Todo

component	task	complexity	potential/willing assignee	comments
kernel/crtools	Make proper "check lock present" API in the kernel	medium	-	Currently we detect where a file lock belongs to by locking the file again with the alternative lock type and check how kernel reacts on that. This is not nice as it may tune the lock state on a file. Instead we need the "check lock on fd" call in the kernel.
kernel/crtools	Put call to mmap into VDSO	easy	Cyrill	To put the parasite code into target process we modify its code to call the mmap() system call (and the unmodify it back) and put the parasite into new area. Oleg Nesterov suggests not to patch victim, but to always have one on VDSO.
crtools	Integration with other projects	hard	-	CRIU is not working great by itself. There's alway some specific about what user wants to dump. Integrating CRIU with other projects will make CRIU work at its best.
crtools	Restore tasks into fresh new pid namespace	easy	-	When we dumped processes, it can be hard to restore it back, if they didn't live in a pid namespace, due to PIDs conflict. It would be nice to have the ability to ask CRIU to create the pid namespace for those guys and restore them there. A thing to worry about is this new namespace's init task.
crtools	Rollback tree state	medium	-	When we checkpointed process tree with -R option (let them run after checkpoint) we might want to return the tasks into checkpointed state on the same machine. Currently this can only be done by killing the processes and restoring them from scratch. If we could ask CRIU to restore the images into the ready processes that could speed things up, especially if carefully caring about memory changes tracking.
crtools	AIO with pending events	medium	-	When we dump AIO ring we check it not to contain events inside and abort the dump otherwise. Need to dump events too and put them back on restore.
crtools	Restore arbitrary mountpoints tree	hard	-	Linux kernel can construct tricky knows with mount points. We don't support arbitrary configuration of such things, only those that are in active use by software. Need to fix them up.
crtools	Lazy migration using userfaultd	medium	xemul	Lazy migration is when we move all the tasks on another node, but leave theirs memory on the source one. Not to allow tasks read garbage from empty address space we protect all of it as inaccessible. When tasks start reading/writing the mem they got page-fault-ed. With the userfaultfd technology it can be possible to intercept the #PF, pull the page from source node and map it into expected address.
crtools	Dump tasks from cgroup	easy	-	Currently criu dumps a subtree from given pid. It makes sense to request CRIU to dump a set of tasks from given cgroup.
crtools	Speed up logging	medium	Cyrill	Synchronous formatting and writes into log files slow things down. On the other hand turning logs off make it impossible to troubleshoot.
crtools	Sanitize logging messages	hard	-	Currently log messages are printed w/o any logic, it's hard to analize what has happened when CRIU fails. Need to improve that by, e.g. categorizing images and explaining them in more details.
crtools	Support OFD posix locks	easy	-	These are still rarely used, but exist. Might make sense to support them in advance, it looks like kernel API allows for that.
crtools	Optimize kcmp calls	medium	-	CRIU build kcmp trees to find out IDs of such objects as MM, FDT and others. Currently we kcmp all tasks to get the ID, but we can improve that by pre-generating ID based on objects that live on MM, FS, etc. If pre-ID of two tasks matches, then we call kcmp, if not -- objects are different.
crtools	Shmem changes tracking	medium	-	Memory changes tracker works on anonymous private mappings only. Anonymous shmem is not in active use by server applications, so we don't support one currently. Supporting it should be done by tracking the changes from all the tasks that could write into the segment. For anon shared memory and sysvipc segment inside IPC namespace this works reliably.
crtools	Page transfer filters	medium	-	The page-xfer engine just splices the pages from stealing pipes into socket. Packing or encrypting the data would be nice. Maybe it's purely for P.Haul?
crtools	FUSE mount points	hard	-	When dumping mountpoints we explicitly check the filesystem mounted. The thing is -- not all filesystems can be just ignored on dump. E.g. FUSE mount involves a user-space daemon that is responsible for the files tree contents. If we just kill one on dump we might not be able to restore it. Need to special-care one.
crtools	32-bit tasks	hard	Cyrill	For x86 we only dump and restore 64-bit tasks. Doing 32-bit should also be done, but keep in mind, that not only 64-bit tree OR 32-bit tree should be supported. There can be mixed 64-and-32-bit trees out there and CRIU should support those too.
crtools	Generate task's core file out of images with CRIT	medium	Ruslan Kuprieiev	Nothing special -- just take core.img, mm.img and pagemap.img and produce the canonical core image out of those.
crtools	Modify restored resources run-time in CRIT daemon	medium	-	Sometimes it might make sense to tune the objects fro images on restore. E.g. -- change the IP address of sockets from task above or fix file paths to be "chroot-ed". The best solution seems to be in launching CRIT in daemon mode, telling it what images and how to modify and teaching CRIU to "filter" the pb objects read from images through this daemon.
crtools	TCP socket migration with changed IP	medium	-	It might make sense to migrate a tcp connection on a box with changed IP address _if_ both boxes are NAT-ed to the destination. We will then have to go to NAT box and fix the conntracks in that case and use CRIT images modifucation facilities.
crtools	Applying images	hard	xemul@ w/ students	Think about ability to take images and apply them to a living task(s). Like it was described in the "rollback" feature above. Another exampl -- repopulate fdtable according to data from image. Yet another use-case -- when doing partial migration (see below) we'll need to modify one part to switch from pipes to sockets. What else? With constant replication of tree state we can do incremental dumps on source node and apply those increments on pre-created replicas on the destination node.
crtools	Partial migration	hard	-	If tasks subtree has connections to the rest of the tree (e.g. with pipes of unix sockets) we try to detect this and refuse the dump. It should be possible to take part of the tree, migrating it somewhere and recreating the mentioned links with some other appropriate IPC channel. E.g. pipes with sockets, shared memory with distributed shared memory and so on.
crtools	Shared objects (mm/fs) support	medium	-	Things created with CLONE_FOO flags are not supported now (exception -- full threads). Now we have the kcmp syscall and can do it. The shared fdtable (CLONE_FILES) is supported, the next candidate is mm sharing, as we do know, that MySQL does so sometimes.
crtools	Smart paths resolution	hard	-	Files can be overmounted. In this case CRIU will refuse the dump saying that file is not invisible files but inaccessible by its name. Need a way to resolve paths to such. There are two ways: 1. Move mounts, that overlap the desired path temporarily, then open the file, then move the mountpoint back. 2. When creating a new mount pre-open an fd keeping the mountpoint. Later, do accurate path resolve and call openat() on proper mountpoint fd.
kernel/crtools	TCP repair fixes	hard	-	TCP repair TODO
kernel?/crtools	TCP conntrack-ed connections	medium	-	Need to check whether connection tracking is ON, dump the needed conntrack info and put the tracker back.
crtools	Bridges in container	medium	-
crtools	VLANs in containers	medium	-
crtools	PPP support	medium	-
crtools/kernel	NFS mount points support	hard	-
kernel	Seamless kernel upgrade	hard	xemul
crtools	Validate .img files	easy	-	CRIT For a given set of image files check, that they are in "restorable" shape
crtools	Restore arbitrary process tree	hard	-	Need to restore any process tree, which could be created with help PR_SET_CHILD_SUBREAPER and CLONE_PARENT. Processes can share other resources clone(2). Look at session02
crtools	C/R X app	hard	Ruslan Kuprieiev	Dump/restore of graphical applications (see about integration)
crtools/kernel	Undo semaphores	medium	Cyrill Gorcunov	Require mods from both sides -- criu and kernel
crtools	More detailed RPC fail codes	easy	-	Currently only 3 typical errors are reported(see include/cr-errno.h)
kernel/criu	FS-notify queues	hard	-	Fsnotify