From patchwork Mon Aug 22 21:17:51 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Guy Yur X-Patchwork-Id: 110992 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id DB655B6F8F for ; Tue, 23 Aug 2011 07:17:58 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753051Ab1HVVRx (ORCPT ); Mon, 22 Aug 2011 17:17:53 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:36333 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751637Ab1HVVRx convert rfc822-to-8bit (ORCPT ); Mon, 22 Aug 2011 17:17:53 -0400 Received: by fxh19 with SMTP id 19so3530939fxh.19 for ; Mon, 22 Aug 2011 14:17:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=9Eggrf3j6BxPu3HFNJbxcpxy4pf+dIpww/xweC0KSQw=; b=Q0i+zmBxdO8MIMWJvLTrMf9CX1B1Xb/48k3hg7mc6iaFU/cMPRmPEhQrgOWTfuLn+w U7dIWkN/8BPZquOJm8474q85wZFrMHfxFQ1JB8ggCizAxBZh8YZ6Qaml9uqe17Xiu0uR PO/dA6spcGQBMdUgtWuQGnTso3CeeOSNo09XQ= MIME-Version: 1.0 Received: by 10.223.16.194 with SMTP id p2mr4226457faa.58.1314047871737; Mon, 22 Aug 2011 14:17:51 -0700 (PDT) Received: by 10.223.95.200 with HTTP; Mon, 22 Aug 2011 14:17:51 -0700 (PDT) In-Reply-To: References: <1314031455.2307.113.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> Date: Tue, 23 Aug 2011 00:17:51 +0300 Message-ID: Subject: Re: [RFC][PATCH] Failed neighbors attached to routes are not released From: Guy Yur To: netdev@vger.kernel.org Cc: eric.dumazet@gmail.com Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Aug 22, 2011 at 10:49 PM, Guy Yur wrote: > On Mon, Aug 22, 2011 at 7:44 PM, Eric Dumazet wrote: >> Le vendredi 19 août 2011 à 21:53 +0300, Guy Yur a écrit : >>> Hi, >>> >>> The issue I am seeing is with a neighbor used as a gateway in a route, >>> when the neighbor gets nud FAILED it will not be removed from the >>> neighbor cache. >>> The reference count for the neighbor remains > 1 >>> when neigh_periodic_work() is called. >>> >>> Issue noticed with IPv6 neighbors on Arch Linux with kernel 3.0.3 >>> kernel config includes CONFIG_IPV6_ROUTER_PREF >>> >>> The problem affects routing when the neighbor loses connectivity and returns. >>> >>> Scenario: Using a default route and a static route through different interfaces. >>> When the neighbor gateway of the static route goes down the traffic >>> will move to the default gateway as expected. >>> Once the static route neighbor comes back up it is not asked for >>> neighbor solicitation >>> because the route is marked as FAILED and the traffic will continue to >>> pass through the default gateway. >>> >>> Steps to reproduce the route not being removed: >>> 1. add an IPv6 address on an interface >>> 2. add a route to a network through a gateway on the interface's network >>> 3. make sure the gateway address is not reachable >>> 4. ping6 a host in the route network >>> 5. "ip -6 nei" will show the gateway neighbor as FAILED and it won't be released >>> >>> Steps to reproduce the routing problem: >>> 1. client and two gateway machines (A and B) >>> 2. on the client define a static route through A and a default route through B >>> 3. disconnect eth on A >>> 4. ping6 a host in the network that should go through A >>>    after a while the traffic will move through B which is the default route >>> 5. reconnect eth on A >>> 6. ping6 a host in the network again, the traffic will still go through B >>>    "ip -6 nei" on the client will still show A as FAILED >>> >>> >>> Patch to change the nud state to NONE if the reference count > 1 >>> allowing the neighbor to be released in a future pass. >> >> I wonder why a 'future pass' is needed at all. >> >> Shouldnt we immediately detect link becomes alive and force an immediate >> flush at this point, before waiting a garbage collect timer ? >> > > I tested removing the neighbor as done in neigh_flush_dev() instead of > just setting to NUD_NONE, > it seems that the neighbor shouldn't be removed if it has routes attached to it. > If the neighbor is removed the route won't be considered at all. > > The problem of the state remaining FAILED does need to be handled. > Like the case of no neighbor, a FAILED state means find_match() won't > try to send neighbor solicitation probes. > The neighbor will remain in a state of NUD_FAILED and the route won't > be used, only a direct communication with the neighbor will change its > state. > > Do you think it is better to change the state from NUD_FAILED to > NUD_NONE in neigh_timer_handler() instead? > > Updated patch to set the state to NUD_NOARP if the state was valid, > same as done in neigh_flush_dev(). > Not sure if it is needed or the state can be set to NUD_NONE in all cases. > Previous patch with NOARP doesn't work. New patch to only deal with FAILD state. when using a neighbor through a route: 1. If no traffic is passed through the neighbor, it will move to STALE state and remain there as before. 2. If the neighbor is unreachable, it will become FAILED. from then it will change periodically to NONE and the reachability tests will resume. If the neighbor becomes reachable again, once the periodic handler sets it to NONE and the routing code probes it, traffic will resume through it. the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html --- linux/net/core/neighbour.c.orig 2011-07-22 05:17:23.000000000 +0300 +++ linux/net/core/neighbour.c 2011-08-22 23:53:21.448424900 +0300 @@ -802,15 +802,18 @@ if (time_before(n->used, n->confirmed)) n->used = n->confirmed; - if (atomic_read(&n->refcnt) == 1 && - (state == NUD_FAILED || - time_after(jiffies, n->used + n->parms->gc_staletime))) { - *np = n->next; - n->dead = 1; - write_unlock(&n->lock); - neigh_cleanup_and_release(n); - continue; + if (state == NUD_FAILED || + time_after(jiffies, n->used + n->parms->gc_staletime)) { + if (atomic_read(&n->refcnt) == 1) { + *np = n->next; + n->dead = 1; + write_unlock(&n->lock); + neigh_cleanup_and_release(n); + continue; + } else if (state == NUD_FAILED) + n->nud_state = NUD_NONE; } write_unlock(&n->lock); next_elt: -- To unsubscribe from this list: send the line "unsubscribe netdev" in