BPF Archive on lore.kernel.org
 help / color / Atom feed
From: Daniel Borkmann <daniel@iogearbox.net>
To: Hangbin Liu <liuhangbin@gmail.com>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
	"Toke Høiland-Jørgensen" <toke@redhat.com>,
	"Jiri Benc" <jbenc@redhat.com>,
	"Jesper Dangaard Brouer" <brouer@redhat.com>,
	"Eelco Chaudron" <echaudro@redhat.com>,
	ast@kernel.org, "Lorenzo Bianconi" <lorenzo.bianconi@redhat.com>
Subject: Re: [PATCHv6 bpf-next 0/3] xdp: add a new helper for dev map multicast support
Date: Fri, 10 Jul 2020 17:02:34 +0200
Message-ID: <9a04393c-f924-5aaf-4644-d7f33350004f@iogearbox.net> (raw)
In-Reply-To: <20200710073652.GC2531@dhcp-12-153.nay.redhat.com>

On 7/10/20 9:36 AM, Hangbin Liu wrote:
> On Fri, Jul 10, 2020 at 12:37:59AM +0200, Daniel Borkmann wrote:
>> On 7/9/20 3:30 AM, Hangbin Liu wrote:
>>> This patch is for xdp multicast support. which has been discussed before[0],
>>> The goal is to be able to implement an OVS-like data plane in XDP, i.e.,
>>> a software switch that can forward XDP frames to multiple ports.
>>>
>>> To achieve this, an application needs to specify a group of interfaces
>>> to forward a packet to. It is also common to want to exclude one or more
>>> physical interfaces from the forwarding operation - e.g., to forward a
>>> packet to all interfaces in the multicast group except the interface it
>>> arrived on. While this could be done simply by adding more groups, this
>>> quickly leads to a combinatorial explosion in the number of groups an
>>> application has to maintain.
>>>
>>> To avoid the combinatorial explosion, we propose to include the ability
>>> to specify an "exclude group" as part of the forwarding operation. This
>>> needs to be a group (instead of just a single port index), because a
>>> physical interface can be part of a logical grouping, such as a bond
>>> device.
>>>
>>> Thus, the logical forwarding operation becomes a "set difference"
>>> operation, i.e. "forward to all ports in group A that are not also in
>>> group B". This series implements such an operation using device maps to
>>> represent the groups. This means that the XDP program specifies two
>>> device maps, one containing the list of netdevs to redirect to, and the
>>> other containing the exclude list.
>>
>> Could you move this description as part of patch 1/3 instead of cover
>> letter? Mostly given this helps understanding the rationale wrt exclusion
>> map which is otherwise lacking from just looking at the patch itself.
> 
> OK, I will
> 
>> Assuming you have a bond, how does this look in practice for your mentioned
>> ovs-like data plane in XDP? The map for 'group A' is shared among all XDP
>> progs and the map for 'group B' is managed per prog? The BPF_F_EXCLUDE_INGRESS
> 
> Yes, kind of. Since we have two maps as parameter. The 'group A map'(include map)
> will be shared between the interfaces in same group/vlan. The 'group B map'
> (exclude map) is interface specific. Each interface will hold it's own exclude map.
> 
> As most time each interface only exclude itself, a null map + BPF_F_EXCLUDE_INGRESS
> should be enough.
> 
> For bond situation. e.g. A active-backup bond0 with eth1 + eth2 as slaves.
> If eth1 is active interface, we can add eth2 to the exclude map.

Right, but what about the other direction where one device forwards to a bond,
presumably eth1 + eth2 are in the include map and shared also between other
ifaces? Given the logic for the bond mode is on bond0, so one layer higher, how
do you determine which of eth1 + eth2 to send to in the BPF prog? Daemon listening
for link events via arp or mii monitor and then update include map? Ideally would
be nice to have some sort of a bond0 pass-through for the XDP buffer so it ends
up eventually at one of the two through the native logic, e.g. what do you do when
it's configured in xor mode or when slave dev is selected via hash or some other
user logic (e.g. via team driver); how would this be modeled via inclusion map? I
guess the issue can be regarded independently to this set, but given you mention
explicitly bond here as a use case for the exclusion map, I was wondering how you
solve the inclusion one for bond devices for your data plane?

>> is clear, but how would this look wrt forwarding from a phys dev /to/ the
>> bond iface w/ XDP?
> 
> As bond interface doesn't support native XDP, This forwarding only works for
> physical slave interfaces.
> 
> For generic xdp, maybe we can forward to bond interface directly, but I
> haven't tried.
> 
>> Also, what about tc BPF helper support for the case where not every device
>> might have native XDP (but they could still share the maps)?
> 
> I haven't tried tc BPF. This helper works for both generic and native xdp
> forwarding. I think it should also works if we load the prog with native
> xdp mode in one interface and generic xdp mode in another interface, couldn't
> we?

Yes, that would work though generic XDP comes with its own set of issues, but
presumably this sort of traffic could be considered slow-path anyway.

Thanks,
Daniel

  reply index

Thread overview: 94+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-15  8:54 [RFC PATCH bpf-next 0/2] xdp: add " Hangbin Liu
2020-04-15  8:54 ` [RFC PATCH bpf-next 1/2] " Hangbin Liu
2020-04-20  9:52   ` Hangbin Liu
2020-04-15  8:54 ` [RFC PATCH bpf-next 2/2] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-04-24  8:56 ` [RFC PATCHv2 bpf-next 0/2] xdp: add dev map multicast support Hangbin Liu
2020-04-24  8:56   ` [RFC PATCHv2 bpf-next 1/2] xdp: add a new helper for " Hangbin Liu
2020-04-24 14:19     ` Lorenzo Bianconi
2020-04-28 11:09       ` Eelco Chaudron
2020-05-06  9:35       ` Hangbin Liu
2020-04-24 14:34     ` Toke Høiland-Jørgensen
2020-05-06  9:14       ` Hangbin Liu
2020-05-06 10:00         ` Toke Høiland-Jørgensen
2020-05-08  8:53           ` Hangbin Liu
2020-05-08 14:58             ` Toke Høiland-Jørgensen
2020-05-18  8:45       ` Hangbin Liu
2020-05-19 10:15         ` Jesper Dangaard Brouer
2020-05-20  1:24           ` Hangbin Liu
2020-04-24  8:56   ` [RFC PATCHv2 bpf-next 2/2] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-04-24 14:21     ` Lorenzo Bianconi
2020-05-23  6:05 ` [PATCHv3 bpf-next 0/2] xdp: add dev map multicast support Hangbin Liu
2020-05-23  6:05   ` [PATCHv3 bpf-next 1/2] xdp: add a new helper for " Hangbin Liu
2020-05-26  7:34     ` kbuild test robot
2020-05-23  6:05   ` [PATCHv3 bpf-next 2/2] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-05-26 14:05 ` [PATCHv4 bpf-next 0/2] xdp: add dev map multicast support Hangbin Liu
2020-05-26 14:05   ` [PATCHv4 bpf-next 1/2] xdp: add a new helper for " Hangbin Liu
2020-05-27 10:29     ` Toke Høiland-Jørgensen
2020-06-10 10:18     ` Jesper Dangaard Brouer
2020-06-12  8:54       ` Hangbin Liu
2020-06-16  8:55         ` Jesper Dangaard Brouer
2020-06-16 10:11           ` Hangbin Liu
2020-06-16 14:38             ` Jesper Dangaard Brouer
2020-06-10 10:21     ` Jesper Dangaard Brouer
2020-06-10 10:29       ` Toke Høiland-Jørgensen
2020-06-16  9:04         ` Jesper Dangaard Brouer
2020-05-26 14:05   ` [PATCHv4 bpf-next 2/2] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-05-27 10:21   ` [PATCHv4 bpf-next 0/2] xdp: add dev map multicast support Toke Høiland-Jørgensen
2020-05-27 10:32     ` Eelco Chaudron
2020-05-27 12:38     ` Hangbin Liu
2020-05-27 15:04       ` Toke Høiland-Jørgensen
2020-06-16  9:09         ` Jesper Dangaard Brouer
2020-06-16  9:47           ` Hangbin Liu
2020-06-03  2:40     ` Hangbin Liu
2020-06-03 11:05       ` Toke Høiland-Jørgensen
2020-06-04  4:09         ` Hangbin Liu
2020-06-04  9:44           ` Toke Høiland-Jørgensen
2020-06-04 12:12             ` Hangbin Liu
2020-06-04 12:37               ` Toke Høiland-Jørgensen
2020-06-04 14:41                 ` Hangbin Liu
2020-06-04 16:02                   ` Toke Høiland-Jørgensen
2020-06-05  6:26                     ` Hangbin Liu
2020-06-08 15:32                       ` Toke Høiland-Jørgensen
2020-06-09  3:03                         ` Hangbin Liu
2020-06-09 20:31                           ` Toke Høiland-Jørgensen
2020-06-10  2:35                             ` Hangbin Liu
2020-06-10 10:03                               ` Jesper Dangaard Brouer
2020-07-01  4:19   ` [PATCHv5 bpf-next 0/3] xdp: add a new helper for " Hangbin Liu
2020-07-01  4:19     ` [PATCHv5 bpf-next 1/3] " Hangbin Liu
2020-07-01  5:09       ` Andrii Nakryiko
2020-07-01  6:51         ` Hangbin Liu
2020-07-01 18:33       ` kernel test robot
2020-07-01  4:19     ` [PATCHv5 bpf-next 2/3] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-07-01  4:19     ` [PATCHv5 bpf-next 3/3] selftests/bpf: add xdp_redirect_multi test Hangbin Liu
2020-07-09  1:30     ` [PATCHv6 bpf-next 0/3] xdp: add a new helper for dev map multicast support Hangbin Liu
2020-07-09  1:30       ` [PATCHv6 bpf-next 1/3] " Hangbin Liu
2020-07-09 16:33         ` David Ahern
2020-07-10  6:55           ` Hangbin Liu
2020-07-10 13:46             ` David Ahern
2020-07-11  0:26               ` Hangbin Liu
2020-07-11 16:09                 ` David Ahern
2020-07-09  1:30       ` [PATCHv6 bpf-next 2/3] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-07-09 22:40         ` Daniel Borkmann
2020-07-10  6:41           ` Hangbin Liu
2020-07-10 14:32             ` Daniel Borkmann
2020-07-11  0:21               ` Hangbin Liu
2020-07-09  1:30       ` [PATCHv6 bpf-next 3/3] selftests/bpf: add xdp_redirect_multi test Hangbin Liu
2020-07-09 22:37       ` [PATCHv6 bpf-next 0/3] xdp: add a new helper for dev map multicast support Daniel Borkmann
2020-07-10  7:36         ` Hangbin Liu
2020-07-10 15:02           ` Daniel Borkmann [this message]
2020-07-10 16:52             ` David Ahern
2020-07-14  6:32       ` [PATCHv7 " Hangbin Liu
2020-07-14  6:32         ` [PATCHv7 bpf-next 1/3] " Hangbin Liu
2020-07-14 21:52           ` Toke Høiland-Jørgensen
2020-07-15 12:25             ` Hangbin Liu
2020-07-14  6:32         ` [PATCHv7 bpf-next 2/3] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-07-14  6:32         ` [PATCHv7 bpf-next 3/3] selftests/bpf: add xdp_redirect_multi test Hangbin Liu
2020-07-14 12:29         ` [PATCHv7 bpf-next 0/3] xdp: add a new helper for dev map multicast support Toke Høiland-Jørgensen
2020-07-14 17:12           ` David Ahern
2020-07-14 21:53             ` Toke Høiland-Jørgensen
2020-07-15 12:31               ` Hangbin Liu
2020-07-15  3:45             ` Hangbin Liu
2020-07-15 13:08         ` [PATCHv8 " Hangbin Liu
2020-07-15 13:08           ` [PATCHv8 bpf-next 1/3] " Hangbin Liu
2020-07-15 13:08           ` [PATCHv8 bpf-next 2/3] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-07-15 13:08           ` [PATCHv8 bpf-next 3/3] selftests/bpf: add xdp_redirect_multi test Hangbin Liu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=9a04393c-f924-5aaf-4644-d7f33350004f@iogearbox.net \
    --to=daniel@iogearbox.net \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=brouer@redhat.com \
    --cc=echaudro@redhat.com \
    --cc=jbenc@redhat.com \
    --cc=liuhangbin@gmail.com \
    --cc=lorenzo.bianconi@redhat.com \
    --cc=netdev@vger.kernel.org \
    --cc=toke@redhat.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

BPF Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/bpf/0 bpf/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 bpf bpf/ https://lore.kernel.org/bpf \
		bpf@vger.kernel.org
	public-inbox-index bpf

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.bpf


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git