[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <1412264648.7227.9.camel@dcbw.local>
Date: Thu, 02 Oct 2014 10:44:08 -0500
From: Dan Williams <dcbw@...hat.com>
To: 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 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
> 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
> > --
> > To unsubscribe from this list: send the line "unsubscribe netdev" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists