netdev - [PATCH net] sch_cake: fix srchost/dsthost hashing mode

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Date:   Mon, 16 Aug 2021 13:59:17 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Toke Høiland-Jørgensen <toke@...hat.com>,
        cake@...ts.bufferbloat.net, Pete Heist <pete@...stp.net>
Subject: [PATCH net] sch_cake: fix srchost/dsthost hashing mode

When adding support for using the skb->hash value as the flow hash in CAKE,
I accidentally introduced a logic error that broke the host-only isolation
modes of CAKE (srchost and dsthost keywords). Specifically, the flow_hash
variable should stay initialised to 0 in cake_hash() in pure host-based
hashing mode. Add a check for this before using the skb->hash value as
flow_hash.

Fixes: b0c19ed6088a ("sch_cake: Take advantage of skb->hash where appropriate")
Reported-by: Pete Heist <pete@...stp.net>
Tested-by: Pete Heist <pete@...stp.net>
Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
 net/sched/sch_cake.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c
index 951542843cab..28af8b1e1bb1 100644
--- a/net/sched/sch_cake.c
+++ b/net/sched/sch_cake.c
@@ -720,7 +720,7 @@ static u32 cake_hash(struct cake_tin_data *q, const struct sk_buff *skb,
 skip_hash:
 	if (flow_override)
 		flow_hash = flow_override - 1;
-	else if (use_skbhash)
+	else if (use_skbhash && (flow_mode & CAKE_FLOW_FLOWS))
 		flow_hash = skb->hash;
 	if (host_override) {
 		dsthost_hash = host_override - 1;
-- 
2.32.0