netdev - Re: [PATCH -next] net: sched: remove TC

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Message-ID: <5542CC25.8060501@mojatatu.com>
Date:	Thu, 30 Apr 2015 20:43:17 -0400
From:	Jamal Hadi Salim <jhs@...atatu.com>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Florian Westphal <fw@...len.de>
CC:	netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH -next] net: sched: remove TC_MUNGED bits

On 04/30/15 17:16, Alexei Starovoitov wrote:
> On Thu, Apr 30, 2015 at 12:12:00PM +0200, Florian Westphal wrote:
>> Not used.
>>
>> pedit sets TC_MUNGED when packet content was altered, but all the core
>> does is unset MUNGED again and then set OK2MUNGE.
>>
>> And the latter isn't tested anywhere. So lets remove both
>> TC_MUNGED and TC_OK2MUNGE.
>>
>> Signed-off-by: Florian Westphal <fw@...len.de>
>
> Wanted to do the same.
> iproute2 doesn't use 'munge' flag either.
>
> Acked-by: Alexei Starovoitov <ast@...mgrid.com>
>

Florian,
If you are going to take this path then fix pedit to do a pskb_expand.

I think it would be better to fix the actions that do
pskb_expand_head() and let them indicated they were munged.
The flag was intended to be an optimization where it would indicate
to the action processing a packet to not bother and just trample
on the packet if noone is referencing it.
That was the rule, unfortunately nobody paid attention and it
didnt matter because it doesnt seem there was a use case where two
actions in a graph would be editing packets one after the other).

cheers,
jamal

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