netdev - [PATCH net-next 04/12] nexthop: Assert the invariant that a NH group is of only one type

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Date:   Thu, 28 Jan 2021 13:49:16 +0100
From:   Petr Machata <petrm@...dia.com>
To:     <netdev@...r.kernel.org>
CC:     David Ahern <dsahern@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Ido Schimmel <idosch@...dia.com>,
        "Petr Machata" <petrm@...dia.com>
Subject: [PATCH net-next 04/12] nexthop: Assert the invariant that a NH group is of only one type

Most of the code that deals with nexthop groups relies on the fact that the
group is of exactly one well-known type. Currently there is only one type,
"mpath", but as more next-hop group types come, it becomes desirable to
have a central place where the setting is validated. Introduce such place
into nexthop_create_group(), such that the check is done before the code
that relies on that invariant is invoked.

Signed-off-by: Petr Machata <petrm@...dia.com>
Reviewed-by: Ido Schimmel <idosch@...dia.com>
---
 net/ipv4/nexthop.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
index 7a30df5aea75..c09b8231f56a 100644
--- a/net/ipv4/nexthop.c
+++ b/net/ipv4/nexthop.c
@@ -1466,10 +1466,13 @@ 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;
+
+	WARN_ON_ONCE(nhg->mpath != 1);
+
+	if (nhg->mpath)
 		nh_group_rebalance(nhg);
-	}
 
 	if (cfg->nh_fdb)
 		nhg->fdb_nh = 1;
-- 
2.26.2