[atlas] some probes not returning NSID

Hi all,

it appears that some probes never return NSID, when requested, while
others do, for the same query.

For example:

https://atlas.ripe.net/measurements/1875836/#!general

As you can see NSID is set to True.

These are the raw results from the two probes, for a one-off DNS UDM:

results = {

u'6012': [{u'lts': 230, u'proto': u'UDP', u'from': u'193.0.19.108',
u'msm_id': 1875836, u'af': 4, u'timestamp': 1424384037, u'fw': 4670,
u'msm_name': u'Tdig', u'prb_id': 6012, u'result': {u'abuf':
u'OQGEAAABAAEAAAABA29yZwAABgABwAwABgABAAADhAAzAmEwA29yZwthZmlsaWFzLW5zdARpbmZvAANub2PAKHfjQ2sAAAcIAAADhAAJOoAAAVGAAAApEAAAAAAAACUAAwAhbnMwMDBiLmFwcDcubnJ0MS5hZmlsaWFzLW5zdC5pbmZv',
u'rt': 312.971, u'NSCOUNT': 0, u'QDCOUNT': 1, u'answers': [{u'RNAME':
u'noc.afilias-nst.info.', u'NAME': u'org.', u'MNAME':
u'a0.org.afilias-nst.info.', u'TTL': 900, u'SERIAL': 2011382635,
u'TYPE': u'SOA'}], u'ID': 14593, u'ARCOUNT': 1, u'ANCOUNT': 1, u'size':
132}, u'src_addr': u'193.0.19.108', u'group_id': 1875836, u'type':
u'dns', u'dst_addr': u'199.19.56.1'}],

u'10039': [{u'lts': 166, u'proto': u'UDP', u'from': u'96.237.232.254',
u'msm_id': 1875836, u'af': 4, u'timestamp': 1424384040, u'fw': 4670,
u'msm_name': u'Tdig', u'prb_id': 10039, u'result': {u'abuf':
u'qxGAgAABAAEAAAABA29yZwAABgABwAwABgABAAAB3QAzAmEwA29yZwthZmlsaWFzLW5zdARpbmZvAANub2PAKHfjQ2UAAAcIAAADhAAJOoAAAVGAAAApD6AAAAAAAAA=',
u'rt': 8.299, u'NSCOUNT': 0, u'QDCOUNT': 1, u'answers': [{u'RNAME':
u'noc.afilias-nst.info.', u'NAME': u'org.', u'MNAME':
u'a0.org.afilias-nst.info.', u'TTL': 477, u'SERIAL': 2011382629,
u'TYPE': u'SOA'}], u'ID': 43793, u'ARCOUNT': 1, u'ANCOUNT': 1, u'size':
95}, u'src_addr': u'192.168.13.40', u'group_id': 1875836, u'type':
u'dns', u'dst_addr': u'199.19.56.1'}]

}

Sagan tells me, for probe 6012, responses[0].abuf.raw_data is:

{'HEADER': {'AA': True, 'QR': True, 'AD': False, 'NSCOUNT': 0,
'QDCOUNT': 1, 'ANCOUNT': 1, 'TC': False, 'RD': False, 'ARCOUNT': 1,
'CD': False, 'ReturnCode': 'NOERROR', 'OpCode': 'QUERY', 'RA': False,
'Z': 0, 'ID': 14593}, 'AnswerSection': [{'Retry': 900, 'Name': u'org.',
'NegativeTtl': 86400, 'Refresh': 1800, 'MasterServerName':
u'a0.org.afilias-nst.info.', 'Expire': 604800, 'MaintainerName':
u'noc.afilias-nst.info.', 'TTL': 900, 'Serial': 2011382635, 'Type':
'SOA', 'Class': 'IN', 'RDlength': 51}], 'QuestionSection': [{'Qclass':
'IN', 'Qtype': 'SOA', 'Qname': u'org.'}], 'EDNS0':
{'ExtendedReturnCode': 0, 'Option': [{'OptionCode': 3, 'OptionName':
'NSID', 'NSID': u'ns000b.app7.nrt1.afilias-nst.info', 'OptionLength':
33}], 'UDPsize': 4096, 'Version': 0, 'Z': 0, 'Type': 'OPT', 'Name': u'.'}}

NSID is present.

And for 10039:

{'HEADER': {'AA': False, 'QR': True, 'AD': False, 'NSCOUNT': 0,
'QDCOUNT': 1, 'ANCOUNT': 1, 'TC': False, 'RD': False, 'ARCOUNT': 1,
'CD': False, 'ReturnCode': 'NOERROR', 'OpCode': 'QUERY', 'RA': True,
'Z': 0, 'ID': 43793}, 'AnswerSection': [{'Retry': 900, 'Name': u'org.',
'NegativeTtl': 86400, 'Refresh': 1800, 'MasterServerName':
u'a0.org.afilias-nst.info.', 'Expire': 604800, 'MaintainerName':
u'noc.afilias-nst.info.', 'TTL': 477, 'Serial': 2011382629, 'Type':
'SOA', 'Class': 'IN', 'RDlength': 51}], 'QuestionSection': [{'Qclass':
'IN', 'Qtype': 'SOA', 'Qname': u'org.'}], 'EDNS0':
{'ExtendedReturnCode': 0, 'Option': [], 'UDPsize': 4000, 'Version': 0,
'Z': 0, 'Type': 'OPT', 'Name': u'.'}}

NSID is missing.

Why is this? I've tried increasing the payload size, this makes no
difference. I get the same when I try for SOA . @ k.root-servers.net:

Compare these outcomes:
https://atlas.ripe.net/measurements/1875933/
https://atlas.ripe.net/measurements/1875926/

It appears to me that probe 10039 (or its network) has a problem of
sorts, causing this. It would be great if faulty probes can be weeded
out, if this is really the case.

BTW, I am always getting "null" on the NSID field in the web interface,
regardless of whether it lives in abuf, or not. This seems to be a bug.

	~paul