dnscommon.r2py cannot parse replies containing MX type of queries and it doesn't support 'AAAA' records

[pranavnyu]

• for MX queries - dnscommon.r2py doesn't create dictionary from packet received from DNS. It gives an IndexError because of https://github.com/SeattleTestbed/seattlelib_v2/blob/master/dnscommon.r2py#L609 function _parse_address as it is limit to IPv4 address only. So, using wireshark and using same technique for the PTR, NS query it can be resolved.

User traceback:
  "dylink.r2py", line 546, in <module>
  "dylink.r2py", line 407, in dylink_dispatch
  "dylink.r2py", line 520, in evaluate
  "librepy.r2py", line 153, in <module>
  "dylink.r2py", line 446, in _dylink_dispatch
  "dylink.r2py", line 407, in dylink_dispatch
  "dylink.r2py", line 520, in evaluate
  "ut_dnsquery_recordsmx.r2py", line 11, in <module>
  "ut_dnsquery_recordsmx.r2py", line 8, in test_recordsMX
  "dnsquery.r2py", line 243, in recordsMX
  "dnsquery.r2py", line 140, in dns_connection
  "dnscommon.r2py", line 406, in convert_packet_to_dictionary
  "dnscommon.r2py", line 459, in _read_answer_section
  "dnscommon.r2py", line 500, in _read_single_answer
  "dnscommon.r2py", line 703, in _parse_address

Exception (with type 'exceptions.IndexError'): string index out of range

---

• for 'AAAA' records - dnscommon doesn't support 'AAAA' i.e. IPv6 records yet. Hence a new function like
  https://github.com/SeattleTestbed/seattlelib_v2/blob/master/dnscommon.r2py#L569 should be created for IPv6
  Few MX queries has 'AAAA' records in Additional section for eg. dig gmail.com mx. So, for implementing complete MX records we need 'AAAA' support too.

[pranavnyu]

We also need an enhancement for 'TXT' types of queries.
eg.

dig @8.8.8.8 google.com txt

; <<>> DiG 9.8.3-P1 <<>> @8.8.8.8 google.com txt
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 51625
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;google.com.            IN  TXT

;; ANSWER SECTION:
google.com.     3599    IN  TXT "v=spf1 include:_spf.google.com ip4:216.73.93.70/31 ip4:216.73.93.72/31 ~all"

So we need to get the text answer from the answer section. We can do something like 'AAAA' records and add this feature too.