netdev - Re: [Patch net] net: invert the check of detecting hardware RX checksum fault

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Message-ID: <20181121033530.ejx73kxq3t475sdh@gondor.apana.org.au>
Date:   Wed, 21 Nov 2018 11:35:30 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     David Miller <davem@...emloft.net>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        netdev <netdev@...r.kernel.org>,
        Tom Herbert <tom@...bertland.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: Re: [Patch net] net: invert the check of detecting hardware RX
 checksum fault

On Tue, Nov 20, 2018 at 10:18:17AM -0800, Eric Dumazet wrote:
>
> > Something like this?  Is it safe to linearize here?

It looks safe to me.  It's only unsafe if your skb is shared which
from my grepping does not appear to be the case (and it cannot be
shared if you're modifying skb->csum which all the callers that
I found were doing for obvious reasons).

If it's cloned skb_linearize will unclone it.

> I guess we should dump from skb->head instead, to show all headers.
>
> Maybe dump the mac header offset as well, so that we can ignore the
> padding bytes (NET_SKB_PAD) if needed.

Yes I agree.  It doesn't hurt to dump more data.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt