From: Ratheesh Kannoth <rkannoth@marvell.com>
To: Mark <mark@yotsuba.nl>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Hans de Goede <hdegoede@redhat.com>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>,
Breno Leitao <leitao@debian.org>, Ingo Molnar <mingo@redhat.com>,
"David S. Miller" <davem@davemloft.net>,
Paolo Abeni <pabeni@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [EXTERNAL] [PATCH] netpoll: support sending over raw IP interfaces
Date: Mon, 18 Mar 2024 14:06:54 +0000 [thread overview]
Message-ID: <MWHPR1801MB191845C94DD80E4CD6C8C962D32D2@MWHPR1801MB1918.namprd18.prod.outlook.com> (raw)
In-Reply-To: <57AE2A31-257C-4702-A571-C590A5DD234A@yotsuba.nl>
> From: Mark <mark@yotsuba.nl>
> Sent: Monday, March 18, 2024 5:13 PM
> To: Ratheesh Kannoth <rkannoth@marvell.com>
> Cc: netdev@vger.kernel.org; Hans de Goede <hdegoede@redhat.com>; Eric
> Dumazet <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Breno
> Leitao <leitao@debian.org>; Ingo Molnar <mingo@redhat.com>; David S.
> Miller <davem@davemloft.net>; Paolo Abeni <pabeni@redhat.com>; linux-
> kernel@vger.kernel.org
> Subject: Re: [EXTERNAL] [PATCH] netpoll: support sending over raw IP
> interfaces
>
>
> Hi Ratheesh,
>
> > Op 14 mrt 6 Reiwa, om 03:46 heeft Ratheesh Kannoth
> <rkannoth@marvell.com> het volgende geschreven:
> >
> >> From: Mark <mark@yotsuba.nl>
> >> […]
> >
> > Hmm. That is not my question. Let me explain it in detail. Netconsole is
> using netpoll_send_udp() to encapsulate the msg over
> > UDP/IP/ MAC headers. Job well done. Now it calls
> > netdev->ops->ndo_start_xmit(skb, dev). If your driver is well aware that
> you can Transmit only from network header, why don’t you dma map from
> network header ?
>
> The rest of the network subsystem seems to not add a header to skbs
> submitted to netdev->ops->ndo_start_xmit() at all, which makes sense
> considering
> netdev->header_ops is either NULL or no-op for these devices.
>
> Following this line of reasoning, from API perspective it made more sense to
> me for netpoll to not submit ‘bogus’ skbs that are out-of-line with what the
> rest of the network subsystem does to ndo_start_xmit() to begin with.
> It really depends on the API guarantees we want to have for netdev, but
> personally I'm wary of introducing an allowance for bogus headers.
>
Is below network topology possible ?
Netpoll()- ------> netdev A ----> raw interface
Where netdev A's netdev->header_ops != NULL
> Additionally from a practical perspective, this would require changing almost
> every, if not every, IP interface driver. I took a look at the WireGuard driver to
> see what it would entail, and from my limited experience with the networking
> code it seems like there's some quite annoying interactions with e.g. GSO
> which would make driver-side handling of such packets quite a bit more
> complex.
ACK.
>
> So from my perspective, fixing this in netpoll is both the more API-correct
> change and introduces the least amount of additional complexity.
ACK.
next prev parent reply other threads:[~2024-03-18 14:07 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-13 12:46 [PATCH] netpoll: support sending over raw IP interfaces Mark Cilissen
2024-03-13 13:36 ` Ratheesh Kannoth
2024-03-13 13:53 ` Mark
2024-03-14 2:46 ` [EXTERNAL] " Ratheesh Kannoth
2024-03-18 11:43 ` [EXTERNAL] " Mark
2024-03-18 14:06 ` Ratheesh Kannoth [this message]
2024-03-21 12:33 ` Mark
2024-03-22 3:33 ` Ratheesh Kannoth
2024-03-14 12:48 ` Paolo Abeni
2024-03-14 18:34 ` Jakub Kicinski
2024-03-18 11:47 ` Mark
2024-03-19 17:10 ` Jakub Kicinski
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