netdev - Re: [net PATCH] net: Copy inner L3 and L4 headers as unaligned on GRE TEB

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Message-ID: <CALx6S34nhTqC71XqRtOfaeDwhXQQfpM2iQHiVvTGJhmpUMYuTw@mail.gmail.com>
Date:	Tue, 9 Feb 2016 15:33:39 +0100
From:	Tom Herbert <tom@...bertland.com>
To:	Alexander Duyck <aduyck@...antis.com>
Cc:	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Alexander Duyck <alexander.duyck@...il.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [net PATCH] net: Copy inner L3 and L4 headers as unaligned on GRE TEB

On Tue, Feb 9, 2016 at 3:14 PM, Alexander Duyck <aduyck@...antis.com> wrote:
> This patch corrects the unaligned accesses seen on GRE TEB tunnels when
> generating hash keys.  Specifically what this patch does is make it so that
> we force the use of skb_copy_bits when the GRE inner headers will be
> unaligned due to NET_IP_ALIGNED being a non-zero value.
>
> Signed-off-by: Alexander Duyck <aduyck@...antis.com>
> ---
>
> I don't have the ability to test it but this should fix flow dissector for
> GRE TEB tunnels traffic seen on architectures that require network and
> transport headers to be 4 byte aligned.
>
>  net/core/flow_dissector.c |    7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> index 699b2c415cb0..9c181ba7263e 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -402,6 +402,13 @@ ip_proto_again:
>                                 goto out_bad;
>                         proto = eth->h_proto;
>                         nhoff += sizeof(*eth);
> +
> +                       /* Cap headers that we access via pointers at the
> +                        * end of the Ethernet header as our maximum alignment
> +                        * at that point is only 2 bytes.
> +                        */
> +                       if (NET_IP_ALIGN)
> +                               hlen = nhoff;

I think this should be:

if (NET_IP_ALIGN)
     goto out_good;

>                 }
>
>                 key_control->flags |= FLOW_DIS_ENCAPSULATION;
>