Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1
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From: Ido Schimmel <hidden>
Date: 2017-08-12 18:11:29
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Hi Wei, On Fri, Aug 11, 2017 at 05:10:02PM -0700, Wei Wang wrote:
I think we have a potential fix for this issue. Martin and I found that when addrconf_dst_alloc() creates a rt6, it is possible that rt6->dst.dev points to loopback device while rt6->rt6i_idev->dev points to a real device. When the real device goes down, the current fib6 clean up code only checks for rt6->dst.dev and assumes rt6->rt6i_idev->dev is the same. That leaves unreleased refcnt on the real device if rt6->dst.dev points to loopback dev.
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From 2d8861808c2029013f6b6e86120ba6902329145b Mon Sep 17 00:00:00 2001 From: Wei Wang <redacted> Date: Fri, 11 Aug 2017 16:36:04 -0700 Subject: [PATCH 1/2] potential fix for unregister_netdevice() Change-Id: I5d5f6f7a7ad0f5dd769f33487db17ff2570d52ea --- net/ipv6/route.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-)diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 4d30c96a819d..105922903932 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c@@ -417,14 +417,12 @@ static void ip6_dst_ifdown(struct dst_entry *dst, struct net_device *dev, struct net_device *loopback_dev = dev_net(dev)->loopback_dev; - if (dev != loopback_dev) { - if (idev && idev->dev == dev) { - struct inet6_dev *loopback_idev = - in6_dev_get(loopback_dev); - if (loopback_idev) { - rt->rt6i_idev = loopback_idev; - in6_dev_put(idev); - } + if (idev && idev->dev != loopback_dev) { + struct inet6_dev *loopback_idev = + in6_dev_get(loopback_dev); + if (loopback_idev) { + rt->rt6i_idev = loopback_idev; + in6_dev_put(idev); } } }@@ -2789,7 +2787,8 @@ static int fib6_ifdown(struct rt6_info *rt, void *arg) const struct arg_dev_net *adn = arg; const struct net_device *dev = adn->dev; - if ((rt->dst.dev == dev || !dev) && + if ((rt->dst.dev == dev || !dev || + rt->rt6i_idev->dev == dev) &&
Can you please explain why this line is needed? While host routes aren't removed from the FIB by rt6_ifdown() (when dst.dev goes down), they are removed later on in addrconf_ifdown(). With your patch, if I check the return value of ip6_del_rt() in __ipv6_ifa_notify() I see that -ENONET is returned. Because the host route was already removed by rt6_ifdown(). When the line in question is removed from the patch I don't get the error anymore. Is it possible that in John's case the host route was correctly removed from the FIB and that the unreleased reference was due to a wrong check in ip6_dst_ifdown() (which you patched correctly AFAICT)? Thanks
rt != adn->net->ipv6.ip6_null_entry && (rt->rt6i_nsiblings == 0 || (dev && netdev_unregistering(dev)) || -- 2.14.0.434.g98096fd7a8-goog