netdev - Re: [PATCH v15 ] net/veth/XDP: Line-rate packet forwarding in kernel

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Date:   Thu, 5 Apr 2018 20:55:21 -0600
From:   David Ahern <dsahern@...il.com>
To:     "Md. Islam" <mislam4@...t.edu>
Cc:     netdev@...r.kernel.org, David Miller <davem@...emloft.net>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Anton Gary Ceph <agaceph@...il.com>,
        Pavel Emelyanov <xemul@...nvz.org>,
        Eric Dumazet <edumazet@...gle.com>,
        alexei.starovoitov@...il.com, brouer@...hat.com
Subject: Re: [PATCH v15 ] net/veth/XDP: Line-rate packet forwarding in kernel

On 4/3/18 9:15 PM, Md. Islam wrote:
>> Have you looked at what I would consider a more interesting use case of
>> packets into a node and delivered to a namespace via veth?
>>
>>    +--------------------------+---------------
>>    | Host                     | container
>>    |                          |
>>    |        +-------{ veth1 }-|-{veth2}----
>>    |       |                  |
>>    +----{ eth1 }------------------
>>
>> Can xdp / bpf on eth1 be used to speed up delivery to the container?
> 
> I didn't consider that, but it sounds like an important use case. How
> do we determine which namespace gets the packet?
> 

FIB lookups of course. Starting with my patch set that handles
forwarding on eth1, what is needed for XDP with veth? ie., a program on
eth1 does the lookup and redirects the packet to veth1 for Tx.
ndo_xdp_xmit for veth knows the packet needs to be forwarded to veth2
internally and there is no skb allocated for the packet yet.