HTTP/2 client inside HTTP/1.1 proxy connection

[levshkatov]

I want to open a connection to proxy server and then establish H2 connection inside first one to target server. I know, that ProxyAgent has allowH2 option, but it doesn't work for me, I suppose because proxy server doesn't support H2.

import { Client, ProxyAgent, request } from 'undici';

const test = async () => {
  try {
    const proxy = new ProxyAgent({
      uri: `http://host:port`,
      token: `Basic ${Buffer.from(`user:pass`).toString('base64')}`,
      // allowH2: true // not working because proxy server seems not handle H2
    });

    const h2Client = new Client('https://api.ipify.org', {
      allowH2: true,
      // connect: {
      //   rejectUnauthorized: false,
      //   ...(await proxy.connect({ origin: 'http://host:port', path: '/' })), // not working
      // },
    });

    const { body, statusCode } = await request(
      `https://api.ipify.org?format=json`,
      {
        dispatcher: h2Client,
      }
    );

    console.log(statusCode);
    const data = await body.json();
    console.log(data);
  } catch (e) {
    console.log(e);
  }
};

await test();

I also tried to implement following answer using undici but didn't get the result.
Is it possible?

[metcoder95]

Do you have the error that is thrown when attempting to connect?

[metcoder95]

That's slightly more complex, another way (and maybe better) it is to do something similar as we do for ProxyAgent, where an Agent is used to manage that upgrade.

See:

undici/lib/dispatcher/proxy-agent.js

Line 63 in 0ad6007

this[kAgent] = new Agent({

Which overall to override the whole connect property.

[levshkatov]

Thank you for your answer, good point to start but it looks a bit difficult to me because of lack of docs about connect and socket upgrade. I tried following code, but got an error

const proxyAgent = new ProxyAgent({
  uri: 'proxy',
  token: `Basic ${Buffer.from('user:pass').toString('base64')}`,
});

const connector = buildConnector({ allowH2: true });

const h2 = new Agent({
  allowH2: true,
  connect: async (opts, callback) => {
    try {
      const { socket } = await proxyAgent.connect({
        origin: 'https://api.ipify.org',
        path: '/',
      });
      connector({ ...opts, servername: 'api.ipify.org', httpSocket: socket }, callback);
    } catch (e) {
      if (err.code === 'ERR_TLS_CERT_ALTNAME_INVALID') {
        // Throw a custom error to avoid loop in client.js#connect
        callback(new SecureProxyConnectionError(err));
      } else {
        callback(err);
      }
    }
  },
});

const { statusCode, headers, body } = await request('https://api.ipify.org/?format=json', {
  dispatcher: h2,
});

Error: Error: 40284C41517F0000:error:0A00010B:SSL routines:ssl3_get_record:wrong version number:../deps/openssl/openssl/ssl/record/ssl3_record.c:354:

    at initRead (node:_tls_wrap:502:25)
    at process.processTicksAndRejections (node:internal/process/task_queues:82:21) {
  library: 'SSL routines',
  reason: 'wrong version number',
  code: 'ERR_SSL_WRONG_VERSION_NUMBER'
}

I'm a bit confused in all these path, origin, servername. Maybe I provide wrong info for any of it. Could you help?

[levshkatov]

My main idea is to build one agent on another (h2 based on proxyAgent), but it is impossible to do by simply passing it like a dispatcher. I understand that it's possible to make via connect function but I'm too new into undici for understanding all machinery there.

[metcoder95]

Yeah, see what you mean. Here what you want to do is to first connect to the Proxy and use that socket to do the requests in the second agent/dispatcher.

What I was suggesting was not to use the Agent and have an internal connect that goes to a Proxy, but actually the other way around.

On the ProxyAgent you pass a custom connect that connects to the proxy with H1 (using an Agent) and returns that socket to the connect callback so it can be reused across request. Similar to what ProxyAgent does to connect to the Proxy.

The error you are receiving seems to be related with you connecting with https but the proxy supporting only http.

[levshkatov]

Thanks a lot for explanation. It helped me rewrite ProxyAgent as a custom one, it worked properly and then I realized that if I simply pass requestTls: {allowH2: true} to ProxyAgent options it will do the same.
First time I tried to pass allowH2 without requestTls, on the first level of options and it didn't work for sure, because my proxy doesn't support H2. Reading source code could be helpful sometimes, haha. Thanks again!