From: Alexander Lobakin <alobakin@dlink.ru>
To: David Miller <davem@davemloft.net>
Cc: rainersickinger.official@gmail.com,
shashidhar.lakkavalli@openmesh.com, john@phrozen.org,
andrew@lunn.ch, vivien.didelot@gmail.com, f.fainelli@gmail.com,
sdf@google.com, daniel@iogearbox.net, songliubraving@fb.com,
ast@kernel.org, mcroce@redhat.com, jakub@cloudflare.com,
edumazet@google.com, paulb@mellanox.com,
komachi.yoshiki@gmail.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH net] net: dsa: fix flow dissection on Tx path
Date: Sat, 07 Dec 2019 11:10:58 +0300 [thread overview]
Message-ID: <ad7dd3a7a1e864939a18343e2e57c50e@dlink.ru> (raw)
In-Reply-To: <20191206.201950.100960973648804142.davem@davemloft.net>
David Miller wrote 07.12.2019 07:19:
> From: Alexander Lobakin <alobakin@dlink.ru>
> Date: Thu, 5 Dec 2019 13:02:35 +0300
>
>> Commit 43e665287f93 ("net-next: dsa: fix flow dissection") added an
>> ability to override protocol and network offset during flow dissection
>> for DSA-enabled devices (i.e. controllers shipped as switch CPU ports)
>> in order to fix skb hashing for RPS on Rx path.
>>
>> However, skb_hash() and added part of code can be invoked not only on
>> Rx, but also on Tx path if we have a multi-queued device and:
>> - kernel is running on UP system or
>> - XPS is not configured.
>>
>> The call stack in this two cases will be like: dev_queue_xmit() ->
>> __dev_queue_xmit() -> netdev_core_pick_tx() -> netdev_pick_tx() ->
>> skb_tx_hash() -> skb_get_hash().
>>
>> The problem is that skbs queued for Tx have both network offset and
>> correct protocol already set up even after inserting a CPU tag by DSA
>> tagger, so calling tag_ops->flow_dissect() on this path actually only
>> breaks flow dissection and hashing.
>>
>> This can be observed by adding debug prints just before and right
>> after
>> tag_ops->flow_dissect() call to the related block of code:
> ...
>> In order to fix that we can add the check 'proto == htons(ETH_P_XDSA)'
>> to prevent code from calling tag_ops->flow_dissect() on Tx.
>> I also decided to initialize 'offset' variable so tagger callbacks can
>> now safely leave it untouched without provoking a chaos.
>>
>> Fixes: 43e665287f93 ("net-next: dsa: fix flow dissection")
>> Signed-off-by: Alexander Lobakin <alobakin@dlink.ru>
>
> Applied and queued up for -stable.
David, Andrew, Florian, Rainer,
Thank you!
Regards,
ᚷ ᛖ ᚢ ᚦ ᚠ ᚱ
prev parent reply other threads:[~2019-12-07 8:11 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-05 10:02 [PATCH net] net: dsa: fix flow dissection on Tx path Alexander Lobakin
2019-12-05 12:58 ` Andrew Lunn
2019-12-05 13:34 ` Alexander Lobakin
2019-12-05 14:01 ` Andrew Lunn
2019-12-05 14:58 ` Alexander Lobakin
2019-12-06 3:32 ` Florian Fainelli
2019-12-06 7:37 ` Alexander Lobakin
2019-12-06 18:05 ` Florian Fainelli
2019-12-06 3:28 ` Florian Fainelli
2019-12-06 15:06 ` Alexander Lobakin
2019-12-06 19:32 ` Rainer Sickinger
2019-12-07 4:19 ` David Miller
2019-12-07 8:10 ` Alexander Lobakin [this message]
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=ad7dd3a7a1e864939a18343e2e57c50e@dlink.ru \
--to=alobakin@dlink.ru \
--cc=andrew@lunn.ch \
--cc=ast@kernel.org \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=f.fainelli@gmail.com \
--cc=jakub@cloudflare.com \
--cc=john@phrozen.org \
--cc=komachi.yoshiki@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mcroce@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=paulb@mellanox.com \
--cc=rainersickinger.official@gmail.com \
--cc=sdf@google.com \
--cc=shashidhar.lakkavalli@openmesh.com \
--cc=songliubraving@fb.com \
--cc=vivien.didelot@gmail.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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).