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torsf: document persistent datadir and rendezvous method
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This diff documents new options we have added to the torsf experiment
after the ooni/probe#2004 discussion.

The related probe-cli PR is: ooni/probe-cli#683
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@bassosimone
bassosimone authored Feb 7, 2022
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163 changes: 147 additions & 16 deletions nettests/ts-030-torsf.md
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# Specification version number

2021-06-18-001
2022-02-07-001

* _status_: experimental

Expand All @@ -20,7 +20,27 @@ pluggable transport (PT) within a reasonable timeout.

# Expected inputs

None
This test does not take any input. Yet, it accepts options when using
`miniooni` via the `-O` command line flag.

These options are available:

- `DisablePersistentDatadir` (type: `bool`, default value: `false)`: this
option allows to disable using a persistent `tor` datadir for the `torsf`
experiment. The default is to use a persistent datadir.

- `DisableProgress` (type: `bool`, default value: `false`): this option
allows you to disable printing progress.

- `RendezvousMethod` (type: `str`, default value: `""`): this option
chooses between the `"amp"` and `"domain_fronting"` Snowflake rendezvous
methods. A `""` value for this option indicates we should be using
the default rendezvous method (`"domain_fronting"` as of 2022-02-07).

These options and their values may change at a later time, once we have
improved our understanding of the `torsf` experiment. See
[probe#2004](https://github.com/ooni/probe/issues/2004) for more context
on what led us to add these options.

# Test description

Expand All @@ -34,9 +54,17 @@ where `PORT` is a port on the local host managed by OONI that speaks
the SOCKS5 protocol, and `ADDR_PORT` and `FINGERPRINT` describe a
Snowflake bridge.

If `DisablePersistentDatadir` is `false`, `torsf` will use a persistent
datadir at `$OONI_HOME/tunnel/torsf/tor` otherwise the datadir will
be inside a temporary directory. Using a persistent datadir means that
`tor` will already have some cached information to make the bootstrap
faster when using Snowflake (more on this later).

The listening port will accept connections from the `tor` daemon and
forward bytes back and forth over a Snowflake connection created using
Snowflake's PTv2.1 capabilities.
Snowflake's PTv2.1 capabilities. Depending on the `RendezvousMethod`
config value, Snowflake will use `"amp"` or `"domain_fronting"` as the
rendezvous method.

The result of this test can be one of the following:

Expand All @@ -58,7 +86,11 @@ considered as a failure to start the test up;
```JSON
{
"bootstrap_time": 1.1,
"failure": null
"failure": null,
"persistent_datadir": true,
"rendezvous_method": "domain_fronting",
"tor_logs": [],
"tor_version": ""
}
```

Expand All @@ -67,41 +99,140 @@ where:
- `bootstrap_time` (`float`) is zero if the bootstrap times out and otherwise is
the number of seconds it required to bootstrap;

- `failure` conforms to `df-007-errors`.
- `failure` conforms to `df-007-errors`;

- `persistent_datadir` (`bool`) is the value of the `PersistentDatadir` option;

- `rendezvous_method` (`string`) is the value of the `RendezvousMethod` option;

- `tor_logs` (`[]string`) is a list of bootstrap-related logs emitted by
the tor daemon during the bootstrap;

- `tor_version` (`string`) is the version of `tor` we're using.

## Possible conclusions

Whether we can successfully bootstrap `tor` using the Snowflake PT.
Whether we can successfully bootstrap `tor` using the Snowflake PT. See also
the [data analysis considerations](#data-analysis-considerations) section below.

## Example output sample

```json
{
"annotations": {
"architecture": "arm64",
"engine_name": "ooniprobe-engine",
"engine_version": "3.11.0-alpha",
"engine_version": "3.14.0-alpha.1",
"platform": "macos"
},
"data_format_version": "0.2.0",
"input": null,
"measurement_start_time": "2021-06-18 10:34:27",
"measurement_start_time": "2022-02-07 11:47:37",
"probe_asn": "AS30722",
"probe_cc": "IT",
"probe_ip": "127.0.0.1",
"probe_network_name": "Vodafone Italia S.p.A.",
"report_id": "",
"report_id": "20220207T114738Z_torsf_IT_30722_n1_rK0MhS3m1DHoXoOm",
"resolver_asn": "AS30722",
"resolver_ip": "91.80.36.92",
"resolver_ip": "91.80.36.88",
"resolver_network_name": "Vodafone Italia S.p.A.",
"software_name": "miniooni",
"software_version": "3.11.0-alpha",
"software_version": "3.14.0-alpha.1",
"test_keys": {
"bootstrap_time": 41.677585167,
"failure": null
"bootstrap_time": 316.569053291,
"failure": null,
"persistent_datadir": true,
"rendezvous_method": "domain_fronting",
"tor_logs": [
"Feb 07 12:42:20.000 [notice] Bootstrapped 0% (starting): Starting",
"Feb 07 12:42:20.000 [notice] new bridge descriptor 'flakey1' (cached): $2B280B23E1107BB62ABFC40DDCC8824814F80A72~flakey1 [1zOHpg+FxqQfi/6jDLtCpHHqBTH8gjYmCKXkus1D5Ko] at 192.0.2.3",
"Feb 07 12:42:20.000 [notice] new bridge descriptor 'flakey3' (cached): $2B280B23E1107BB62ABFC40DDCC8824814F80A72~flakey3 [1zOHpg+FxqQfi/6jDLtCpHHqBTH8gjYmCKXkus1D5Ko] at 192.0.2.3",
"Feb 07 12:42:20.000 [notice] Bootstrapped 1% (conn_pt): Connecting to pluggable transport",
"Feb 07 12:42:20.000 [notice] Bootstrapped 2% (conn_done_pt): Connected to pluggable transport",
"Feb 07 12:42:20.000 [notice] Bootstrapped 10% (conn_done): Connected to a relay",
"Feb 07 12:47:32.000 [notice] Bootstrapped 14% (handshake): Handshaking with a relay",
"Feb 07 12:47:33.000 [notice] Bootstrapped 15% (handshake_done): Handshake with a relay done",
"Feb 07 12:47:33.000 [notice] Bootstrapped 75% (enough_dirinfo): Loaded enough directory info to build circuits",
"Feb 07 12:47:34.000 [notice] Bootstrapped 90% (ap_handshake_done): Handshake finished with a relay to build circuits",
"Feb 07 12:47:34.000 [notice] Bootstrapped 95% (circuit_create): Establishing a Tor circuit",
"Feb 07 12:47:37.000 [notice] Bootstrapped 100% (done): Done"
],
"tor_version": "0.4.6.9"
},
"test_name": "torsf",
"test_runtime": 41.890146875,
"test_start_time": "2021-06-18 10:34:27",
"test_version": "0.1.0"
"test_runtime": 316.935133083,
"test_start_time": "2022-02-07 11:42:20",
"test_version": "0.2.0"
}
```

## Data analysis considerations

From [probe#2004](https://github.com/ooni/probe/issues/2004), we know that
_generally_ using a persistent data dir improves the bootstrap time. We have
seen this strategy to be particularly successful on mobile devices.

That said, we have empirically also seen cases of long bootstraps when
using a persistent data dir. So, we cannot conclude _a priori_ that using
a persistent data dir necessarily leads to faster bootstrap times _in
all cases_.

To figure out whether `tor` had enough cached information to perform an
in-theory-fastest bootstrap, you should look into the sequence of bootstrap
events. The following bootstrap (which, by the way, too 316 seconds to
complete) did not require `tor` to fetch _additional_ information because
its datadir already contained a fresh cache:

```json
{
"tor_logs": [
"Feb 07 12:42:20.000 [notice] Bootstrapped 0% (starting): Starting",
"Feb 07 12:42:20.000 [notice] new bridge descriptor 'flakey1' (cached): $2B280B23E1107BB62ABFC40DDCC8824814F80A72~flakey1 [1zOHpg+FxqQfi/6jDLtCpHHqBTH8gjYmCKXkus1D5Ko] at 192.0.2.3",
"Feb 07 12:42:20.000 [notice] new bridge descriptor 'flakey3' (cached): $2B280B23E1107BB62ABFC40DDCC8824814F80A72~flakey3 [1zOHpg+FxqQfi/6jDLtCpHHqBTH8gjYmCKXkus1D5Ko] at 192.0.2.3",
"Feb 07 12:42:20.000 [notice] Bootstrapped 1% (conn_pt): Connecting to pluggable transport",
"Feb 07 12:42:20.000 [notice] Bootstrapped 2% (conn_done_pt): Connected to pluggable transport",
"Feb 07 12:42:20.000 [notice] Bootstrapped 10% (conn_done): Connected to a relay",
"Feb 07 12:47:32.000 [notice] Bootstrapped 14% (handshake): Handshaking with a relay",
"Feb 07 12:47:33.000 [notice] Bootstrapped 15% (handshake_done): Handshake with a relay done",
"Feb 07 12:47:33.000 [notice] Bootstrapped 75% (enough_dirinfo): Loaded enough directory info to build circuits",
"Feb 07 12:47:34.000 [notice] Bootstrapped 90% (ap_handshake_done): Handshake finished with a relay to build circuits",
"Feb 07 12:47:34.000 [notice] Bootstrapped 95% (circuit_create): Establishing a Tor circuit",
"Feb 07 12:47:37.000 [notice] Bootstrapped 100% (done): Done"
],
}
```

Conversely, this bootstrap required `tor` to fetch additional information (and, again,
anecdotally, it took 67 seconds to complete):

```json
{
"tor_logs": [
"Feb 07 12:38:29.000 [notice] Bootstrapped 0% (starting): Starting",
"Feb 07 12:38:29.000 [notice] Bootstrapped 1% (conn_pt): Connecting to pluggable transport",
"Feb 07 12:38:29.000 [notice] Bootstrapped 2% (conn_done_pt): Connected to pluggable transport",
"Feb 07 12:38:29.000 [notice] Bootstrapped 10% (conn_done): Connected to a relay",
"Feb 07 12:38:43.000 [notice] Bootstrapped 14% (handshake): Handshaking with a relay",
"Feb 07 12:38:45.000 [notice] Bootstrapped 15% (handshake_done): Handshake with a relay done",
"Feb 07 12:38:45.000 [notice] Bootstrapped 20% (onehop_create): Establishing an encrypted directory connection",
"Feb 07 12:38:46.000 [notice] Bootstrapped 25% (requesting_status): Asking for networkstatus consensus",
"Feb 07 12:38:46.000 [notice] new bridge descriptor 'flakey1' (fresh): $2B280B23E1107BB62ABFC40DDCC8824814F80A72~flakey1 [1zOHpg+FxqQfi/6jDLtCpHHqBTH8gjYmCKXkus1D5Ko] at 192.0.2.3",
"Feb 07 12:38:49.000 [notice] Bootstrapped 30% (loading_status): Loading networkstatus consensus",
"Feb 07 12:38:52.000 [notice] Bootstrapped 45% (requesting_descriptors): Asking for relay descriptors",
"Feb 07 12:38:52.000 [notice] Bootstrapped 58% (loading_descriptors): Loading relay descriptors",
"Feb 07 12:38:58.000 [notice] Bootstrapped 65% (loading_descriptors): Loading relay descriptors",
"Feb 07 12:39:04.000 [notice] Bootstrapped 73% (loading_descriptors): Loading relay descriptors",
"Feb 07 12:39:04.000 [notice] Bootstrapped 75% (enough_dirinfo): Loaded enough directory info to build circuits",
"Feb 07 12:39:05.000 [notice] Bootstrapped 76% (ap_conn_pt): Connecting to pluggable transport to build circuits",
"Feb 07 12:39:05.000 [notice] Bootstrapped 77% (ap_conn_done_pt): Connected to pluggable transport to build circuits",
"Feb 07 12:39:05.000 [notice] Bootstrapped 85% (ap_conn_done): Connected to a relay to build circuits",
"Feb 07 12:39:13.000 [notice] Bootstrapped 89% (ap_handshake): Finishing handshake with a relay to build circuits",
"Feb 07 12:39:15.000 [notice] Bootstrapped 90% (ap_handshake_done): Handshake finished with a relay to build circuits",
"Feb 07 12:39:15.000 [notice] Bootstrapped 95% (circuit_create): Establishing a Tor circuit",
"Feb 07 12:39:36.000 [notice] Bootstrapped 100% (done): Done"
],
}
```

Thus, we can say that there is enough cached information is the bootstrap jumps from
`15% (handshake_done)` to `75% (enough_dirinfo)`.

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