David Howells <dhowells@xxxxxxxxxx> writes: > Aleksa Sarai <asarai@xxxxxxx> wrote: > >> >> The reason I think this is necessary is that the kernel has no idea >> >> how to direct upcalls to what userspace considers to be a container - >> >> current Linux practice appears to make a "container" just an >> >> arbitrarily chosen junction of namespaces, control groups and files, >> >> which may be changed individually within the "container". >> >> Just want to point out that if the kernel APIs for containers massively >> change, then the OCI will have to completely rework how we describe containers >> (and so will all existing runtimes). >> >> Not to mention that while I don't like how hard it is (from a runtime >> perspective) to actually set up a container securely, there are undoubtedly >> benefits to having namespaces split out. The network namespace being separate >> means that in certain contexts you actually don't want to create a new network >> namespace when creating a container. > > Yep, I quite agree. > > However, certain things need to be made per-net namespace that *aren't*. DNS > results, for instance. > > As an example, I could set up a client machine with two ethernet ports, set up > two DNS+NFS servers, each of which think they're called "foo.bar" and attach > each server to a different port on the client machine. Then I could create a > pair of containers on the client machine and route the network in each > container to a different port. Now there's a problem because the names of the > cached DNS records for each port overlap. Please look at ip netns add. It does solve this in userspace rather simply. > Further, the NFS idmapper needs to be able to direct its calls to the > appropriate network. Eric
