nexthop: Add a dedicated flag for multipath next-hop groups

With the introduction of resilient nexthop groups, there will be two types
of multipath groups: the current hash-threshold "mpath" ones, and resilient
groups. Both are multipath, but to determine the fact, the system needs to
consider two flags. This might prove costly in the datapath. Therefore,
introduce a new flag, that should be set for next-hop groups that have more
than one nexthop, and should be considered multipath.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/nexthop.h

@@ -80,6 +80,7 @@ struct nh_grp_entry {
 struct nh_group {
 	struct nh_group		*spare; /* spare group for removals */
 	u16			num_nh;
+	bool			is_multipath;
 	bool			mpath;
 	bool			fdb_nh;
 	bool			has_v4;
@@ -212,7 +213,7 @@ static inline bool nexthop_is_multipath(const struct nexthop *nh)
 		struct nh_group *nh_grp;
 
 		nh_grp = rcu_dereference_rtnl(nh->nh_grp);
-		return nh_grp->mpath;
+		return nh_grp->is_multipath;
 	}
 	return false;
 }
@@ -227,7 +228,7 @@ static inline unsigned int nexthop_num_path(const struct nexthop *nh)
 		struct nh_group *nh_grp;
 
 		nh_grp = rcu_dereference_rtnl(nh->nh_grp);
-		if (nh_grp->mpath)
+		if (nh_grp->is_multipath)
 			rc = nh_grp->num_nh;
 	}
 
@@ -308,7 +309,7 @@ struct fib_nh_common *nexthop_fib_nhc(struct nexthop *nh, int nhsel)
 		struct nh_group *nh_grp;
 
 		nh_grp = rcu_dereference_rtnl(nh->nh_grp);
-		if (nh_grp->mpath) {
+		if (nh_grp->is_multipath) {
 			nh = nexthop_mpath_select(nh_grp, nhsel);
 			if (!nh)
 				return NULL;

net/ipv4/nexthop.c

@@ -967,6 +967,7 @@ static void remove_nh_grp_entry(struct net *net, struct nh_grp_entry *nhge,
 	}
 
 	newg->has_v4 = false;
+	newg->is_multipath = nhg->is_multipath;
 	newg->mpath = nhg->mpath;
 	newg->fdb_nh = nhg->fdb_nh;
 	newg->num_nh = nhg->num_nh;
@@ -1488,8 +1489,10 @@ static struct nexthop *nexthop_create_group(struct net *net,
 		nhg->nh_entries[i].nh_parent = nh;
 	}
 
-	if (cfg->nh_grp_type == NEXTHOP_GRP_TYPE_MPATH)
+	if (cfg->nh_grp_type == NEXTHOP_GRP_TYPE_MPATH) {
 		nhg->mpath = 1;
+		nhg->is_multipath = true;
+	}
 
 	WARN_ON_ONCE(nhg->mpath != 1);