feat: add experimental http2 support #539

mafredri · 2025-09-29T17:49:20Z

This change adds experimental support for WebSockets over HTTP/2 (RFC 8441).

Implementation notes:

To avoid breaking any flows, HTTP/2 functionality is currently opt-in on both server and client
The HTTP/2 tests are currently kept in internal/thirdparty/http2 (they require importing golang.org/x/net/http2, see net/http: move HTTP/2 into std golang/go#67810)
HTTP/2 extended CONNECT must currently be enabled via GODEBUG, see net/http: add support for SETTINGS_ENABLE_CONNECT_PROTOCOL golang/go#53208
Explicit selection of HTTP/1 or HTTP/2 is required during Dial because we cannot test the underlying transport for support (for instance, http.Transport does not allow setting the HTTP/2 pseudo-header :protocol)
To Dial with HTTP/2 support, a http2.Transport must be provided via DialOptions.Client (since we do not import golang.org/x/net/http2)
There are a few changes and cleanups unrelated to this feature, if needed they can be broken out into a separate branch

Closes #4

This change does not yet include benchmark tests for HTTP/2, those will be added at a later date as a follow-up.

Closes #4

zedkipp · 2025-10-02T14:45:22Z

.github/workflows/ci.yml

      - uses: actions/setup-go@v5
        with:
-          go-version-file: ./go.mod
+          # HACK(mafredri): The exampels and thirdparty library require Go 1.24


typo here and on line 33

Suggested change

# HACK(mafredri): The exampels and thirdparty library require Go 1.24

# HACK(mafredri): The examples and thirdparty library require Go 1.24

code-asher

Very nice 🤌 I messed around with the example as well and it all looks good.

code-asher · 2025-10-02T21:10:21Z

internal/examples/http2/README.md

+
+```console
+# Server.
+$ cd examples/http2


Should it be cd internal/examples/http2 or is the readme from the context of being in internal already? (And same for the other cds below).

Actually yeah, good catch, we'll need to update the other examples too but I can do that in a separate PR.

code-asher · 2025-10-02T21:30:10Z

internal/examples/http2/server.go

+func visibleAddr(addr string) string {
+	// If binding to all interfaces with ":port", display "127.0.0.1:port".
+	if strings.HasPrefix(addr, ":") {
+		return "127.0.0.1" + addr


Would 0.0.0.0:port be better to indicate binding on all interfaces? To me 127.0.0.1 implies loopback only.

code-asher · 2025-10-02T22:28:34Z

dial.go

+}
+
+func verifyServerResponseH1(opts *DialOptions, copts *compressionOptions, secWebSocketKey string, resp *http.Response) (*compressionOptions, error) {
 	if resp.StatusCode != http.StatusSwitchingProtocols {


Would it make sense to check resp.ProtoMajor here like the other verify functions?

I guess it wouldn't hurt 🤔, I'll do that in a separate PR though as it's touching the H1 code, want to avoid changing it too much in this PR.

mtojek

Amazing skills 👍 👍

Have you tried to establish a connection using other tools? JS possibly?

mtojek · 2025-10-03T10:28:07Z

.github/workflows/daily.yml

        with:
          name: coverage.html
          path: ./ci/out/coverage.html
-  bench-dev:


nit: is this just maintenance or related to this PR? If the first one, perhaps split it... just in case we have to revert this one :)

Maintenance, I'll break the unrelated stuff into a separate PR 👍🏻

mtojek · 2025-10-03T10:29:29Z

protocol.go

+// an http2.Transport (from golang.org/x/net/http2).
+//
+// Experimental: This type is experimental and may change in the future.
+type Protocol int


nit: s/Protocol/HTTPProtocolVersion? I suppose there won't be different protocols than HTTP.

Honestly I was a bit on the fence about this myself, I almost did HTTPProtocol but it's a mouth/eyefull with the PP. 😅

On Dial we do have HTTPClient, HTTPHeader, so it's not too much of a stretch to do HTTPProtocol.

mtojek · 2025-10-03T10:31:46Z

protocol.go

+
+	// ProtocolHTTP1 selects HTTP/1.1 GET+Upgrade for the WebSocket handshake.
+	// This is the default (zero value).
+	ProtocolHTTP1


This model will work until one day we will need to switch to HTTP3.99 :)

ProtocolHTTP3_99 😂

mtojek · 2025-10-03T10:32:54Z

ci/test.sh

+coverpkgsjoined=$(IFS=,; echo "${coverpkgs[*]}")
+
+echo "++++ Running main tests"
+go test --bench=. --timeout=1h -cover -covermode=atomic -coverpkg="$coverpkgsjoined" -test.gocoverdir="$coverbase/race=0" "$@" ./...


It's a typical timeout in this project all around. I'll keep it like that but we can follow-up with a cleanup regarding that.

mtojek · 2025-10-03T10:33:58Z

ci/static.sh

+mkdir -p ./ci/out/static
+cp ./ci/out/coverage.html ./ci/out/static/coverage.html
+percent=$(go tool cover -func ./ci/out/profile.txt | tail -n1 | awk '{print $3}' | tr -d '%')
+wget -O ./ci/out/static/coverage.svg "https://img.shields.io/badge/coverage-${percent}%25-success"


nit: perhaps extract it to a different PR?

mtojek · 2025-10-03T10:34:44Z

autobahn_test.go

 				case "OK", "INFORMATIONAL":
 				default:
-					t.Errorf("bad close behaviour")
+					t.Errorf("bad close behavior")


internal/examples/http2/main.go

internal/examples/http2/server.go

mtojek · 2025-10-03T10:55:31Z

internal/examples/http2/server.go

+		}
+
+		selfSigned := ""
+		if *certFile == "" && *keyFile == "" {


correct me if I'm wrong, a certificate is mandatory, right? if not, I would just simplify the example

I added the auto-generated self-signed cert to make testing the example easier, but we can enforce cert/key, I was on the fence about adding cert generation anyway 👍🏻

mtojek · 2025-10-03T11:04:10Z

accept.go

-	}); ok {
-		ginWriter.WriteHeaderNow()
+	switch opts.Protocol {
+	case ProtocolHTTP2:


Should we support http.UnencryptedHTTP2?

I did not know about this, I'll need to investigate. Thanks for the heads up 👍🏻

code-asher · 2025-10-03T19:24:55Z

Have you tried to establish a connection using other tools? JS possibly?

While I was testing I experimented with connecting to the server example from a JS (Node) client. Here is what I used for anyone interested (needs ws).

const http2 = require("http2")
const { Receiver, Sender } = require("ws")

const client = http2.connect("http://127.0.0.1:8080")

const req = client.request({
 ":method": "CONNECT",
 ":protocol": "websocket",
 ":scheme": "http",
 ":path": "/",
 ":authority": "127.0.0.1",
 "Sec-WebSocket-Key": "AQIDBAUGBwgJCgsMDQ4PEC==",
 "Sec-WebSocket-Version": "13",
})

req.on("response", (headers) => {
 console.log("status:", headers[":status"])
})

req.on("error", (err) => {
 console.log("error:", err)
})

const receiver = new Receiver()
receiver.on("message", (data) => {
 console.log("got message:", data.toString())
})

req.on("data", (chunk) => {
 receiver.write(chunk)
})

setInterval(() => {
 const sender = new Sender(req)
 sender.send("hey", { binary: false, mask: true, fin: true })
}, 1000)

sample output:

status: 200
got message: hey
got message: hey
got message: hey

mafredri force-pushed the mafredri/http2 branch 11 times, most recently from 469125f to 9470379 Compare September 29, 2025 18:59

mafredri self-assigned this Sep 29, 2025

feat: add experimental http2 support

047d1c0

Closes #4

mafredri force-pushed the mafredri/http2 branch from 0616f05 to 047d1c0 Compare October 1, 2025 11:08

mafredri marked this pull request as ready for review October 1, 2025 13:09

mafredri requested a review from code-asher October 1, 2025 13:10

mtojek self-requested a review October 1, 2025 14:06

zedkipp reviewed Oct 2, 2025

View reviewed changes

code-asher approved these changes Oct 2, 2025

View reviewed changes

mtojek approved these changes Oct 3, 2025

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	# HACK(mafredri): The exampels and thirdparty library require Go 1.24
	# HACK(mafredri): The examples and thirdparty library require Go 1.24

feat: add experimental http2 support #539

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mafredri commented Sep 29, 2025 •

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