[libvirt] [PATCH V2 00/10] Make inner workings of nwfilters more flexible + extensions

The following series of patches re-does some of the inner workings of nwfilters with the goal to enable users to write filters that have other than the system-known chains supported right now ('root','arp','rarp','ipv4' and 'ipv6'). Ideally users should be able to provide a chain name in the chains XML attribute and either be able to jump to it as an 'action' or have the chain created automatically as it is the case right now for those chains enumerated before. The latter is now added in this patch series as well. I am first introducing internal priorities for the chains mentioned above so that their creation can be made more flexible -- currently their creation and the order in which they are accessed is hardcoded. This largely does away with the hardcoded stuff. All assigned priorities have negative values. Later on the priorities for the chains are made accessible via an XML attribute. Further, filters will be automatically accessed from the (ebtables) interface 'root' chain using the prefix of the name of the chain. As an example, the following filter will be accessed from the root chain for 'arp' packets since its name 'arp-xyz' has the prefix 'arp'. <filter name='test-arp-xyz' chain='arp-xyz' priority='-650'> <uuid>94abeecc-c956-0ac8-1f49-a06ee8995688</uuid> <rule action='accept' direction='out' priority='100'> <arp opcode='Request_Reverse' arpsrcmacaddr='$MAC' arpdstmacaddr='$MAC' arpsrcipaddr='0.0.0.0' arpdstipaddr='0.0.0.0'/> </rule> <rule action='accept' direction='inout' priority='500'/> </filter> In another step the priorities of rules is extended to also allow negativ values. This then allows the creation of rules and chains in the interface 'root' chain to be mixed so that the following layout becomes possible: Bridge chain: libvirt-I-vnet0, entries: 6, policy: ACCEPT -p IPv4 -j I-vnet0-ipv4 -p ARP -j I-vnet0-arp -p ARP -j ACCEPT -p 0x8035 -j I-vnet0-rarp -p 0x835 -j ACCEPT -j DROP In the above list of rules the '-p ARP -j ACCEPT' can now be found in between the 'jumps' to protocol-specific chains, which allows for more efficient rule evaluation. I did testing with the test cases in libvirt-tck as well as those in the tests/ directory and did not see any regressions. Regards, Stefan