[atlas] Effect of "Resolve on Probe"-option

On Fri, Dec 01, 2017 at 03:44:22PM +0100,
 Tim Wattenberg <mail at timwattenberg.de> wrote 
 a message of 123 lines which said:

> In my measurement I activated the option to use the probes
> resolver(s) and left the option to resolve on the probe deactivated.

The documentation
<https://atlas.ripe.net/docs/api/v2/reference/#!/measurements/Dns_Type_Measurement_List_POST>
appears misleading here, for the specific case of DNS.

For DNS measurements:

'use_probe_resolver': True means using the probe's resolver(s),
typically obtained through DHCP

'use_probe_resolver': False means you have to indicate a name server
(resolver or authoritative) as a target.

Atlas rejects 'use_probe_resolver': False if you did not specify a
target:

Status 400, reason "{"error":{"status":400,"errors":[{"source":{"pointer":"/definitions/0"},"detail":"`target` cannot be null if `use_probe_resolver` is not specified"}],"code":102,"detail":"There was a problem with your request","title":"Bad Request"}}"

'resolve_on_probe' seems ignored.

Examples with atlas-resolve:

1) Use the probe's resolver(s):

% atlas-resolve -r 5 -v thepiratebay.org
{'definitions': [{'protocol': 'UDP', 'description': 'DNS resolution of thepiratebay.org', 'af': 4, 'query_argument': 'thepiratebay.org', 'query_type': 'A', 'query_class': 'IN', 'set_rd_bit': True, 'type': 'dns', 'use_probe_resolver': True}], 'is_oneoff': True, 'probes': [{'requested': 5, 'type': 'area', 'value': 'WW', 'tags': {'include': ['system-resolves-a-correctly', 'system-resolves-aaaa-correctly', 'system-ipv4-works']}}]}
Measurement #10397465 for thepiratebay.org/A uses 5 probes
[104.27.216.28 104.27.217.28] : 4 occurrences 
[213.46.185.10] : 1 occurrences 
Test #10397465 done at 2017-12-03T16:18:22Z

2) Use an external server (here, Quad9, option -e):

% atlas-resolve -r 5 -v -e 9.9.9.9 thepiratebay.org 
{'definitions': [{'protocol': 'UDP', 'description': 'DNS resolution of thepiratebay.org via nameserver 9.9.9.9', 'af': 4, 'query_argument': 'thepiratebay.org', 'query_type': 'A', 'query_class': 'IN', 'target': '9.9.9.9', 'set_rd_bit': True, 'type': 'dns', 'use_probe_resolver': False}], 'is_oneoff': True, 'probes': [{'requested': 5, 'type': 'area', 'value': 'WW', 'tags': {'include': ['system-ipv4-works']}}]}
Measurement #10397471 for thepiratebay.org/A uses 5 probes
Nameserver 9.9.9.9
[104.27.216.28 104.27.217.28] : 5 occurrences 
Test #10397471 done at 2017-12-03T16:19:41Z

In the case 1), measurement #10397465, the "dst_addr" field will indicate
the address of the resolver:

%         wget -q -O - https://atlas.ripe.net/api/v2/measurements/10397465/results/ | jq "map(.resultset) | flatten(1) | map(.dst_addr)" 
[
  "172.29.253.203",
  "172.29.254.203",
  "80.58.61.250",
  "80.58.61.254",
  "62.179.104.196",
  "213.46.228.196",
  "217.11.217.3",
  "217.11.217.13",
  "192.168.10.2",
  "208.67.222.222"
]

In the case 2), measurement #10397471:

 %  wget -q -O - https://atlas.ripe.net/api/v2/measurements/10397471/results/ | jq "map(.dst_addr)"
[
  "9.9.9.9",
  "9.9.9.9",
  "9.9.9.9",
  "9.9.9.9",
  "9.9.9.9"
]