netdev - Re: [PATCH] net: ipv6: Always leave subnet anycast group on link down

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Message-ID: <8246d7f6-49ba-408c-6a2e-f06ad8c7ae46@cumulusnetworks.com>
Date:	Thu, 21 Jul 2016 14:11:11 -0600
From:	David Ahern <dsa@...ulusnetworks.com>
To:	Mike Manning <mmanning@...cade.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: ipv6: Always leave subnet anycast group on link down

On 7/21/16 7:44 AM, Mike Manning wrote:
>
> Default kernel behavior is to delete IPv6 addresses on link
> down, which entails deletion of the address-derived
> subnet-router anycast address. The latter does not happen
> with sysctl setting to keep global IPv6 addrs on link down,
> so every link down/up causes an increment of the anycast
> refcount, cf aca_users in __ipv6_dev_ac_inc(). This bogus
> refcount stops the anycast being removed on subsequent
> calls to delete the address. The solution is to leave the
> group for this subnet anycast on link down also for the
> callflow when global IPv6 addresses are kept.
>
> Fixes: f1705ec197e7 ("net: ipv6: Make address flushing on ifdown optional")
> Signed-off-by: Mike Manning <mmanning@...cade.com>
> ---
>  net/ipv6/addrconf.c |    2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index 47f837a..3c69e56 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -3562,6 +3562,8 @@ restart:
>  		if (state != INET6_IFADDR_STATE_DEAD) {
>  			__ipv6_ifa_notify(RTM_DELADDR, ifa);
>  			inet6addr_notifier_call_chain(NETDEV_DOWN, ifa);
> +		} else if (idev->cnf.forwarding) {
> +			addrconf_leave_anycast(ifa);
>  		}
>
>  		write_lock_bh(&idev->lock);
>


mcast has the same problem, so this should be:

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 24f1b0898e40..6287a8b9f428 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3636,6 +3636,10 @@ static int addrconf_ifdown(struct net_device 
*dev, int how)
                 if (state != INET6_IFADDR_STATE_DEAD) {
                         __ipv6_ifa_notify(RTM_DELADDR, ifa);
                         inet6addr_notifier_call_chain(NETDEV_DOWN, ifa);
+               } else {
+                       if (idev->cnf.forwarding)
+                               addrconf_leave_anycast(ifa);
+                       addrconf_leave_solict(ifa->idev, &ifa->addr);
                 }

                 write_lock_bh(&idev->lock);