proposal: x/net/http2: add "SETTINGS_NO_RFC7540_PRIORITIES"

[Colduction]

Proposal Details

According to RFC 9217: Section 2, P1, the SETTINGS_NO_RFC7540_PRIORITIES is now a known setting in SETTINGS frame.

It is also used in Firefox 132.0-b8 (Dev channel), if you could add it in net/http2 for devs who have experimental usages, that would be awesome.

Like listing it's ID beside other settings here:

// A SettingID is an HTTP/2 setting as defined in
// https://httpwg.org/specs/rfc7540.html#iana-settings
type SettingID uint16

const (
	SettingHeaderTableSize      SettingID = 0x1
	SettingEnablePush           SettingID = 0x2
	SettingMaxConcurrentStreams SettingID = 0x3
	SettingInitialWindowSize    SettingID = 0x4
	SettingMaxFrameSize         SettingID = 0x5
	SettingMaxHeaderListSize    SettingID = 0x6
        SettingNoRFC7540Priorities  SettingID = 0x9
)

var settingName = map[SettingID]string{
	SettingHeaderTableSize:      "HEADER_TABLE_SIZE",
	SettingEnablePush:           "ENABLE_PUSH",
	SettingMaxConcurrentStreams: "MAX_CONCURRENT_STREAMS",
	SettingInitialWindowSize:    "INITIAL_WINDOW_SIZE",
	SettingMaxFrameSize:         "MAX_FRAME_SIZE",
	SettingMaxHeaderListSize:    "MAX_HEADER_LIST_SIZE",
        SettingNoRFC7540Priorities:  "NO_RFC7540_PRIORITIES",
}

Thanks to Go team!

[ianlancetaylor]

CC @neild

[neild]

I have no objection to adding the field to the enum. I don't think we really should be in the business of providing an enumeration of HTTP/2 settings ids, but given that we already have one there doesn't seem to be any harm in staying up to date.

[Colduction]

In fact I didn't mean just adding it's ID, I meant it would be great to make it easier to configure and use this setting like other SETTING frame's settings for ease of use for custom/experimental usages.

Also thanks for your replies.

[neild]

x/net/http2 currently doesn't support RFC 7540 stream prioritization by default.

We have http2.NewPriorityWriteScheduler, but this is known to be buggy (see https://go.dev/issue/58804), we have no evidence that it's useful (https://go.dev/issue/58804#issuecomment-1470330633), RFC 7540 prioritization is deprecated (https://www.rfc-editor.org/rfc/rfc9113.html#section-5.3), and we have a proposal to deprecate the x/net/http2 WriteScheduler interface entirely (https://go.dev/issue/67817).

So I think the only reasonable thing x/net/http2 could do with SETTINGS_NO_RFC7540_PRIORITIES is to unilaterally send it with a value of '1'.

[Colduction]

Yes, that would be great to send this (SETTINGS_NO_RFC7540_PRIORITIES) SETTING frame's setting with a default value of '1'.

I hope the Go community adds this feature for the next x/net/http2 update.

Thanks in advance!

[neild]

I have no objection to sending SETTINGS_NO_RFC7530_PRIORITIES=1 when using the default WriteScheduler. (And always, if/when we drop WriteScheduler support someday.)

[gopherbot]

Change https://go.dev/cl/621175 mentions this issue: http2: support SETTINGS_NO_RFC7540_PRIORITIES