hang when client receives header response that's too big in http2

[ajwerner]

Version
Hyper @ 7de0237

Platform
Linux 6.5.0-42-generic

Description
When the server sends a response with headers that are too big, hyper can sometimes just hang.

I wrote this test:

hyper/tests/integration.rs

Lines 64 to 86 in bdd112e

	// Test that clients get responses when the server sends a response with
	// headers that are too large by just a bit.
	t! {
	long_header_response,
	client:
	request:
	;
	response:
	status: 500,
	headers: {
	},
	;
	server:
	request:
	;
	response:
	status: 500,
	headers: {
	// Just above DEFAULT_SETTINGS_MAX_HEADER_LIST_SIZE.
	"error" => ("a".repeat(16 << 10 + 1)),
	},
	;
	}

I expected to see an error. Instead the test just blocks forever.

See grpc/grpc-rust#1834 and https://discord.com/channels/500028886025895936/1268954374634471484 for context.

[futile]

Hi, I think we might be running into this with lots of headers being sent to us by https://console.cloud.google.com. Thanks for the documentation, issues and PROTOCOL_ERROR-change in h2 already, which turned the hang into a PROTOCOL_ERROR for us instead!

Do you have any further updates on this already?

[ajwerner]

Perhaps with hyperium/h2#791 this is resolved. What do y'all think?

[futile]

Mhhm, could it be possible to increase the header size limit on-demand (up to a fixed maximum)? Just thinking about a version that will allow clients/servers to work with large headers, instead of throwing an error.

[seanmonstar]

Perhaps with hyperium/h2#791 this is resolved. What do y'all think?

Yea, the hang is likely solved, thanks!

increase the header size limit on-demand (up to a fixed maximum)

That's what a maximum does already. You can adjust the maximum with builder options.