Subject: Re: [PATCH] ipv6: don't call addrconf_dst_alloc again when enable lo

From: Gao feng <[email-masked]>
Date: Wed, 08 Jan 2014 15:50:09 +0800

On 01/03/2014 02:53 PM, Hannes Frederic Sowa wrote:
> On Thu, Jan 02, 2014 at 05:33:15PM +0800, chenweilong wrote:
>> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
>> index 62d1799..d2f8c0a 100644
>> --- a/net/ipv6/addrconf.c
>> +++ b/net/ipv6/addrconf.c
>> @@ -2422,8 +2422,9 @@ static void init_loopback(struct net_device *dev)
>>  			if (sp_ifa->flags & (IFA_F_DADFAILED | IFA_F_TENTATIVE))
>>  				continue;
>>
>> -			if (sp_ifa->rt)
>> -				continue;
>> +			if (sp_ifa->rt && sp_ifa->rt->dst.dev == dev) {
>> +				ip6_del_rt(sp_ifa->rt);
>> +			}
>>
>>  			sp_rt = addrconf_dst_alloc(idev, &sp_ifa->addr, 0);
>>
> 
> Maybe this change would not be that bad after all, as those ifa attached dsts
> are already dead and queued up for gc and should not get inserted back.

I like this idea, maybe the below patch is better. we only need to delete this
route when it has been added to garbage list.

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 1a341f7..4dca886 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2610,8 +2610,16 @@ static void init_loopback(struct net_device *dev)
                        if (sp_ifa->flags & (IFA_F_DADFAILED | IFA_F_TENTATIVE))
                                continue;

-                       if (sp_ifa->rt)
-                               continue;
+                       if (sp_ifa->rt) {
+                               /* This dst has been added to garbage list when
+                                * lo device down, delete this obsolete dst and
+                                * reallocate new router for ifa. */
+                               if (sp_ifa->rt->dst.obsolete > 0) {
+                                       ip6_del_rt(sp_ifa->rt);
+                                       sp_ifa->rt = NULL;
+                               } else
+                                       continue;
+                       }

                        sp_rt = addrconf_dst_alloc(idev, &sp_ifa->addr, false);

> 
> I'll try to just disable routes without removing them at all when we set an
> interface to down at the weekend.
> 

How do you decide which route should be disabled?  use rt6_flags? I don't know
if your way will cause miscarriage.