From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.zx2c4.com (lists.zx2c4.com [165.227.139.114]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 43B70C61DC6 for ; Thu, 27 Aug 2026 13:28:29 +0000 (UTC) Received: by lists.zx2c4.com (OpenSMTPD) with ESMTP id 9bc157f8; Thu, 27 Aug 2026 13:28:28 +0000 (UTC) Received: from sea.source.kernel.org (sea.source.kernel.org [2600:3c0a:e001:78e:0:1991:8:25]) by lists.zx2c4.com (OpenSMTPD) with ESMTPS id 9ffa0cf0 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO) for ; Thu, 27 Aug 2026 13:28:24 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id E8E3A409CF; Thu, 27 Aug 2026 13:28:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9FAF41F000E9; Thu, 27 Aug 2026 13:28:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787837302; bh=Wfbt9FdAIskXDj0zssRilPrFLn0V1tVO14o+L9rnNos=; h=From:To:Cc:Subject:In-Reply-To:References:Date; b=nbZNSEOL+SKVTNrDJkClzkwQgFzbPuRQftnxOzrPG5yrzAIjCmJrbHlqkBqOHRY2n KHWo7iXfbd1Om4bVehvhtWAnorazhuMddC4npXfeoykAabTAT+Z1x3CsK+eN4/93KX fwAamkDqzQqdSCmsoYLNHIksJLvY3aEG0mQ9zLVCsd1ghaPbZ+E+zkuiT9Ah/q6e7k qe23BgsgCpfEMnZzBt/k/cTc8nfR3BqqQ2pK7vU/RYgAE4mY3ak287cbPz5igY17Jw D7hpDH/MrvidKDlpX+c3xRffmaS5K32Q5x0nuYNkZ7oWcNNISLzpfhPiJb1+R0Tktz Ea13wMtUL/JPg== Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id B52B0979E5E; Thu, 27 Aug 2026 15:28:19 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Ramses de Norre via B4 Relay , "Jason A. Donenfeld" , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Martin KaFai Lau Cc: wireguard@lists.zx2c4.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Ramses de Norre Subject: Re: [PATCH net] wireguard: queueing: preserve tstamp_type in wg_reset_packet() In-Reply-To: <20260827-wg-tstamp-v1-1-4acfebb855ef@well-founded.dev> References: <20260827-wg-tstamp-v1-1-4acfebb855ef@well-founded.dev> X-Clacks-Overhead: GNU Terry Pratchett Date: Thu, 27 Aug 2026 15:28:19 +0200 Message-ID: <87a4q74rrg.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: wireguard@lists.zx2c4.com X-Mailman-Version: 2.1.30rc1 Precedence: list List-Id: Development discussion of WireGuard List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: wireguard-bounces@lists.zx2c4.com Sender: "WireGuard" Ramses de Norre via B4 Relay writes: > From: Ramses de Norre > > Sending traffic through a wireguard tunnel on a host using the fq > qdisc fills the log with: > > fq: likely mono tstamp with tstamp_type 0 > > An skb carries a timestamp in skb->tstamp and, separately, a > skb->tstamp_type field recording which clock that timestamp came from. > The two have to agree. > > When wireguard encapsulates a packet it calls wg_reset_packet(), which > clears the fields that must not leak from the inner packet into the > tunnel packet. It does so in two steps: > > skb_scrub_packet(skb, true); > memset(&skb->headers, 0, sizeof(skb->headers)); > > skb_scrub_packet() deliberately keeps skb->tstamp when it holds a > monotonic timestamp: that value is the time the packet is scheduled to > be sent, and the qdisc still needs it. The memset then zeroes > skb->tstamp_type, because that field sits inside the headers group > while skb->tstamp does not. The packet therefore leaves wireguard > carrying a monotonic timestamp labelled as a realtime one. > > Nothing noticed until commit c4f796c4f16b ("net_sched: sch_fq: convert > skb->tstamp if not monotonic"): fq used to assume every timestamp was > monotonic. It now consults tstamp_type, spots the mismatch, warns, and > falls back to treating the value as monotonic. Pacing still ends up > correct, so the log spam is the actual problem. > > Save tstamp_type before the memset and restore it when encapsulating, > next to the hash fields that are already carried over this way. When > decapsulating it stays zeroed, which is right: an incoming packet's > timestamp is a realtime receive timestamp. > > Fixes: de799101519a ("net: Add skb_clear_tstamp() to keep the mono delive= ry_time") > Signed-off-by: Ramses de Norre Seems reasonable: Reviewed-by: Toke H=C3=B8iland-J=C3=B8rgensen