netdev - Re: interface down: v6/v4 address deletion difference

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <48A49498.4010601@hp.com>
Date:	Thu, 14 Aug 2008 16:24:56 -0400
From:	Vlad Yasevich <vladislav.yasevich@...com>
To:	Pekka Savola <pekkas@...core.fi>
Cc:	netdev@...r.kernel.org
Subject: Re: interface down: v6/v4 address deletion difference

Pekka Savola wrote:
> Hi,
> 
> I recall there was discussion about this a couple of years back, but I
> couldn't find it for all I could try.
> 
> There seems to be a difference in how v4/v6 addresses are handled when
> interface goes down (manually added addresses are gone forever
> regardless of whether it's tentative or nor; link local address is
> deleted but reappears when link is back).
> 
> Example on 2.6.25.10-86.fc9 using pan0 interface (just because it's
> easiest to play with it):
> 
> # ip l set up dev pan
> # ip a a 10.0.0.1/24 dev pan0
> # ip -6 a a 2001::1/64 dev pan0
> # ip a l dev pan0
> 8: pan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state
> UNKNOWN
>     link/ether 36:ca:62:2a:71:7b brd ff:ff:ff:ff:ff:ff
>     inet 10.0.0.1/24 scope global pan0
>     inet6 2001::1/64 scope global
>        valid_lft forever preferred_lft forever
>     inet6 fe80::34ca:62ff:fe2a:717b/64 scope link
>        valid_lft forever preferred_lft forever
> # ip l set down dev pan0
> # ip a l dev pan0
> 8: pan0: <BROADCAST,MULTICAST> mtu 1500 qdisc noqueue state DOWN
>     link/ether 36:ca:62:2a:71:7b brd ff:ff:ff:ff:ff:ff
>     inet 10.0.0.1/24 scope global pan0
> # ip l set up dev pan0
> # ip a l dev pan0
> 8: pan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state
> UNKNOWN
>     link/ether 36:ca:62:2a:71:7b brd ff:ff:ff:ff:ff:ff
>     inet 10.0.0.1/24 scope global pan0
>     inet6 fe80::34ca:62ff:fe2a:717b/64 scope link tentative
>        valid_lft forever preferred_lft forever
> (and after a while 'tentative' flag goes away)
> 
> Shouldn't behaviour be consistent across v4/v6?
> 

>From what I remember explained to me, this is due to different
host models of operation between IPv4 and IPv6 in linux.  IPv4 is
implemented using a weak host mode, while IPv6 is a strong host model.
So, when the interface is brought down, all IPv6 addresses
are removed since Linux considers them assigned to the interface
and not the host.

-vlad
--
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