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Libvirt native C API and daemons
b19863640d
When libvirt added support for firewalld, we were unable to use firewalld's higher level rules, because they weren't detailed enough and could not be applied to the iptables FORWARD or OUTPUT chains (only to the INPUT chain). Instead we changed our code so that rather than running the iptables/ip6tables/ebtables binaries ourselves, we would send these commands to firewalld as "passthrough commands", and firewalld would run the appropriate program on our behalf. This was done under the assumption that firewalld was somehow tracking all these rules, and that this tracking was benefitting proper operation of firewalld and the system in general. Several years later this came up in a discussion on IRC, and we learned from the firewalld developers that, in fact, adding iptables and ebtables rules with firewalld's passthrough commands actually has *no* advantage; firewalld doesn't keep track of these rules in any way, and doesn't use them to tailor the construction of its own rules. Meanwhile, users have been complaining for some time that whenever firewalld is restarted on a system with libvirt virtual networks and/or nwfilter rules active, the system logs would be flooded with warning messages whining that [lots of different rules] could not be deleted because they didn't exist. For example: firewalld[3536040]: WARNING: COMMAND_FAILED: '/usr/sbin/iptables -w10 -w --table filter --delete LIBVIRT_OUT --out-interface virbr4 --protocol udp --destination-port 68 --jump ACCEPT' failed: iptables: Bad rule (does a matching rule exist in that chain?). (See https://bugzilla.redhat.com/1790837 for many more examples and a discussion) Note that these messages are created by iptables, but are logged by firewalld - when an iptables/ebtables command fails, firewalld grabs whatever is in stderr of the program, and spits it out to the system log as a warning. We've requested that firewalld not do this (and instead leave it up to the calling application to do the appropriate logging), but this request has been respectfully denied. But combining the two problems above ( 1) firewalld doesn't do anything useful when you use it as a proxy to add/remove iptables rules, 2) firewalld often insists on logging lots of annoying/misleading/useless "error" messages when you use it as a proxy to remove iptables rules that don't already exist), leads to a solution - simply stop using firewalld to add and remove iptables rules. Instead, exec iptables/ip6tables/ebtables directly in the same way we do when firewalld isn't active. We still need to keep track of whether or not firewalld is active, as there are some things that must be done, e.g. we need to add some actual firewalld rules in the firewalld "libvirt" zone, and we need to take notice when firewalld restarts, so that we can reload all our rules. This patch doesn't remove the infrastructure that allows having different firewall backends that perform their functions in different ways, as that will very possibly come in handy in the future when we want to have an nftables direct backend, and possibly a "pure" firewalld backend (now that firewalld supports more complex rules, and can add those rules to the FORWARD and OUTPUT chains). Instead, it just changes the action when the selected backend is "firewalld" so that it adds rules directly rather than through firewalld, while leaving as much of the existing code intact as possible. In order for tests to still pass, virfirewalltest also had to be modified to behave in a different way (i.e. by capturing the generated commandline as it does for the DIRECT backend, rather than capturing dbus messages using a mocked dbus API). Signed-off-by: Laine Stump <laine@redhat.com> Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com> |
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==============================
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:
https://libvirt.org
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:
https://libvirt.org/contact.html