 ++--
 6 files changed, 99 insertions(+), 65 deletions(-)

-- 
2.1.4

[PATCH v2 net-next 1/3] netlink: Allow ext_ack to carry non-error messages

[David Ahern]

The NLMSGERR API already carries data (eg, a cookie) on the success path.
Allow a message string to be returned as well.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 net/netlink/af_netlink.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 767c84e10e20..26ded4239611 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2313,17 +2313,16 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 	 * requests to cap the error message, and get extra error data if
 	 * requested.
 	 */
+	if (nlk_has_extack && extack && extack->_msg)
+		tlvlen += nla_total_size(strlen(extack->_msg) + 1);
+
 	if (err) {
 		if (!(nlk->flags & NETLINK_F_CAP_ACK))
 			payload += nlmsg_len(nlh);
 		else
 			flags |= NLM_F_CAPPED;
-		if (nlk_has_extack && extack) {
-			if (extack->_msg)
-				tlvlen += nla_total_size(strlen(extack->_msg) + 1);
-			if (extack->bad_attr)
-				tlvlen += nla_total_size(sizeof(u32));
-		}
+		if (nlk_has_extack && extack && extack->bad_attr)
+			tlvlen += nla_total_size(sizeof(u32));
 	} else {
 		flags |= NLM_F_CAPPED;
 
@@ -2348,10 +2347,11 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 	memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg) ? nlh->nlmsg_len : sizeof(*nlh));
 
 	if (nlk_has_extack && extack) {
+		if (extack->_msg) {
+			WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG,
+					       extack->_msg));
+		}
 		if (err) {
-			if (extack->_msg)
-				WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG,
-						       extack->_msg));
 			if (extack->bad_attr &&
 			    !WARN_ON((u8 *)extack->bad_attr < in_skb->data ||
 				     (u8 *)extack->bad_attr >= in_skb->data +
-- 
2.1.4

[PATCH v2 net-next 2/3] net: Add extack to fib_notifier_info

[David Ahern]

Add extack to fib_notifier_info and plumb through stack to
call_fib_rule_notifiers, call_fib_entry_notifiers and
call_fib6_entry_notifiers. This allows notifer handlers to
return messages to user.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 include/net/fib_notifier.h |  1 +
 net/core/fib_rules.c       |  9 ++++++---
 net/ipv4/fib_trie.c        | 13 ++++++++-----
 net/ipv6/ip6_fib.c         | 15 +++++++++------
 4 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/include/net/fib_notifier.h b/include/net/fib_notifier.h
index 54cd6b839d2f..c91ec732afd6 100644
--- a/include/net/fib_notifier.h
+++ b/include/net/fib_notifier.h
@@ -9,6 +9,7 @@
 struct fib_notifier_info {
 	struct net *net;
 	int family;
+	struct netlink_ext_ack  *extack;
 };
 
 enum fib_event_type {
diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 9a6d97c1d810..fafd0a41e3f7 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -314,10 +314,12 @@ static int call_fib_rule_notifier(struct notifier_block *nb, struct net *net,
 static int call_fib_rule_notifiers(struct net *net,
 				   enum fib_event_type event_type,
 				   struct fib_rule *rule,
-				   struct fib_rules_ops *ops)
+				   struct fib_rules_ops *ops,
+				   struct netlink_ext_ack *extack)
 {
 	struct fib_rule_notifier_info info = {
 		.info.family = ops->family,
+		.info.extack = extack,
 		.rule = rule,
 	};
 
@@ -609,7 +611,7 @@ int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (rule->tun_id)
 		ip_tunnel_need_metadata();
 
-	call_fib_rule_notifiers(net, FIB_EVENT_RULE_ADD, rule, ops);
+	call_fib_rule_notifiers(net, FIB_EVENT_RULE_ADD, rule, ops, extack);
 	notify_rule_change(RTM_NEWRULE, rule, ops, nlh, NETLINK_CB(skb).portid);
 	flush_route_cache(ops);
 	rules_ops_put(ops);
@@ -749,7 +751,8 @@ int fib_nl_delrule(struct sk_buff *skb, struct nlmsghdr *nlh,
 			}
 		}
 
-		call_fib_rule_notifiers(net, FIB_EVENT_RULE_DEL, rule, ops);
+		call_fib_rule_notifiers(net, FIB_EVENT_RULE_DEL, rule, ops,
+					NULL);
 		notify_rule_change(RTM_DELRULE, rule, ops, nlh,
 				   NETLINK_CB(skb).portid);
 		fib_rule_put(rule);
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index aaa1ba09afaa..5ddc4aefff12 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -102,9 +102,11 @@ static int call_fib_entry_notifier(struct notifier_block *nb, struct net *net,
 
 static int call_fib_entry_notifiers(struct net *net,
 				    enum fib_event_type event_type, u32 dst,
-				    int dst_len, struct fib_alias *fa)
+				    int dst_len, struct fib_alias *fa,
+				    struct netlink_ext_ack *extack)
 {
 	struct fib_entry_notifier_info info = {
+		.info.extack = extack,
 		.dst = dst,
 		.dst_len = dst_len,
 		.fi = fa->fa_info,
@@ -1214,7 +1216,7 @@ int fib_table_insert(struct net *net, struct fib_table *tb,
 			new_fa->fa_default = -1;
 
 			call_fib_entry_notifiers(net, FIB_EVENT_ENTRY_REPLACE,
-						 key, plen, new_fa);
+						 key, plen, new_fa, extack);
 			rtmsg_fib(RTM_NEWROUTE, htonl(key), new_fa, plen,
 				  tb->tb_id, &cfg->fc_nlinfo, nlflags);
 
@@ -1269,7 +1271,7 @@ int fib_table_insert(struct net *net, struct fib_table *tb,
 		tb->tb_num_default++;
 
 	rt_cache_flush(cfg->fc_nlinfo.nl_net);
-	call_fib_entry_notifiers(net, event, key, plen, new_fa);
+	call_fib_entry_notifiers(net, event, key, plen, new_fa, extack);
 	rtmsg_fib(RTM_NEWROUTE, htonl(key), new_fa, plen, new_fa->tb_id,
 		  &cfg->fc_nlinfo, nlflags);
 succeeded:
@@ -1569,7 +1571,7 @@ int fib_table_delete(struct net *net, struct fib_table *tb,
 		return -ESRCH;
 
 	call_fib_entry_notifiers(net, FIB_EVENT_ENTRY_DEL, key, plen,
-				 fa_to_delete);
+				 fa_to_delete, extack);
 	rtmsg_fib(RTM_DELROUTE, htonl(key), fa_to_delete, plen, tb->tb_id,
 		  &cfg->fc_nlinfo, 0);
 
@@ -1886,7 +1888,8 @@ int fib_table_flush(struct net *net, struct fib_table *tb)
 
 			call_fib_entry_notifiers(net, FIB_EVENT_ENTRY_DEL,
 						 n->key,
-						 KEYLENGTH - fa->fa_slen, fa);
+						 KEYLENGTH - fa->fa_slen, fa,
+						 NULL);
 			hlist_del_rcu(&fa->fa_list);
 			fib_release_info(fa->fa_info);
 			alias_free_mem_rcu(fa);
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 1ada9672d198..2e2804f5823e 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -353,9 +353,11 @@ static int call_fib6_entry_notifier(struct notifier_block *nb, struct net *net,
 
 static int call_fib6_entry_notifiers(struct net *net,
 				     enum fib_event_type event_type,
-				     struct rt6_info *rt)
+				     struct rt6_info *rt,
+				     struct netlink_ext_ack *extack)
 {
 	struct fib6_entry_notifier_info info = {
+		.info.extack = extack,
 		.rt = rt,
 	};
 
@@ -868,7 +870,8 @@ static void fib6_purge_rt(struct rt6_info *rt, struct fib6_node *fn,
  */
 
 static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
-			    struct nl_info *info, struct mx6_config *mxc)
+			    struct nl_info *info, struct mx6_config *mxc,
+			    struct netlink_ext_ack *extack)
 {
 	struct rt6_info *leaf = rcu_dereference_protected(fn->leaf,
 				    lockdep_is_held(&rt->rt6i_table->tb6_lock));
@@ -1011,7 +1014,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
 		rcu_assign_pointer(rt->rt6i_node, fn);
 		rcu_assign_pointer(*ins, rt);
 		call_fib6_entry_notifiers(info->nl_net, FIB_EVENT_ENTRY_ADD,
-					  rt);
+					  rt, extack);
 		if (!info->skip_notify)
 			inet6_rt_notify(RTM_NEWROUTE, rt, info, nlflags);
 		info->nl_net->ipv6.rt6_stats->fib_rt_entries++;
@@ -1040,7 +1043,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
 		rt->dst.rt6_next = iter->dst.rt6_next;
 		rcu_assign_pointer(*ins, rt);
 		call_fib6_entry_notifiers(info->nl_net, FIB_EVENT_ENTRY_REPLACE,
-					  rt);
+					  rt, extack);
 		if (!info->skip_notify)
 			inet6_rt_notify(RTM_NEWROUTE, rt, info, NLM_F_REPLACE);
 		if (!(fn->fn_flags & RTN_RTINFO)) {
@@ -1225,7 +1228,7 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt,
 	}
 #endif
 
-	err = fib6_add_rt2node(fn, rt, info, mxc);
+	err = fib6_add_rt2node(fn, rt, info, mxc, extack);
 	if (!err) {
 		fib6_update_sernum_upto_root(rt, sernum);
 		fib6_start_gc(info->nl_net, rt);
@@ -1686,7 +1689,7 @@ static void fib6_del_route(struct fib6_table *table, struct fib6_node *fn,
 
 	fib6_purge_rt(rt, fn, net);
 
-	call_fib6_entry_notifiers(net, FIB_EVENT_ENTRY_DEL, rt);
+	call_fib6_entry_notifiers(net, FIB_EVENT_ENTRY_DEL, rt, NULL);
 	if (!info->skip_notify)
 		inet6_rt_notify(RTM_DELROUTE, rt, info, 0);
 	rt6_release(rt);
-- 
2.1.4

[PATCH v2 net-next 3/3] mlxsw: spectrum_router: Return extack message on abort due to fib rules

[David Ahern]

Adding a FIB rule on a spectrum platform silently aborts FIB offload:
    $ ip ru add pref 99 from all to 192.168.1.1 table 10
    $ dmesg -c
    [  623.144736] mlxsw_spectrum 0000:03:00.0: FIB abort triggered. Note that FIB entries are no longer being offloaded to this device.

This patch reworks FIB rule handling to return a message to the user:
    $ ip ru add pref 99 from all to 8.8.8.8 table 11
    Error: spectrum: FIB rules not supported. Aborting offload.

spectrum currently only checks whether the fib rule is a default rule or
an l3mdev rule, both of which it knows how to handle. Any other it aborts
FIB offload. Move the processing to check the rule type inline with the
user request. If the rule is an unsupported one, then a work queue entry
is used to abort the offload. Change the rule delete handling to just
return since it does nothing at the moment.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 .../net/ethernet/mellanox/mlxsw/spectrum_router.c  | 108 +++++++++++++--------
 1 file changed, 66 insertions(+), 42 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
index 27b632cac991..9fe4cdb23189 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
@@ -5234,7 +5234,6 @@ static void mlxsw_sp_router_fib4_event_work(struct work_struct *work)
 	struct mlxsw_sp_fib_event_work *fib_work =
 		container_of(work, struct mlxsw_sp_fib_event_work, work);
 	struct mlxsw_sp *mlxsw_sp = fib_work->mlxsw_sp;
-	struct fib_rule *rule;
 	bool replace, append;
 	int err;
 
@@ -5256,12 +5255,11 @@ static void mlxsw_sp_router_fib4_event_work(struct work_struct *work)
 		mlxsw_sp_router_fib4_del(mlxsw_sp, &fib_work->fen_info);
 		fib_info_put(fib_work->fen_info.fi);
 		break;
-	case FIB_EVENT_RULE_ADD: /* fall through */
-	case FIB_EVENT_RULE_DEL:
-		rule = fib_work->fr_info.rule;
-		if (!fib4_rule_default(rule) && !rule->l3mdev)
-			mlxsw_sp_router_fib_abort(mlxsw_sp);
-		fib_rule_put(rule);
+	case FIB_EVENT_RULE_ADD:
+		/* if we get here, a rule was added that we do not support.
+		 * just do the fib_abort
+		 */
+		mlxsw_sp_router_fib_abort(mlxsw_sp);
 		break;
 	case FIB_EVENT_NH_ADD: /* fall through */
 	case FIB_EVENT_NH_DEL:
@@ -5279,7 +5277,6 @@ static void mlxsw_sp_router_fib6_event_work(struct work_struct *work)
 	struct mlxsw_sp_fib_event_work *fib_work =
 		container_of(work, struct mlxsw_sp_fib_event_work, work);
 	struct mlxsw_sp *mlxsw_sp = fib_work->mlxsw_sp;
-	struct fib_rule *rule;
 	bool replace;
 	int err;
 
@@ -5298,12 +5295,11 @@ static void mlxsw_sp_router_fib6_event_work(struct work_struct *work)
 		mlxsw_sp_router_fib6_del(mlxsw_sp, fib_work->fen6_info.rt);
 		mlxsw_sp_rt6_release(fib_work->fen6_info.rt);
 		break;
-	case FIB_EVENT_RULE_ADD: /* fall through */
-	case FIB_EVENT_RULE_DEL:
-		rule = fib_work->fr_info.rule;
-		if (!fib6_rule_default(rule) && !rule->l3mdev)
-			mlxsw_sp_router_fib_abort(mlxsw_sp);
-		fib_rule_put(rule);
+	case FIB_EVENT_RULE_ADD:
+		/* if we get here, a rule was added that we do not support.
+		 * just do the fib_abort
+		 */
+		mlxsw_sp_router_fib_abort(mlxsw_sp);
 		break;
 	}
 	rtnl_unlock();
@@ -5315,7 +5311,6 @@ static void mlxsw_sp_router_fibmr_event_work(struct work_struct *work)
 	struct mlxsw_sp_fib_event_work *fib_work =
 		container_of(work, struct mlxsw_sp_fib_event_work, work);
 	struct mlxsw_sp *mlxsw_sp = fib_work->mlxsw_sp;
-	struct fib_rule *rule;
 	bool replace;
 	int err;
 
@@ -5347,12 +5342,11 @@ static void mlxsw_sp_router_fibmr_event_work(struct work_struct *work)
 					      &fib_work->ven_info);
 		dev_put(fib_work->ven_info.dev);
 		break;
-	case FIB_EVENT_RULE_ADD: /* fall through */
-	case FIB_EVENT_RULE_DEL:
-		rule = fib_work->fr_info.rule;
-		if (!ipmr_rule_default(rule) && !rule->l3mdev)
-			mlxsw_sp_router_fib_abort(mlxsw_sp);
-		fib_rule_put(rule);
+	case FIB_EVENT_RULE_ADD:
+		/* if we get here, a rule was added that we do not support.
+		 * just do the fib_abort
+		 */
+		mlxsw_sp_router_fib_abort(mlxsw_sp);
 		break;
 	}
 	rtnl_unlock();
@@ -5363,7 +5357,6 @@ static void mlxsw_sp_router_fib4_event(struct mlxsw_sp_fib_event_work *fib_work,
 				       struct fib_notifier_info *info)
 {
 	struct fib_entry_notifier_info *fen_info;
-	struct fib_rule_notifier_info *fr_info;
 	struct fib_nh_notifier_info *fnh_info;
 
 	switch (fib_work->event) {
@@ -5379,13 +5372,6 @@ static void mlxsw_sp_router_fib4_event(struct mlxsw_sp_fib_event_work *fib_work,
 		 */
 		fib_info_hold(fib_work->fen_info.fi);
 		break;
-	case FIB_EVENT_RULE_ADD: /* fall through */
-	case FIB_EVENT_RULE_DEL:
-		fr_info = container_of(info, struct fib_rule_notifier_info,
-				       info);
-		fib_work->fr_info = *fr_info;
-		fib_rule_get(fib_work->fr_info.rule);
-		break;
 	case FIB_EVENT_NH_ADD: /* fall through */
 	case FIB_EVENT_NH_DEL:
 		fnh_info = container_of(info, struct fib_nh_notifier_info,
@@ -5400,7 +5386,6 @@ static void mlxsw_sp_router_fib6_event(struct mlxsw_sp_fib_event_work *fib_work,
 				       struct fib_notifier_info *info)
 {
 	struct fib6_entry_notifier_info *fen6_info;
-	struct fib_rule_notifier_info *fr_info;
 
 	switch (fib_work->event) {
 	case FIB_EVENT_ENTRY_REPLACE: /* fall through */
@@ -5411,13 +5396,6 @@ static void mlxsw_sp_router_fib6_event(struct mlxsw_sp_fib_event_work *fib_work,
 		fib_work->fen6_info = *fen6_info;
 		rt6_hold(fib_work->fen6_info.rt);
 		break;
-	case FIB_EVENT_RULE_ADD: /* fall through */
-	case FIB_EVENT_RULE_DEL:
-		fr_info = container_of(info, struct fib_rule_notifier_info,
-				       info);
-		fib_work->fr_info = *fr_info;
-		fib_rule_get(fib_work->fr_info.rule);
-		break;
 	}
 }
 
@@ -5437,12 +5415,47 @@ mlxsw_sp_router_fibmr_event(struct mlxsw_sp_fib_event_work *fib_work,
 		memcpy(&fib_work->ven_info, info, sizeof(fib_work->ven_info));
 		dev_hold(fib_work->ven_info.dev);
 		break;
-	case FIB_EVENT_RULE_ADD: /* fall through */
-	case FIB_EVENT_RULE_DEL:
-		memcpy(&fib_work->fr_info, info, sizeof(fib_work->fr_info));
-		fib_rule_get(fib_work->fr_info.rule);
+	}
+}
+
+static int mlxsw_sp_router_fib_rule_event(unsigned long event,
+					  struct fib_notifier_info *info,
+					  struct mlxsw_sp *mlxsw_sp)
+{
+	struct netlink_ext_ack *extack = info->extack;
+	struct fib_rule_notifier_info *fr_info;
+	struct fib_rule *rule;
+	int err = 0;
+
+	/* nothing to do at the moment */
+	if (event == FIB_EVENT_RULE_DEL)
+		return 0;
+
+	if (mlxsw_sp->router->aborted)
+		return 0;
+
+	fr_info = container_of(info, struct fib_rule_notifier_info, info);
+	rule = fr_info->rule;
+
+	switch (info->family) {
+	case AF_INET:
+		if (!fib4_rule_default(rule) && !rule->l3mdev)
+			err = -1;
+		break;
+	case AF_INET6:
+		if (!fib6_rule_default(rule) && !rule->l3mdev)
+			err = -1;
+		break;
+	case RTNL_FAMILY_IPMR:
+		if (!ipmr_rule_default(rule) && !rule->l3mdev)
+			err = -1;
 		break;
 	}
+
+	if (err < 0)
+		NL_SET_ERR_MSG(extack, "spectrum: FIB rules not supported. Aborting offload");
+
+	return err;
 }
 
 /* Called with rcu_read_lock() */
@@ -5452,17 +5465,28 @@ static int mlxsw_sp_router_fib_event(struct notifier_block *nb,
 	struct mlxsw_sp_fib_event_work *fib_work;
 	struct fib_notifier_info *info = ptr;
 	struct mlxsw_sp_router *router;
+	int err;
 
 	if (!net_eq(info->net, &init_net) ||
 	    (info->family != AF_INET && info->family != AF_INET6 &&
 	     info->family != RTNL_FAMILY_IPMR))
 		return NOTIFY_DONE;
 
+	router = container_of(nb, struct mlxsw_sp_router, fib_nb);
+
+	switch (event) {
+	case FIB_EVENT_RULE_ADD: /* fall through */
+	case FIB_EVENT_RULE_DEL:
+		err = mlxsw_sp_router_fib_rule_event(event, info,
+						     router->mlxsw_sp);
+		if (!err)
+			return NOTIFY_DONE;
+	}
+
 	fib_work = kzalloc(sizeof(*fib_work), GFP_ATOMIC);
 	if (WARN_ON(!fib_work))
 		return NOTIFY_BAD;
 
-	router = container_of(nb, struct mlxsw_sp_router, fib_nb);
 	fib_work->mlxsw_sp = router->mlxsw_sp;
 	fib_work->event = event;
 
-- 
2.1.4

Re: [PATCH v2 net-next 2/3] net: Add extack to fib_notifier_info

[Ido Schimmel]

On Fri, Oct 27, 2017 at 05:37:13PM -0700, David Ahern wrote:
> Add extack to fib_notifier_info and plumb through stack to
> call_fib_rule_notifiers, call_fib_entry_notifiers and
> call_fib6_entry_notifiers. This allows notifer handlers to
> return messages to user.
> 
> Signed-off-by: David Ahern <dsahern@gmail.com>

Reviewed-by: Ido Schimmel <idosch@mellanox.com>

Re: [PATCH v2 net-next 3/3] mlxsw: spectrum_router: Return extack message on abort due to fib rules

[Ido Schimmel]

On Fri, Oct 27, 2017 at 05:37:14PM -0700, David Ahern wrote:
> Adding a FIB rule on a spectrum platform silently aborts FIB offload:
>     $ ip ru add pref 99 from all to 192.168.1.1 table 10
>     $ dmesg -c
>     [  623.144736] mlxsw_spectrum 0000:03:00.0: FIB abort triggered. Note that FIB entries are no longer being offloaded to this device.
> 
> This patch reworks FIB rule handling to return a message to the user:
>     $ ip ru add pref 99 from all to 8.8.8.8 table 11
>     Error: spectrum: FIB rules not supported. Aborting offload.
> 
> spectrum currently only checks whether the fib rule is a default rule or
> an l3mdev rule, both of which it knows how to handle. Any other it aborts
> FIB offload. Move the processing to check the rule type inline with the
> user request. If the rule is an unsupported one, then a work queue entry
> is used to abort the offload. Change the rule delete handling to just
> return since it does nothing at the moment.
> 
> Signed-off-by: David Ahern <dsahern@gmail.com>

Reviewed-by: Ido Schimmel <idosch@mellanox.com>

I'll follow-up with a patch to notify about IPv6 source-specific routes
that also trigger abort.

Another possible use case for this, is something Petr is working on. We
currently assume IP-in-IP tunnel parameters don't change after creation,
but Petr has a patchset that adds support for NETDEV_CHANGE events in
mlxsw.

It's possible that after parameters are changed, we can no longer
offload the tunnel (for example, because user enabled sequence
counters). With this infrastructure, we can let the user know about it.

Thanks!

Re: [PATCH v2 net-next 0/3] net: Allow non-fatal messages to be passed in extack

[David Miller]

From: David Ahern <dsahern@gmail.com>
Date: Fri, 27 Oct 2017 17:37:11 -0700

> There are many cases where networking subsystems throw non-fatal warning
> messages that end up in dmesg / kernel log to which a user making the
> change is completely oblivious. This set makes the extack facility
> usable for returning such messages.
> 
> The case in point here is spectrum and adding FIB rules which causes an
> offload abort. Make the use case more user friendly by letting the user
> know that offload is no longer happening because of the rule change.
> 
> v2
> - kept the offload abort in a work queue entry per Ido's comment

Series applied, thanks David.