From: Jesper Dangaard Brouer <brouer@redhat.com>
To: netdev <netdev@vger.kernel.org>,
"Björn Töpel" <bjorn.topel@gmail.com>,
"Jesse Brandeburg" <jesse.brandeburg@intel.com>,
"Tony Nguyen" <anthony.l.nguyen@intel.com>,
"Marek Majtyka" <alardam@gmail.com>
Cc: brouer@redhat.com,
intel-wired-lan <intel-wired-lan@lists.osuosl.org>,
"Jakub Kicinski" <kuba@kernel.org>,
"Alexei Starovoitov" <alexei.starovoitov@gmail.com>,
"Maciej Fijalkowski" <maciej.fijalkowski@intel.com>,
"Tony Brelinski" <tonyx.brelinski@intel.com>,
"Toke Høiland-Jørgensen" <toke@redhat.com>
Subject: Driver i40e have XDP-redirect bug
Date: Mon, 1 Mar 2021 13:18:32 +0100 [thread overview]
Message-ID: <20210301131832.0d765179@carbon> (raw)
Hi i40e-people + XDP-feature-people,
The driver i40e have a XDP-redirect bug, where is it partly broken. It can
transmit a redirected xdp_frame (from another driver). But broken when
redirecting a xdp_frame that is received by the driver itself.
This reminds me about lacking XDP-features, as this "state" is actually
"supported" (for Intel drivers), when running in 'legacy-rx' mode. This can
be configured (via: 'ethtool --set-priv-flags i40e2 legacy-rx on'). When
running in 'legacy-rx' mode the headroom is zero, which means that xdp_frame
cannot be created as it is stored in this headroom, but an XDP-prog can
still run a (DDoS) filter. (Hint grepping after xdp_redirect stats is not enough).
The BUG I experience *is* that headroom is zero, but 'legacy-rx' mode is off:
$ ethtool --show-priv-flags i40e2 | grep legacy-rx
legacy-rx : off
This is clearly a driver initialization bug as the headroom should not
be zero in this configuration. Further indication that this is related
to init order: If while xdp_redirect is running, I change RX-ring size
(e.g. 'ethtool -G i40e2 rx 1024') then redirect starts working again.
I will continue to find the offending commit... (to-be-continued)
(p.s. testing on net-next on top of commit d310ec03a34e92).
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
next reply other threads:[~2021-03-01 12:20 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-01 12:18 Jesper Dangaard Brouer [this message]
2021-03-01 18:46 ` Driver i40e have XDP-redirect bug Jesper Dangaard Brouer
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