From patchwork Sun Oct 6 16:36:03 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ronan Pigott X-Patchwork-Id: 1993278 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=2604:1380:4601:e00::3; helo=am.mirrors.kernel.org; envelope-from=netfilter-devel+bounces-4271-incoming=patchwork.ozlabs.org@vger.kernel.org; receiver=patchwork.ozlabs.org) Received: from am.mirrors.kernel.org (am.mirrors.kernel.org [IPv6:2604:1380:4601:e00::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (secp384r1) server-digest SHA384) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4XM7Gt1vjqz1xtN for ; Mon, 7 Oct 2024 03:37:10 +1100 (AEDT) Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by am.mirrors.kernel.org (Postfix) with ESMTPS id E2C011F215CF for ; Sun, 6 Oct 2024 16:37:06 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D47BD189B8B; Sun, 6 Oct 2024 16:37:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=rjp.ie header.i=@rjp.ie header.b="rmCk3RmL" X-Original-To: netfilter-devel@vger.kernel.org Received: from out-183.mta0.migadu.com (out-183.mta0.migadu.com [91.218.175.183]) (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 4A25A28EC for ; Sun, 6 Oct 2024 16:36:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.183 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728232620; cv=none; b=N3w8sBHKm8rK7m5tMuSZtq1r8nuf9JYD3vQkzo0h+jbH34uqhygksBJBWez8feGC94voOXuhvIFssyTsrwlmeWTAuxWe/khWVRuiJFEB0XHC1ek1akIXDbUmUfQqVpWBaYl423cgzy5ZDGBo2EEfddS1oWj9wnBp8VcztlKc1BM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728232620; c=relaxed/simple; bh=7aIJceFZoCbWppGkbD1g85RdznYyiV0RP83KyCETycw=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=nn25PxLZwP+HxfpmhN4KRGoDUOruRm4j8L6KPKgK/8dWS4naDirhDKsYhY48hxgVz5mXBi6bMKSqnEbyZ7YTEh2cnUiqLo1c+ENk9A6+iv1HmEY+z1ixizORQwwxF502hmx1Bx/MkfB+8lydPYftXSsgrMFUmYZWAyf+h0Bw9KE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=rjp.ie; spf=pass smtp.mailfrom=rjp.ie; dkim=pass (1024-bit key) header.d=rjp.ie header.i=@rjp.ie header.b=rmCk3RmL; arc=none smtp.client-ip=91.218.175.183 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=rjp.ie Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rjp.ie X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rjp.ie; s=key1; t=1728232613; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=BoUXcAMgqM3pZ7FPTKhdgEtKgsGu2WEJX0fOIVAjpvA=; b=rmCk3RmL4QFpgpNekQvZKeIbFf1hy5M1PDicwIEUPw1VK3E9RcVKPXwSCYPJDQUVqhvbLR T5hTALBlQkMueoeWjLe6ksjtCAWx7vHSsBDBsd+tEvKxmh/1qyylmq4Y4iyFMTANBXXjVZ ds3TwRk8nB4gJo9M35UYc1/IB4KCc0Y= From: Ronan Pigott To: netfilter-devel@vger.kernel.org Cc: Ronan Pigott Subject: [PATCH] doc: don't suggest to disable GSO Date: Sun, 6 Oct 2024 09:36:03 -0700 Message-ID: <20241006163621.22929-1-ronan@rjp.ie> Precedence: bulk X-Mailing-List: netfilter-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT The kernel can form aggregate packets whether or not GSO is enabled. Disabling GSO is not a useful suggestion in this case. Fixes: 05628cdd677d (doc: describe behaviour of {ip,ip6} length) --- doc/payload-expression.txt | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/doc/payload-expression.txt b/doc/payload-expression.txt index 7bc24a8a6502..18ad0215baaa 100644 --- a/doc/payload-expression.txt +++ b/doc/payload-expression.txt @@ -134,13 +134,12 @@ Destination address | ipv4_addr |====================== -Careful with matching on *ip length*: If GRO/GSO is enabled, then the Linux -kernel might aggregate several packets into one big packet that is larger than -MTU. Moreover, if GRO/GSO maximum size is larger than 65535 (see man ip-link(8), -specifically gro_ipv6_max_size and gso_ipv6_max_size), then *ip length* might -be 0 for such jumbo packets. *meta length* allows you to match on the packet -length including the IP header size. If you want to perform heuristics on the -*ip length* field, then disable GRO/GSO. +Careful with matching on *ip length*: The Linux kernel might aggregate several +packets into one big packet that is larger than MTU. Moreover, if GRO/GSO +maximum size is larger than 65535 (see man ip-link(8), specifically +gro_ipv6_max_size and gso_ipv6_max_size), then *ip length* might be 0 for such +jumbo packets. *meta length* allows you to match on the packet length including +the IP header size. ICMP HEADER EXPRESSION ~~~~~~~~~~~~~~~~~~~~~~