Invalid HTTP2 headers should be recoverable

[dhalbrook]

Bug Description

If an invalid HTTP2 header is sent by the server, the client should be able to recover by retrying the operation. Right now it results in an uncaughtException. See #4341 for more details.

Reproducible By

To reproduce, a mock reply will need to be constructed where an HTTP2 connection to a server gets a response with an HTTP1 header like "http2-settings".

Ideally a runtime error is thrown, which can be caught in a block where Undici can be directed to retry the operation with a new connection.

Logs & Screenshots

Here is an example stack trace from when this occurs:

{err":{"type":"TypeError","message":"HTTP/1 Connection specific headers are forbidden: \"http2-settings\"","stack":"TypeError: HTTP/1 Connection specific headers are forbidden: \"http2-settings\"\n    
at mapToHeaders (node:internal/http2/util:651:13)\n    
at ClientHttp2Session.request (node:internal/http2/core:1813:25)\n    
at writeH2 (/.../node_modules/undici/lib/dispatcher/client-h2.js:469:22)\n    
at Object.write (/.../node_modules/undici/lib/dispatcher/client-h2.js:119:14)\n    
at _resume (/.../node_modules/undici/lib/dispatcher/client.js:601:50)\n    
at resume (/.../node_modules/undici/lib/dispatcher/client.js:303:28\n    
at node:internal/process/task_queues:140:7\n    
at AsyncResource.runInAsyncScope (node:async_hooks:206:9)\n    
at AsyncResource.runMicrotask (node:internal/process/task_queues:137:8)","code":"ERR_HTTP2_INVALID_CONNECTION_HEADERS"}

Environment

This was encountered using Node.js 22 on RHEL9.

Additional context

[eryue0220]

I’d like to try to work on this.

[metcoder95]

go for it

[webcarrot]

This on is quite critical as h2 is enabled by default in v8 and it just crash services.

For example:

import { request } from 'undici';

try {
	await request('https://nodejs.org/en', {
		method: 'POST',
		headers: {
			'content-type': 'foo/bar',
			'Content-Type': 'foo/bar',
		},
		body: 'foo-bar',
	});
} catch (err) {
	console.log(`I want to be printed ${err}`);
}

[webcarrot]

Looks like fix is just to:

    try {
      stream = session.request(headers, { endStream: shouldEndStream, signal })
      // or stream = session.request(headers, { endStream: false, signal })
    } catch(err) {
      util.errorRequest(client, request, err)
      // maybe session.unref() ?
      return false
    }

in writeH2

[webcarrot]

undici v8.3.0 still crash node process ☝🏻 #4356 (comment) (👉🏻 #5101 (comment))

node ./test.ts
/Users/wojtek/git/tmp/undici/node_modules/undici/lib/dispatcher/client-h2.js:740
        throw err
        ^

TypeError [ERR_HTTP2_HEADER_SINGLE_VALUE]: Header field "content-type" must only have a single value
    at processHeader (node:internal/http2/util:787:15)
    at buildNgHeaderString (node:internal/http2/util:834:7)
    at prepareRequestHeadersObject (node:internal/http2/util:734:23)
    at ClientHttp2Session.request (node:internal/http2/core:1831:11)
    at requestStream (/Users/wojtek/git/tmp/undici/node_modules/undici/lib/dispatcher/client-h2.js:737:22)
    at writeH2 (/Users/wojtek/git/tmp/undici/node_modules/undici/lib/dispatcher/client-h2.js:925:12)
    at Object.write (/Users/wojtek/git/tmp/undici/node_modules/undici/lib/dispatcher/client-h2.js:210:14)
    at _resume (/Users/wojtek/git/tmp/undici/node_modules/undici/lib/dispatcher/client.js:658:50)
    at resume (/Users/wojtek/git/tmp/undici/node_modules/undici/lib/dispatcher/client.js:576:3)
    at Client.<computed> (/Users/wojtek/git/tmp/undici/node_modules/undici/lib/dispatcher/client.js:295:31) {
  code: 'ERR_HTTP2_HEADER_SINGLE_VALUE'
}

Node.js v24.11.0

[mcollina]

Reopening: the original fix only handled ERR_HTTP2_INVALID_CONNECTION_HEADERS, but #4356 (comment) reproduces another synchronous session.request() failure (ERR_HTTP2_HEADER_SINGLE_VALUE) that still crashes the process. I'll work on broadening the recovery path.