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 X-Spam-Level: X-Spam-Status: No, score=-6.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8416FC65C20 for ; Mon, 8 Oct 2018 18:49:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 49FF3214C2 for ; Mon, 8 Oct 2018 18:49:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="u47kSUgF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 49FF3214C2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731861AbeJICCb (ORCPT ); Mon, 8 Oct 2018 22:02:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:51744 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726991AbeJICCa (ORCPT ); Mon, 8 Oct 2018 22:02:30 -0400 Received: from localhost (ip-213-127-77-176.ip.prioritytelecom.net [213.127.77.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 39DAC214C4; Mon, 8 Oct 2018 18:49:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1539024562; bh=B8wllEKNdFb4EvGYxsT7OLkv7ZVMoOrZ+aCjdjs3fqU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=u47kSUgFgQBg0/oxENi6rEtihrL/iLPfXl16N9Wf3E/2wjkenUfkeocQvw/HocRpW aaRFYIEOHb4sIbJUIPwt6DOhwpWZKxl1+zUmiRrux8W5UEv5u288/FtbOmiEV988KG yrR2eXm6IHUkFKVKaY+rXiK+7uyN9MRJXu5h7NOk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Satish Patel , Markos Chandras , Michal Kubecek , Florian Westphal , Pablo Neira Ayuso , Sasha Levin Subject: [PATCH 4.18 080/168] netfilter: xt_checksum: ignore gso skbs Date: Mon, 8 Oct 2018 20:31:00 +0200 Message-Id: <20181008175623.100651819@linuxfoundation.org> X-Mailer: git-send-email 2.19.0 In-Reply-To: <20181008175620.043587728@linuxfoundation.org> References: <20181008175620.043587728@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Florian Westphal [ Upstream commit 10568f6c5761db24249c610c94d6e44d5505a0ba ] Satish Patel reports a skb_warn_bad_offload() splat caused by -j CHECKSUM rules: -A POSTROUTING -p tcp -m tcp --sport 80 -j CHECKSUM The CHECKSUM target has never worked with GSO skbs, and the above rule makes no sense as kernel will handle checksum updates on transmit. Unfortunately, there are 3rd party tools that install such rules, so we cannot reject this from the config plane without potential breakage. Amend Kconfig text to clarify that the CHECKSUM target is only useful in virtualized environments, where old dhcp clients that use AF_PACKET used to discard UDP packets with a 'bad' header checksum and add a one-time warning in case such rule isn't restricted to UDP. v2: check IP6T_F_PROTO flag before cmp (Michal Kubecek) Reported-by: Satish Patel Reported-by: Markos Chandras Reported-by: Michal Kubecek Signed-off-by: Florian Westphal Reviewed-by: Michal Kubecek Signed-off-by: Pablo Neira Ayuso Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- net/netfilter/Kconfig | 12 ++++++------ net/netfilter/xt_CHECKSUM.c | 22 +++++++++++++++++++++- 2 files changed, 27 insertions(+), 7 deletions(-) --- a/net/netfilter/Kconfig +++ b/net/netfilter/Kconfig @@ -740,13 +740,13 @@ config NETFILTER_XT_TARGET_CHECKSUM depends on NETFILTER_ADVANCED ---help--- This option adds a `CHECKSUM' target, which can be used in the iptables mangle - table. + table to work around buggy DHCP clients in virtualized environments. - You can use this target to compute and fill in the checksum in - a packet that lacks a checksum. This is particularly useful, - if you need to work around old applications such as dhcp clients, - that do not work well with checksum offloads, but don't want to disable - checksum offload in your device. + Some old DHCP clients drop packets because they are not aware + that the checksum would normally be offloaded to hardware and + thus should be considered valid. + This target can be used to fill in the checksum using iptables + when such packets are sent via a virtual network device. To compile it as a module, choose M here. If unsure, say N. --- a/net/netfilter/xt_CHECKSUM.c +++ b/net/netfilter/xt_CHECKSUM.c @@ -16,6 +16,9 @@ #include #include +#include +#include + MODULE_LICENSE("GPL"); MODULE_AUTHOR("Michael S. Tsirkin "); MODULE_DESCRIPTION("Xtables: checksum modification"); @@ -25,7 +28,7 @@ MODULE_ALIAS("ip6t_CHECKSUM"); static unsigned int checksum_tg(struct sk_buff *skb, const struct xt_action_param *par) { - if (skb->ip_summed == CHECKSUM_PARTIAL) + if (skb->ip_summed == CHECKSUM_PARTIAL && !skb_is_gso(skb)) skb_checksum_help(skb); return XT_CONTINUE; @@ -34,6 +37,8 @@ checksum_tg(struct sk_buff *skb, const s static int checksum_tg_check(const struct xt_tgchk_param *par) { const struct xt_CHECKSUM_info *einfo = par->targinfo; + const struct ip6t_ip6 *i6 = par->entryinfo; + const struct ipt_ip *i4 = par->entryinfo; if (einfo->operation & ~XT_CHECKSUM_OP_FILL) { pr_info_ratelimited("unsupported CHECKSUM operation %x\n", @@ -43,6 +48,21 @@ static int checksum_tg_check(const struc if (!einfo->operation) return -EINVAL; + switch (par->family) { + case NFPROTO_IPV4: + if (i4->proto == IPPROTO_UDP && + (i4->invflags & XT_INV_PROTO) == 0) + return 0; + break; + case NFPROTO_IPV6: + if ((i6->flags & IP6T_F_PROTO) && + i6->proto == IPPROTO_UDP && + (i6->invflags & XT_INV_PROTO) == 0) + return 0; + break; + } + + pr_warn_once("CHECKSUM should be avoided. If really needed, restrict with \"-p udp\" and only use in OUTPUT\n"); return 0; }