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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E990CC43217 for ; Wed, 9 Feb 2022 13:36:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234110AbiBINgY (ORCPT ); Wed, 9 Feb 2022 08:36:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53398 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234084AbiBINgW (ORCPT ); Wed, 9 Feb 2022 08:36:22 -0500 Received: from mail.netfilter.org (mail.netfilter.org [217.70.188.207]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id A4BC8C061355; Wed, 9 Feb 2022 05:36:24 -0800 (PST) Received: from localhost.localdomain (unknown [78.30.32.163]) by mail.netfilter.org (Postfix) with ESMTPSA id E5A54601CB; Wed, 9 Feb 2022 14:36:12 +0100 (CET) From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org Subject: [PATCH net-next 01/14] netfilter: conntrack: mark UDP zero checksum as CHECKSUM_UNNECESSARY Date: Wed, 9 Feb 2022 14:36:03 +0100 Message-Id: <20220209133616.165104-2-pablo@netfilter.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220209133616.165104-1-pablo@netfilter.org> References: <20220209133616.165104-1-pablo@netfilter.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org From: Kevin Mitchell The udp_error function verifies the checksum of incoming UDP packets if one is set. This has the desirable side effect of setting skb->ip_summed to CHECKSUM_COMPLETE, signalling that this verification need not be repeated further up the stack. Conversely, when the UDP checksum is empty, which is perfectly legal (at least inside IPv4), udp_error previously left no trace that the checksum had been deemed acceptable. This was a problem in particular for nf_reject_ipv4, which verifies the checksum in nf_send_unreach() before sending ICMP_DEST_UNREACH. It makes no accommodation for zero UDP checksums unless they are already marked as CHECKSUM_UNNECESSARY. This commit ensures packets with empty UDP checksum are marked as CHECKSUM_UNNECESSARY, which is explicitly recommended in skbuff.h. Signed-off-by: Kevin Mitchell Acked-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_conntrack_proto_udp.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/netfilter/nf_conntrack_proto_udp.c b/net/netfilter/nf_conntrack_proto_udp.c index 3b516cffc779..12f793d8fe0c 100644 --- a/net/netfilter/nf_conntrack_proto_udp.c +++ b/net/netfilter/nf_conntrack_proto_udp.c @@ -63,8 +63,10 @@ static bool udp_error(struct sk_buff *skb, } /* Packet with no checksum */ - if (!hdr->check) + if (!hdr->check) { + skb->ip_summed = CHECKSUM_UNNECESSARY; return false; + } /* Checksum invalid? Ignore. * We skip checking packets on the outgoing path -- 2.30.2