[CRIU] [PATCH 3/5] net: c/r ipv6 addresses for links

[Tycho Andersen]

On Tue, Nov 24, 2015 at 12:22:59PM +0300, Andrew Vagin wrote:
> On Mon, Nov 23, 2015 at 01:55:26PM -0700, Tycho Andersen wrote:
> > Here's a start at checkpoint/restore of links with ipv6 addresses. Each
> > link can have more than one ipv6 address:
> > 
> > eth0      Link encap:Ethernet  HWaddr 1c:6f:65:d5:56:98
> >           inet addr:192.168.0.69  Bcast:192.168.0.255  Mask:255.255.255.0
> >           inet6 addr: fe80::1e6f:65ff:fed5:5698/64 Scope:Link
> >           inet6 addr: fd5d:e5bb:c5f9::c0c/128 Scope:Global
> >           inet6 addr: fd5d:e5bb:c5f9:0:1e6f:65ff:fed5:5698/64 Scope:Global
> >           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
> >           RX packets:63439992 errors:0 dropped:0 overruns:0 frame:0
> >           TX packets:44446651 errors:0 dropped:0 overruns:0 carrier:0
> >           collisions:0 txqueuelen:1000
> >           RX bytes:56986160322 (56.9 GB)  TX bytes:20927902606 (20.9 GB)
> > 
> > This patch doesn't dump any flags right now (and only restores with NODAD), but
> > I don't know enough about ipv6 to say how to c/r flags, or even if anything is
> > needed.
> 
> We use "ip addr save" to dump addresses and it works for ipv4. Why this
> doesn't work for ipv6?

It can, but stuff like DAD means that we may have to wait for a long
time to actually use the addresses, since you can't bind() to an
address that has the TENATIVE flag. Since we are binding to an ipv6
link local address by default in xenial ubuntu images, I was hitting
this.

For a while I had an implementation that just waited for the flag to
clear, but that can take a few seconds and we probably don't want to
do that in the hot path of restore. I could see about adding a
--set-nodad flag on ip addr restore instead, though.

Tycho