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Message-ID: <542E3B2E.2020909@ericsson.com>
Date: Fri, 3 Oct 2014 07:59:10 +0200
From: Ulf Samuelsson <ulf.samuelsson@...csson.com>
To: Dan Williams <dcbw@...hat.com>, Ulf samuelsson <netdev@...gii.com>
CC: Hannes Frederic Sowa <hannes@...essinduktion.org>,
Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: netlink NETLINK_ROUTE failure & Can the kernel really handle
IPv6 properly
On 10/02/2014 05:44 PM, Dan Williams wrote:
> On Thu, 2014-10-02 at 14:38 +0200, Ulf samuelsson wrote:
>> This is the significant code, and it is wrong.
>>
>> static struct notifier_block my_ipv6_address_notifier =
>> {
>> my_ipv6_address_notifier_cb,
>> NULL,
>> 0
>> };
>>
>> register_inet6addr_notifier (&my_ipv6_address_notifier );
>>
>> int
>> my_ipv6_address_notifier_cb (struct notifier_block *self,
>> unsigned long event, void *val)
>> {
>> struct inet6_ifaddr *ifaddr = (struct inet6_ifaddr *)val;
>>
>>
>> /* We are only interested in address add/delete events */
>> /* IPv6 address add comes as NETDEV_UP and delete comes as
>> * NETDEV_DOWN
>> */
>> if ((event != NETDEV_UP) && (event != NETDEV_DOWN))
>> return ret;
>>
>> if (ifaddr == NULL)
>> return ret;
>> /* Now that we are sure that it is a IPv6 address being added deleted,
>> * verify that it is a link local address.
>> */
>> if (!IPV6_IS_ADDR_LINKLOCAL (&ifaddr->addr))
>> {
>> return ret;
>> }
>> ...
>> send_message_to_app(LINK_LOCAL_UP, ip);
>> ...
>> return ret;
>> }
>>
>>
>> Application tries to send message to "ip" and fails, because the link-local adress is still
>> in "tentative state"
> It seems to me that a better architecture would be to have the app
> itself listen for RTM_NEWADDR netlink event and look for lack of
> IFA_F_TENTATIVE in the IFA_FLAGS attribute. Using a kernel module to do
> the same thing seems pretty wrong.
>
> Dan
Thanks, Maybe you are right but I do not have all the details.
The kernel module is part of a driver for a Broadcom router chip.
The guys writing the driver might want to know as well.
I will see what they say.
Best Regards,
Ulf Samuelsson
>> Best Regards
>> Ulf Samuelsson
>> ulf@...gii.com
>> +46 (722) 427 437
>>
>>
>>> 1 okt 2014 kl. 23:30 skrev Hannes Frederic Sowa <hannes@...essinduktion.org>:
>>>
>>> Hello,
>>>
>>>> On Wed, Oct 1, 2014, at 22:28, Ulf Samuelsson wrote:
>>>> BTW, the problem I am trying to solve is how to connect to an I/F with
>>>> an IPv6 link-local address.
>>>>
>>>> An existing kernel module waits for a NETDEV_UP event, and then tries to
>>>> communicate
>>>> with the link-local address.
>>>>
>>>> This will fail, because (according to a colleague) the I/F enters a
>>>> "tentative" state,
>>>> where it is trying to decide if it is unique or not.
>>>> It will remain in that state for 1-2 seconds, and only afterwards is the
>>>> link-local address
>>>> available for normal use.
>>>>
>>>> The guys writing the module, claim that the kernel is using NETDEV_UP.
>>>> There is very little code in the kernel using NETLINK_ROUTE, even in
>>>> latest stable.
>>>> It is using NETDEV_UP.
>>>>
>>>> If my colleague is right, the kernel really cannot handle IPv6
>>>> link-local addresses properly.
>>> Sorry, I cannot really follow you, can you send example code or be a bit
>>> more precise?
>>>
>>> Thanks,
>>> Hannes
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