netdev - Re: [net-next 02/10] udp: Expand UDP tunnel common APIs

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Date:	Tue, 22 Jul 2014 16:24:20 -0700
From:	Tom Herbert <therbert@...gle.com>
To:	Alexander Duyck <alexander.h.duyck@...el.com>
Cc:	Jesse Gross <jesse@...ira.com>, Andy Zhou <azhou@...ira.com>,
	David Miller <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [net-next 02/10] udp: Expand UDP tunnel common APIs

On Tue, Jul 22, 2014 at 3:55 PM, Alexander Duyck
<alexander.h.duyck@...el.com> wrote:
> On 07/22/2014 03:38 PM, Tom Herbert wrote:
>> On Tue, Jul 22, 2014 at 2:56 PM, Jesse Gross <jesse@...ira.com> wrote:
>>> On Tue, Jul 22, 2014 at 5:16 PM, Tom Herbert <therbert@...gle.com> wrote:
>>>> On Tue, Jul 22, 2014 at 2:02 PM, Andy Zhou <azhou@...ira.com> wrote:
>>>>> On Tue, Jul 22, 2014 at 12:52 PM, Tom Herbert <therbert@...gle.com> wrote:
>>>>>>> --- a/include/net/udp_tunnel.h
>>>>>>> +++ b/include/net/udp_tunnel.h
>>>>>>> @@ -1,7 +1,10 @@
>>>>>>>  #ifndef __NET_UDP_TUNNEL_H
>>>>>>>  #define __NET_UDP_TUNNEL_H
>>>>>>>
>>>>>>> -#define UDP_TUNNEL_TYPE_VXLAN 0x01
>>>>>>> +#include <net/ip_tunnels.h>
>>>>>>> +
>>>>>>> +#define UDP_TUNNEL_TYPE_VXLAN  0x01
>>>>>>> +#define UDP_TUNNEL_TYPE_GENEVE 0x02
>>>>>>>
>>>>>> Why do we need to define these? Caller should know what type of port is
>>>>>> being opened and provide appropriate encap_rcv.
>>>>>
>>>>> Assume udp tunnel layer needs to keep track of open ports, should it
>>>>> also keep track of the protocol associated with the port?
>>>>>
>>>> For what purpose? Other than for offloads and rcv_encap functions that
>>>> provide the service function anyway, what need is there for UDP layer
>>>> to know about this. More to the point, if I add a module to the kernel
>>>> with a new flavor of UDP tunneling, I shouldn't have to touch any core
>>>> code for things to work correctly. So by this line of thinking,
>>>> neither the terms VXLAN nor GENEVE should appear in any common code.
>>>
>>> The hardware will need to know what the header format is so that it
>>> can parse the packets on receive. And since the NIC can't exactly call
>>> into a function pointer like GRO can, I'm not sure that there is a
>>> solution that doesn't involve an identifier that needs to be listed
>>> somewhere. This is a pretty minimal impact - it doesn't actually
>>> appear in the core code.
>>
>> The hardware doesn't *need* to know this, it's must be optional and
>> should have no bearing on the software stack. Suggest to put them in
>> their own header file. Also, as HW features these should appear in
>> NETIF_F_* list so that we can control on a per device level rather to
>> enable this feature (something like how NETIF_F_GSO_* was done).
>>
>> What about support for L2TP/UDP?
>
> The hardware needs some means of knowing what UDP port numbers are used
> for VXLAN and/or GENEVE as the two formats contain subtle differences
> that we have to be ready for on the Rx path as we have to parse out the
> frames.
>
> We already have feature flags controlling the offloads, what the port
> numbers provide is a means for us to determine what Rx packets we should
> parse as tunnels vs standard UDP and which tunnel type we should parse
> it as.
>
Which feature flags control the receive side parsing in the device?

> Thanks,
>
> Alex
>
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