From patchwork Fri Mar 19 18:33:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tong Zhu X-Patchwork-Id: 405819 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=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_SANE_1 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 B378CC433C1 for ; Fri, 19 Mar 2021 18:34:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D07361980 for ; Fri, 19 Mar 2021 18:34:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230384AbhCSSeG (ORCPT ); Fri, 19 Mar 2021 14:34:06 -0400 Received: from smtp-fw-4101.amazon.com ([72.21.198.25]:34715 "EHLO smtp-fw-4101.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230308AbhCSSdy (ORCPT ); Fri, 19 Mar 2021 14:33:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1616178834; x=1647714834; h=date:from:to:cc:subject:message-id:mime-version; bh=MFCVtENjBI3XFTYruH+r3sdrMzrerZrdEDh6dTMmGfU=; b=Owgj/AGX8LAonSVhXrxbTNyNnpNJ1U4bRYhsFvDfZfbtgvEGL70ZDriz PBs5mJWV4UejFIXMiiIBc3xhvaYChPjJdfI6xMwlELTtS4ikLQkeCzhhB 35guWMK6FkLiaqfazZXrb6C8N5OD/l0YKz7SjjrmbQ8CzZOlVmSo0MaYF w=; X-IronPort-AV: E=Sophos;i="5.81,262,1610409600"; d="scan'208";a="94599431" Received: from iad12-co-svc-p1-lb1-vlan2.amazon.com (HELO email-inbound-relay-1d-16425a8d.us-east-1.amazon.com) ([10.43.8.2]) by smtp-border-fw-out-4101.iad4.amazon.com with ESMTP; 19 Mar 2021 18:33:44 +0000 Received: from EX13MTAUEE001.ant.amazon.com (iad12-ws-svc-p26-lb9-vlan3.iad.amazon.com [10.40.163.38]) by email-inbound-relay-1d-16425a8d.us-east-1.amazon.com (Postfix) with ESMTPS id 5426D100AB0; Fri, 19 Mar 2021 18:33:43 +0000 (UTC) Received: from EX13D06UEA002.ant.amazon.com (10.43.61.198) by EX13MTAUEE001.ant.amazon.com (10.43.62.226) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 19 Mar 2021 18:33:42 +0000 Received: from ucf43ac461c9a53.ant.amazon.com (10.43.161.86) by EX13D06UEA002.ant.amazon.com (10.43.61.198) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 19 Mar 2021 18:33:40 +0000 Date: Fri, 19 Mar 2021 14:33:37 -0400 From: Tong Zhu To: , , , , , CC: Subject: [PATCH] neighbour: Disregard DEAD dst in neigh_update Message-ID: <20210319183327.GA25778@ucf43ac461c9a53.ant.amazon.com> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) X-Originating-IP: [10.43.161.86] X-ClientProxiedBy: EX13D41UWB002.ant.amazon.com (10.43.161.109) To EX13D06UEA002.ant.amazon.com (10.43.61.198) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org After a short network outage, the dst_entry is timed out and put in DST_OBSOLETE_DEAD. We are in this code because arp reply comes from this neighbour after network recovers. There is a potential race condition that dst_entry is still in DST_OBSOLETE_DEAD. With that, another neighbour lookup causes more harm than good. In best case all packets in arp_queue are lost. This is counterproductive to the original goal of finding a better path for those packets. I observed a worst case with 4.x kernel where a dst_entry in DST_OBSOLETE_DEAD state is associated with loopback net_device. It leads to an ethernet header with all zero addresses. A packet with all zero source MAC address is quite deadly with mac80211, ath9k and 802.11 block ack. It fails ieee80211_find_sta_by_ifaddr in ath9k (xmit.c). Ath9k flushes tx queue (ath_tx_complete_aggr). BAW (block ack window) is not updated. BAW logic is damaged and ath9k transmission is disabled. Signed-off-by: Tong Zhu --- net/core/neighbour.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/core/neighbour.c b/net/core/neighbour.c index e2982b3970b8..8379719d1dce 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -1379,7 +1379,7 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr, * we can reinject the packet there. */ n2 = NULL; - if (dst) { + if (dst && dst->obsolete != DST_OBSOLETE_DEAD) { n2 = dst_neigh_lookup_skb(dst, skb); if (n2) n1 = n2;