feat: add /websocket/echo endpoint (#155)

Here we add a new `/websocket/echo` endpoint, which implements a basic
WebSocket echo service.

The endpoint is powered by our own basic, zero-dependency WebSocket
implementation, which passes _almost_ every test in the invaluable
[Autobahn Testsuite](https://github.com/crossbario/autobahn-testsuite)
"fuzzingclient" set of integration tests, which will be run
automatically as part of our continuous integration tests going forward.

Closes #151.

Author: mccutchen

.gitignore

@@ -1,27 +1,6 @@
-# Compiled Object files, Static and Dynamic libs (Shared Objects)
-*.o
-*.a
-*.so
-
-# Folders
-_obj
-_test
-
-# Architecture specific extensions/prefixes
-*.[568vq]
-[568vq].out
-
-*.cgo1.go
-*.cgo2.c
-_cgo_defun.c
-_cgo_gotypes.go
-_cgo_export.*
-
-_testmain.go
-
+.*
 *.exe
 *.test
 *.prof
-
 dist/*
 coverage.txt

DEVELOPMENT.md

@@ -0,0 +1,113 @@
+# Development
+
+## Local development
+
+For interactive local development, use `make run` to build and run go-httpbin
+or `make watch` to automatically re-build and re-run go-httpbin on every
+change:
+
+    make run
+    make watch
+
+By default, the server will listen on `http://127.0.0.1:8080`, but the host,
+port, or any other [configuration option][config] may be overridden by
+specifying the relevant environment variables:
+
+    make run PORT=9999
+    make run PORT=9999 MAX_DURATION=60s
+    make watch HOST=0.0.0.0 PORT=8888
+
+## Testing
+
+Run `make test` to run unit tests, using `TEST_ARGS` to pass arguments through
+to `go test`:
+
+    make test
+    make test TEST_ARGS="-v -race -run ^TestDelay"
+
+### Integration tests
+
+go-httpbin includes its own minimal WebSocket echo server implementation, and
+we use the incredibly helpful [Autobahn Testsuite][] to ensure that the
+implementation conforms to the spec.
+
+These tests can be slow to run (~40 seconds on my machine), so they are not run
+by default when using `make test`.
+
+They are run automatically as part of our extended "CI" test suite, which is
+run on every pull request:
+
+    make testci
+
+### WebSocket development
+
+When working on the WebSocket implementation, it can also be useful to run
+those integration tests directly, like so:
+
+    make testautobahn
+
+Use the `AUTOBAHN_CASES` var to run a specific subset of the Autobahn tests,
+which may or may not include wildcards:
+
+    make testautobahn AUTOBAHN_CASES=6.*
+    make testautobahn AUTOBAHN_CASES=6.5.*
+    make testautobahn AUTOBAHN_CASES=6.5.4
+
+
+### Test coverage
+
+We use [Codecov][] to measure and track test coverage as part of our continuous
+integration test suite. While we strive for as much coverage as possible and
+the Codecov CI check is configured with fairly strict requirements, 100% test
+coverage is not an explicit goal or requirement for all contributions.
+
+To view test coverage locally, use
+
+    make testcover
+
+which will run the full suite of unit and integration tests and pop open a web
+browser to view coverage results.
+
+
+## Linting and code style
+
+Run `make lint` to run our suite of linters and formatters, which include
+gofmt, [revive][], and [staticcheck][]:
+
+    make lint
+
+
+## Docker images
+
+To build a docker image locally:
+
+    make image
+
+To build a docker image an push it to a remote repository:
+
+    make imagepush
+
+By default, images will be tagged as `mccutchen/go-httpbin:${COMMIT}` with the
+current HEAD commit hash.
+
+Use `VERSION` to override the tag value
+
+    make imagepush VERSION=v1.2.3
+
+or `DOCKER_TAG` to override the remote repo and version at once:
+
+    make imagepush DOCKER_TAG=my-org/my-fork:v1.2.3
+
+### Automated docker image builds
+
+When a new release is created, the [Release][] GitHub Actions workflow
+automatically builds and pushes new Docker images for both linux/amd64 and
+linux/arm64 architectures.
+
+
+[config]: /README.md#configuration
+[revive]: https://github.com/mgechev/revive
+[staticcheck]: https://staticcheck.dev/
+[Release]: /.github/workflows/release.yaml
+[Codecov]: https://app.codecov.io/gh/mccutchen/go-httpbin
+[Autobahn Testsuite]: https://github.com/crossbario/autobahn-testsuite

Makefile

@@ -38,7 +38,7 @@ buildtests:
 .PHONY: buildtests
 
 clean:
-	rm -rf $(DIST_PATH) $(COVERAGE_PATH)
+	rm -rf $(DIST_PATH) $(COVERAGE_PATH) .integrationtests
 .PHONY: clean
 
 
@@ -53,14 +53,18 @@ test:
 # based on codecov.io's documentation:
 # https://github.com/codecov/example-go/blob/b85638743b972bd0bd2af63421fe513c6f968930/README.md
 testci: build buildexamples
-	go test $(TEST_ARGS) $(COVERAGE_ARGS) ./...
-	git diff --exit-code
+	AUTOBAHN_TESTS=1 go test $(TEST_ARGS) $(COVERAGE_ARGS) ./...
 .PHONY: testci
 
 testcover: testci
 	go tool cover -html=$(COVERAGE_PATH)
 .PHONY: testcover
 
+# Run the autobahn fuzzingclient test suite
+testautobahn:
+	AUTOBAHN_TESTS=1 AUTOBAHN_OPEN_REPORT=1 go test -v -run ^TestWebSocketServer$$ $(TEST_ARGS) ./...
+.PHONY: autobahntests
+
 lint:
 	test -z "$$(gofmt -d -s -e .)" || (echo "Error: gofmt failed"; gofmt -d -s -e . ; exit 1)
 	go vet ./...

README.md

@@ -169,17 +169,7 @@ public internet, consider tuning it appropriately:
 
 ## Development
 
-```bash
-# local development
-make
-make test
-make testcover
-make run
-
-# building & pushing docker images
-make image
-make imagepush
-```
+See [DEVELOPMENT.md][].
 
 ## Motivation & prior art
 
@@ -218,3 +208,4 @@ Compared to [ahmetb/go-httpbin][ahmet]:
 [Observer]: https://pkg.go.dev/github.com/mccutchen/go-httpbin/v2/httpbin#Observer
 [Production considerations]: #production-considerations
 [zerolog]: https://github.com/rs/zerolog
+[DEVELOPMENT.md]: ./DEVELOPMENT.md

httpbin/handlers.go

@@ -15,6 +15,7 @@ import (
 	"time"
 
 	"github.com/mccutchen/go-httpbin/v2/httpbin/digest"
+	"github.com/mccutchen/go-httpbin/v2/httpbin/websocket"
 )
 
 var nilValues = url.Values{}
@@ -1112,3 +1113,51 @@ func (h *HTTPBin) Hostname(w http.ResponseWriter, _ *http.Request) {
 		Hostname: h.hostname,
 	})
 }
+
+// WebSocketEcho - simple websocket echo server, where the max fragment size
+// and max message size can be controlled by clients.
+func (h *HTTPBin) WebSocketEcho(w http.ResponseWriter, r *http.Request) {
+	var (
+		maxFragmentSize = h.MaxBodySize / 2
+		maxMessageSize  = h.MaxBodySize
+		q               = r.URL.Query()
+		err             error
+	)
+
+	if userMaxFragmentSize := q.Get("max_fragment_size"); userMaxFragmentSize != "" {
+		maxFragmentSize, err = strconv.ParseInt(userMaxFragmentSize, 10, 32)
+		if err != nil {
+			writeError(w, http.StatusBadRequest, fmt.Errorf("invalid max_fragment_size: %w", err))
+			return
+		} else if maxFragmentSize < 1 || maxFragmentSize > h.MaxBodySize {
+			writeError(w, http.StatusBadRequest, fmt.Errorf("invalid max_fragment_size: %d not in range [1, %d]", maxFragmentSize, h.MaxBodySize))
+			return
+		}
+	}
+
+	if userMaxMessageSize := q.Get("max_message_size"); userMaxMessageSize != "" {
+		maxMessageSize, err = strconv.ParseInt(userMaxMessageSize, 10, 32)
+		if err != nil {
+			writeError(w, http.StatusBadRequest, fmt.Errorf("invalid max_message_size: %w", err))
+			return
+		} else if maxMessageSize < 1 || maxMessageSize > h.MaxBodySize {
+			writeError(w, http.StatusBadRequest, fmt.Errorf("invalid max_message_size: %d not in range [1, %d]", maxMessageSize, h.MaxBodySize))
+			return
+		}
+	}
+
+	if maxFragmentSize > maxMessageSize {
+		writeError(w, http.StatusBadRequest, fmt.Errorf("max_fragment_size %d must be less than or equal to max_message_size %d", maxFragmentSize, maxMessageSize))
+		return
+	}
+
+	ws := websocket.New(w, r, websocket.Limits{
+		MaxFragmentSize: int(maxFragmentSize),
+		MaxMessageSize:  int(maxMessageSize),
+	})
+	if err := ws.Handshake(); err != nil {
+		writeError(w, http.StatusBadRequest, err)
+		return
+	}
+	ws.Serve(websocket.EchoHandler)
+}

httpbin/handlers_test.go

@@ -2911,6 +2911,78 @@ func TestHostname(t *testing.T) {
 	})
 }
 
+func TestWebSocketEcho(t *testing.T) {
+	// ========================================================================
+	// Note: Here we only test input validation for the websocket endpoint.
+	//
+	// See websocket/*_test.go for in-depth integration tests of the actual
+	// websocket implementation.
+	// ========================================================================
+
+	handshakeHeaders := map[string]string{
+		"Connection":            "upgrade",
+		"Upgrade":               "websocket",
+		"Sec-WebSocket-Key":     "dGhlIHNhbXBsZSBub25jZQ==",
+		"Sec-WebSocket-Version": "13",
+	}
+
+	t.Run("handshake ok", func(t *testing.T) {
+		t.Parallel()
+
+		req := newTestRequest(t, http.MethodGet, "/websocket/echo")
+		for k, v := range handshakeHeaders {
+			req.Header.Set(k, v)
+		}
+
+		resp, err := client.Do(req)
+		assert.NilError(t, err)
+		assert.StatusCode(t, resp, http.StatusSwitchingProtocols)
+	})
+
+	t.Run("handshake failed", func(t *testing.T) {
+		t.Parallel()
+		req := newTestRequest(t, http.MethodGet, "/websocket/echo")
+		resp, err := client.Do(req)
+		assert.NilError(t, err)
+		assert.StatusCode(t, resp, http.StatusBadRequest)
+	})
+
+	paramTests := []struct {
+		query      string
+		wantStatus int
+	}{
+		// ok
+		{"max_fragment_size=1&max_message_size=2", http.StatusSwitchingProtocols},
+		{fmt.Sprintf("max_fragment_size=%d&max_message_size=%d", app.MaxBodySize, app.MaxBodySize), http.StatusSwitchingProtocols},
+
+		// bad max_framgent_size
+		{"max_fragment_size=-1&max_message_size=2", http.StatusBadRequest},
+		{"max_fragment_size=0&max_message_size=2", http.StatusBadRequest},
+		{"max_fragment_size=3&max_message_size=2", http.StatusBadRequest},
+		{"max_fragment_size=foo&max_message_size=2", http.StatusBadRequest},
+		{fmt.Sprintf("max_fragment_size=%d&max_message_size=2", app.MaxBodySize+1), http.StatusBadRequest},
+
+		// bad max_message_size
+		{"max_fragment_size=1&max_message_size=0", http.StatusBadRequest},
+		{"max_fragment_size=1&max_message_size=-1", http.StatusBadRequest},
+		{"max_fragment_size=1&max_message_size=bar", http.StatusBadRequest},
+		{fmt.Sprintf("max_fragment_size=1&max_message_size=%d", app.MaxBodySize+1), http.StatusBadRequest},
+	}
+	for _, tc := range paramTests {
+		tc := tc
+		t.Run(tc.query, func(t *testing.T) {
+			t.Parallel()
+			req := newTestRequest(t, http.MethodGet, "/websocket/echo?"+tc.query)
+			for k, v := range handshakeHeaders {
+				req.Header.Set(k, v)
+			}
+			resp, err := client.Do(req)
+			assert.NilError(t, err)
+			assert.StatusCode(t, resp, tc.wantStatus)
+		})
+	}
+}
+
 func newTestServer(handler http.Handler) (*httptest.Server, *http.Client) {
 	srv := httptest.NewServer(handler)
 	client := srv.Client()

httpbin/httpbin.go

@@ -153,6 +153,8 @@ func (h *HTTPBin) Handler() http.Handler {
 
 	mux.HandleFunc("/dump/request", h.DumpRequest)
 
+	mux.HandleFunc("/websocket/echo", h.WebSocketEcho)
+
 	// existing httpbin endpoints that we do not support
 	mux.HandleFunc("/brotli", notImplementedHandler)
 

httpbin/middleware.go

@@ -1,8 +1,10 @@
 package httpbin
 
 import (
+	"bufio"
 	"fmt"
 	"log"
+	"net"
 	"net/http"
 	"time"
 )
@@ -123,6 +125,10 @@ func (mw *metaResponseWriter) Size() int64 {
 	return mw.size
 }
 
+func (mw *metaResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	return mw.w.(http.Hijacker).Hijack()
+}
+
 func observe(o Observer, h http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		mw := &metaResponseWriter{w: w}