Fix fast-reboot-dump.py ipaddress error

[kuanyu99]

- What I did

Fix weird behavior when using ipaddress to parse the ipv4 and ipv6 address.

- How I did it

Instead of using ipaddress.ip_interface(IP_ADDR), I change to use ipaddress.IPv4Address to check if the ip address is ipv4.
The same method is also used inside sonic-utilities/config/nat.py

- How to verify it

When there are some mac learned by SONIC, execute the fast-reboot. It should not return error.

- Previous command output (if the output of a command-line utility has changed)

Sep 28 08:26:16.418276 as8000-3 ERR fast-reboot-dump: Got an exception '192.168.0.208' does not appear to be an IPv4 or IPv6 interface:
Traceback:
 Traceback (most recent call last):
  File "/usr/bin/fast-reboot-dump.py", line 298, in <module>
    res = main()
  File "/usr/bin/fast-reboot-dump.py", line 289, in main
    neighbor_entries = generate_neighbor_entries(root_dir + '/arp.json', all_available_macs)
  File "/usr/bin/fast-reboot-dump.py", line 42, in generate_neighbor_entries
    if ipaddress.ip_interface(ip_addr).ip.version != 4:
  File "/usr/local/lib/python2.7/dist-packages/ipaddress.py", line 239, in ip_interface
    address)
ValueError: '192.168.0.208' does not appear to be an IPv4 or IPv6 interface

- New command output (if the output of a command-line utility has changed)

[kuanyu99]

Retest this please

[kuanyu99]

Retest this please

[tahmed-dev]

@kuanyu99 Thanks for efforts. the issue could be fixed in Python 2 bu decoding the string as unicode:

print("IP version: %s" % ipaddress.ip_interface('192.168.0.208'.decode()).ip.version)
IP version: 4

In Python 3 this above is not required.

[kuanyu99]

@tahmed-dev Thank you very much! This information help me a lot.

But there are still have other problems.
The ipv6 version fdb items in the redis-db looks like "NEIGH_TABLE:Vlan1000:fe80::XXXXXX". After parsing, the ip_addr equal to "fe80" which will return AddressValueError during calling ipaddress.

[lguohan]

is there anything missing in the unit test?

[bingwang-ms]

I found the same issue and created another PR #1164 to do a fix. Sorry for not founding this PR. Both PR address the issue, but I think #1164 is more elegant in both python 2 and python 3.

[kuanyu99]

I found the same issue and created another PR #1164 to do a fix. Sorry for not founding this PR. Both PR address the issue, but I think #1164 is more elegant in both python 2 and python 3.

No problem. I didn't consider the python3 case. I also think your solution is better.
I will close this ticket once that PR is merged.

[kuanyu99]

Due to #1164 has been merged, close this PR.