netdev - [PATCH net-next] net/sched: cls_api: increase max_reclassify

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Message-Id: <3ab4c68503a3e3e1b4f11a0c0900b872cfc806f6.1621426820.git.dcaratti@redhat.com>
Date:   Wed, 19 May 2021 15:17:21 +0200
From:   Davide Caratti <dcaratti@...hat.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: [PATCH net-next] net/sched: cls_api: increase max_reclassify_loop

modern userspace applications, like OVN, can configure the TC datapath to
"recirculate" packets several times. If more than 4 "recirculation" rules
are configured, packets can be dropped by __tcf_classify().
Changing the maximum number of reclassifications (from 4 to 16) should be
sufficient to prevent drops in most use cases, and guard against loops at
the same time.

Signed-off-by: Davide Caratti <dcaratti@...hat.com>
---
 net/sched/cls_api.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 40fbea626dfd..75e3a288a7c8 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -1531,7 +1531,7 @@ static inline int __tcf_classify(struct sk_buff *skb,
 				 u32 *last_executed_chain)
 {
 #ifdef CONFIG_NET_CLS_ACT
-	const int max_reclassify_loop = 4;
+	const int max_reclassify_loop = 16;
 	const struct tcf_proto *first_tp;
 	int limit = 0;
 
-- 
2.31.1