Quoting Stéphane Graber (stgraber@xxxxxxxxxx): > On Tue, Sep 15, 2015 at 06:01:38PM +0300, Konstantin Khlebnikov wrote: > > On 15.09.2015 17:27, Eric W. Biederman wrote: > > >Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> writes: > > > > > >>pid_t getvpid(pid_t pid, pid_t source, pid_t target); > > >> > > >>This syscall converts pid from one pid-ns into pid in another pid-ns: > > >>it takes @pid in namespace of @source task (zero for current) and > > >>returns related pid in namespace of @target task (zero for current too). > > >>If pid is unreachable from target pid-ns then it returns zero. > > > > > >This interface as presented is inherently racy. It would be better > > >if source and target were file descriptors referring to the namespaces > > >you wish to translate between. > > > > Yep, it's racy. As well as any operation with non-child pids. > > With file descriptors for source/target result will be racy anyway. > > > > > > > >>Such conversion is required for interaction between processes from > > >>different pid-namespaces. For example when system service talks with > > >>client from isolated container via socket about task in container: > > > > > >Sockets are already supported. At least the metadata of sockets is. > > > > > >Maybe we need this but I am not convinced of it's utility. > > > > > >What are you trying to do that motivates this? > > > > I'm working on hierarchical container management system which > > allows to create and control nested sub-containers from containers > > ( https://github.com/yandex/porto ). Main server works in host and > > have to interact with all levels of nested namespaces. This syscall > > makes some operations much easier: server must remember only pid in > > host pid namespace and convert it into right vpid on demand. > > Note that as Eric said earlier, sending a PID inside a ucred through a > unix socket will have the pid translated. > > So while your solution certainly should be faster, you can already achieve > what you want today by doing: > > == Translate PID in container to PID in host > - open a socket > - setns to container's pidns > - send ucred from that container containing the requested container PID > - host sees the host PID > > == Translate PID on host to PID in container > - open a socket > - setns to container's pidns > - send ucred from the host containing the request host PID > (send will fail if the host PID isn't part of that container) > - container sees the container PID In addition, since commit e4bc332451 : /proc/PID/status: show all sets of pid according to ns we now also have 'NSpid' etc in /proc/$$/status. -serge _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
