From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Magnus Karlsson <magnus.karlsson@gmail.com>,
Christian Deacon <christian.m.deacon@gmail.com>
Cc: xdp-newbies@vger.kernel.org
Subject: Re: Redirect to AF_XDP socket not working with bond interface in native mode
Date: Tue, 19 Mar 2024 12:57:34 +0100 [thread overview]
Message-ID: <87a5muzb69.fsf@toke.dk> (raw)
In-Reply-To: <CAJ8uoz25bTNDXsDDd1J5zKcoTAtEpAf35WTkFBZi6hyMJvRsRA@mail.gmail.com>
Magnus Karlsson <magnus.karlsson@gmail.com> writes:
> On Mon, 18 Mar 2024 at 19:41, Christian Deacon
> <christian.m.deacon@gmail.com> wrote:
>>
>> Resending the following email to the XDP Newbies mailing list since it
>> was rejected due to HTML contents (I've switched email clients and
>> forgot to disable HTML, I apologize).
>>
>> Hey everyone,
>>
>> I was wondering if there was an update to this. I'm currently running
>> into the same issue with a similar setup.
>>
>> When running the XDP program on a bonding device via native mode,
>> packets redirected to the AF_XDP sockets with `bpf_redirect_map()`
>> inside the XDP program do not make it to the AF_XDP sockets. Switching
>> between zero copy and copy mode does not make a difference along with
>> setting the need wakeup flag.
>>
>> I've tried the latest mainline kernel `6.8.1-060801`, but that did not
>> make a difference. If the XDP program is attached with SKB mode,
>> packets do show up on the AF_XDP sockets as mentioned in this thread
>> already.
>>
>> While I haven't confirmed it on my side, I'm assuming the
>> `xsk_rcv_check()` function is the issue here. I'm unsure if skipping
>> this check for the time being would work for my needs, but I'm hoping
>> a better solution will be implemented to the mainline kernel.
>>
>> I also saw there was another similar issue on this mailing list with
>> the title "Switching packets between queues in XDP program". However,
>> judging from the last reply in that thread, the fix implemented
>> wouldn't help with the bonding driver.
>>
>> Any help is appreciated and thank you for your time!
>
> You are correct in that the fix above does not address the bonding
> case and that the problem is indeed that XDP reports the device as the
> real NIC and that the AF_XDP socket is bound to the bonding device.
> Therefore xdp->dev != xsk->dev (in principle, not the actual code) and
> all packets will be discarded. I got as far as sketching on a solution
> but I do not have the bandwidth at the moment to implement it.
> Unfortunately it is not a one-liner or even just one hundred lines of
> code. Let me know what you think, or if someone can come up with an
> easier solution.
>
> *** Suggestion on how to implement AF_XDP for the bond device
>
> Two steps: XDP_DRV mode then zero-copy mode
>
> * XDP_DRV:
>
> For XDP_DRV mode, the problem to overcome is this piece of code
> in xsk_rcv_check():
>
> struct net_device *dev = xdp->rxq->dev;
> u32 qid = xdp->rxq->queue_index;
>
> if (!dev->_rx[qid].pool || xs->umem != dev->_rx[qid].pool->umem)
> return -EINVAL;
>
> xs is the socket that was bound to the bonding device e.g., bond0. So
> xs->dev points to bond0. xdp->rxq->dev, on the other hand, comes from
> XDP and the real driver e.g. eth0, thus xs->dev != xdp->rxq->dev. The
> problem here is that only _rx[] of bond0 is populated with the pool
> pointer at bind time, so dev->_rx[qid].pool is NULL as it refers to
> the _rx of eth0 that was never set. The solution here is then to make
> sure that the _rx[] of bond0 is propagated to eth0 (and any other device
> bonded to bond0).
>
> Two new features are needed to support this:
>
> 1) A helper that copies _rx[].pool from one struct to another
> 2) A new xsk_bind netdev event that a driver can subscribe to. Will be called
> whenever a xsk socket is bound to a device.
>
> In the case the socket is bound to bond0 before eth0 is bonded to
> bond0, only 1) needs to be used in the bonding driver.
>
> In the case the socket is bound to bond0 after bonding of eth0 to
> bond0, the bonding driver need to subscribe to 2) and in the event
> handle call 1).
>
> * ZERO-COPY
>
> 1) Relay through the XDP_SETUP_XSK_POOL command in NDO_BPF to the
> bonded devices.
>
> 2) Relay through the ndo_xsk_wakeup to the bonded devices.
>
> Standby mode seems straight-forward to support.
>
> How to deal with round-robin mode in the bonding driver? Not possible
> to have multiple bonded devices access the same ring. Would require
> multiple rings and copying to them. Also not clear how to propagate
> the need_wakeup flags of the individual network devices to the one of
> the bond device. I think this kind of functionality is much better
> performed in user-space with a lib. Simpler and faster.
I think this goes for all the things you mentioned above. There is no
way we can make this consistent with the in-kernel bond behaviour, so
it's going to be a pretty leaky abstraction anyway. So I don't think we
should add all this complexity, it's better to handle this in userspace
(and just attach to the component interfaces).
In fact, I think supporting XDP at all on the bond interface was a
mistake; let's not exacerbate it :/
-Toke
next prev parent reply other threads:[~2024-03-19 11:57 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-19 10:45 Redirect to AF_XDP socket not working with bond interface in native mode Prashant Batra
2023-12-19 10:58 ` Prashant Batra
2023-12-19 13:47 ` Magnus Karlsson
2023-12-19 20:18 ` Prashant Batra
2023-12-20 8:24 ` Magnus Karlsson
2023-12-21 12:39 ` Prashant Batra
2023-12-21 13:45 ` Magnus Karlsson
2023-12-22 11:23 ` Prashant Batra
2024-01-02 9:57 ` Magnus Karlsson
2024-01-11 10:41 ` Prashant Batra
2024-01-15 9:22 ` Magnus Karlsson
2024-01-16 12:48 ` Prashant Batra
2024-01-16 12:59 ` Magnus Karlsson
2024-01-17 6:07 ` Prashant Batra
2024-01-17 7:41 ` Magnus Karlsson
2024-01-19 12:43 ` Prashant Batra
2024-01-19 13:04 ` Toke Høiland-Jørgensen
[not found] ` <CAD0p+fUM5DcG44cxYXU3fMd9PgTjhTaMCH_oy=4iejJ41zxHpA@mail.gmail.com>
2024-03-18 18:41 ` Christian Deacon
2024-03-19 7:52 ` Magnus Karlsson
2024-03-19 11:57 ` Toke Høiland-Jørgensen [this message]
2024-03-19 12:29 ` Magnus Karlsson
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