On Thu, Oct 2, 2014 at 12:45 PM, Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote: > Andy Lutomirski <luto@xxxxxxxxxxxxxx> writes: > >> On Thu, Oct 2, 2014 at 12:20 PM, Eric W. Biederman >> <ebiederm@xxxxxxxxxxxx> wrote: >>> Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx> writes: >>> >>>> Le 29/09/2014 20:43, Eric W. Biederman a écrit : >>>>> Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx> writes: >>>>> >>>>>> Le 26/09/2014 20:57, Eric W. Biederman a écrit : >>>>>>> Andy Lutomirski <luto@xxxxxxxxxxxxxx> writes: >>>>>>> >>>>>>>> On Fri, Sep 26, 2014 at 11:10 AM, Eric W. Biederman >>>>>>>> <ebiederm@xxxxxxxxxxxx> wrote: >>>>>>>>> I see two ways to go with this. >>>>>>>>> >>>>>>>>> - A per network namespace table to that you can store ids for ``peer'' >>>>>>>>> network namespaces. The table would need to be populated manually by >>>>>>>>> the likes of ip netns add. >>>>>>>>> >>>>>>>>> That flips the order of assignment and makes this idea solid. >>>>>> I have a preference for this solution, because it allows to have a full >>>>>> broadcast messages. When you have a lot of network interfaces (> 10k), >>>>>> it saves a lot of time to avoid another request to get all informations. >>>>> >>>>> My practical question is how often does it happen that we care? >>>> In fact, I don't think that scenarii with a lot of netns have a full mesh of >>>> x-netns interfaces. It will be more one "link" netns with the physical >>>> interface and all other with one interface with the link part in this "link" >>>> netns. Hence, only one nsid is needing in each netns. >>> >>> I will buy that a full mesh is unlikely. >>> >>> For people doing simulations anything physical has a limited number of >>> links. >>> >>> For people wanting all to all connectivity setting up an internal >>> macvlan (or the equivalent) is likely much simpler and more efficient >>> that a full mesh. >>> >>> So the question in my mind is how do we create these identifiers at need >>> (when we create the cross network namespace links) instead of at network >>> namespace creation time. I don't see an answer to that in your patches, >>> and perhaps it obvious. >>> >> >> I wonder whether part of the problem is that we're thinking about >> scoping wrong. What if we made the hierarchy more explicit? >> >> For example, we could give each netns an admin-assigned identifier >> (e.g. a 64-bit number, maybe required to be unique, maybe not) >> relative to its containing userns. Then we could come up with a way >> to identify user namespaces (i.e. inode number relative to containing >> user ns, if that's well-defined). > > If as suggested we only assign ids when a tunnel (or equivalent) is > created between two network namespaces the space cost is a non-issue. > The ids become at worst a constant factor addition to the cost of the > tunnel. > > To keep things simple we may want to assign a free id (if one does not > exist) when we connect a tunnel to a network namespace. > >> From user code's perspective, netnses that are in the requester's >> userns or its descendents are identified by a path through a (possibly >> zero-length) sequence of userns ids followed by a netns id. Netnses >> outside the requester's userns hierarchy cannot be named at all. >> >> Would this make sense? > > Nope. What happens if I migrate 2 of the 4 network namespaces in a user > namespace? The migration potentially fails. Application migration does > not require user namespace migration. Hmm. I guess that, as long as those network namespaces aren't connected to anything else, migrating like that makes sense and ought to work. Fair enough. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
