February 2010 - Devel - libvirt List Archives

[libvirt] libvirt/dnsmasq integration.
by Simon Kelley 01 Mar '10

01 Mar '10

As the principal maintainer of dnsmasq, I'm seeing increasing reports of problems on systems which run both dnsmasq and libvirt. I'm fairly sure I understand what's going on in these cases, and I have a few proposals for changes in libvir and dnsmasq that should fix things. The problem is that libvirt runs a private instance of dnsmasq: on machines which are also running a "system" dnsmasq daemon, this can cause problems. Some background: dnsmasq can run in two modes. Default mode: dnsmasq binds the wildcard address and does network magic to determine which interface request packets actually come from, so that the results can be sent back with the correct source address. This has the advantage that network interfaces can come and go and change IP address and dnsmasq will keep working. It's possible to restrict dnsmasq to only reply to requests on some interfaces; requests from other interfaces will be read by dnsmasq and then silently dropped. Telling dnsmasq to use an interface which doesn't exist but might in the future will result in a logged warning, but dnsmasq will still start and when the interface comes up it will work. Bind-interfaces mode: This is the traditional way to do UDP servers. At startup dnsmasq enumerates all the extant interfaces and then opens a socket for each one, listening on the interfaces's IP address. Interfaces may be skipped if excluded by the --interface and --except-interface flags, and any interface specified in --interface which doesn't exist at start-up will generate a fatal error. In almost all cases, default mode is better: --bind-interfaces is only there to cope with old platforms which don't support enough socket options to do default mode. The only time when --bind-interfaces works better is when it's desirable to run more than one instance of dnsmasq or have dnsmasq co-exist with another DNS server. This is not possible in default mode, but it does work in bind-interfaces mode, providing than _all_ instances of dnsmasq are in bind-interfaces mode, and that they listen on a disjoint set of interfaces. Therefore, to allow multiple dnsmasq instances libvirt's private dnsmasq instance is started in bind-interfaces mode: that forces one of the dnsmasq instances to do bind-interfaces. Many of the Linux distibution dnsmasq packages have now implemented an /etc/dnsmasq.d directory where configuration fragments can be dropped. Their libvirt packages are putting a file there which contains a bind-interfaces command, so that the "system" dnsmasq is automatically forced into the same mode, and the two can co-exist. This works, sort-of, but there some disadvantages. Installing libvirt drops the configuration change for the system dnsmasq, but the packages frequently don't restart the system daemon, so that things transiently fail until everything has rebooted. Much worse, the system dnsmasq is forced into bind-interfaces mode and then service to transient interfaces (usb, ad-hoc wifi) no longer works, or, because those interfaces are mentioned in the dnsmasq configuration, dnsmasq now fails at start-up when the interfaces don't exist. I don't think there is a solution to this problem wholly within dnsmasq: the nature of the BSD-sockets universe means that there never be two instances of dnsmasq without bind-interfaces, and it's, at best, difficult to get round the limitations of that WRT transient network interfaces. There is, an alternative solution, which would involve changes to both dnsmasq, libvirt and their packaging. Hence this mail. My proposal is to get rid of the necessity for two dnsmasq instances. Libvirt should check for the existance of a "system" dnsmasq and, if the system daemon exists, libvirt should drop the required configuration into /etc/dnsmasq.d and then restart it. If the system daemon is not installed or enabled, libvirt can start a private instance as now. The difficulty with this scheme is that libvirt needs to create some configuration which enables the services it needs on the virtual network without disturbing, or being disturbed by, whatever configuration exists for the system daemon. That's not currently possible, but it can be made possible. I'm assuming that libvirt needs to provide a set of IP address / MAC address mappings, and range of IP addresses on a virtual network. It needs DHCP and DNS service on the virtual network. The dhcp-host IP/MAC mappings are a non-problem: they will be ignored for any other subnet where the IP addresses don't fit, and any other dhcp-hosts in the system configuration will be similarly ignored for DHCP on the virtual network subnet. The dhcp-range is more of a problem. Service to particular networks in dnsmasq is controlled by interface=<interface name"> lines in the configuration. If there are none of these, service is provided to all interfaces. If they exist, service is limited to the interfaces specified. The existence of any dhcp-range line in dnsmasq's configuration enables the DHCP server for any subnet unless explicitly limited to particular interfaces. So a default dnsmasq installation, (with no interface=<interface>) which provides DNS everywhere but DHCP nowhere would be turned into one which provided DHCP on every interface by libvirt adding a dhcp-range. Since there wouldn't be a suitable DHCP range for most subnets, this would only result in logged errors, but it is still not good. Worse, there's no good answer to the question 'should libvirt include interface=virt0"' in the configuration it supplies? If it does, then the "enable DHCP on all interfaces" problem is solved, but a default system configuration with no interface declaration is transformed from one which provides DNS everywhere to one which provides DNS only to the virtual interface. If libvirt doesn't provide "interface=virt0" and the system configuration includes interface declarations, then there will be no DNS or DHCP service to the virtual network. To solve this, I propose to add an optional interface name to the dhcp-range declaration. The semantics of this would be rather odd, but solve the problem perfectly. 1) for DHCP, if any other dhcp-range exists _without_ an interface name, them the interface name is ignored and and things behave as before, otherwise DHCP is only provided to interfaces mentioned in dhcp-range declarations. 2) for DNS, if there are no interface declarations, things work as before. If there are interface declarations, the interfaces mentioned in dhcp-ranges are added to the set which get DNS service. With these rules, it should be possible for libvirt to drop eg dhcp-range=interface:virt0,192.168.0.1,192.168.0.240 into the configuration of the system dnsmasq and get DHCP and DNS service for virt0, irrespective of any other configuration in the system dnsmasq, and doing so shouldn't affect the services supplied elsewhere. The code in libvirt to make this work looks like this: echo dhcp-range=interface:virt0,<ip range> >>/etc/dnsmasq.d/libvirt if <system dnsmasq is not installed or not enabled> dnsmasq --interface=virt0\ --bind-interfaces --conf-file=/etc/dnsmasq.d/libvirt else /etc/init.d/dnsmasq restart (The --bind-interfaces in the private-dnsmasq instance keeps dnsmasq from clashing with other nameservers eg BIND which may be running.) The system dnsmasq package has to ensure that /etc/dnsmasq.d is read for configuration fragments, and the dnsmasq package and the libvirt package will have to co-operate to manage transitions between private and system dnsmasq mode caused by package installation or removal. Does that make sense? It's a long and involved explanation to come to cold. I fear I may have over-simplified what libvirt is doing with dnsmasq, in which case please enlighten me and I'll modify my scheme to take that into account. If this looks good I can easily have the necessary dnsmasq changes in the next release. Cheers, Simon.

3 8

[libvirt] Problems with attach-device/detach-device using libvirt 0.7.6
by Rolf Eike Beer 01 Mar '10

01 Mar '10

Hi, first a short summary of what the situation is: I'm running qemu 0.12.2, libvirt 0.7.6 on a E5520 based machine with kernel 2.6.33. I also tried 2.6.32.7 as I was using that before and still had the old kernel around, but kernel version doesn't matter AFAICT. The host is a gentoo AMD64 installation, the client is SuSE 11.0 (both 32 and 64 bit tested). This system is our machine to run automated PCIe device tests on, so the idea is to move PCIe devices from the host to different vms, run some testcases there and then move them away again. This has worked before (I'm not absolutely sure, but I would bet a bit of money that it was libvirt 0.7.5). So, what I'm going to do is simply virsh # attach-device suse11.0-AMD64 dev-pci-AD1-CL.xml Device attached successfully virsh # detach-device suse11.0-AMD64 dev-pci-AD1-CL.xml Device detached successfully This is just was I expect and what I now get with the two patches attached. The original situation was somewhat different (i.e. broken): -first I got complains in the log stating: tried to create id "(null)" twice for "device" Well, adding two devices with the same id is bad, and if that id is a NULL pointer anyway IMHO it's better to not pass the parameter at all. That's what the "null-pci-id" patch does. -next, detaching failed. I found out that the command sent to qemu was " pci_del pci_addr=fc67add0:7f41:fe38b65a" which is obviously bogus. After some hours of digging through the command stack up and down I found that it was the memcpy addressed in the "pci_memcpy" patch. When the device is attached qemu just replies with an empty string. Afterwards from the guestAddr the address of the PCI device in the client is copied back to the info structure. Too bad that this structure was never initialized to anything useful (at least not for me). When I kick out the memcpy() everything works fine. Configuration files of one device and one guest are attached, the others look similar. Note: when the client PCI id is passed to qemu anyway it would be cool if that could be specified in the device XML. For USB devices, too. Eike Please keep me CC'ed as I'm not on the list.

2 3

[libvirt] [RFC] Proposal for introduction of network traffic filtering capabilities for filtering of network traffic from and to VMs
by Stefan Berger 01 Mar '10

01 Mar '10

Hello! The following is a proposal to introduce network traffic filtering capabilities for the network traffic originating from and destined to virtual machines. Libvirt's capabilities will be extended to allow users to describe what traffic filtering rules are to be applied on a virtual machine (using XML) and libvirt then creates the appropriate ebtables and iptables rules and applies those on the host when the virtual machine starts up, resumes after suspension or resumes on a new host after migration. libvirt tears down the traffic filtering rules when the virtual machine shuts down, suspends, or a VM is migrated to another host. It will also be possible to modify the filtering rules while a virtual machine is running. In this architecture we apply the firewall rules on the outside of the virtual machines on the Linux host and make use of the fact that virtual machines can be configured by libvirt to have their network traffic pass through the host and the host exposes (tap) 'backend' interfaces on which the firewall rules can be applied. The application of the firewall rules is optional and those who do not want to introduce a raw network throughput performance hit on their system due to the evaluation of every packet passing through the filtering chains, do not have to use these capabilities. An initial implementation would be done for libvirt's Qemu support. As stated above, the application of firewall rules on virtual machines will require some form of XML description that lets the user choose what type of filtering is to be performed. In effect the user needs to be able to tell libvirt which ebtables and iptables rules to generate so that the appropriate filtering can be done. We realize that ebtables and iptables have lots of capabilities but think that we need to restrict which capabilities can actually be 'reached' through this XML. The following proposal is based on an XML as defined by the DMTF ( http://www.dmtf.org/standards/cim/cim_schema_v2230/CIM_Network.pdf, slide 10) with extensions for processing of ARP packets.It gives control over the evaluation of Ethernet (MAC) frames, ARP packet data and IP header information. A (draft) XML skeleton in this case could look as follows: <FilterEntry> <Action>DROP|ACCEPT</Action>  <TrafficType>incoming [to VM]|outgoing [from VM]</TrafficType> <Hdr8021Filter> <HdrSrcMACAddr8021> </HdrSrcMACAddr8021> <HdrSrcMACMask8021> </HdrSrcMACMask8021> <HdrDestMACAddr8021> </HdrDestMACAddr8021> <HdrDestMACMask8021> </HdrDestMACMask8021> <HdrProtocolID8021> numeric and/or string? </HdrProtocolID8021> <HdrPriorityValue8021></HdrPriorityValue8021> <HdrVLANID8021> </HdrVLANID8021> </Hdr8021Filter> <ARPFilter> <HWType> </HWType> <ProtocolType> </ProtocolType> <OPCode> </OPCode> <SrcMACAddr> </SrcMACAddr> <SrcIPAddr> </SrcIPAddr> <DestMACAddr> </DestMACAddr> <DestIPAddr> </DestIPAddr> </ARPFilter> <IPHeadersFilter> <HdrIPVersion> </HdrIPVersion> <HdrSrcAddress> </HdrSrcAddress> <HdrSrcMask> </HdrSrcMask> <HdrDestAddress> </HdrDestAddress> <HdrDestMask> </HdrDestMask> <HdrProtocolID> numeric and/or string? </HdrProtocolID> <HdrSrcPortStart> </HdrSrcPortStart> <HdrSrcPortEnd> </HdrSrcPortEnd> <HdrDestPortStart> </HdrDestPortStart> <HdrDestPortEnd> </HdrDestPortEnd> <HdrDSCP> </HdrDSCP> </IPHeadersFilter> </FilterEntry> Since the ebtables and iptables command cannot accept all possible parameters at the same time, only a certain subset of the above parameters may be set for any given filter command. Higher level application writers will likely use a library that lets them choose which features they would want to have enforced, such as no-broadcast or no-multicast, enforcement of MAC spoofing prevention or ARP poisoning prevention, which then generates this lower level XML rules in the appropriate order of the rules. Further, we will introduce filter pools where a collection of the above filter rules can be stored and referenced to by virtual machines' individual interface. A reference to such a filter pool entry will be given in the interface description and may look as in the following draft XML: <interface type='bridge'> <source bridge='virbr0'/> <script path='vif-bridge'/> <firewall> <reference profile='generic-layer2' ip_address='10.0.0.1'/> <reference profile='VM-specific-layer3'/> </firewall> </interface> The above XML has one reference to a generic layer2 filter template XML that should be usable by multiple virtual machines but would need to be customized with interface-specific parameters. In this case, the IP address of the interface is explicitly provided in order to make the filter XML template a concrete XML for the particular interface. The MAC address of the interface is not explicitly provided since it will already have been randomly generated by libvirt at the point when this layer2 filter XML needs to be converted into concrete ebtables commands/rules. We still need to determine how the format of a template should look like, though an idea would be to indicate a placeholder for a VM's MAC address using THIS_MAC and similarly for the IP address with THIS_IP as placeholder. Further, we would introduce the management of filter 'pools'. Considering existing functionality in libvirt and CLI commands for similar type of management functionality, the following CLI commands would be added: virsh nwfilter-create <file> virsh nwfilter-destroy <profile name> virsh nwfilter-list <options> virsh nwfilter-dumpxml <profile name> virsh nwfilter-update <filename> (performs an update on an existing profile replacing all rules) possibly also: virsh nwfilter-edit <profile name> virsh nwfilter-create-from <profile name> Please let us know what you think of this proposal. Regards Stefan, Gerhard and Vivek

8 25

[libvirt] [PATCH] qemu: avoid null dereference on failed migration
by Eric Blake 01 Mar '10

01 Mar '10

From: Eric Blake <eblake(a)redhat.com> * src/qemu/qemu_monitor_text.c (qemuMonitorTextGetMigrationStatus): Check for failed strchr, to silence a coverity warning. Signed-off-by: Eric Blake <eblake(a)redhat.com> --- src/qemu/qemu_monitor_text.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-) diff --git a/src/qemu/qemu_monitor_text.c b/src/qemu/qemu_monitor_text.c index 62ffcc6..e7b4b1f 100644 --- a/src/qemu/qemu_monitor_text.c +++ b/src/qemu/qemu_monitor_text.c @@ -989,6 +989,11 @@ int qemuMonitorTextGetMigrationStatus(qemuMonitorPtr mon, if ((tmp = strstr(reply, MIGRATION_PREFIX)) != NULL) { tmp += strlen(MIGRATION_PREFIX); end = strchr(tmp, '\r'); + if (end == NULL) { + qemuReportError(VIR_ERR_INTERNAL_ERROR, + _("unexpected migration status in %s"), reply); + goto cleanup; + } *end = '\0'; if ((*status = qemuMonitorMigrationStatusTypeFromString(tmp)) < 0) { -- 1.6.6.1

3 2

[libvirt] [PATCH] Do not search xenstore for disk device IDs
by Jim Fehlig 01 Mar '10

01 Mar '10

Disk devices can be referenced by name in Xen, e.g. when modifying their configuration or remvoving them. As such, don't search xenstore for a device ID corresponding to the disk device. Instead, search the disks contained in the domain definition and use the disk's target name if found. This approach allows removing a disk when domain is inactive. We obviously can't search xenstore when the domain is inactive. --- src/xen/xend_internal.c | 38 +++++++++++++++++++++++--------------- 1 files changed, 23 insertions(+), 15 deletions(-) diff --git a/src/xen/xend_internal.c b/src/xen/xend_internal.c index 9d95291..d0d32e2 100644 --- a/src/xen/xend_internal.c +++ b/src/xen/xend_internal.c @@ -93,6 +93,7 @@ xenDaemonFormatSxprOnePCI(virConnectPtr conn, static int virDomainXMLDevID(virDomainPtr domain, + virDomainDefPtr domDef, virDomainDeviceDefPtr dev, char *class, char *ref, @@ -4212,7 +4213,7 @@ xenDaemonAttachDeviceFlags(virDomainPtr domain, const char *xml, sexpr = virBufferContentAndReset(&buf); - if (virDomainXMLDevID(domain, dev, class, ref, sizeof(ref))) { + if (virDomainXMLDevID(domain, def, dev, class, ref, sizeof(ref))) { /* device doesn't exist, define it */ ret = xend_op(domain->conn, domain->name, "op", "device_create", "config", sexpr, NULL); @@ -4306,7 +4307,7 @@ xenDaemonDetachDeviceFlags(virDomainPtr domain, const char *xml, def, xml, VIR_DOMAIN_XML_INACTIVE))) goto cleanup; - if (virDomainXMLDevID(domain, dev, class, ref, sizeof(ref))) + if (virDomainXMLDevID(domain, def, dev, class, ref, sizeof(ref))) goto cleanup; if (dev->type == VIR_DOMAIN_DEVICE_HOSTDEV) { @@ -6048,6 +6049,7 @@ error: */ static int virDomainXMLDevID(virDomainPtr domain, + virDomainDefPtr domDef, virDomainDeviceDefPtr dev, char *class, char *ref, @@ -6056,27 +6058,33 @@ virDomainXMLDevID(virDomainPtr domain, xenUnifiedPrivatePtr priv = domain->conn->privateData; char *xref; char *tmp; + unsigned int i; + virDomainDiskDefPtr disk; if (dev->type == VIR_DOMAIN_DEVICE_DISK) { + if (dev->data.disk->dst == NULL) + return -1; if (dev->data.disk->driverName && STREQ(dev->data.disk->driverName, "tap")) strcpy(class, "tap"); else strcpy(class, "vbd"); - if (dev->data.disk->dst == NULL) - return -1; - xenUnifiedLock(priv); - xref = xenStoreDomainGetDiskID(domain->conn, domain->id, - dev->data.disk->dst); - xenUnifiedUnlock(priv); - if (xref == NULL) - return -1; - - tmp = virStrcpy(ref, xref, ref_len); - VIR_FREE(xref); - if (tmp == NULL) - return -1; + /* For disks, the device name can be used directly. + * If disk device exists in domain definintion, + * copy it to ref and return success. + */ + for (i = 0; i < domDef->ndisks; i++) { + disk = domDef->disks[i]; + if (STREQ(dev->data.disk->dst, disk->dst)) { + tmp = virStrcpy(ref, disk->dst, ref_len); + if (tmp == NULL) + return -1; + else + return 0; + } + } + return -1; } else if (dev->type == VIR_DOMAIN_DEVICE_NET) { char mac[30]; virDomainNetDefPtr def = dev->data.net; -- 1.6.0.2

3 4

[libvirt] (no subject)
by Daniel P. Berrange 01 Mar '10

01 Mar '10

Repost of http://www.redhat.com/archives/libvir-list/2010-February/msg00177.html The virsh output is now scaled to show KB/MB as needed, instead of always bytes. The public API gained extra status VIR_DOMAIN_JOB_COMPLETED = 3, /* Job has finished, but isn't cleaned up */ VIR_DOMAIN_JOB_FAILED = 4, /* Job hit error, but isn't cleaned up */ VIR_DOMAIN_JOB_CANCELLED = 6, /* Job was aborted, but isn't cleaned up */ to allow to more easily detecting end of a job, once we allow for truely async usage

2 21

[libvirt] [PATCH] [macvtap] interface type direct web docs addition
by Stefan Berger 01 Mar '10

01 Mar '10

This adds a description about the 'direct' type of interface recently added for macvtap device type support on the host.

3 2

[libvirt] [PATCH] Free the macvtap mode string
by Stefan Berger 01 Mar '10

01 Mar '10

I forgot to free the macvtap mode string. This fixes it. Signed-off-by: Stefan Berger <stefanb(a)us.ibm.com>

3 2

[libvirt] Hypervisor raw options
by Daniel Dehennin 01 Mar '10

01 Mar '10

Hello, I wonder if it's possible to add hypervisor pass-through options, I add some usage of kvm -startdate and need to use a script which call kvm with the desired option. Something like: <emulator>/usr/bin/kvm</emulator> <emulator-options> <option>-option1</option> <option>-option2</option> </emulator-options> The several <option/> will be passed to the <emulator/> command. Regards. -- Daniel Dehennin Récupérer ma clef GPG: gpg --keyserver pgp.mit.edu --recv-keys 0x6A2540D1

2 1

[libvirt] [PATCH] build: avoid warning about unused variables
by Jim Meyering 01 Mar '10

01 Mar '10

>From 8ddff3e6cdccc2b4289509c6941b43f2ddf8e643 Mon Sep 17 00:00:00 2001 From: Jim Meyering <meyering(a)redhat.com> Date: Thu, 25 Feb 2010 14:19:33 +0100 Subject: [PATCH] build: avoid warning about unused variables * tools/virsh.c (cmdCPUBaseline): Remove declarations of unused variables, p and cur. --- tools/virsh.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/tools/virsh.c b/tools/virsh.c index 5fdbbe5..89eefcf 100644 --- a/tools/virsh.c +++ b/tools/virsh.c @@ -7048,12 +7048,11 @@ cmdCPUBaseline(vshControl *ctl, const vshCmd *cmd) int found; int ret = TRUE; char *buffer; - char *p; char *result = NULL; const char **list = NULL; unsigned int count = 0; xmlDocPtr doc = NULL; - xmlNodePtr node_list, cur; + xmlNodePtr node_list; xmlXPathContextPtr ctxt = NULL; xmlSaveCtxtPtr sctxt = NULL; xmlBufferPtr buf = NULL; -- 1.7.0.401.g84adb

2 1