[LIBCLOUD-820] added check if libvirt uri is local

[Katana-Steel]

LIBCLOUD-820 added check if libvirt uri is local

Description

without this listing nodes on a remote libvirtd server will fail to
lookup the IPs in the arp cache.

Status

• done, ready for review

Checklist (tick everything that applies)

• Code linting (required, can be done after the PR checks)
• Documentation
• Tests
• ICLA (required for bigger changes)

[Katana-Steel]

a thing to note running arp on the systems I have access to (CentOS 6+7) requires root access.
maybe iproute2 should be a consideration to get IP from MAC address?

[Kami]

@Katana-Steel Thanks!

The change looks good to me.

As far as root requirement goes - I would prefer to stick to a tool which is available by default on most Linux distributions. Having said that, I would be fine with trying to use iproute2 first and falling back to arp if iproute2 is not available.

[Kami]

Minor improvement which would also make it easier to test separately would be to refactor this into two methods (e.g. _get_arp_table_using_arp_cmd and _get_arp_table_using_ip_cmd or something along those lines).

Anyways, not a blocker.

[Katana-Steel]

Hi Tomaz,

I had a version calling a different function for parsing the arp table of
'ip neighbor' but it looked like code duplication to me. So I rolled it
into the existing one.

I'd be happy to refactor it out into 2 functions. And update the tests when
they get in.

thanks
Rene
On May 28, 2016 10:25 AM, "Tomaz Muraus" notifications@github.com wrote:

In libcloud/compute/drivers/libvirt_driver.py
#788 (comment):

     mac_addresses = self._get_mac_addresses_for_domain(domain=domain)

•    cmd = ['arp', '-an']
  

•    child = subprocess.Popen(cmd, stdout=subprocess.PIPE,
  

•                             stderr=subprocess.PIPE)
  

•    stdout, _ = child.communicate()
  

•    arp_table = self._parse_arp_table(arp_output=stdout)
  

•    arp_table = {}
  

•    try:
  

•        cmd = ['arp', '-an']
  

•        child = subprocess.Popen(cmd, stdout=subprocess.PIPE,
  

Minor improvement which would also make it easier to test separately would
be to refactor this into two methods (e.g. _get_arp_table_using_arp_cmd
and _get_arp_table_using_ip_cmd or something along those lines).

Anyways, not a blocker.

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[Kami]

Thanks, I went ahead and merged changes into trunk.

I will add some tests in a separate commit (I was the one who originally added the driver without any tests, yeah, bad me!) :)