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 44FB8C88E77 for ; Wed, 16 Sep 2026 09:26:33 +0000 (UTC) Received: by lists.zx2c4.com (OpenSMTPD) with ESMTP id 1a004298; Wed, 16 Sep 2026 09:26:32 +0000 (UTC) Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by lists.zx2c4.com (OpenSMTPD) with ESMTPS id 76497abb (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO) for ; Wed, 16 Sep 2026 09:26:25 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 9D6796053E; Wed, 16 Sep 2026 09:26:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 55F041F000FF; Wed, 16 Sep 2026 09:26:23 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=zx2c4.com header.i=@zx2c4.com header.a=rsa-sha256 header.s=20210105 header.b=Y1/NzFiF DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1789550782; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=PtlHtwIG4pv+W9xhPsusT4EJ1S00TAe8zhG6Y8xxYWk=; b=Y1/NzFiFpPTZ6x6FibTU62lW3TlgiKgNv/JHKtD1grj11j8QK77dhETrucfNT4r/+wejZC TIRRHB4G1gFUOVPLxhwVFWlKE0zjw51zWO9pewZkF+SD8vCJn3QQYvmT/dsr4htwaTpPwR KWxdBa5kfjN2nYsBkO2MeObIKs5d6FM= Received: by mail.zx2c4.com (OpenSMTPD) with ESMTPSA id 9dcbb453 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Wed, 16 Sep 2026 09:26:22 +0000 (UTC) Date: Wed, 16 Sep 2026 11:26:19 +0200 From: "Jason A. Donenfeld" To: Ramses Cc: Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Martin KaFai Lau , Wireguard , Netdev , Linux Kernel Mailing List Subject: Re: [PATCH net] wireguard: queueing: preserve tstamp_type in wg_reset_packet() Message-ID: References: <20260827-wg-tstamp-v1-1-4acfebb855ef@well-founded.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: 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" On Mon, Aug 31, 2026 at 12:24:15PM +0200, Ramses wrote: > Aug 31, 2026, 05:25 by Jason@zx2c4.com: > > > Hi Ramses, > > > > On Thu, Aug 27, 2026 at 01:52:56PM +0200, Ramses de Norre via B4 Relay wrote: > > > >> 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 delivery_time") > >> Signed-off-by: Ramses de Norre > >> > > > > Thanks for this. I've queued this up in the wireguard tree. > > > > One thing I'm wondering is whether your Fixes: line is correct. Would > > c4f796c4f16b be a better candidate than de799101519a? Or maybe even > > 4d25ca2d6801 is best? > > > > Jason > > > Hi Jason > > I think you are right, but I think d98d58a00261 is actually the commit that introduced the issue then (but no warnings were logged yet at that point). > The patch doesn't apply cleanly to that version though, I think it only applies starting from 6.11 because of a rename, so we can't backport all the way back. It's probably fine though, since the warnings weren't being logged yet at that point. > Do you want me to send an updated patch, or will you just fix this up in your tree? I'll fix it in my tree to be: Fixes: d98d58a00261 ("net: Set skb->mono_delivery_time and clear it after sch_handle_ingress()")