netdev - Re: [PATCH] netpoll: support sending over raw IP interfaces

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Message-Id: <93E237FA-9F0B-48E4-8A89-B9C2619B90A5@yotsuba.nl>
Date: Mon, 18 Mar 2024 12:47:46 +0100
From: Mark <mark@...suba.nl>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org,
 Hans de Goede <hdegoede@...hat.com>,
 Eric Dumazet <edumazet@...gle.com>,
 Breno Leitao <leitao@...ian.org>,
 Ingo Molnar <mingo@...hat.com>,
 "David S. Miller" <davem@...emloft.net>,
 Paolo Abeni <pabeni@...hat.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] netpoll: support sending over raw IP interfaces

Hi Jakub,

> Op 14 mrt 6 Reiwa, om 19:34 heeft Jakub Kicinski <kuba@...nel.org> het volgende geschreven:
> 
> On Wed, 13 Mar 2024 13:46:13 +0100 Mark Cilissen wrote:
>> Currently, netpoll only supports interfaces with an ethernet-compatible
>> link layer. Certain interfaces like SLIP do not have a link layer
>> on the network interface level at all and expect raw IP packets,
>> and could benefit from being supported by netpoll.
>> 
>> This commit adds support for such interfaces by using the network device's
>> `hard_header_len` field as an indication that no link layer is present.
>> If that is the case we simply skip adding the ethernet header, causing
>> a raw IP packet to be sent over the interface. This has been confirmed
>> to add netconsole support to at least SLIP and WireGuard interfaces.
> 
> Would be great if this could come with a simple selftest under
> tools/testing/selftests/net. Preferably using some simple tunnel
> device, rather than wg to limit tooling dependencies ;)

Yes, that makes a lot of sense. I wrote a selftest that tests netconsole
using IPIP and GRE tunnels, and they too seem to work correctly and pass (and
more importantly, fail without the patch ;-). Would you prefer me to submit
a v2 with that test now, or when net-next reopens in a week?

Thanks and regards,
Mark