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[Libvir] save/restore support for KVM
by Jim Paris 13 Aug '07

13 Aug '07

Hi, I've implemented save/restore support for KVM using the live migration feature. First, a few patches to KVM to fix bugs: Subject: [PATCH 1/3] qemu: fix freed pointer dereference http://article.gmane.org/gmane.comp.emulators.kvm.devel/5572 Subject: [PATCH 2/3] qemu: don't start a new migration if one is already in progress http://article.gmane.org/gmane.comp.emulators.kvm.devel/5575 Subject: [PATCH 3/3] qemu: reset buffer pointers after CR/LF http://article.gmane.org/gmane.comp.emulators.kvm.devel/5573 (If compatibility with old KVM is wanted, it might be possible to work around the kvm bugs in other ways, but I'm not sure). Then, another patch to KVM to support inbound migration from a filename. It already supports migration from stdin, but adding this seemed easier from a libvirt perspective. Subject: [PATCH] qemu: accept filename for incoming migration http://article.gmane.org/gmane.comp.emulators.kvm.devel/5590 Finally, the libvirt side. Some notes: - Arbitrary decisions about VM status: I pause the VM before starting migration, and destroy it once it's finished. Neither is required by KVM but I'd be concerned about the disk image state otherwise. Also, after resuming, the VM is still paused. I don't know how Xen behaves in this regard but the behavior here is easy enough to change. - I append the domain's UUID at the end of the migration image. This doesn't affect KVM at all (it ignores the extra data). Does that seem reasonable? It's unclear how the saved image is supposed to get associated with a particular VM configuration without doing something like this. - I added the migrateFrom field to the qemu_vm struct. Dunno if that's the best place. Could also add put it in qemu_vm_def, or add parameters to qemudStartVMDaemon, etc.. Patch against current CVS is below. Signed-off-by: Jim Paris <jim(a)jtan.com> -jim Index: src/qemu_conf.c =================================================================== RCS file: /data/cvs/libvirt/src/qemu_conf.c,v retrieving revision 1.10 diff -u -r1.10 qemu_conf.c --- src/qemu_conf.c 7 Aug 2007 13:02:35 -0000 1.10 +++ src/qemu_conf.c 9 Aug 2007 21:15:10 -0000 @@ -1518,7 +1518,8 @@ (vm->def->os.initrd[0] ? 2 : 0) + /* initrd */ (vm->def->os.cmdline[0] ? 2 : 0) + /* cmdline */ (vm->def->graphicsType == QEMUD_GRAPHICS_VNC ? 2 : - (vm->def->graphicsType == QEMUD_GRAPHICS_SDL ? 0 : 1)); /* graphics */ + (vm->def->graphicsType == QEMUD_GRAPHICS_SDL ? 0 : 1)) + /* graphics */ + (vm->migrateFrom[0] ? 3 : 0); /* migrateFrom */ snprintf(memory, sizeof(memory), "%d", vm->def->memory/1024); snprintf(vcpus, sizeof(vcpus), "%d", vm->def->vcpus); @@ -1767,6 +1768,15 @@ /* SDL is the default. no args needed */ } + if (vm->migrateFrom[0]) { + if (!((*argv)[++n] = strdup("-S"))) + goto no_memory; + if (!((*argv)[++n] = strdup("-incoming"))) + goto no_memory; + if (!((*argv)[++n] = strdup(vm->migrateFrom))) + goto no_memory; + } + (*argv)[++n] = NULL; return 0; Index: src/qemu_conf.h =================================================================== RCS file: /data/cvs/libvirt/src/qemu_conf.h,v retrieving revision 1.6 diff -u -r1.6 qemu_conf.h --- src/qemu_conf.h 30 Jul 2007 09:59:06 -0000 1.6 +++ src/qemu_conf.h 9 Aug 2007 21:15:10 -0000 @@ -213,6 +213,7 @@ char configFile[PATH_MAX]; char autostartLink[PATH_MAX]; + char migrateFrom[PATH_MAX]; struct qemud_vm_def *def; /* The current definition */ struct qemud_vm_def *newDef; /* New definition to activate at shutdown */ Index: src/qemu_driver.c =================================================================== RCS file: /data/cvs/libvirt/src/qemu_driver.c,v retrieving revision 1.14 diff -u -r1.14 qemu_driver.c --- src/qemu_driver.c 30 Jul 2007 09:59:06 -0000 1.14 +++ src/qemu_driver.c 9 Aug 2007 21:15:10 -0000 @@ -656,7 +656,7 @@ if (virExecNonBlock(conn, argv, &vm->pid, &vm->stdout, &vm->stderr) == 0) { vm->id = driver->nextvmid++; - vm->state = VIR_DOMAIN_RUNNING; + vm->state = vm->migrateFrom[0] ? VIR_DOMAIN_PAUSED : VIR_DOMAIN_RUNNING; driver->ninactivevms--; driver->nactivevms++; @@ -1852,29 +1852,151 @@ return 0; } +#define QEMUD_SAVE_MAGIC "LibvirtQemudUUID" -static int qemudDomainSave(virDomainPtr dom, - const char *path ATTRIBUTE_UNUSED) { +static int qemudDomainSave(virDomainPtr dom, + const char *path) { struct qemud_driver *driver = (struct qemud_driver *)dom->conn->privateData; struct qemud_vm *vm = qemudFindVMByID(driver, dom->id); + char *command, *info; + int fd; + if (!vm) { - qemudReportError(dom->conn, dom, NULL, VIR_ERR_INVALID_DOMAIN, "no domain with matching id %d", dom->id); + qemudReportError(dom->conn, dom, NULL, VIR_ERR_INVALID_DOMAIN, + "no domain with matching id %d", dom->id); return -1; } + if (!qemudIsActiveVM(vm)) { - qemudReportError(dom->conn, dom, NULL, VIR_ERR_OPERATION_FAILED, "domain is not running"); + qemudReportError(dom->conn, dom, NULL, VIR_ERR_OPERATION_FAILED, + "domain is not running"); return -1; } - qemudReportError(dom->conn, dom, NULL, VIR_ERR_OPERATION_FAILED, "save is not supported"); - return -1; + + if (strchr(path, '\'') || strchr(path, '\\') ) { + qemudReportError(dom->conn, dom, NULL, VIR_ERR_OPERATION_FAILED, + "invalid filename"); + return -1; + } + + /* Pause */ + if (qemudDomainSuspend(dom) != 0) { + qemudReportError(dom->conn, dom, NULL, VIR_ERR_OPERATION_FAILED, + "failed to pause domain"); + return -1; + } + + /* Migrate to file. */ + if (asprintf (&command, "migrate \"exec:dd of='%s' 2>/dev/null\"\n", + path) == -1) { + qemudReportError(dom->conn, dom, NULL, VIR_ERR_OPERATION_FAILED, + "out of memory"); + return -1; + } + + if (qemudMonitorCommand(driver, vm, command, &info) < 0) { + qemudReportError(dom->conn, dom, NULL, VIR_ERR_OPERATION_FAILED, + "migrate operation failed"); + free(command); + return -1; + } + + free(info); + free(command); + + /* Append the UUID, which we'll need in order to restore the domain. */ + if ((fd = open(path, O_APPEND|O_WRONLY)) < 0) { + qemudReportError(dom->conn, dom, NULL, VIR_ERR_OPERATION_FAILED, + "failed to open '%s'", path); + return -1; + } + + if (write(fd, QEMUD_SAVE_MAGIC, sizeof(QEMUD_SAVE_MAGIC)) != + sizeof(QEMUD_SAVE_MAGIC)) { + qemudReportError(dom->conn, dom, NULL, VIR_ERR_OPERATION_FAILED, + "failed to write magic"); + close(fd); + return -1; + } + + if (write(fd, dom->uuid, VIR_UUID_BUFLEN) != VIR_UUID_BUFLEN) { + qemudReportError(dom->conn, dom, NULL, VIR_ERR_OPERATION_FAILED, + "failed to write uuid"); + close(fd); + return -1; + } + close(fd); + + /* Shut it down */ + qemudShutdownVMDaemon(dom->conn, driver, vm); + if (!vm->configFile[0]) + qemudRemoveInactiveVM(driver, vm); + + return 0; } static int qemudDomainRestore(virConnectPtr conn, - const char *path ATTRIBUTE_UNUSED) { - /*struct qemud_driver *driver = (struct qemud_driver *)conn->privateData;*/ - qemudReportError(conn, NULL, NULL, VIR_ERR_OPERATION_FAILED, "restore is not supported"); - return -1; + const char *path) { + struct qemud_driver *driver = (struct qemud_driver *)conn->privateData; + unsigned char uuid[VIR_UUID_BUFLEN]; + unsigned char magic[sizeof(QEMUD_SAVE_MAGIC)]; + virDomainPtr dom; + struct qemud_vm *vm; + int fd; + + /* Find the UUID */ + if ((fd = open(path, O_RDONLY)) < 0) { + qemudReportError(conn, NULL, NULL, VIR_ERR_OPERATION_FAILED, + "cannot read domain image"); + return -1; + } + if (lseek(fd, 0 - (sizeof(magic) + sizeof(uuid)), SEEK_END) == -1) { + qemudReportError(conn, NULL, NULL, VIR_ERR_OPERATION_FAILED, + "failed to seek to end of domain image"); + close(fd); + return -1; + } + if (read(fd, magic, sizeof(magic)) != sizeof(magic)) { + qemudReportError(conn, NULL, NULL, VIR_ERR_OPERATION_FAILED, + "failed to read domain image"); + close(fd); + return -1; + } + if (memcmp(magic, QEMUD_SAVE_MAGIC, sizeof(magic))) { + qemudReportError(conn, NULL, NULL, VIR_ERR_OPERATION_FAILED, + "image magic is not correct"); + close(fd); + return -1; + } + if (read(fd, uuid, sizeof(uuid)) != sizeof(uuid)) { + qemudReportError(conn, NULL, NULL, VIR_ERR_OPERATION_FAILED, + "failed to read domain UUID from image"); + close(fd); + return -1; + } + close(fd); + + /* Find the domain & vm */ + dom = qemudDomainLookupByUUID(conn, uuid); + if (!dom) { + qemudReportError(conn, NULL, NULL, VIR_ERR_INVALID_DOMAIN, + "no domain with matching uuid"); + return -1; + } + + vm = qemudFindVMByUUID(driver, dom->uuid); + if (!vm) { + qemudReportError(conn, dom, NULL, VIR_ERR_INVALID_DOMAIN, + "no vm with matching uuid"); + return -1; + } + + /* Set the migration source and start it up. */ + snprintf(vm->migrateFrom, sizeof(vm->migrateFrom), "file://%s", path); + vm->migrateFrom[sizeof(vm->migrateFrom)-1] = '\0'; + + return qemudStartVMDaemon(dom->conn, driver, vm); } @@ -1931,6 +2053,7 @@ return -1; } + vm->migrateFrom[0] = '\0'; return qemudStartVMDaemon(dom->conn, driver, vm); }

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[Libvir] [PATCH] Block device and network stats
by Richard W.M. Jones 13 Aug '07

13 Aug '07

This is the implementation (currently Xen, local only). It includes a couple of virsh commands if you want to play with looking at the stats. Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903

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[Libvir] PATCH: Fix paravirt FB with xm driver
by Daniel P. Berrange 10 Aug '07

10 Aug '07

The code for dealing with the paravirt framebuffer was missing code to deal with an explicit vncdisplay=N setting - only working for vncunused=1. It was also not flexible enough in processing the 2 different styles of FB config. Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|

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[Libvir] PATCH: Fix virtual neworks with xm driver
by Daniel P. Berrange 10 Aug '07

10 Aug '07

The virtual networks stuff was never added to the xm driver for Xen 3.0.3 or earlier. This means that if adding a virtual network the bridge device won't get defined in the config. This patch addreses this, and also fixes a tiny mem leak in the equivalent code in the xend driver. Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|

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[Libvir] PATCH: Improve performance on Xen
by Daniel P. Berrange 10 Aug '07

10 Aug '07

The Xen implementations of virDomainLookupByID virDomainLookupByUUID virDomainLookupByName virDomainGetOSType all have sub-optimal performance since they speak to XenD. The lookupXXX functions all basically require 3 pieces of info in the end (name,id,uuid). They each get given one piece & have to lookup the other piece. Every running domain has to have an entry in XenStore on /local/domain/N where 'N' is the id. Under this location there is always a 'name' field. So if we have the id we can efficiently get the name. I just realized that the getdomaininfo hypercall struct contains the uuid and id. So for the ByID and ByUUID calls we can get all the info we need with a hypercall and a read of xenstore. This is very efficient compared to hitting XenD. As of Xen 3.1.0 hypervisor the flags in the getdomaininfo hypercall struct also mark whether the guest is HVM vs paraivrt, so we can also implement the GetOSType api with a single hypercall. That just leaves the ByName impl. The only way I can think of doing this is to scan /local/domain/N in xenstore until we find it. I'm going to try this, but I'm not convinced it'll be any significantly than talking to XenD. I may be surprised though. Any for the 3 improvements I have done, the 'virsh dominfo' call has improved when using either ID or UUID: Create a set of UUIDs & IDs # for i in `seq 1 500` ; do echo dominfo 73 ; done > ids.txt # for i in `seq 1 500` ; do echo dominfo 8f07fe28-753f-2729-d76d-bdbd892f949a ; done > uuids.txt Now before measurements: # time ./virsh < ids.txt > /dev/null real 0m17.317s user 0m0.144s sys 0m0.164s # time ./virsh < uuids.txt > /dev/null real 0m14.432s user 0m0.236s sys 0m0.460s Against the after measurements: # time ./virsh < demo.txt > /dev/null real 0m0.259s user 0m0.100s sys 0m0.072s # time ./virsh < demo.txt > /dev/null real 0m0.482s user 0m0.324s sys 0m0.108s A pretty good speedup really considering how frequently these calls are made if you're monitoring domains frequently. Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|

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[Libvir] Proposal: Block device and network stats
by Richard W.M. Jones 10 Aug '07

10 Aug '07

With the very timely question that has been raised about block and network device stats, I'm posting my proposed interface. I almost have this working for the Xen case on my test machine. The idea of this interface is to be optimised for the following case: * stats need to be fetched frequently (eg. once per second) * the layout of devices doesn't change often (ie. adding or removing devices from domains is very infrequent) * most domains have only a single block and single network device With the above assumptions, the idea is that you would use the API like this: (1) When the program starts up or (infrequently) is notified of a change or when a new domain appears, the program calls virDomainGetXMLDesc and parses out the //domain/devices/interface and //domain/devices/disk fields to get the list of network interfaces and block devices. So for each domain, you'll have two lists like this: dom[1]["blockdevs"] = ["xvda"] dom[1]["interfaces"] = ["virbr0"] (2) Frequently (eg. once per second) the program calls (in the above case): virDomainBlockStats (dom1, "xvda", &bstats, sizeof bstats); virDomainInterfaceStats (dom1, "virbr0", &istats, sizeof istats); (3) Since stats are cumulative the program must do its own subtraction and calculation in order to display throughput per second. The implementation goes directly from the name "xvda" to the backend device (/sys/devices/xen-backend/- [type]-[domid]-[major:minor]/statistics) for block devices, and slightly more complicatedly to a particular line in /proc/net/dev for network interfaces. (Note in the Xen case, the name "virbr0" is little more than a placeholder to mean "the zeroth interface for domain d"). In particular the current implementation doesn't cache anything. This should all work fine in the Linux / Xen case. libxenstat gives us sample code that we can copy for the Solaris / Xen case, but it would need testing from someone with access to such a machine. I don't think qemu supports stats at all. Initially we won't support stats for tap devices because there needs to be an upstream patch to support this (http://lists.xensource.com/archives/html/xen-changelog/2007-02/msg00278.html) The extra size parameter will allow us to extend the stats structures in future, maintaining binary backwards compatibility with existing clients. Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903

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[Libvir] Xen physical host statistics
by Mindaugas Kiznis 10 Aug '07

10 Aug '07

Hello, - I am trying to make an application, which would connect to a remote xen host and fetch some information about total (physical) CPU usage, total memory usage, network and disk I/O. I have managed to do a remote statistics grabber for CPU and memory usage using libvirt. I couldn't find any source of information about libvirt ability to return I/O numbers. Also haven't found any other solution yet. Any suggestions? Thank you in advance! Best regards, Mindaugas Kiznis

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[Libvir] PATCH: UUID code cleanup
by Daniel P. Berrange 09 Aug '07

09 Aug '07

Browsing the source I noticed we have many differents constants for UUID length, many ways of turning a UUID into a string, 2 ways of turning a string into a UUID (one with some scary signed <-> unsigned casting). This is just a result of the way the code evolved & I figured it could do with cleaning up a little. So I added a virUUIDFormat(const unsigned char uuid, char *uuidstr) method to the uuid.c, removed all the other equivalent code throughout and kiled all the duplicate constants. So now everything UUID related is in the one place uuid.c, while the constants are in libvirt/libvirt.h Its a surprisingly big patch, but it should not have any functional change with one exception. The XenD driver used to generate XML <uuid>...</uuid> tags without any '-' embedded in them. All other places use the '-' and technically the RFC requires them. Our parser is flexible enough to cope with, or without '-'. diffstat ~/libvirt-uuid-cleanup.patch proxy/Makefile.am | 2 - qemud/internal.h | 2 - src/libvirt.c | 34 +++------------------------- src/openvz_conf.c | 14 +++++------ src/openvz_conf.h | 3 -- src/qemu_conf.c | 20 ++++++---------- src/qemu_conf.h | 5 +--- src/test.c | 18 +++++---------- src/uuid.c | 57 +++++++++++++++++++++++++++++++++-------------- src/uuid.h | 13 ++++------ src/xend_internal.c | 62 +++++++++++++++++++--------------------------------- src/xm_internal.c | 31 +++++--------------------- src/xml.c | 61 --------------------------------------------------- src/xml.h | 1 14 files changed, 104 insertions(+), 219 deletions(-) Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|

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[Libvir] ANNOUNCE: Virt-top - a top-like utility for displaying virtualization stats
by Richard W.M. Jones 09 Aug '07

09 Aug '07

I'm pleased to announce the first release of virt-top, which is a top-like utility for displaying virtualization stats. It aims to look and feel very much like regular 'top', so as to be as familiar as possible for systems administrators. You can also use it as a pleasant replacement for xentop. It uses libvirt, so can display stats across a variety of different hypervisors and virtualization systems (not just Xen, although that is where the testing has gone so far). http://et.redhat.com/~rjones/virt-top/ The license is a combination of LGPL (for the library) and GPL (for the virt-top program). Current status -------------- You can view domains and use familiar keys like 'P'/'M'/... to sort by processor/memory/..., and 'd'/'s' to set the delay between updates. Also some common top command-line options are implemented. The man page is here: http://et.redhat.com/~rjones/virt-top/virt-top.txt There are a variety of source and binary RPMs available for Fedora users. I don't yet have a working Debian/Ubuntu package, but will have a go at making one tomorrow. The next thing I'll be working on is showing virtual and physical CPU usage of guests. After that I'm hoping to discuss extensions to libvirt to make other interesting statistics available to virt-top, in particular disk and network I/O stats. There are a few data collection artifacts which need to be investigated. In particular, %CPU sometimes goes over 100%. Obviously accurate data collection is an important goal for this tool. Memory usage is good: typical 'RES' (in regular top) for virt-top is just under 2.5 MB, and I've had it running for hours at a time without memory usage increasing, which seems to indicate that there aren't any major memory leaks. Development ----------- The program is currently very small: exactly 500 lines of code! If you want to dive in and send me patches they are most welcome, but remember that I'm trying to make this utility act as much like 'top' as possible, so if 'top' does it in a particular way, then I'd prefer virt-top to do the same thing. (May not apply to obscure top functionality, if top does something silly). If you're a systems administrator, not a programmer, and you'd like virt-top to have some particular feature, then please let me know, and I will be happy to review it and code it for you. Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903

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[Libvir] libvirt daemon UNIX socket auth with PolicyKit
by Daniel P. Berrange 08 Aug '07

08 Aug '07

Currently our authentication model for local connections is using the basic UNIX file permissions, possibly with a setuid helper (in Xen case only). It can be summarized as - If app using libvirt is running as root => full access - Else => read only access The latter is enforced by fact that in Xen case libvirt_proxy only has impl for a handful of read only APIs, or in non-Xen case that the UNIX domain socket for the daemon /var/run/libvirt/libvirt-sock is mode 0700, while /var/run/libvirt/libvirt-sock-ro is 0777 & the daemon enforces based on which socket the client connects to. This is good because it allows non-root to at least monitor guest state while requiring root authentication for actually changing state. This is bad because it requires any app which wants to change state to run as root. ie we are required to launch virt-manager as root to gain ability to manage local guests. Problem with this include: - running the entire PyGTK & GTK & X codebase as root is undesirable - no integration with the DBus desktop session (gnome-vfs integartion) - no integration with the GNOME keyring (for VNC server passwords) - redundant (&dangerous) if all you want to do is manage remote libvirt hosts In summary what I really need for virt-manager is - Always run as non-root - Authenticate for local guest management (ie read+write) UNIX domain sockets already provide a way for each end to identify the PID and UID of the other end. This enables the libvirt daemon to determine the identity of the application on the other end. With this information the daemon merely needs to check this identity against some access control policy rules. Where to get/define these rules though ? Enter PolicyKit. http://lists.freedesktop.org/archives/hal/2006-March/004770.html http://lists.freedesktop.org/archives/hal/2007-June/008815.html PolicyKit is a freedesktop.org project to replace all the distro specific 'do admin stuff as root' hacks like consolehelper[1], sudo, gksudo with a standard mechanism. Most importantly this mechanism does not require that the application in question run as root, or ever gain root privileges. In addition this is completely configurable by the administrator in a application independant manner. How would the daemon use PolicyKit for authenticating clients on UNIX domain sockets - libvirtd defines two actions it can check called 'libvirt-local-monitor (read only monitoring of state), and 'libvirt-local-manage' (full read-write management). - Both libvirt-sock and libvirt-sock-ro are mode 0777 (ie all users) - A connection arrives on the UNIX domain socket either libvirt-sock-ro or libvirt-sock - libvirtd use SO_PEERCRED to get the PID of the client - If the connection is on libvirt-sock-ro 'action' is 'libvirt-local-monitor' Else if connection is on libvirt-sock 'action' is 'libvirt-local-manage' - Libvirt asks policy kit if PID is allowed to perform the 'action' -> Yes, connection proceeds -> No, connection is dropped NB, having two separate UNIX domain sockets is strictly speaking redundant now - the daemon could simply check each 'action' in turn - but keeping the separate sockets simplifies the code, because it minimises the diffs when PolicyKit is not enabled by the 'configure' script. How is policy determined by PolicyKit ? - libvirt RPM provides /usr/share/PolicyKit/policy/libvirt.policy - This file defines the two actions it supports 'libvirt-local-monitor' and 'libvirt-local-manage'. - For each action we define a default policy for an active desktop session, and an inactive desktop session. The sample policy is to allow 'libvirt-local-monitor' for any local desktop session, but only allow 'libvirt-local-manage' for the active session with the additional requirement that the user authenticate with PolicyKit using the root password. This basically replicates the existing security semantics, without requiring that we run virt-manager itself as root. This accomplishes the core goal. There are other benefits to PolicyKit though - the administrator can override the application provided default Policy. For example, could add a rule that says "if the user fred is logged into the local X session, allow them to do 'libvirt-local-manage' without any further prompts for root password" Since PolicyKit is a general framework, that rule could be generalized beyond just virt-manager "if the user fred is logged into the local X session, allow them to do any defined action without any further prompts for root password" Or going the other way the administrator can lock things down requiring a root password even for read only monitoring of VMs. Or a halfway house of requiring the user's own password (sudo equiv, instead of su equiva). If course this doesn't just apply to virt-manager either. This transparently 'just works' for virsh too & any other apps using libvirt - eg if policy grants 'libvirt-local-manage' then you can do full management whether virsh is root or not. This all talks about enforcement of policy from the daemon side. There is one outstanding question - if the policy so requires, where/how do we ask the user to enter their credentials. PolicyKit provides two mechanisms for this: - A command line tool polkit-grant which uses pam to authenticate you as root, or using your own user password. If successful you will have been granted the permission to perform that action for the remainder of the session. - A DBus service for triggering display of some UI for authenticating. There is a GNOME impl of this service & likely a KDE impl too. eg with virsh start off without any priveleges $ virsh --connect qemu:///system net-list libvir: Remote error : Connection reset by peer error: failed to connect to the hypervisor error: no valid connection $ polkit-grant --action libvirtd-local-manage2 Authentication is required. Password: Keep this privilege for the session? [no/session]? $ ./src/virsh --connect qemu:///system net-list --all Name State Autostart ----------------------------------------- default active yes One option is to have the libvirt library spawn polkit-grant if not finding any $DISPLAY, and call the DBus service (for UI prompt) if finding any. The other option is to punt this code upto the application - eg virt-manager always call the DBus service, while virsh always call polkit-grant. Finally, PolicyKit is new in Fedora 8 if you wish to try this out. The configure script is setup so that it automagically detects presence of PolicyKit and only turns it on at compile time if its available. The fallback is to continue current behaviour of restricting based on the socket permissions. http://fedoraproject.org/wiki/Releases/FeaturePolicyKit Finally, finally, if we enable PolicyKit support, then we should disable the Xen specific libvirt_proxy setuid binary, since it would subvert the policy for libvirt-local-monitor. IMHO we should just kill the setuid binary altogether, since we already require that the libvirt daemon be running for the networking APIs & this provides read-only access already which works for non-Xen drivers too. Attaching the patch implementing the proof of concept $ diffstat ~/libvirt-policykit.patch configure.in | 60 ++++++++++++++++++-- qemud/Makefile.am | 12 +++- qemud/internal.h | 23 ++++++- qemud/libvirtd.policy | 41 ++++++++++++++ qemud/qemud.c | 145 ++++++++++++++++++++++++++++++++++++++++++++------ qemud/remote.c | 6 +- 6 files changed, 258 insertions(+), 29 deletions(-) Oh, finally, finally, finally. PolicyKit is pretty new so I'd understand if there's some resistance to including it in an official libvirt release at this point. I think the patch is small enough that we could carry it as add-on in the Fedora RPMs only to start with untill its proved to be maintainable long term - I really need this for Fedora 8 to make virt-manager work sanely - ie not need to run as root. Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|

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