From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9FFB9212FB9; Thu, 8 Jan 2026 15:17:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767885425; cv=none; b=txrYIR2SmieGqZSzCSELfxkbC6bhdm49Oz/TSvWm9Rkl0Ko5zhTIQua5yvpDzz/2bxbmm9iwCQMddVU1WQt+4r63Pf7X+z4BUUdN7lXGxNjNREXHxzGXNpvDDqWJwSFWkFwWpbObeyJAmqixFPByiAnTnzsOPVMPNU+Qw/bcOyU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767885425; c=relaxed/simple; bh=f0CvU2tIQVYrHZLwRGFpAIZTZzQEZlmsLyp505OcoT8=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=u7p5E5iY3fBt3Oxo04+ELXVDWW4yc6be9OuPLAlSbleQILJ0zdKTZZgVFpqD/CgskbAp+yHoqfryBTudsVN2I6RHNphTPIQro5ksgGByKH0DkttnI9vi9+leTsBEILq8r344AXujUclffMW8+a97wAFTQL9VTS7TvUPQC/bB0TQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q/pe9NNM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q/pe9NNM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D9FDC116C6; Thu, 8 Jan 2026 15:17:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767885424; bh=f0CvU2tIQVYrHZLwRGFpAIZTZzQEZlmsLyp505OcoT8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Q/pe9NNMiNxz34hUsWNmWKU2WKqFubbla3Wr7oWeH8vOiu/jI6KQbvAGDiyqebpee zueXbvVoEBUbdilVPWFJqRuNuBAGfpQY2nYSH9LvfR+BEfmKbAmTaTk3QHLESwLWxL c135xytcgj5cRVkPduRTaYTXtd8dD4ewUE3Z//Eazp9mW0O7lbVosamcHzpVBpSAh4 obT6D1ou2uLjkRk25+UQt+57hKnWBZQhox46TD8U12AduKkVvhG7W33xnvNXXjjSLx lR+Mn0/snAZwvs+38w+8/rWcw4jdjKomYHqwq+hCNYv4L7gB3mBokXbb7PQnPcYV5H MZ5zw230QRGUw== Date: Thu, 8 Jan 2026 07:17:03 -0800 From: Jakub Kicinski To: Oliver Hartkopp Cc: mkl@pengutronix.de, Prithvi , andrii@kernel.org, linux-can@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, netdev@vger.kernel.org Subject: Re: [bpf, xdp] headroom - was: Re: Question about to KMSAN: uninit-value in can_receive Message-ID: <20260108071703.788c67ed@kernel.org> In-Reply-To: <8b55ae26-daba-4b2e-a10b-4be367fb42d0@hartkopp.net> References: <20251117173012.230731-1-activprithvi@gmail.com> <0c98b1c4-3975-4bf5-9049-9d7f10d22a6d@hartkopp.net> <20251220173338.w7n3n4lkvxwaq6ae@inspiron> <01190c40-d348-4521-a2ab-3e9139cc832e@hartkopp.net> <20260102153611.63wipdy2meh3ovel@inspiron> <20260102120405.34613b68@kernel.org> <63c20aae-e014-44f9-a201-99e0e7abadcb@hartkopp.net> <20260104074222.29e660ac@kernel.org> <20260105152638.74cfea6c@kernel.org> <904fa297-b657-4f5b-9999-b8cfcc11bfa9@hartkopp.net> <20260106162306.0649424c@kernel.org> <8b55ae26-daba-4b2e-a10b-4be367fb42d0@hartkopp.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 7 Jan 2026 16:34:13 +0100 Oliver Hartkopp wrote: > > Alternatively perhaps for this particular use case you could use > > something like metadata_dst to mark the frame as forwarded / annotate > > with the originating ifindex? > > I looked into it and the way how skb_dst is shared in the union behind > cb[] does not look very promising for skbs that wander up and down in > the network layer. Maybe I'm misunderstanding, but skb_dst is only unioned with some socket layer (TCP and sockmsg) fields, not with cb[]. It'd be problematic if CAN gw frames had to traverse routing but I don't think they do?