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When it is starting up, firewalld will delete all existing iptables rules and chains before adding its own rules. If libvirtd were to try to directly add iptables rules during the time before firewalld has finished initializing, firewalld would end up deleting the rules that libvirtd has just added. Currently this isn't a problem, since libvirtd only adds iptables rules via the firewalld "passthrough command" API, and so firewalld is able to properly serialize everything. However, we will soon be changing libvirtd to add its iptables and ebtables rules by directly calling iptables/ebtables rather than via firewalld, thus removing the serialization of libvirtd adding rules vs. firewalld deleting rules. This will especially apparent (if we don't fix it in advance, as this patch does) when libvirtd is responding to the dbus NameOwnerChanged event, which is used to learn when firewalld has been restarted. In that case, dbus sends the event before firewalld has been able to complete its initialization, so when libvirt responds to the event by adding back its iptables rules (with direct calls to /usr/bin/iptables), some of those rules are added before firewalld has a chance to do its "remove everything" startup protocol. The usual result of this is that libvirt will successfully add its private chains (e.g. LIBVIRT_INP, etc), but then fail when it tries to add a rule jumping to one of those chains (because in the interim, firewalld has deleted the new chains). The solution is for libvirt to preface it's direct calling to iptables with a iptables command sent via firewalld's passthrough command API. Since commands sent to firewalld are completed synchronously, and since firewalld won't service them until it has completed its own initialization, this will assure that by the time libvirt starts calling iptables to add rules, that firewalld will not be following up by deleting any of those rules. To minimize the amount of extra overhead, we request the simplest iptables command possible: "iptables -V" (and aside from logging a debug message, we ignore the result, for good measure). (This patch is being done *before* the patch that switches to calling iptables directly, so that everything will function properly with any fractional part of the series applied). Signed-off-by: Laine Stump <laine@redhat.com> Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Libvirt API for virtualization
Libvirt provides a portable, long term stable C API for managing the virtualization technologies provided by many operating systems. It includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER Hypervisor.
For some of these hypervisors, it provides a stateful management daemon which runs on the virtualization host allowing access to the API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other languages including Python, Perl, PHP, Go, Java, OCaml, as well as mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the website:
License
The libvirt C API is distributed under the terms of GNU Lesser
General Public License, version 2.1 (or later). Some parts of the code
that are not part of the C library may have the more restrictive GNU
General Public License, version 2.0 (or later). See the files
COPYING.LESSER and COPYING for full license
terms & conditions.
Installation
Instructions on building and installing libvirt can be found on the website:
https://libvirt.org/compiling.html
Contributing
The libvirt project welcomes contributions in many ways. For most components the best way to contribute is to send patches to the primary development mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
The libvirt project has two primary mailing lists:
- libvirt-users@redhat.com (for user discussions)
- libvir-list@redhat.com (for development only)
Further details on contacting the project are available on the website: