I am adding braces around the for statement that are now needed to due the
new sa_assert immediately following the for statement.

* src/nwfilter/nwfilter_ebiptables_driver.c (ebiptablesApplyNewRules):
Don't dereference a NULL or uninitialized pointer when given
an empty list of rules.  Add an sa_assert(inst) in each loop to
tell clang that the uses of "inst[i]" are valid.

I am getting rid of determining the path to necessary CLI tools at
compile time. Instead, now the firewall driver has an initialization
function that uses virFindFileInPath() to determine the path to
necessary CLI tools and a shutdown function to free allocated memory.
The rest of the patch mostly deals with availability of the CLI tools
and to not call certain code blocks if a tool is not available and that
strings now have to be built slightly differently.

Changes from V1 to V2 of this patch
- I had reversed the logic thinking that icmp type 0 is a echo
request,but it's reply -- needed to reverse the logic
- Found that ebtables takes the --ip-tos argument only as a hex number

This patch enables the skipping of some of the ICMP traffic rules on the
iptables level under certain circumstances so that the following filter
properly enables unidirectional pings:

<filter name='testcase'>
    <uuid>d6b1a2af-def6-2898-9f8d-4a74e3c39558</uuid>
    <!-- allow incoming ICMP Echo Request -->
    <rule action='accept' direction='in' priority='500'>
        <icmp type='8'/>
    </rule>
    <!-- allow outgoing ICMP Echo Reply -->
    <rule action='accept' direction='out' priority='500'>
        <icmp type='0'/>
    </rule>
    <!-- drop all other ICMP traffic -->
    <rule action='drop' direction='inout' priority='600'>
        <icmp/>
    </rule>
</filter>

This patch implements support for learning a VM's IP address. It uses
the pcap library to listen on the VM's backend network interface (tap)
or the physical ethernet device (macvtap) and tries to capture packets
with source or destination MAC address of the VM and learn from DHCP
Offers, ARP traffic, or first-sent IPv4 packet what the IP address of
the VM's interface is. This then allows to instantiate the network
traffic filtering rules without the user having to provide the IP
parameter somewhere in the filter description or in the interface
description as a parameter. This only supports to detect the parameter
IP, which is for the assumed single IPv4 address of a VM. There is not
support for interfaces that may have multiple  IP addresses (IP
aliasing) or IPv6 that may then require more than one valid IP address
to be detected. A VM can have multiple independent interfaces that each
uses a different IP address and in that case it will be attempted to
detect each one of the address independently.

So, when for example an interface description in the domain XML has
looked like this up to now:

    <interface type='bridge'>
      <source bridge='mybridge'/>
      <model type='virtio'/>
      <filterref filter='clean-traffic'>
        <parameter name='IP' value='10.2.3.4'/>
      </filterref>
    </interface>

you may omit the IP parameter:

    <interface type='bridge'>
      <source bridge='mybridge'/>
      <model type='virtio'/>
      <filterref filter='clean-traffic'/>
    </interface>

Internally I am walking the 'tree' of a VM's referenced network filters
and determine with the given variables which variables are missing. Now,
the above IP parameter may be missing and this causes a libvirt-internal
thread to be started that uses the pcap library's API to listen to the
backend interface  (in case of macvtap to the physical interface) in an
attempt to determine the missing IP parameter. If the backend interface
disappears the thread terminates assuming the VM was brought down. In
case of a macvtap device a timeout is being used to wait for packets
from the given VM (filtering by VM's interface MAC address). If the VM's
macvtap device disappeared the thread also terminates. In all other
cases it tries to determine the IP address of the VM and will then apply
the rules late on the given interface, which would have happened
immediately if the IP parameter had been explicitly given. In case an
error happens while the firewall rules are applied, the VM's backend
interface is 'down'ed preventing it to communicate. Reasons for failure
for applying the network firewall rules may that an ebtables/iptables
command failes or OOM errors. Essentially the same failure reasons may
occur as when the firewall rules are applied immediately on VM start,
except that due to the late application of the filtering rules the VM
now is already running and cannot be hindered anymore from starting.
Bringing down the whole VM would probably be considered too drastic.
While a VM's IP address is attempted to be determined only limited
updates to network filters are allowed. In particular it is prevented
that filters are modified in such a way that they would introduce new
variables.

A caveat: The algorithm does not know which one is the appropriate IP
address of a VM. If the VM spoofs an IP address in its first ARP traffic
or IPv4 packets its filtering rules will be instantiated for this IP
address, thus 'locking' it to the found IP address. So, it's still
'safer' to explicitly provide the IP address of a VM's interface in the
filter description if it is known beforehand.

* configure.ac: detect libpcap
* libvirt.spec.in: require libpcap[-devel] if qemu is built
* src/internal.h: add the new ATTRIBUTE_PACKED define
* src/Makefile.am src/libvirt_private.syms: add the new modules and symbols
* src/nwfilter/nwfilter_learnipaddr.[ch]: new module being added
* src/nwfilter/nwfilter_driver.c src/conf/nwfilter_conf.[ch]
  src/nwfilter/nwfilter_ebiptables_driver.[ch]
  src/nwfilter/nwfilter_gentech_driver.[ch]: plu the new functionality in
* tests/nwfilterxml2xmltest: extend testing

The attached patch fixes a problem due to the mac match in iptables only
supporting --mac-source and no --mac-destination, thus it not being
symmetric. Therefore a rule like this one

<rule action='drop' direction='out'>
  <all match='no' srcmacaddr='$MAC'/>
</rule>

should only have the MAC match on traffic leaving the VM and not test
for the same source MAC address on traffic that the VM receives.

With Eric Blake's suggestions applied.

The following rule for direction 'in'

<rule direction='in' action='drop'>
  <mac srcmacaddr='1:2:3:4:5:6'/>
</rule>

drops all traffic from the given mac address.
The following rule for direction 'out'

<rule direction='out' action='drop'>
  <mac dstmacaddr='1:2:3:4:5:6'/>
</rule>

drops all traffic to the given mac address.
The following rule in direction 'inout'

<rule direction='inout' action='drop'>
  <mac srcmacaddr='1:2:3:4:5:6'/>
</rule>

now drops all traffic from and to the given MAC address.
So far it would have dropped traffic from the given MAC address
and outgoing traffic with the given source MAC address, which is not useful
since the packets will always have the VM's MAC address as source
MAC address. The attached patch fixes this.

This is the last bug I currently know of and want to fix.

This patch removes the virConnectPtr parameter from all functions where it's not necessary starting out with removing it as a parameter to the error reporting function.

- ebtables requires that some of the command line parameters are passed as hex numbers; so have those attributes call a function that prints 16 and 8 bit integers as hex nunbers.

- ip6tables requires '--icmpv6-type' rather than '--icmp-type'

- ebtables complains about protocol identifiers lower than 0x600, so already discard anything lower than 0x600 in the parser

- make the protocol entry types more readable using a #define for its entries

- continue parsing a filtering rule even if a faulty entry is encountered; return an error value at the end and let the caller decide what to do with the rule's object

- fix an error message

found some cases where the output ended up not looking as expected. So
the following changes are in the patch below:

- if the protocol ID in the MAC header is an integer, just write it into
the datastructure without trying to find a corresponding string for it
and if none is found failing
- when writing the protocol ID as string, simply write it as integer if
no corresponding string can be found
- same changes for arpOpcode parsing and printing
- same changes for protocol ID in an IP packet
- DSCP value needs to be written into the data structure
- IP protocol version number is redundant at this level, so remove it
- parse the protocol ID found inside an IP packet not only as string but
also as uint8
- arrange the display of the src and destination masks to be shown after
the src and destination ip address respectively in the XML
- the existing libvirt IP address parser accepts for example '25' as an
IP address. I want this to be parsed as a CIDR type netmask. So try to
parse it as an integer first (CIDR netmask) and if that doesn't work as
a dotted IP address style netmask.
- instantiation of rules with MAC masks didn't work because they weren't
printed into a buffer, yet.

This patch changes the network filtering code to use libvirt's existing
IPv4 and IPv6 address parsers/printers rather than my self-written ones.

I am introducing a new function in network.c that counts the number of
bits in a netmask and ensures that the given address is indeed a netmask,
return -1 on error or values of 0-32 for IPv4 addresses and 0-128 for
IPv6 addresses. I then based the function checking for valid netmask
on invoking this function.

This patch adds IPv6 filtering support for the following protocols:
- tcp-ipv6
- udp-ipv6
- udplite-ipv6
- esp-ipv6
- ah-ipv6
- sctp-ipv6
- all-ipv6
- icmpv6

Many of the IPv4 data structure could be re-used for IPv6 support.
Since ip6tables also supports pretty much the same command line parameters
as iptables does, also much of the code could be re-used and now
command lines are invoked with the ip(6)tables tool parameter passed
through the functions as a parameter.

This patch adds filtering support for the so-far missing protocols 'ah',
'esp' and 'udplite'.

This patch adds support for L3/L4 filtering using iptables. This adds
support for 'tcp', 'udp', 'icmp', 'igmp', 'sctp' etc. filtering.

As mentioned in the introduction, a .c file provided by this patch
is #include'd into a .c file. This will need work, but should be alright
for review.
Signed-off-by: NStefan Berger <stefanb@us.ibm.com>

This patch adds IPv6 support for the ebtables layer. Since the parser
etc. are all parameterized, it was fairly easy to add this...
Signed-off-by: NStefan Berger <stefanb@us.ibm.com>

This patch implements the core driver and provides
- management functionality for managing the filter XMLs
- compiling the internal filter representation into ebtables rules
- applying ebtables rules on a network (tap,macvtap) interface
- tearing down ebtables rules that were applied on behalf of an
interface
- updating of filters while VMs are running and causing the firewalls to
be rebuilt
- other bits and pieces
Signed-off-by: NStefan Berger <stefanb@us.ibm.com>