From: David Laight <David.Laight@ACULAB.COM>
To: 'Vladimir Oltean' <olteanv@gmail.com>,
Eric Dumazet <edumazet@google.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, netdev <netdev@vger.kernel.org>
Subject: RE: [PATCH net-next 2/2] net: optimize skb_postpull_rcsum()
Date: Thu, 2 Dec 2021 20:58:46 +0000 [thread overview]
Message-ID: <9eefc224988841c9b1a0b6c6eb3348b8@AcuMS.aculab.com> (raw)
In-Reply-To: <20211202204036.negad3mnrm2gogjd@skbuf>
> To me it looks like the strange part is that the checksum of the removed
> block (printed by me as "csum_partial(start, len, 0)" inside
> skb_postpull_rcsum()) is the same as the skb->csum itself.
If you are removing all the bytes that made the original checksum
that will happen.
And that might be true for the packets you are building.
Try replacing both ~ with -.
So replace:
skb->csum = ~csum_partial(start, len, ~skb->csum);
with:
skb->csum = -csum_partial(start, len, -skb->csum);
That should geneate ~0u instead 0 (if I've got my maths right).
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2021-12-02 21:00 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-24 20:24 [PATCH net-next 0/2] net: small csum optimizations Eric Dumazet
2021-11-24 20:24 ` [PATCH net-next 1/2] gro: optimize skb_gro_postpull_rcsum() Eric Dumazet
2021-11-24 20:24 ` [PATCH net-next 2/2] net: optimize skb_postpull_rcsum() Eric Dumazet
2021-11-25 9:41 ` David Laight
2021-11-25 13:32 ` Eric Dumazet
2021-11-25 14:29 ` David Laight
2021-12-02 13:10 ` Vladimir Oltean
2021-12-02 14:51 ` Eric Dumazet
2021-12-02 16:29 ` Vladimir Oltean
2021-12-02 19:32 ` Eric Dumazet
2021-12-02 20:37 ` Eric Dumazet
2021-12-02 21:07 ` Vladimir Oltean
2021-12-02 20:40 ` Vladimir Oltean
2021-12-02 20:58 ` Vladimir Oltean
2021-12-02 20:58 ` David Laight [this message]
2021-12-02 21:40 ` Vladimir Oltean
2021-12-03 14:51 ` David Laight
2021-12-03 14:57 ` David Laight
2021-12-03 16:14 ` Vladimir Oltean
2021-12-03 16:30 ` Eric Dumazet
2021-12-03 16:47 ` David Laight
2021-12-03 16:58 ` Eric Dumazet
2021-12-03 17:41 ` David Laight
2021-12-02 15:06 ` David Laight
2021-12-02 15:22 ` Eric Dumazet
2021-11-26 5:20 ` [PATCH net-next 0/2] net: small csum optimizations patchwork-bot+netdevbpf
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