netdev - Re: ipv6 addrconfg warn_on hit: WARN_ON(ifp->idev->valid_ll_addr

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Date:	Thu, 16 Jan 2014 18:27:06 +0100
From:	Jiri Pirko <jiri@...nulli.us>
To:	netdev@...r.kernel.org
Cc:	hannes@...essinduktion.org
Subject: Re: ipv6 addrconfg warn_on hit: WARN_ON(ifp->idev->valid_ll_addr_cnt
 < 0);

Thu, Jan 16, 2014 at 04:18:12PM CET, hannes@...essinduktion.org wrote:
>On Thu, Jan 16, 2014 at 03:38:17PM +0100, Hannes Frederic Sowa wrote:
>> On Thu, Jan 16, 2014 at 03:07:01PM +0100, Jiri Pirko wrote:
>> > Thu, Jan 16, 2014 at 02:53:23PM CET, jiri@...nulli.us wrote:
>> > >Hi Hannes.
>> > >
>> > >WARN_ON(ifp->idev->valid_ll_addr_cnt < 0);
>> > >
>> > >We did hit once this warning during the tests. The person who hit this
>> > >says that it was during the setup of many macvlan devices.
>> > >
>> > >I examined the code but I'm not sure how this could happen. Looks like a
>> > >race condition between addrconf_dad_completed() and addrconf_ifdown(). 
>> > >Not sure how to easily resolve that though.
>> 
>> That seems to be the case. Actually we don't need to count precisiely
>> here, we just must precisiely identify the situation where the first
>> LL address comes into operational state. Maybe we can implement this
>> somehow differently. I'll play with the code soon.
>
>Maybe something like this and then throw out the whole ll counting stuff:
>
>diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
>index 6913a82..105105a 100644
>--- a/net/ipv6/addrconf.c
>+++ b/net/ipv6/addrconf.c
>@@ -3233,6 +3233,19 @@ out:
> 	in6_ifa_put(ifp);
> }
> 
>+/* idev must be at least read locked */
>+static bool ipv6_lonely_lladdr(struct inet6_dev *idev, struct inet6_ifaddr *ifp)
>+{
>+	bool ret = true;
>+	struct inet6_ifaddr *ifpiter;
>+
>+	list_for_each_entry(ifpiter, &idev->addr_list, if_list) {
>+		if (ifp != ifpiter && ifpiter->scope == IFA_LINK)
>+			ret = false;
>+	}
>+	return ret;
>+}
>+
> static void addrconf_dad_completed(struct inet6_ifaddr *ifp)
> {
> 	struct net_device *dev = ifp->idev->dev;
>@@ -3253,8 +3266,7 @@ static void addrconf_dad_completed(struct inet6_ifaddr *ifp)
> 
> 	read_lock_bh(&ifp->idev->lock);
> 	spin_lock(&ifp->lock);
>-	send_mld = ipv6_addr_type(&ifp->addr) & IPV6_ADDR_LINKLOCAL &&
>-		   ifp->idev->valid_ll_addr_cnt == 1;
>+	send_mld = ifp->scope == IFA_LINK && ipv6_lonely_lladdr(ifp->idev, ifp);
> 	send_rs = send_mld &&
> 		  ipv6_accept_ra(ifp->idev) &&
> 		  ifp->idev->cnf.rtr_solicits > 0 &&

Sounds sane to me. Would you care to submit this please?
Do not forget to remove all the valid_ll_addr_cnt stuff :)

>
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