From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.16]) (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 0EDCA4028E2; Tue, 25 Aug 2026 12:13:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787660026; cv=none; b=tIw0dxudbBP0V21I/Q0+iHYIBWGYxkRVd2IMz0VuENwV/TA7BVRwpo+nWXWGzNdX2eacrAINF4O5mq+/0LtAmTeWodrKBWP0qgPALEsaqKQkEXAlfd5WZoVQsTcxVSid690P+/WbS/r+PjAttuQipf9lBiY68GLz8O82/cJBHsc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787660026; c=relaxed/simple; bh=BPqTzFySuXaMGgmAsoD7CPkggXOSjTbdKBOovyqrngE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hNTDa/JEwYJtbtbBWyO4tj2jaGZY1JBmbKadgKTO6fjkhIQCJ7h64iy7p25LnJRGGBREyA0cptZelpAWTnmYT2jNsBz9Bj5tX40Haw1RoUDX3Bim3WyeNmm5jnbK+t+zepkJsk23ZXPPafQLn0px5uQO3TCOZgWxnXv3Uk6Sru4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=IHUo30jq; arc=none smtp.client-ip=198.175.65.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="IHUo30jq" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1787660024; x=1819196024; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=BPqTzFySuXaMGgmAsoD7CPkggXOSjTbdKBOovyqrngE=; b=IHUo30jq/tPOe/Q+F3AfAUvNoXFgUEIlP+IN5h7xYQe0VCwLPiqESd7a yN45mZjgu1wKFo+hs0RbtDCOd2dZkMeexq6idO/FZ0+yeKuQo3rL4m5F6 gSUJhinJ/qDSyrh2c4sDEOLKFALEvhA37XOrjRybpowSoXB2dYCLkrfGQ XBm6juES9czrj3pmyKHBSBvW1K5s5X5vo4kjggmzmQgBnYAzQK7V85NzL fr3+l0NlwCCn+ABiT1ZHgBfaH5j6a1Yq1C7uqgjxc2R/Br37zn9WYrKsB 1CZc2P6B4oCqdxTJg9dh1hU0KzXcuqSQz6eKBae3jFa6Dmmtqn+jtA9ZX w==; X-CSE-ConnectionGUID: UZ4f3WTOQGKN1okn5sybzA== X-CSE-MsgGUID: SZrp7jbSS6iQwU8VGvJOWQ== X-IronPort-AV: E=McAfee;i="6800,10657,11885"; a="88327262" X-IronPort-AV: E=Sophos;i="6.25,242,1779174000"; d="scan'208";a="88327262" Received: from fmviesa005.fm.intel.com ([10.60.135.145]) by orvoesa108.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2026 05:13:43 -0700 X-CSE-ConnectionGUID: EiOGuw5fQraGTHU7MR3K0A== X-CSE-MsgGUID: /3VGv8cIQ4iCr/3zvvu75w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,242,1779174000"; d="scan'208";a="272512677" Received: from junjie-desk-dev.bj.intel.com (HELO junjie-desk-dev.tail2c02c1.ts.net) ([10.238.152.71]) by fmviesa005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2026 05:13:41 -0700 From: Junjie Cao To: Fernando Fernandez Mancera Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, dsahern@kernel.org, idosch@nvidia.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] net: dropreason: add SKB_DROP_REASON_IP_TTL_EXCEEDED Date: Tue, 25 Aug 2026 20:13:30 +0800 Message-ID: <20260825121330.338380-1-junjie.cao@intel.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <9abd7020-90b3-45e3-84ef-ca31b760feaf@suse.de> References: <9abd7020-90b3-45e3-84ef-ca31b760feaf@suse.de> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Tue, Aug 25, 2026 at 11:36 AM Fernando Fernandez Mancera wrote: > The patch is sound but isn't this drop reason a bit redundant? I mean, a > simple check on traffic should have shown to the user that TTL is been > exceeded. Checking traffic for TTL presumes TTL is already the suspect. The reason string is what points the investigation: in the linked bug, IP_INHDR read as a broken header and the capture time went to checksums -- RX offload, tc csum actions, both libvirt firewall backends. Nobody filters on TTL while the kernel is saying the header is bad. dropwatch and perf report the reason without a capture; that only helps if the string is precise. IPV6_NDISC_HOP_LIMIT and TCP_MINTTL are as visible in a capture as this one, and both have their own reason. The exthdrs.c hunks also cover three drops that report no reason at all. > In any case, net-next is currently closed [1]. Please send this after it > re-opens. Will repost when it reopens.