net/sched: Load modules via their alias

The cls_,sch_,act_ modules may be loaded lazily during network
configuration but without user's awareness and control.

Switch the lazy loading from canonical module names to a module alias.
This allows finer control over lazy loading, the precedent from
commit 7f78e03 ("fs: Limit sys_mount to only request filesystem
modules.") explains it already:

	Using aliases means user space can control the policy of which
	filesystem^W net/sched modules are auto-loaded by editing
	/etc/modprobe.d/*.conf with blacklist and alias directives.
	Allowing simple, safe, well understood work-arounds to known
	problematic software.

By default, nothing changes. However, if a specific module is
blacklisted (its canonical name), it won't be modprobe'd when requested
under its alias (i.e. kernel auto-loading). It would appear as if the
given module was unknown.

The module can still be loaded under its canonical name, which is an
explicit (privileged) user action.

Signed-off-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20240201130943.19536-4-mkoutny@suse.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Werkov

net/sched/act_api.c

@@ -1363,7 +1363,7 @@ struct tc_action_ops *tc_action_load_ops(struct nlattr *nla, u32 flags,
 
 		if (rtnl_held)
 			rtnl_unlock();
-		request_module("act_%s", act_name);
+		request_module(NET_ACT_ALIAS_PREFIX "%s", act_name);
 		if (rtnl_held)
 			rtnl_lock();
 

net/sched/cls_api.c

@@ -257,7 +257,7 @@ tcf_proto_lookup_ops(const char *kind, bool rtnl_held,
 #ifdef CONFIG_MODULES
 	if (rtnl_held)
 		rtnl_unlock();
-	request_module("cls_%s", kind);
+	request_module(NET_CLS_ALIAS_PREFIX "%s", kind);
 	if (rtnl_held)
 		rtnl_lock();
 	ops = __tcf_proto_lookup_ops(kind);

net/sched/sch_api.c

@@ -228,7 +228,7 @@ int qdisc_set_default(const char *name)
 	if (!ops) {
 		/* Not found, drop lock and try to load module */
 		write_unlock(&qdisc_mod_lock);
-		request_module("sch_%s", name);
+		request_module(NET_SCH_ALIAS_PREFIX "%s", name);
 		write_lock(&qdisc_mod_lock);
 
 		ops = qdisc_lookup_default(name);
@@ -1275,7 +1275,7 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 			 * go away in the mean time.
 			 */
 			rtnl_unlock();
-			request_module("sch_%s", name);
+			request_module(NET_SCH_ALIAS_PREFIX "%s", name);
 			rtnl_lock();
 			ops = qdisc_lookup_ops(kind);
 			if (ops != NULL) {