Quoting Guillaume ZITTA (l...@zitta.fr): > Le 24/12/2013 15:32, Stéphane Graber a écrit : > >On Tue, Dec 24, 2013 at 03:01:38PM +0100, Guillaume ZITTA wrote: > >>Hi, > >> > >>I'm coding a new template (for gentoo). > >> > >>I saw this kind of tweak in many templates : > >> > >> if [ "$nics" -eq 1 ] && ! grep -q "^lxc.network.hwaddr" > >>$path/config; then > >> # see > >> http://sourceforge.net/tracker/?func=detail&aid=3411497&group_id=163076&atid=826303 > >> hwaddr="fe:$(dd if=/dev/urandom bs=8 count=1 2>/dev/null |od > >>-t x8 | \ > >> head -1 |awk '{print $2}' | cut -c1-10 |\ > >> sed 's/\(..\)/\1:/g; s/.$//')" > >> echo "lxc.network.hwaddr = $hwaddr" >> $path/config > >> fi > >> > >>The url no longer exists and I didn't catch the explaination in ML > >>archive. > >> > >>Someone has a new pointer to the explaination? > >>Was it a workaround for a no longuer existing bug? > >> > >>Regards, > >> > >>Guillaume ZITTA > > > >Yeah, I guess the bug report got lost in the migration to github. > > > >So let me try to explain what's going on there and why we are doing > >this. Note that it's not really a bug has much as just having to cope > >with the way things work in the kernel. > > > >We want all containers to have a static mac address for a simple > >reason, > >it's no fun if your IP addresses change every time you boot it (as if > >not specified, a random one assigned by the kernel will be used). > > > >On top of that, we can't just use any randomly generated mac > >address. We > >need one that'll typically be higher than a regular MAC address. That's > >because of the way bridges work in Linux. A bridge has its own mac > >address and whenever that address changes trafic is cut for around 30s > >(STP delay and similar stuff). The Linux kernel always uses the lowest > >MAC address in the bridge for the bridge's own address, so we need to > >make sure our addresses tend to be higher than that. > > > >Not all templates care about that though. In Ubuntu we provide a routed > >bridge so we don't have that concern and we instead choose to use the > >Xen MAC range which has the advantage of being properly registered > >specifically for use with VMs and containers. > > > It's pretty clear, thanks a lot. > > Templates do it only if there is one NIC. is it because doing it on > multiNIC in bash is a pain in the a*s ? > > Is there a plan for lxc to allocate this kind of "high static > hwaddr" in pre-template config ? > If not, my proposal: > I set an incomplete (prefix) lxc.network.hwaddr in default conf. > lxc-create complete it randomly and write it to the container's config. > > Does it make sense?
I think so. Just 'xx' in place of real numbers? > I do not/can't code in C, but perhaps I should try ... > > Guillaume ZITTA > _______________________________________________ > lxc-devel mailing list > lxc-devel@lists.linuxcontainers.org > http://lists.linuxcontainers.org/listinfo/lxc-devel _______________________________________________ lxc-devel mailing list lxc-devel@lists.linuxcontainers.org http://lists.linuxcontainers.org/listinfo/lxc-devel
