On Wed, 2014-02-19 at 09:20 -0800, Luis R. Rodriguez wrote: > On Wed, Feb 19, 2014 at 8:45 AM, Dan Williams <dcbw@xxxxxxxxxx> wrote: > > On Tue, 2014-02-18 at 13:19 -0800, Luis R. Rodriguez wrote: > >> On Mon, Feb 17, 2014 at 12:23 PM, Dan Williams <dcbw@xxxxxxxxxx> wrote: > >> > On Fri, 2014-02-14 at 18:59 -0800, Luis R. Rodriguez wrote: > >> >> From: "Luis R. Rodriguez" <mcgrof@xxxxxxxx> > >> >> > >> >> Some interfaces do not need to have any IPv4 or IPv6 > >> >> addresses, so enable an option to specify this. One > >> >> example where this is observed are virtualization > >> >> backend interfaces which just use the net_device > >> >> constructs to help with their respective frontends. > >> >> > >> >> This should optimize boot time and complexity on > >> >> virtualization environments for each backend interface > >> >> while also avoiding triggering SLAAC and DAD, which is > >> >> simply pointless for these type of interfaces. > >> > > >> > Would it not be better/cleaner to use disable_ipv6 and then add a > >> > disable_ipv4 sysctl, then use those with that interface? > >> > >> Sure, but note that the both disable_ipv6 and accept_dada sysctl > >> parameters are global. ipv4 and ipv6 interfaces are created upon > >> NETDEVICE_REGISTER, which will get triggered when a driver calls > >> register_netdev(). The goal of this patch was to enable an early > >> optimization for drivers that have no need ever for ipv4 or ipv6 > >> interfaces. > > > > Each interface gets override sysctls too though, eg: > > > > /proc/sys/net/ipv6/conf/enp0s25/disable_ipv6 > > I hadn't seen those, thanks! Note that there isn't yet a disable_ipv4 knob though, I was perhaps-too-subtly trying to get you to send a patch for it, since I can use it too :) Dan > > which is the one I meant; you're obviously right that the global ones > > aren't what you want here. But the specific ones should be suitable? > > Under the approach Stephen mentioned by first ensuring the interface > is down yes. There's one use case I can consider to still want the > patch though, more on that below. > > > If you set that on a per-interface basis, then you'll get EPERM or > > something whenever you try to add IPv6 addresses or do IPv6 routing. > > Neat, thanks. > > >> Zoltan has noted though some use cases of IPv4 or IPv6 addresses on > >> backends though, as such this is no longer applicable as a > >> requirement. The ipv4 sysctl however still seems like a reasonable > >> approach to enable optimizations of the network in topologies where > >> its known we won't need them but -- we'd need to consider a much more > >> granular solution, not just global as it is now for disable_ipv6, and > >> we'd also have to figure out a clean way to do this to not incur the > >> cost of early address interface addition upon register_netdev(). > >> > >> Given that we have a use case for ipv4 and ipv6 addresses on > >> xen-netback we no longer have an immediate use case for such early > >> optimization primitives though, so I'll drop this. > >> > >> > The IFF_SKIP_IP seems to duplicate at least part of what disable_ipv6 is > >> > already doing. > >> > >> disable_ipv6 is global, the goal was to make this granular and skip > >> the cost upon early boot, but its been clarified we don't need this. > > > > Like Stephen says, you need to make sure you set them before IFF_UP, but > > beyond that, wouldn't the interface-specific sysctls work? > > Yeah that'll do it, unless there is a measurable run time benefit cost > to never even add these in the first place. Consider a host with tons > of guests, not sure how many is 'a lot' these days. One would have to > measure the cost of reducing the amount of time it takes to boot these > up. As discussed in the other threads though there *is* some use cases > of assigning IPv4 or IPv6 addresses to the backend interfaces though: > routing them (although its unclear to me if iptables can be used > instead, Zoltan?). So at least now there no clear requirement to > remove these interfaces or not have them at all. The boot time cost > savings should be considered though if this is ultimately desirable. I > saw tons of timers and events that'd get triggered with any IPv4 or > IPv6 interface laying around. > > Luis > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
