nexthop: Factor out hash threshold fdb nexthop selection

The loop in nexthop_select_path_hthr() includes code to check for neighbor
validity. Since this does not apply to fdb nexthops, simplify the loop by
moving the fdb nexthop selection to its own function.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20230719-nh_select-v2-1-04383e89f868@nvidia.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/nexthop.c

@@ -1152,11 +1152,31 @@ static bool ipv4_good_nh(const struct fib_nh *nh)
 	return !!(state & NUD_VALID);
 }
 
+static struct nexthop *nexthop_select_path_fdb(struct nh_group *nhg, int hash)
+{
+	int i;
+
+	for (i = 0; i < nhg->num_nh; i++) {
+		struct nh_grp_entry *nhge = &nhg->nh_entries[i];
+
+		if (hash > atomic_read(&nhge->hthr.upper_bound))
+			continue;
+
+		return nhge->nh;
+	}
+
+	WARN_ON_ONCE(1);
+	return NULL;
+}
+
 static struct nexthop *nexthop_select_path_hthr(struct nh_group *nhg, int hash)
 {
 	struct nexthop *rc = NULL;
 	int i;
 
+	if (nhg->fdb_nh)
+		return nexthop_select_path_fdb(nhg, hash);
+
 	for (i = 0; i < nhg->num_nh; ++i) {
 		struct nh_grp_entry *nhge = &nhg->nh_entries[i];
 		struct nh_info *nhi;
@@ -1165,8 +1185,6 @@ static struct nexthop *nexthop_select_path_hthr(struct nh_group *nhg, int hash)
 			continue;
 
 		nhi = rcu_dereference(nhge->nh->nh_info);
-		if (nhi->fdb_nh)
-			return nhge->nh;
 
 		/* nexthops always check if it is good and does
 		 * not rely on a sysctl for this behavior