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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30B96C433F5 for ; Thu, 14 Oct 2021 18:55:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0D89C60F36 for ; Thu, 14 Oct 2021 18:55:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232123AbhJNS5X (ORCPT ); Thu, 14 Oct 2021 14:57:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44848 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231327AbhJNS5X (ORCPT ); Thu, 14 Oct 2021 14:57:23 -0400 Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 173ABC061570 for ; Thu, 14 Oct 2021 11:55:18 -0700 (PDT) Received: by mail-pl1-x632.google.com with SMTP id g5so4808386plg.1 for ; Thu, 14 Oct 2021 11:55:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=message-id:subject:from:to:date:in-reply-to:references:user-agent :mime-version:content-transfer-encoding; bh=j7wDhfUYmgwotP1y7gzXQPMh0D1p5UqPh72hBSBD4Qc=; b=lun74KBrBj2/0VKpxEMxdXYS9uGj/cnpxqRj85owJApxk47olqfgZpmgeVPcdIRfqa kv8EHF8pGz07CPy6tBdCgDChR1gNHzqP3xV+/8ywliLFqAN4S8014rty6Ug3fLp+gMLj G610N6C8ZWbLbeAGB8URHF2FYgXpLAcUasKsEK9PJsm0YFE1WjcYGL7UkAaesfNXCr2l OJWXHL8UG9oOyM/nKFOW/wMQffreNitxEAHVUpo62P7l3Dccf4ITAk4MXTIwV397JY77 bv5gKjyagQEVDRjXrF9OEyGx0LLCLjvpfaauAtYPGi2hUHpr+rJd9BWMB5LPPuCEoK5M OefQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:subject:from:to:date:in-reply-to :references:user-agent:mime-version:content-transfer-encoding; bh=j7wDhfUYmgwotP1y7gzXQPMh0D1p5UqPh72hBSBD4Qc=; b=1k7tD9vwJmB6m2Ki65ULAqhv3wWsZiV4BuGd5bxVxuGdBG7G/UmXXTextbCmk+4E8v KzpnhUiUFtnLgyM9RzE8LoSFlcGPP+DsGSk2afU9TR5zeQoCJ8TMMfKwBeKvTSeLdIGW OnS1QDHYdlSHgRGZ7a0uQykCWQpuzBEAEfy+J5waEU8Aovtq/g2/SBqhGw+ylmKjDSow g3yXfem95TDeZL+M6qgsjcPgkKzBwF+QmGshOX8wgP61qqEIwm4imCU6LUtntR7zxq+A wBCNOVYkg4mkSak1vxGOujN9WWQSzK1WGo7T4/rPn9d78Fey4LT2myskKiP0hAoXagpS rjOg== X-Gm-Message-State: AOAM533uLgDdi7ueoZU/D+hB4MIIyQG30fysRIT+7RHsxqJ8/V1RslLr yczOP3DHAJONVFZs+z2BGhw= X-Google-Smtp-Source: ABdhPJwHBaUw13G4UA8teOg204EBZVH8DEk0p0EqTVqo2ZFmeh4FF6BTuJV44+qNZbmPE9ilU+Hn6g== X-Received: by 2002:a17:902:6b86:b0:13f:8d7a:397c with SMTP id p6-20020a1709026b8600b0013f8d7a397cmr655812plk.50.1634237717587; Thu, 14 Oct 2021 11:55:17 -0700 (PDT) Received: from [192.168.254.55] ([50.39.163.188]) by smtp.gmail.com with ESMTPSA id t126sm3178139pfc.80.2021.10.14.11.55.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Oct 2021 11:55:17 -0700 (PDT) Message-ID: <81cd604b9d44d2058464d90788f43d6803f7eea3.camel@gmail.com> Subject: Re: [PATCH 1/4] net: arp: introduce arp_evict_nocarrier sysctl parameter From: James Prestwood To: David Ahern , netdev@vger.kernel.org Date: Thu, 14 Oct 2021 11:52:00 -0700 In-Reply-To: <1d503584-e463-3324-140a-14c86521cd59@gmail.com> References: <20211013222710.4162634-1-prestwoj@gmail.com> <1d503584-e463-3324-140a-14c86521cd59@gmail.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.40.4 (3.40.4-1.fc34) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi David, On Thu, 2021-10-14 at 12:34 -0600, David Ahern wrote: > On 10/13/21 4:27 PM, James Prestwood wrote: > > This change introduces a new sysctl parameter, arp_evict_nocarrier. > > When set (default) the ARP cache will be cleared on a NOCARRIER > > event. > > This new option has been defaulted to '1' which maintains existing > > behavior. > > > > Clearing the ARP cache on NOCARRIER is relatively new, introduced > > by: > > > > commit 859bd2ef1fc1110a8031b967ee656c53a6260a76 > > Author: David Ahern > > Date:   Thu Oct 11 20:33:49 2018 -0700 > > > >     net: Evict neighbor entries on carrier down > > > > The reason for this changes is to prevent the ARP cache from being > > cleared when a wireless device roams. Specifically for wireless > > roams > > the ARP cache should not be cleared because the underlying network > > has not > > changed. Clearing the ARP cache in this case can introduce > > significant > > delays sending out packets after a roam. > > how do you know if the existing ARP / ND entries are valid when > roaming? > I guess there is no way of really knowing, but since your roaming in the same network I think we can assume the entries are just as valid prior to the roam as after it right? If there are invalid entries, they were likely invalid prior to the roam too. I obviously cant speak to all network configurations, but I think if your network infrastructure is set up to roam you into a different subnet you're doing something wrong. Or I can't think of a reason to do this, it would defeat the purpose of quickly roaming between BSS's since you would then have to do DHCP aftewards. Thanks, James