netdev - Re: With disable_ipv6 set to 1 on an interface, ff00:/8 and fe80::/64 are still added on device UP

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Date:	Thu, 22 Jul 2010 10:03:03 -0400
From:	Mahesh Kelkar <maheshkelkar@...il.com>
To:	Brian Haley <brian.haley@...com>
Cc:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: With disable_ipv6 set to 1 on an interface, ff00:/8 and fe80::/64 
	are still added on device UP

Brian,

Overall the patch seem to work.

On one occasion I saw an error when it tried get rtnl_trylock() in
"addrconf_disable_ipv6" in addrconf.c. I am investigating into it. If
you could think of anything, please let me know.

I also came across another odd behavior (unrelated to disable_ipv6 but
related to multicast & link local route):
A. configure unicast Ipv6 address (say 123:2:3:4:5:6:7:8/64) on an
interface. (link-local will be assigned when interface comes up)
B. Bring the interface down (ip link set eth0 down),

you will get following set of netlink notifications (ip monitor all):
1. Deleted - unicast address connected route (123:2:3:4::/64)
2. Deleted - link local (fe80::/64) route
3. Deleted - multicast (ff00::/8) route
4. Deleted - unicast address (123:2:3:4:5:6:7:8/64)
5. Deleted - link local address

C. re-configure the unicast Ipv6 address (say 123:2:3:4:5:6:7:8/64) on
the interface. (link-local will NOT be assigned as interface is down)

You wil see following netlink notifications:
6. Added - unicast address (123:2:3:4:5:6:7:8/64)
7. Added - unicast address connected route (123:2:3:4::/64)
8. Added - multicast (ff00::/8) route
9. Added - link local (fe80::/64) route
etc.

I am not sure why #7, #8 & #9 occured. It doesn't happen in case of
IPv4. The routes show up when interface reaches up state. Perhaps my
kernel is old and that could be reason for this beahvior.

BTW I am using 2.6.21 with following cherry-picked disable_ipv6 patches:
- ipv6: Add disable_ipv6 sysctl to disable IPv6 operaion on specific
interface(commit:778d80be52699596bf70e0eb0761cf5e1e46088d)
- ipv6: Plug sk_buff leak in ipv6_rcv (net/ipv6/ip6_input.c) (commit:
71f6f6dfdf7c7a67462386d9ea05c1095a89c555)
- IPv6: Add 'autoconf' and 'disable_ipv6' module parameters (ONLY
interface specific behavior)

Thanks very much for your help.
Mahesh

On Tue, Jul 20, 2010 at 4:48 PM, David Miller <davem@...emloft.net> wrote:
> From: Brian Haley <brian.haley@...com>
> Date: Tue, 20 Jul 2010 16:34:30 -0400
>
>> I believe the easiest way to fix this is the following patch, can
>> you please test it?
>  ...
>> If the interface has IPv6 disabled, don't add a multicast or
>> link-local route since we won't be adding a link-local address.
>>
>> Reported-by: Mahesh Kelkar <maheshkelkar@...il.com>
>> Signed-off-by: Brian Haley <brian.haley@...com>
>
> This looks good to me, let me know when it has been tested.
>
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