Smart Dialer Config

The Smart Dialer searches for a strategy that unblocks DNS and TLS for a given list of test domains. It takes a config describing multiple strategies to pick from.

YAML config for the Smart Dialer

The config that the Smart Dialer takes is in a YAML format. Here is an example:

dns:
  - system: {}
  - https:
      name: 8.8.8.8
  - https:
      name: 9.9.9.9
tls:
  - ""
  - split:2
  - tlsfrag:1

fallback:
  - ss://Y2hhY2hhMjAtaWV0Zi1wb2x5MTMwNTprSzdEdHQ0MkJLOE9hRjBKYjdpWGFK@1.2.3.4:9999/?outline=1

DNS Configuration

The dns field specifies a list of DNS resolvers to test.
Each DNS resolver can be one of the following types:
- system: Use the system resolver. Specify with an empty object.
- https: Use an encrypted DNS over HTTPS (DoH) resolver.
- tls: Use an encrypted DNS over TLS (DoT) resolver.
- udp: Use a UDP resolver.
- tcp: Use a TCP resolver.

DNS-over-HTTPS Resolver (DoH)

https:
  name: dns.google
  address: 8.8.8.8

name: The domain name of the DoH server.
address: The host:port of the DoH server. Defaults to name:443.

DNS-over-TLS Resolver (DoT)

tls:
  name: dns.google
  address: 8.8.8.8

name: The domain name of the DoT server.
address: The host:port of the DoT server. Defaults to name:853.

UDP Resolver

udp:
  address: 8.8.8.8

address: The host:port of the UDP resolver.

TCP Resolver

tcp:
  address: 8.8.8.8

address: The host:port of the TCP resolver.

TLS Configuration

The tls field specifies a list of TLS transports to test.
Each TLS transport is a string that specifies the transport to use.
For example, override:host=cloudflare.net|tlsfrag:1 specifies a transport that uses domain fronting with Cloudflare and TLS fragmentation. See the config documentation for details.

Fallback Configuration

A fallback configuration is used if none of the proxyless strategies are able to connect. For example it can specify a backup proxy server to attempt the user's connection. Using a fallback will be slower to start, since first the other DNS/TLS strategies must fail/timeout.

The fallback strings should be:

A valid StreamDialer config string as defined in configurl.
A valid Psiphon configuration object as a child of a psiphon field.

Shadowsocks server example

fallback:
  - ss://Y2hhY2hhMjAtaWV0Zi1wb2x5MTMwNTprSzdEdHQ0MkJLOE9hRjBKYjdpWGFK@1.2.3.4:9999/?outline=1

SOCKS5 server example

fallback:
  - socks5://[USERINFO]@[HOST]:[PORT]

Psiphon config example

To use the Psiphon network, you will need to:

Reach out to the Psiphon team to obtain a config that gives you access to their network. This may require a contract.
Add the received Psiphon config to the fallback section of your Smart Dialer config. Since JSON is compatible with YAML, you can copy and paste your Psiphon config directly into the fallback section, like this:

fallback:
  - psiphon: {
      "PropagationChannelId": "FFFFFFFFFFFFFFFF",
      "SponsorId": "FFFFFFFFFFFFFFFF",
      "DisableLocalSocksProxy" : true,
      "DisableLocalHTTPProxy" : true,
      ...
    }

How to Use the Smart Dialer

To use the Smart Dialer, create a StrategyFinder object and call the NewDialer method, passing in the list of test domains and the YAML config. The NewDialer method will return a transport.StreamDialer that can be used to create connections using the found strategy. For example:

finder := &smart.StrategyFinder{
    TestTimeout:  5 * time.Second,
    LogWriter:   os.Stdout,
    StreamDialer: &transport.TCPDialer{},
    PacketDialer: &transport.UDPDialer{},
}

configBytes := []byte(`
dns:
  - system: {}
  - https:
      name: 8.8.8.8
  - https:
      name: 9.9.9.9
tls:
  - ""
  - split:2
  - tlsfrag:1
fallback:
  - ss://Y2hhY2hhMjAtaWV0Zi1wb2x5MTMwNTprSzdEdHQ0MkJLOE9hRjBKYjdpWGFK@1.2.3.4:9999/?outline=1
`)

dialer, err := finder.NewDialer(
  context.Background(),
  []string{"www.google.com"},
  configBytes
)
if err != nil {
    // Handle error.
}

// Use dialer to create connections.

This is a basic example and may need to be adapted for your specific use case.