From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 564682D63F7 for ; Tue, 15 Jul 2025 09:43:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752572624; cv=none; b=Ed5AIofdMjhYroS5QtFfAlOHg6CEY20EBf7Tj9dLHXk94+uelkN45thail1TNFpjYJfz1hRmnsR9LhABtAvH7tSjyzaPpaNpqThkfowDqjSpblC83CFq30YfeyUF4K/CLwe/yA8TVwEITAszzk4CEVEVDxaOL1PthGGvYNcOooI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752572624; c=relaxed/simple; bh=izVGqEo59aQaJ/J3dKmYZUnzyzOQr38MLYsTGyUr5V0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KiZCxR2nIgqJdYY05ZviztncQLWDMuNUU/UdOSqpOT4Pnw2X8KMXzKBV5+q2LMlQjzWlc3VDK12iWKxoJ2qFCR8I+C6kV0mo7gsYRebztmARF3fem5AjUR8/XBKbEwuQjUjWPJocUehJaXK1X6Ss426qZSyT1kq1t7+tPGEVU0E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=i/scXD9g; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="i/scXD9g" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1752572621; 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=wHMd57pfXhcnKNyhyGblHFv+xYATdiBZA7QtN8Jk8ZM=; b=i/scXD9gn3sFhebCDM0YGxdKzuxmxltdxJTn573pWYkavICZk2EkJb+U4av+2O1plOj1/B veZashgaAeBIlJaIEjJ3rtfyZhkqzEXlOfo7rd+pu5bcLlNgOtJUMpwtQs+pODR4T+Kua7 eLf8mg7Br6sEn+Iqq0bEhzOD3v9OLLg= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-646-9bdf-JUfOxGRvfrzIhSfMA-1; Tue, 15 Jul 2025 05:43:37 -0400 X-MC-Unique: 9bdf-JUfOxGRvfrzIhSfMA-1 X-Mimecast-MFC-AGG-ID: 9bdf-JUfOxGRvfrzIhSfMA_1752572616 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-45626532e27so4666415e9.1 for ; Tue, 15 Jul 2025 02:43:37 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1752572616; x=1753177416; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=wHMd57pfXhcnKNyhyGblHFv+xYATdiBZA7QtN8Jk8ZM=; b=g1M6alrCA/aaiFTEJgWSwZlZaeKlMrOBo+Ss3LZK9t1PQKCW5ZGO1j1H05g3RqryiC P+T5Q7pPxRpfaI5pH2Nt0pJtSLvpJQuP2XSc/wuubyjbENFjccxdPeKnQG1l3O1jnR6z vVmhWC7fN4kxk6M3OB5reovObPpiLCrG3AEeIfmvNJoT+ByiemuCldV9FMzbpIetBiPw dBpsoIyoJ0zTmpjFPJ7gZlKZW2KdXBPt5ZKBtxlNAW+zJzJPPZHcW1SCb/V0VfRF7sa5 JMtcIsrh0ZssqCoyJM0/KpfFq9eB8gV2Ax+uuq2r/oJEKLD3GkPutq0wPN+2eQK7uT+p nujA== X-Forwarded-Encrypted: i=1; AJvYcCVPbXx7tIPC54KNYswinvos25usj/aWzFd/4v6b0r5Q5IW9LJkiVKi1kLB7JpEAlahuCO9mjPBFYo/78PY=@vger.kernel.org X-Gm-Message-State: AOJu0Yy/iV7D7/DlWiKvK6nkPDL71K1EvcHwDE6vwf3yrgVLhGtvW1VF bD6C3tEuoIXmAOFlakBV673psPK8iOZHxp7/8JiP2oE1uRxvdTNMJU26rAbj5epl/k3yKWYk0l6 nnzVrkZ/m74yrXk2qJ/NWhuav6Rn3ektvmdKvXjwrOymcCLo+c22TLQLh37ez5h5BUw== X-Gm-Gg: ASbGncvEsHgZ5BvLWjlmAIKbBCav1ttWxvIbI6D+cAl4OVB9QoZFyQKBH5kMDZPFR7X zg/8vBDn/8BpbWFE4I/FyR09jH6co8JYqIAYLbSRTjowyVwPC64TO2/iMxdq2HzoCIyS0fPJC25 7zOeP0foc4OawNHLQt0YnJSM9iPA3ZJvLalOUFnaVN+4QTMR4UiSohlnNbhh0saXUR1AxpUZOjo uZTdplBB2PQ0lrW7KnQ4Fr1Zlxi2EIp3JjKmLQVhO/epADCwBb58JHdxNfc/yZ9koXus0LnrDyE vR/euDQSy6SbcvLnuX0x1DKFBgc= X-Received: by 2002:a05:600c:821b:b0:43c:ec4c:25b4 with SMTP id 5b1f17b1804b1-4555f89f507mr187240825e9.10.1752572616447; Tue, 15 Jul 2025 02:43:36 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFN73ANiZ06ERUP471KmOgFnUFAPyMUPH/okS1ibcPZuQjxLvuh1FG3xOFXv+UfdNO1P57u2Q== X-Received: by 2002:a05:600c:821b:b0:43c:ec4c:25b4 with SMTP id 5b1f17b1804b1-4555f89f507mr187240285e9.10.1752572615932; Tue, 15 Jul 2025 02:43:35 -0700 (PDT) Received: from debian ([2001:4649:f075:0:a45e:6b9:73fc:f9aa]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b5e8bd1833sm14279030f8f.8.2025.07.15.02.43.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Jul 2025 02:43:34 -0700 (PDT) Date: Tue, 15 Jul 2025 11:43:30 +0200 From: Guillaume Nault To: Salvatore Bonaccorso Cc: Stefano Brivio , Aaron Conole , Jakub Kicinski , "David S. Miller" , David Ahern , Eric Dumazet , Simon Horman , netdev@vger.kernel.org, Paolo Abeni , Charles Bordet , linux-kernel@vger.kernel.org, regressions@lists.linux.dev, stable@vger.kernel.org, 1108860@bugs.debian.org Subject: Re: [regression] Wireguard fragmentation fails with VXLAN since 8930424777e4 ("tunnels: Accept PACKET_HOST skb_tunnel_check_pmtu().") causing network timeouts Message-ID: References: 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-Disposition: inline In-Reply-To: On Mon, Jul 14, 2025 at 09:57:52PM +0200, Salvatore Bonaccorso wrote: > Hi, > > Charles Bordet reported the following issue (full context in > https://bugs.debian.org/1108860) > > > Dear Maintainer, > > > > What led up to the situation? > > We run a production environment using Debian 12 VMs, with a network > > topology involving VXLAN tunnels encapsulated inside Wireguard > > interfaces. This setup has worked reliably for over a year, with MTU set > > to 1500 on all interfaces except the Wireguard interface (set to 1420). > > Wireguard kernel fragmentation allowed this configuration to function > > without issues, even though the effective path MTU is lower than 1500. > > > > What exactly did you do (or not do) that was effective (or ineffective)? > > We performed a routine system upgrade, updating all packages include the > > kernel. After the upgrade, we observed severe network issues (timeouts, > > very slow HTTP/HTTPS, and apt update failures) on all VMs behind the > > router. SSH and small-packet traffic continued to work. > > > > To diagnose, we: > > > > * Restored a backup (with the previous kernel): the problem disappeared. > > * Repeated the upgrade, confirming the issue reappeared. > > * Systematically tested each kernel version from 6.1.124-1 up to > > 6.1.140-1. The problem first appears with kernel 6.1.135-1; all earlier > > versions work as expected. > > * Kernel version from the backports (6.12.32-1) did not resolve the > > problem. > > > > What was the outcome of this action? > > > > * With kernel 6.1.135-1 or later, network timeouts occur for > > large-packet protocols (HTTP, apt, etc.), while SSH and small-packet > > protocols work. > > * With kernel 6.1.133-1 or earlier, everything works as expected. > > > > What outcome did you expect instead? > > We expected the network to function as before, with Wireguard handling > > fragmentation transparently and no application-level timeouts, > > regardless of the kernel version. > > While triaging the issue we found that the commit 8930424777e4 > ("tunnels: Accept PACKET_HOST in skb_tunnel_check_pmtu()." introduces > the issue and Charles confirmed that the issue was present as well in > 6.12.35 and 6.15.4 (other version up could potentially still be > affected, but we wanted to check it is not a 6.1.y specific > regression). > > Reverthing the commit fixes Charles' issue. > > Does that ring a bell? It doesn't ring a bell. Do you have more details on the setup that has the problem? Or, ideally, a self-contained reproducer? > Regards, > Salvatore >