Date: Tue, 03 Nov 2020 20:20:02 +0100 From: "Kristof Provost" <kp@FreeBSD.org> To: "John-Mark Gurney" <jmg@funkthat.com> Cc: "Carsten =?utf-8?q?B=C3=A4cker?=" <carbaecker@gmx.de>, freebsd-hackers@freebsd.org, freebsd-arm@freebsd.org Subject: Re: Problem with checksum offloading on RPi3 (PF + Jails involved) Message-ID: <E77BCC85-DBDE-4B61-A005-BF4E871B326F@FreeBSD.org> In-Reply-To: <20201103191439.GV31099@funkthat.com> References: <748edc3d-4ef7-c4de-291f-7c0b460a6052@gmx.de> <D8CE4762-4D94-47C7-A8D1-6C537766813B@FreeBSD.org> <5130ee46-5832-d4df-d774-c6bd32e10b30@gmx.de> <A3890336-BE8F-438C-8C3E-7B21FB729FCA@FreeBSD.org> <20201029213622.GM31099@funkthat.com> <55713894-A896-4F12-ABB9-93DFEB2F16B9@FreeBSD.org> <f2a38b96-917b-c723-f44f-043abe6c4629@gmx.de> <DF9D466D-BF09-427F-A781-9FF6D31EF274@FreeBSD.org> <20201103191439.GV31099@funkthat.com>
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On 3 Nov 2020, at 20:14, John-Mark Gurney wrote: > Kristof Provost wrote this message on Sun, Nov 01, 2020 at 19:48 > +0100: >> On 31 Oct 2020, at 16:06, Carsten Bäcker wrote: >>> Packet-capture from the router is attached. >>> >> Okay??? but that doesn???t actually demonstrate anything at all. >> It shows an outbound packet with an incorrect checksum. See what >> I???ve >> mentioned before about checksums potentially being calculated by >> hardware. >> Given that there???s been a reply to that DNS query the checksum >> clearly >> got set correctly after the packet was captured. > > Actually, isn't that odd that the outbound checksum is wrong? Since > the chip doesn't advertise (or it shouldn't) tx checksum handling, > FreeBSD's stack should have computed the checksum. > Bear in mind that this capture was made with pflog, not the usual BTF_MTAP() in the driver. That means it was captured before the stack does checksum calculations. Just before it, in fact. See ip_output(). The checksum calculation is pretty much immediately after the pfil hook. Best regards, Kristof
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