netdev - Re: [RFC net-next v2 1/1] net: sched: protect against loops in TC filter hooks

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Message-Id: <20190606.111954.2036000288766363267.davem@davemloft.net>
Date:   Thu, 06 Jun 2019 11:19:54 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     fw@...len.de
Cc:     john.hurley@...ronome.com, netdev@...r.kernel.org,
        simon.horman@...ronome.com, jakub.kicinski@...ronome.com,
        jhs@...atatu.com, oss-drivers@...ronome.com
Subject: Re: [RFC net-next v2 1/1] net: sched: protect against loops in TC
 filter hooks

From: Florian Westphal <fw@...len.de>
Date: Thu, 6 Jun 2019 14:58:18 +0200

>> @@ -827,6 +828,7 @@ struct sk_buff {
>>  	__u8			tc_at_ingress:1;
>>  	__u8			tc_redirected:1;
>>  	__u8			tc_from_ingress:1;
>> +	__u8			tc_hop_count:2;
> 
> I dislike this, why can't we just use a pcpu counter?

I understand that it's because the only precise context is per-SKB not
per-cpu doing packet processing.  This has been discussed before.