netdev - Re: [PATCH v2 net-next] net: ipv6: put host and anycast routes on device with address

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Message-ID: <0bcba874-7fc3-508c-bf78-ae5832312845@gmail.com>
Date:   Fri, 18 Aug 2017 18:14:18 -0600
From:   David Ahern <dsahern@...il.com>
To:     David Ahern <dsahern@...il.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:     netdev@...r.kernel.org, yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH v2 net-next] net: ipv6: put host and anycast routes on
 device with address

On 8/18/17 6:05 PM, David Ahern wrote:
> On 8/18/17 5:15 PM, Hannes Frederic Sowa wrote:
>> Hello David,
>>
>> David Ahern <dsahern@...il.com> writes:
>>
>>> @@ -2688,15 +2716,9 @@ struct rt6_info *addrconf_dst_alloc(struct inet6_dev *idev,
>>>  {
>>>  	u32 tb_id;
>>>  	struct net *net = dev_net(idev->dev);
>>> -	struct net_device *dev = net->loopback_dev;
>>> +	struct net_device *dev = idev->dev;
>>>  	struct rt6_info *rt;
>>>  
>>> -	/* use L3 Master device as loopback for host routes if device
>>> -	 * is enslaved and address is not link local or multicast
>>> -	 */
>>> -	if (!rt6_need_strict(addr))
>>> -		dev = l3mdev_master_dev_rcu(idev->dev) ? : dev;
>>> -
>>>  	rt = ip6_dst_alloc(net, dev, DST_NOCOUNT);
>>>  	if (!rt)
>>>  		return ERR_PTR(-ENOMEM);
>>
>> I am afraid this change might break Java:
>>
>> <http://hg.openjdk.java.net/jdk9/jdk9/jdk/file/65464a307408/src/java.base/unix/native/libnet/net_util_md.c#l574>
>>
>> I am all in for this change, but maybe it might be necessary to mask
>> RTF_LOCAL routes with "lo" somehow.
> 
> That's asinine. The if_inet6 processing is just getting the 'lo'
> interface index. Why scan the file looking for that? The ipv6_route
> processing is assembling routes against the loopback device regardless
> of what the route is. Do you know why - what the route list is used for?


If I read it correctly, seems to be a 2.4 workaround:
- only user of the route list is needsLoopbackRoute()
- only caller of needsLoopbackRoute is here:

http://hg.openjdk.java.net/jdk9/jdk9/jdk/file/65464a307408/src/java.base/unix/native/libnet/net_util_md.c#l828