From: Michal Kubecek <mkubecek@suse.cz>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: pshelar@nicira.com, netdev@vger.kernel.org
Subject: Re: GRE: Refactor GRE tunneling code.
Date: Tue, 2 Apr 2013 09:44:42 +0200 [thread overview]
Message-ID: <20130402074441.GA28378@unicorn.suse.cz> (raw)
In-Reply-To: <20130402063421.GA4826@longonot.mountain>
On Tue, Apr 02, 2013 at 09:34:21AM +0300, Dan Carpenter wrote:
>
> I had a question about c54419321455: "GRE: Refactor GRE tunneling code."
> from Mar 25, 2013:
>
> net/ipv4/ip_gre.c
> 392 if (tpi->flags&TUNNEL_CSUM &&
> 393 !(skb_shinfo(skb)->gso_type & SKB_GSO_GRE)) {
> 394 *(__sum16 *)ptr = 0;
> 395 *(__sum16 *)ptr = csum_fold(skb_checksum(skb, 0,
> 396 skb->len, 0));
>
> What are we doing here when we set *ptr = 0 and then reset it on the
> next line? Is there a ptr++ or ptr-- missing?
AFAICS, skb_checksum() calculates the checksum over a block containing
the checksum field the result is to be written into (which is where ptr
points). This fields needs to be reset first.
Michal Kubecek
prev parent reply other threads:[~2013-04-02 7:44 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-02 6:34 GRE: Refactor GRE tunneling code Dan Carpenter
2013-04-02 7:44 ` Michal Kubecek [this message]
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