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From: Xie He <xie.he.0141@gmail.com>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>,
	Network Development <netdev@vger.kernel.org>,
	syzbot <syzbot+4a2c52677a8a1aa283cb@syzkaller.appspotmail.com>,
	William Tu <u9012063@gmail.com>
Subject: Re: [Patch net] ip_gre: set dev->hard_header_len properly
Date: Thu, 8 Oct 2020 14:35:43 -0700	[thread overview]
Message-ID: <CAJht_ENmrPbhfPaD5kkiDVWQsvA_LRndPiCMrS9zdje6sVPk=g@mail.gmail.com> (raw)
In-Reply-To: <CA+FuTScizeZC-ndVvXj4VyArth2gnxoh3kTSoe5awGoiFXtkBA@mail.gmail.com>

On Thu, Oct 8, 2020 at 1:32 PM Willem de Bruijn
<willemdebruijn.kernel@gmail.com> wrote:
>
> On Thu, Oct 8, 2020 at 4:11 PM Xie He <xie.he.0141@gmail.com> wrote:
> >
> > OK. I understand that t->tun_hlen is the GRE header length. What is
> > t->encap_hlen?
>
> I've looked at that closely either.
>
> Appears to be to account for additional FOU/GUE encap:
>
> "
> commit 56328486539ddd07cbaafec7a542a2c8a3043623
> Author: Tom Herbert <therbert@google.com>
> Date:   Wed Sep 17 12:25:58 2014 -0700
>     net: Changes to ip_tunnel to support foo-over-udp encapsulation
>
>     This patch changes IP tunnel to support (secondary) encapsulation,
>     Foo-over-UDP. Changes include:
>
>     1) Adding tun_hlen as the tunnel header length, encap_hlen as the
>        encapsulation header length, and hlen becomes the grand total
>        of these.
>     2) Added common netlink define to support FOU encapsulation.
>     3) Routines to perform FOU encapsulation.
>
>     Signed-off-by: Tom Herbert <therbert@google.com>
>     Signed-off-by: David S. Miller <davem@davemloft.net>
> "

I see the ipgre_xmit function would pull the header our header_ops
creates, and then call __gre_xmit. __gre_xmit will call
gre_build_header to complete the GRE header. gre_build_header expects
to find the base GRE header after pushing tunnel->tun_hlen. However,
if tunnel->encap_hlen is not 0, it couldn't find the base GRE header
there. Is there a problem?

Where exactly should we put the tunnel->encap_hlen header? Before the
GRE header or after?

  reply	other threads:[~2020-10-08 21:35 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-08  1:21 [Patch net] ip_gre: set dev->hard_header_len properly Cong Wang
2020-10-08 11:48 ` Willem de Bruijn
2020-10-08 17:33   ` Cong Wang
2020-10-08 19:04     ` Willem de Bruijn
2020-10-08 19:16       ` Xie He
2020-10-08 19:19         ` Willem de Bruijn
2020-10-08 20:10           ` Xie He
2020-10-08 20:31             ` Willem de Bruijn
2020-10-08 21:35               ` Xie He [this message]
2020-10-08 21:47                 ` Willem de Bruijn
2020-10-08 21:54                   ` Xie He
2020-10-08 23:40                     ` Xie He
2020-10-09 17:43                       ` Cong Wang
2020-10-09 19:41                         ` Xie He
2020-10-09 19:51                           ` Xie He
2020-10-09 20:38                             ` Cong Wang
2020-10-10  1:07                               ` Cong Wang
2020-10-10  3:10                                 ` Xie He
2020-10-10 18:58                                   ` Cong Wang
2020-10-10 21:49                                     ` Xie He
2020-10-11  3:55                                       ` Xie He
2020-10-11 14:35                                     ` Xie He
2020-10-08 19:18       ` Willem de Bruijn
2020-10-08 19:50         ` Cong Wang
2020-10-08 20:19 ` Willem de Bruijn

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