netdev - Re: [PATCH 1/5] vxlan: Group Policy extension

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Date:	Wed, 14 Jan 2015 17:08:21 -0800
From:	Tom Herbert <therbert@...gle.com>
To:	Thomas Graf <tgraf@...g.ch>
Cc:	David Miller <davem@...emloft.ne>, Jesse Gross <jesse@...ira.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Pravin B Shelar <pshelar@...ira.com>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	Linux Netdev List <netdev@...r.kernel.org>,
	"dev@...nvswitch.org" <dev@...nvswitch.org>
Subject: Re: [PATCH 1/5] vxlan: Group Policy extension

On Wed, Jan 14, 2015 at 4:23 PM, Thomas Graf <tgraf@...g.ch> wrote:
> On 01/14/15 at 04:18pm, Tom Herbert wrote:
>> > diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
>> > index 99df0d7..06f7196 100644
>> > --- a/drivers/net/vxlan.c
>> > +++ b/drivers/net/vxlan.c
>> > @@ -126,6 +126,7 @@ struct vxlan_dev {
>> >         __u8              tos;          /* TOS override */
>> >         __u8              ttl;
>> >         u32               flags;        /* VXLAN_F_* in vxlan.h */
>> > +       u32               exts;         /* Enabled extensions */
>> >
>>
>> Thomas, why not just make a VXAM_F_GPB flag? Then this setting can be
>> saved in the flags for vxlan_dev and vxlan_sock so no exts field.
>
> Because we need to compare enabled extensions in vxlan_find_sock() to
> make sure we are not sharing a VXLAN socket with extensions enabled
> with a user which does not have the same extensions enabled.
>
> However, we do not want vxlan_find_sock() to compare all flags.
>
> So we need a bitmap that is ignored during the share check (flags) and
> a bitmap that must match to allow sharing (exts).
>
> The RCO extension is currently suffering from this bug which is causing
> a compatibility issue. I explained in the thread of your patch. I was
> under the imrpession that you would either send a v2 or fix it in a
> follow-up.

As I mentioned, we would also need to match receive checksum settings
which is not appropriately called an extension. A mask of interesting
flags could be used to do the comparison in vxlan_find_sock.
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