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Message-Id: <9330C415-574C-492B-A7AE-92EBCF6D1A26@emagii.com>
Date: Thu, 2 Oct 2014 14:38:30 +0200
From: Ulf samuelsson <netdev@...gii.com>
To: Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc: Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: netlink NETLINK_ROUTE failure & Can the kernel really handle IPv6 properly
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"
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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