Messages in this thread | | | Subject | Re: [PATCH net-next 0/3 V1] rtnetlink: enable IFLA_IF_NETNSID for RTM_{DEL,SET}LINK | From | Nicolas Dichtel <> | Date | Fri, 26 Jan 2018 10:28:31 +0100 |
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Le 26/01/2018 à 09:36, Jiri Benc a écrit : > On Fri, 26 Jan 2018 00:34:51 +0100, Nicolas Dichtel wrote: >> Why meaningful? The user knows that the answer is like if if was done in another >> netns. It enables to have only one netlink socket instead of one per netns. But >> the code using it will be the same. > > Because you can't use it to query the linked interface. You can't even > use it as an opaque value to track interfaces (netnsid+ifindex) because > netnsids are not unique across net name spaces. You can easily have two > interfaces that have all the ifindex, ifname, netnsid (and basically > everything else) identical but being completely different interfaces. Yes, the user have to map those info correctly. And this complexifies the (user) code a lot.
> That's really not helpful. > >> I fear that with your approach, it will results to a lot of complexity in the >> kernel. > > The complexity is (at least partly) already there. It's an inevitable > result of the design decision to have relative identifiers. Yes, you're right. My approach moves the complexity to the user, which make this feature hard to use.
> > I agree that we should think about how to make this easy to implement. > I like your idea of doing this somehow generically. Perhaps it's > possible to do while keeping the netnsids valid in the caller's netns? Yes. I agree that it will be a lot easier to use if the conversion is done in the kernel. And having a generic mechanism will also help a lot to use it.
> >> What is really missing for me, is a way to get a fd from an nsid. The user >> should be able to call RTM_GETNSID with an fd and a nsid and the kernel performs >> the needed operations so that the fd points to the corresponding netns. > > That's what I was missing, too. I even looked into implementing it. But > opening a fd on behalf of the process and returning it over netlink is a > wrong thing to do. Netlink messages can get lost. Then you have a fd > leak you can do nothing about. Yes, I also looked at this ;-)
> > Given that we have netnsids used for so much stuff already (like > NETLINK_LISTEN_ALL_NSID) you need to track them anyway. And if you need > to track them, why bother with another identifier? It would be better > if netnsid can be used universally for anything. Then there will be no > need for the conversion. I like this idea a lot. So the missing part is a setns() using the nsid ;-)
Regards, Nicolas
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