Source file src/net/http/clientserver_test.go

     1  // Copyright 2015 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Tests that use both the client & server, in both HTTP/1 and HTTP/2 mode.
     6  
     7  package http_test
     8  
     9  import (
    10  	"bytes"
    11  	"compress/gzip"
    12  	"context"
    13  	"crypto/rand"
    14  	"crypto/sha1"
    15  	"crypto/tls"
    16  	"fmt"
    17  	"hash"
    18  	"io"
    19  	"log"
    20  	"maps"
    21  	"net"
    22  	. "net/http"
    23  	"net/http/httptest"
    24  	"net/http/httptrace"
    25  	"net/http/httputil"
    26  	"net/textproto"
    27  	"net/url"
    28  	"os"
    29  	"reflect"
    30  	"runtime"
    31  	"slices"
    32  	"strings"
    33  	"sync"
    34  	"sync/atomic"
    35  	"testing"
    36  	"testing/synctest"
    37  	"time"
    38  )
    39  
    40  type testMode string
    41  
    42  const (
    43  	http1Mode            = testMode("h1")            // HTTP/1.1
    44  	https1Mode           = testMode("https1")        // HTTPS/1.1
    45  	http2Mode            = testMode("h2")            // HTTP/2
    46  	http2UnencryptedMode = testMode("h2unencrypted") // HTTP/2
    47  )
    48  
    49  func (m testMode) Scheme() string {
    50  	switch m {
    51  	case http1Mode, http2UnencryptedMode:
    52  		return "http"
    53  	case https1Mode, http2Mode:
    54  		return "https"
    55  	}
    56  	panic("unknown testMode")
    57  }
    58  
    59  type testNotParallelOpt struct{}
    60  
    61  var (
    62  	testNotParallel = testNotParallelOpt{}
    63  )
    64  
    65  type TBRun[T any] interface {
    66  	testing.TB
    67  	Run(string, func(T)) bool
    68  }
    69  
    70  // run runs a client/server test in a variety of test configurations.
    71  //
    72  // Tests execute in HTTP/1.1 and HTTP/2 modes by default.
    73  // To run in a different set of configurations, pass a []testMode option.
    74  //
    75  // Tests call t.Parallel() by default.
    76  // To disable parallel execution, pass the testNotParallel option.
    77  func run[T TBRun[T]](t T, f func(t T, mode testMode), opts ...any) {
    78  	t.Helper()
    79  	modes := []testMode{http1Mode, http2Mode}
    80  	parallel := true
    81  	for _, opt := range opts {
    82  		switch opt := opt.(type) {
    83  		case []testMode:
    84  			modes = opt
    85  		case testNotParallelOpt:
    86  			parallel = false
    87  		default:
    88  			t.Fatalf("unknown option type %T", opt)
    89  		}
    90  	}
    91  	if t, ok := any(t).(*testing.T); ok && parallel {
    92  		setParallel(t)
    93  	}
    94  	for _, mode := range modes {
    95  		t.Run(string(mode), func(t T) {
    96  			t.Helper()
    97  			if t, ok := any(t).(*testing.T); ok && parallel {
    98  				setParallel(t)
    99  			}
   100  			t.Cleanup(func() {
   101  				afterTest(t)
   102  			})
   103  			f(t, mode)
   104  		})
   105  	}
   106  }
   107  
   108  // runSynctest is run combined with synctest.Run.
   109  //
   110  // The TB passed to f arranges for cleanup functions to be run in the synctest bubble.
   111  func runSynctest(t *testing.T, f func(t *testing.T, mode testMode), opts ...any) {
   112  	run(t, func(t *testing.T, mode testMode) {
   113  		synctest.Test(t, func(t *testing.T) {
   114  			f(t, mode)
   115  		})
   116  	}, opts...)
   117  }
   118  
   119  type clientServerTest struct {
   120  	t  testing.TB
   121  	h2 bool
   122  	h  Handler
   123  	ts *httptest.Server
   124  	tr *Transport
   125  	c  *Client
   126  	li *fakeNetListener
   127  }
   128  
   129  func (t *clientServerTest) close() {
   130  	t.tr.CloseIdleConnections()
   131  	t.ts.Close()
   132  }
   133  
   134  func (t *clientServerTest) getURL(u string) string {
   135  	res, err := t.c.Get(u)
   136  	if err != nil {
   137  		t.t.Fatal(err)
   138  	}
   139  	defer res.Body.Close()
   140  	slurp, err := io.ReadAll(res.Body)
   141  	if err != nil {
   142  		t.t.Fatal(err)
   143  	}
   144  	return string(slurp)
   145  }
   146  
   147  func (t *clientServerTest) scheme() string {
   148  	if t.h2 {
   149  		return "https"
   150  	}
   151  	return "http"
   152  }
   153  
   154  var optQuietLog = func(ts *httptest.Server) {
   155  	ts.Config.ErrorLog = quietLog
   156  }
   157  
   158  func optWithServerLog(lg *log.Logger) func(*httptest.Server) {
   159  	return func(ts *httptest.Server) {
   160  		ts.Config.ErrorLog = lg
   161  	}
   162  }
   163  
   164  var optFakeNet = new(struct{})
   165  
   166  // newClientServerTest creates and starts an httptest.Server.
   167  //
   168  // The mode parameter selects the implementation to test:
   169  // HTTP/1, HTTP/2, etc. Tests using newClientServerTest should use
   170  // the 'run' function, which will start a subtests for each tested mode.
   171  //
   172  // The vararg opts parameter can include functions to configure the
   173  // test server or transport.
   174  //
   175  //	func(*httptest.Server) // run before starting the server
   176  //	func(*http.Transport)
   177  //
   178  // The optFakeNet option configures the server and client to use a fake network implementation,
   179  // suitable for use in testing/synctest tests.
   180  func newClientServerTest(t testing.TB, mode testMode, h Handler, opts ...any) *clientServerTest {
   181  	if mode == http2Mode {
   182  		CondSkipHTTP2(t)
   183  	}
   184  	cst := &clientServerTest{
   185  		t:  t,
   186  		h2: mode == http2Mode,
   187  		h:  h,
   188  	}
   189  
   190  	var transportFuncs []func(*Transport)
   191  
   192  	if idx := slices.Index(opts, any(optFakeNet)); idx >= 0 {
   193  		opts = slices.Delete(opts, idx, idx+1)
   194  		cst.li = fakeNetListen()
   195  		cst.ts = &httptest.Server{
   196  			Config:   &Server{Handler: h},
   197  			Listener: cst.li,
   198  		}
   199  		transportFuncs = append(transportFuncs, func(tr *Transport) {
   200  			tr.DialContext = func(ctx context.Context, network, addr string) (net.Conn, error) {
   201  				return cst.li.connect(), nil
   202  			}
   203  		})
   204  	} else {
   205  		cst.ts = httptest.NewUnstartedServer(h)
   206  	}
   207  
   208  	if mode == http2UnencryptedMode {
   209  		p := &Protocols{}
   210  		p.SetUnencryptedHTTP2(true)
   211  		cst.ts.Config.Protocols = p
   212  	}
   213  
   214  	for _, opt := range opts {
   215  		switch opt := opt.(type) {
   216  		case func(*Transport):
   217  			transportFuncs = append(transportFuncs, opt)
   218  		case func(*httptest.Server):
   219  			opt(cst.ts)
   220  		case func(*Server):
   221  			opt(cst.ts.Config)
   222  		default:
   223  			t.Fatalf("unhandled option type %T", opt)
   224  		}
   225  	}
   226  
   227  	if cst.ts.Config.ErrorLog == nil {
   228  		cst.ts.Config.ErrorLog = log.New(testLogWriter{t}, "", 0)
   229  	}
   230  
   231  	switch mode {
   232  	case http1Mode:
   233  		cst.ts.Start()
   234  	case https1Mode:
   235  		cst.ts.StartTLS()
   236  	case http2UnencryptedMode:
   237  		ExportHttp2ConfigureServer(cst.ts.Config, nil)
   238  		cst.ts.Start()
   239  	case http2Mode:
   240  		ExportHttp2ConfigureServer(cst.ts.Config, nil)
   241  		cst.ts.TLS = cst.ts.Config.TLSConfig
   242  		cst.ts.StartTLS()
   243  	default:
   244  		t.Fatalf("unknown test mode %v", mode)
   245  	}
   246  	cst.c = cst.ts.Client()
   247  	cst.tr = cst.c.Transport.(*Transport)
   248  	if mode == http2Mode || mode == http2UnencryptedMode {
   249  		if err := ExportHttp2ConfigureTransport(cst.tr); err != nil {
   250  			t.Fatal(err)
   251  		}
   252  	}
   253  	for _, f := range transportFuncs {
   254  		f(cst.tr)
   255  	}
   256  
   257  	if mode == http2UnencryptedMode {
   258  		p := &Protocols{}
   259  		p.SetUnencryptedHTTP2(true)
   260  		cst.tr.Protocols = p
   261  	}
   262  
   263  	t.Cleanup(func() {
   264  		cst.close()
   265  	})
   266  	return cst
   267  }
   268  
   269  type testLogWriter struct {
   270  	t testing.TB
   271  }
   272  
   273  func (w testLogWriter) Write(b []byte) (int, error) {
   274  	w.t.Logf("server log: %v", strings.TrimSpace(string(b)))
   275  	return len(b), nil
   276  }
   277  
   278  // Testing the newClientServerTest helper itself.
   279  func TestNewClientServerTest(t *testing.T) {
   280  	modes := []testMode{http1Mode, https1Mode, http2Mode}
   281  	t.Run("realnet", func(t *testing.T) {
   282  		run(t, func(t *testing.T, mode testMode) {
   283  			testNewClientServerTest(t, mode)
   284  		}, modes)
   285  	})
   286  	t.Run("synctest", func(t *testing.T) {
   287  		runSynctest(t, func(t *testing.T, mode testMode) {
   288  			testNewClientServerTest(t, mode, optFakeNet)
   289  		}, modes)
   290  	})
   291  }
   292  func testNewClientServerTest(t *testing.T, mode testMode, opts ...any) {
   293  	var got struct {
   294  		sync.Mutex
   295  		proto  string
   296  		hasTLS bool
   297  	}
   298  	h := HandlerFunc(func(w ResponseWriter, r *Request) {
   299  		got.Lock()
   300  		defer got.Unlock()
   301  		got.proto = r.Proto
   302  		got.hasTLS = r.TLS != nil
   303  	})
   304  	cst := newClientServerTest(t, mode, h, opts...)
   305  	if _, err := cst.c.Head(cst.ts.URL); err != nil {
   306  		t.Fatal(err)
   307  	}
   308  	var wantProto string
   309  	var wantTLS bool
   310  	switch mode {
   311  	case http1Mode:
   312  		wantProto = "HTTP/1.1"
   313  		wantTLS = false
   314  	case https1Mode:
   315  		wantProto = "HTTP/1.1"
   316  		wantTLS = true
   317  	case http2Mode:
   318  		wantProto = "HTTP/2.0"
   319  		wantTLS = true
   320  	}
   321  	if got.proto != wantProto {
   322  		t.Errorf("req.Proto = %q, want %q", got.proto, wantProto)
   323  	}
   324  	if got.hasTLS != wantTLS {
   325  		t.Errorf("req.TLS set: %v, want %v", got.hasTLS, wantTLS)
   326  	}
   327  }
   328  
   329  func TestChunkedResponseHeaders(t *testing.T) { run(t, testChunkedResponseHeaders) }
   330  func testChunkedResponseHeaders(t *testing.T, mode testMode) {
   331  	log.SetOutput(io.Discard) // is noisy otherwise
   332  	defer log.SetOutput(os.Stderr)
   333  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
   334  		w.Header().Set("Content-Length", "intentional gibberish") // we check that this is deleted
   335  		w.(Flusher).Flush()
   336  		fmt.Fprintf(w, "I am a chunked response.")
   337  	}))
   338  
   339  	res, err := cst.c.Get(cst.ts.URL)
   340  	if err != nil {
   341  		t.Fatalf("Get error: %v", err)
   342  	}
   343  	defer res.Body.Close()
   344  	if g, e := res.ContentLength, int64(-1); g != e {
   345  		t.Errorf("expected ContentLength of %d; got %d", e, g)
   346  	}
   347  	wantTE := []string{"chunked"}
   348  	if mode == http2Mode {
   349  		wantTE = nil
   350  	}
   351  	if !slices.Equal(res.TransferEncoding, wantTE) {
   352  		t.Errorf("TransferEncoding = %v; want %v", res.TransferEncoding, wantTE)
   353  	}
   354  	if got, haveCL := res.Header["Content-Length"]; haveCL {
   355  		t.Errorf("Unexpected Content-Length: %q", got)
   356  	}
   357  }
   358  
   359  type reqFunc func(c *Client, url string) (*Response, error)
   360  
   361  // h12Compare is a test that compares HTTP/1 and HTTP/2 behavior
   362  // against each other.
   363  type h12Compare struct {
   364  	Handler            func(ResponseWriter, *Request)    // required
   365  	ReqFunc            reqFunc                           // optional
   366  	CheckResponse      func(proto string, res *Response) // optional
   367  	EarlyCheckResponse func(proto string, res *Response) // optional; pre-normalize
   368  	Opts               []any
   369  }
   370  
   371  func (tt h12Compare) reqFunc() reqFunc {
   372  	if tt.ReqFunc == nil {
   373  		return (*Client).Get
   374  	}
   375  	return tt.ReqFunc
   376  }
   377  
   378  func (tt h12Compare) run(t *testing.T) {
   379  	setParallel(t)
   380  	cst1 := newClientServerTest(t, http1Mode, HandlerFunc(tt.Handler), tt.Opts...)
   381  	defer cst1.close()
   382  	cst2 := newClientServerTest(t, http2Mode, HandlerFunc(tt.Handler), tt.Opts...)
   383  	defer cst2.close()
   384  
   385  	res1, err := tt.reqFunc()(cst1.c, cst1.ts.URL)
   386  	if err != nil {
   387  		t.Errorf("HTTP/1 request: %v", err)
   388  		return
   389  	}
   390  	res2, err := tt.reqFunc()(cst2.c, cst2.ts.URL)
   391  	if err != nil {
   392  		t.Errorf("HTTP/2 request: %v", err)
   393  		return
   394  	}
   395  
   396  	if fn := tt.EarlyCheckResponse; fn != nil {
   397  		fn("HTTP/1.1", res1)
   398  		fn("HTTP/2.0", res2)
   399  	}
   400  
   401  	tt.normalizeRes(t, res1, "HTTP/1.1")
   402  	tt.normalizeRes(t, res2, "HTTP/2.0")
   403  	res1body, res2body := res1.Body, res2.Body
   404  
   405  	eres1 := mostlyCopy(res1)
   406  	eres2 := mostlyCopy(res2)
   407  	if !reflect.DeepEqual(eres1, eres2) {
   408  		t.Errorf("Response headers to handler differed:\nhttp/1 (%v):\n\t%#v\nhttp/2 (%v):\n\t%#v",
   409  			cst1.ts.URL, eres1, cst2.ts.URL, eres2)
   410  	}
   411  	if !reflect.DeepEqual(res1body, res2body) {
   412  		t.Errorf("Response bodies to handler differed.\nhttp1: %v\nhttp2: %v\n", res1body, res2body)
   413  	}
   414  	if fn := tt.CheckResponse; fn != nil {
   415  		res1.Body, res2.Body = res1body, res2body
   416  		fn("HTTP/1.1", res1)
   417  		fn("HTTP/2.0", res2)
   418  	}
   419  }
   420  
   421  func mostlyCopy(r *Response) *Response {
   422  	c := *r
   423  	c.Body = nil
   424  	c.TransferEncoding = nil
   425  	c.TLS = nil
   426  	c.Request = nil
   427  	return &c
   428  }
   429  
   430  type slurpResult struct {
   431  	io.ReadCloser
   432  	body []byte
   433  	err  error
   434  }
   435  
   436  func (sr slurpResult) String() string { return fmt.Sprintf("body %q; err %v", sr.body, sr.err) }
   437  
   438  func (tt h12Compare) normalizeRes(t *testing.T, res *Response, wantProto string) {
   439  	if res.Proto == wantProto || res.Proto == "HTTP/IGNORE" {
   440  		res.Proto, res.ProtoMajor, res.ProtoMinor = "", 0, 0
   441  	} else {
   442  		t.Errorf("got %q response; want %q", res.Proto, wantProto)
   443  	}
   444  	slurp, err := io.ReadAll(res.Body)
   445  
   446  	res.Body.Close()
   447  	res.Body = slurpResult{
   448  		ReadCloser: io.NopCloser(bytes.NewReader(slurp)),
   449  		body:       slurp,
   450  		err:        err,
   451  	}
   452  	for i, v := range res.Header["Date"] {
   453  		res.Header["Date"][i] = strings.Repeat("x", len(v))
   454  	}
   455  	if res.Request == nil {
   456  		t.Errorf("for %s, no request", wantProto)
   457  	}
   458  	if (res.TLS != nil) != (wantProto == "HTTP/2.0") {
   459  		t.Errorf("TLS set = %v; want %v", res.TLS != nil, res.TLS == nil)
   460  	}
   461  }
   462  
   463  // Issue 13532
   464  func TestH12_HeadContentLengthNoBody(t *testing.T) {
   465  	h12Compare{
   466  		ReqFunc: (*Client).Head,
   467  		Handler: func(w ResponseWriter, r *Request) {
   468  		},
   469  	}.run(t)
   470  }
   471  
   472  func TestH12_HeadContentLengthSmallBody(t *testing.T) {
   473  	h12Compare{
   474  		ReqFunc: (*Client).Head,
   475  		Handler: func(w ResponseWriter, r *Request) {
   476  			io.WriteString(w, "small")
   477  		},
   478  	}.run(t)
   479  }
   480  
   481  func TestH12_HeadContentLengthLargeBody(t *testing.T) {
   482  	h12Compare{
   483  		ReqFunc: (*Client).Head,
   484  		Handler: func(w ResponseWriter, r *Request) {
   485  			chunk := strings.Repeat("x", 512<<10)
   486  			for i := 0; i < 10; i++ {
   487  				io.WriteString(w, chunk)
   488  			}
   489  		},
   490  	}.run(t)
   491  }
   492  
   493  func TestH12_200NoBody(t *testing.T) {
   494  	h12Compare{Handler: func(w ResponseWriter, r *Request) {}}.run(t)
   495  }
   496  
   497  func TestH2_204NoBody(t *testing.T) { testH12_noBody(t, 204) }
   498  func TestH2_304NoBody(t *testing.T) { testH12_noBody(t, 304) }
   499  func TestH2_404NoBody(t *testing.T) { testH12_noBody(t, 404) }
   500  
   501  func testH12_noBody(t *testing.T, status int) {
   502  	h12Compare{Handler: func(w ResponseWriter, r *Request) {
   503  		w.WriteHeader(status)
   504  	}}.run(t)
   505  }
   506  
   507  func TestH12_SmallBody(t *testing.T) {
   508  	h12Compare{Handler: func(w ResponseWriter, r *Request) {
   509  		io.WriteString(w, "small body")
   510  	}}.run(t)
   511  }
   512  
   513  func TestH12_ExplicitContentLength(t *testing.T) {
   514  	h12Compare{Handler: func(w ResponseWriter, r *Request) {
   515  		w.Header().Set("Content-Length", "3")
   516  		io.WriteString(w, "foo")
   517  	}}.run(t)
   518  }
   519  
   520  func TestH12_FlushBeforeBody(t *testing.T) {
   521  	h12Compare{Handler: func(w ResponseWriter, r *Request) {
   522  		w.(Flusher).Flush()
   523  		io.WriteString(w, "foo")
   524  	}}.run(t)
   525  }
   526  
   527  func TestH12_FlushMidBody(t *testing.T) {
   528  	h12Compare{Handler: func(w ResponseWriter, r *Request) {
   529  		io.WriteString(w, "foo")
   530  		w.(Flusher).Flush()
   531  		io.WriteString(w, "bar")
   532  	}}.run(t)
   533  }
   534  
   535  func TestH12_Head_ExplicitLen(t *testing.T) {
   536  	h12Compare{
   537  		ReqFunc: (*Client).Head,
   538  		Handler: func(w ResponseWriter, r *Request) {
   539  			if r.Method != "HEAD" {
   540  				t.Errorf("unexpected method %q", r.Method)
   541  			}
   542  			w.Header().Set("Content-Length", "1235")
   543  		},
   544  	}.run(t)
   545  }
   546  
   547  func TestH12_Head_ImplicitLen(t *testing.T) {
   548  	h12Compare{
   549  		ReqFunc: (*Client).Head,
   550  		Handler: func(w ResponseWriter, r *Request) {
   551  			if r.Method != "HEAD" {
   552  				t.Errorf("unexpected method %q", r.Method)
   553  			}
   554  			io.WriteString(w, "foo")
   555  		},
   556  	}.run(t)
   557  }
   558  
   559  func TestH12_HandlerWritesTooLittle(t *testing.T) {
   560  	h12Compare{
   561  		Handler: func(w ResponseWriter, r *Request) {
   562  			w.Header().Set("Content-Length", "3")
   563  			io.WriteString(w, "12") // one byte short
   564  		},
   565  		CheckResponse: func(proto string, res *Response) {
   566  			sr, ok := res.Body.(slurpResult)
   567  			if !ok {
   568  				t.Errorf("%s body is %T; want slurpResult", proto, res.Body)
   569  				return
   570  			}
   571  			if sr.err != io.ErrUnexpectedEOF {
   572  				t.Errorf("%s read error = %v; want io.ErrUnexpectedEOF", proto, sr.err)
   573  			}
   574  			if string(sr.body) != "12" {
   575  				t.Errorf("%s body = %q; want %q", proto, sr.body, "12")
   576  			}
   577  		},
   578  	}.run(t)
   579  }
   580  
   581  // Tests that the HTTP/1 and HTTP/2 servers prevent handlers from
   582  // writing more than they declared. This test does not test whether
   583  // the transport deals with too much data, though, since the server
   584  // doesn't make it possible to send bogus data. For those tests, see
   585  // transport_test.go (for HTTP/1) or x/net/http2/transport_test.go
   586  // (for HTTP/2).
   587  func TestHandlerWritesTooMuch(t *testing.T) { run(t, testHandlerWritesTooMuch) }
   588  func testHandlerWritesTooMuch(t *testing.T, mode testMode) {
   589  	wantBody := []byte("123")
   590  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
   591  		rc := NewResponseController(w)
   592  		w.Header().Set("Content-Length", fmt.Sprintf("%v", len(wantBody)))
   593  		rc.Flush()
   594  		w.Write(wantBody)
   595  		rc.Flush()
   596  		n, err := io.WriteString(w, "x") // too many
   597  		if err == nil {
   598  			err = rc.Flush()
   599  		}
   600  		// TODO: Check that this is ErrContentLength, not just any error.
   601  		if err == nil {
   602  			t.Errorf("for proto %q, final write = %v, %v; want _, some error", r.Proto, n, err)
   603  		}
   604  	}))
   605  
   606  	res, err := cst.c.Get(cst.ts.URL)
   607  	if err != nil {
   608  		t.Fatal(err)
   609  	}
   610  	defer res.Body.Close()
   611  
   612  	gotBody, _ := io.ReadAll(res.Body)
   613  	if !bytes.Equal(gotBody, wantBody) {
   614  		t.Fatalf("got response body: %q; want %q", gotBody, wantBody)
   615  	}
   616  }
   617  
   618  // Verify that both our HTTP/1 and HTTP/2 request and auto-decompress gzip.
   619  // Some hosts send gzip even if you don't ask for it; see golang.org/issue/13298
   620  func TestH12_AutoGzip(t *testing.T) {
   621  	h12Compare{
   622  		Handler: func(w ResponseWriter, r *Request) {
   623  			if ae := r.Header.Get("Accept-Encoding"); ae != "gzip" {
   624  				t.Errorf("%s Accept-Encoding = %q; want gzip", r.Proto, ae)
   625  			}
   626  			w.Header().Set("Content-Encoding", "gzip")
   627  			gz := gzip.NewWriter(w)
   628  			io.WriteString(gz, "I am some gzipped content. Go go go go go go go go go go go go should compress well.")
   629  			gz.Close()
   630  		},
   631  	}.run(t)
   632  }
   633  
   634  func TestH12_AutoGzip_Disabled(t *testing.T) {
   635  	h12Compare{
   636  		Opts: []any{
   637  			func(tr *Transport) { tr.DisableCompression = true },
   638  		},
   639  		Handler: func(w ResponseWriter, r *Request) {
   640  			fmt.Fprintf(w, "%q", r.Header["Accept-Encoding"])
   641  			if ae := r.Header.Get("Accept-Encoding"); ae != "" {
   642  				t.Errorf("%s Accept-Encoding = %q; want empty", r.Proto, ae)
   643  			}
   644  		},
   645  	}.run(t)
   646  }
   647  
   648  // Test304Responses verifies that 304s don't declare that they're
   649  // chunking in their response headers and aren't allowed to produce
   650  // output.
   651  func Test304Responses(t *testing.T) { run(t, test304Responses) }
   652  func test304Responses(t *testing.T, mode testMode) {
   653  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
   654  		w.WriteHeader(StatusNotModified)
   655  		_, err := w.Write([]byte("illegal body"))
   656  		if err != ErrBodyNotAllowed {
   657  			t.Errorf("on Write, expected ErrBodyNotAllowed, got %v", err)
   658  		}
   659  	}))
   660  	defer cst.close()
   661  	res, err := cst.c.Get(cst.ts.URL)
   662  	if err != nil {
   663  		t.Fatal(err)
   664  	}
   665  	if len(res.TransferEncoding) > 0 {
   666  		t.Errorf("expected no TransferEncoding; got %v", res.TransferEncoding)
   667  	}
   668  	body, err := io.ReadAll(res.Body)
   669  	if err != nil {
   670  		t.Error(err)
   671  	}
   672  	if len(body) > 0 {
   673  		t.Errorf("got unexpected body %q", string(body))
   674  	}
   675  }
   676  
   677  func TestH12_ServerEmptyContentLength(t *testing.T) {
   678  	h12Compare{
   679  		Handler: func(w ResponseWriter, r *Request) {
   680  			w.Header()["Content-Type"] = []string{""}
   681  			io.WriteString(w, "<html><body>hi</body></html>")
   682  		},
   683  	}.run(t)
   684  }
   685  
   686  func TestH12_RequestContentLength_Known_NonZero(t *testing.T) {
   687  	h12requestContentLength(t, func() io.Reader { return strings.NewReader("FOUR") }, 4)
   688  }
   689  
   690  func TestH12_RequestContentLength_Known_Zero(t *testing.T) {
   691  	h12requestContentLength(t, func() io.Reader { return nil }, 0)
   692  }
   693  
   694  func TestH12_RequestContentLength_Unknown(t *testing.T) {
   695  	h12requestContentLength(t, func() io.Reader { return struct{ io.Reader }{strings.NewReader("Stuff")} }, -1)
   696  }
   697  
   698  func h12requestContentLength(t *testing.T, bodyfn func() io.Reader, wantLen int64) {
   699  	h12Compare{
   700  		Handler: func(w ResponseWriter, r *Request) {
   701  			w.Header().Set("Got-Length", fmt.Sprint(r.ContentLength))
   702  			fmt.Fprintf(w, "Req.ContentLength=%v", r.ContentLength)
   703  		},
   704  		ReqFunc: func(c *Client, url string) (*Response, error) {
   705  			return c.Post(url, "text/plain", bodyfn())
   706  		},
   707  		CheckResponse: func(proto string, res *Response) {
   708  			if got, want := res.Header.Get("Got-Length"), fmt.Sprint(wantLen); got != want {
   709  				t.Errorf("Proto %q got length %q; want %q", proto, got, want)
   710  			}
   711  		},
   712  	}.run(t)
   713  }
   714  
   715  // Tests that closing the Request.Cancel channel also while still
   716  // reading the response body. Issue 13159.
   717  func TestCancelRequestMidBody(t *testing.T) { run(t, testCancelRequestMidBody) }
   718  func testCancelRequestMidBody(t *testing.T, mode testMode) {
   719  	unblock := make(chan bool)
   720  	didFlush := make(chan bool, 1)
   721  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
   722  		io.WriteString(w, "Hello")
   723  		w.(Flusher).Flush()
   724  		didFlush <- true
   725  		<-unblock
   726  		io.WriteString(w, ", world.")
   727  	}))
   728  	defer close(unblock)
   729  
   730  	req, _ := NewRequest("GET", cst.ts.URL, nil)
   731  	cancel := make(chan struct{})
   732  	req.Cancel = cancel
   733  
   734  	res, err := cst.c.Do(req)
   735  	if err != nil {
   736  		t.Fatal(err)
   737  	}
   738  	defer res.Body.Close()
   739  	<-didFlush
   740  
   741  	// Read a bit before we cancel. (Issue 13626)
   742  	// We should have "Hello" at least sitting there.
   743  	firstRead := make([]byte, 10)
   744  	n, err := res.Body.Read(firstRead)
   745  	if err != nil {
   746  		t.Fatal(err)
   747  	}
   748  	firstRead = firstRead[:n]
   749  
   750  	close(cancel)
   751  
   752  	rest, err := io.ReadAll(res.Body)
   753  	all := string(firstRead) + string(rest)
   754  	if all != "Hello" {
   755  		t.Errorf("Read %q (%q + %q); want Hello", all, firstRead, rest)
   756  	}
   757  	if err != ExportErrRequestCanceled {
   758  		t.Errorf("ReadAll error = %v; want %v", err, ExportErrRequestCanceled)
   759  	}
   760  }
   761  
   762  // Tests that clients can send trailers to a server and that the server can read them.
   763  func TestTrailersClientToServer(t *testing.T) { run(t, testTrailersClientToServer) }
   764  func testTrailersClientToServer(t *testing.T, mode testMode) {
   765  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
   766  		slurp, err := io.ReadAll(r.Body)
   767  		if err != nil {
   768  			t.Errorf("Server reading request body: %v", err)
   769  		}
   770  		if string(slurp) != "foo" {
   771  			t.Errorf("Server read request body %q; want foo", slurp)
   772  		}
   773  		if r.Trailer == nil {
   774  			io.WriteString(w, "nil Trailer")
   775  		} else {
   776  			decl := slices.Sorted(maps.Keys(r.Trailer))
   777  			fmt.Fprintf(w, "decl: %v, vals: %s, %s",
   778  				decl,
   779  				r.Trailer.Get("Client-Trailer-A"),
   780  				r.Trailer.Get("Client-Trailer-B"))
   781  		}
   782  	}))
   783  
   784  	var req *Request
   785  	req, _ = NewRequest("POST", cst.ts.URL, io.MultiReader(
   786  		eofReaderFunc(func() {
   787  			req.Trailer["Client-Trailer-A"] = []string{"valuea"}
   788  		}),
   789  		strings.NewReader("foo"),
   790  		eofReaderFunc(func() {
   791  			req.Trailer["Client-Trailer-B"] = []string{"valueb"}
   792  		}),
   793  	))
   794  	req.Trailer = Header{
   795  		"Client-Trailer-A": nil, //  to be set later
   796  		"Client-Trailer-B": nil, //  to be set later
   797  	}
   798  	req.ContentLength = -1
   799  	res, err := cst.c.Do(req)
   800  	if err != nil {
   801  		t.Fatal(err)
   802  	}
   803  	if err := wantBody(res, err, "decl: [Client-Trailer-A Client-Trailer-B], vals: valuea, valueb"); err != nil {
   804  		t.Error(err)
   805  	}
   806  }
   807  
   808  // Tests that servers send trailers to a client and that the client can read them.
   809  func TestTrailersServerToClient(t *testing.T) {
   810  	run(t, func(t *testing.T, mode testMode) {
   811  		testTrailersServerToClient(t, mode, false)
   812  	})
   813  }
   814  func TestTrailersServerToClientFlush(t *testing.T) {
   815  	run(t, func(t *testing.T, mode testMode) {
   816  		testTrailersServerToClient(t, mode, true)
   817  	})
   818  }
   819  
   820  func testTrailersServerToClient(t *testing.T, mode testMode, flush bool) {
   821  	const body = "Some body"
   822  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
   823  		w.Header().Set("Trailer", "Server-Trailer-A, Server-Trailer-B")
   824  		w.Header().Add("Trailer", "Server-Trailer-C")
   825  
   826  		io.WriteString(w, body)
   827  		if flush {
   828  			w.(Flusher).Flush()
   829  		}
   830  
   831  		// How handlers set Trailers: declare it ahead of time
   832  		// with the Trailer header, and then mutate the
   833  		// Header() of those values later, after the response
   834  		// has been written (we wrote to w above).
   835  		w.Header().Set("Server-Trailer-A", "valuea")
   836  		w.Header().Set("Server-Trailer-C", "valuec") // skipping B
   837  		w.Header().Set("Server-Trailer-NotDeclared", "should be omitted")
   838  	}))
   839  
   840  	res, err := cst.c.Get(cst.ts.URL)
   841  	if err != nil {
   842  		t.Fatal(err)
   843  	}
   844  
   845  	wantHeader := Header{
   846  		"Content-Type": {"text/plain; charset=utf-8"},
   847  	}
   848  	wantLen := -1
   849  	if mode == http2Mode && !flush {
   850  		// In HTTP/1.1, any use of trailers forces HTTP/1.1
   851  		// chunking and a flush at the first write. That's
   852  		// unnecessary with HTTP/2's framing, so the server
   853  		// is able to calculate the length while still sending
   854  		// trailers afterwards.
   855  		wantLen = len(body)
   856  		wantHeader["Content-Length"] = []string{fmt.Sprint(wantLen)}
   857  	}
   858  	if res.ContentLength != int64(wantLen) {
   859  		t.Errorf("ContentLength = %v; want %v", res.ContentLength, wantLen)
   860  	}
   861  
   862  	delete(res.Header, "Date") // irrelevant for test
   863  	if !reflect.DeepEqual(res.Header, wantHeader) {
   864  		t.Errorf("Header = %v; want %v", res.Header, wantHeader)
   865  	}
   866  
   867  	if got, want := res.Trailer, (Header{
   868  		"Server-Trailer-A": nil,
   869  		"Server-Trailer-B": nil,
   870  		"Server-Trailer-C": nil,
   871  	}); !reflect.DeepEqual(got, want) {
   872  		t.Errorf("Trailer before body read = %v; want %v", got, want)
   873  	}
   874  
   875  	if err := wantBody(res, nil, body); err != nil {
   876  		t.Fatal(err)
   877  	}
   878  
   879  	if got, want := res.Trailer, (Header{
   880  		"Server-Trailer-A": {"valuea"},
   881  		"Server-Trailer-B": nil,
   882  		"Server-Trailer-C": {"valuec"},
   883  	}); !reflect.DeepEqual(got, want) {
   884  		t.Errorf("Trailer after body read = %v; want %v", got, want)
   885  	}
   886  }
   887  
   888  // Don't allow a Body.Read after Body.Close. Issue 13648.
   889  func TestResponseBodyReadAfterClose(t *testing.T) { run(t, testResponseBodyReadAfterClose) }
   890  func testResponseBodyReadAfterClose(t *testing.T, mode testMode) {
   891  	const body = "Some body"
   892  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
   893  		io.WriteString(w, body)
   894  	}))
   895  	res, err := cst.c.Get(cst.ts.URL)
   896  	if err != nil {
   897  		t.Fatal(err)
   898  	}
   899  	res.Body.Close()
   900  	data, err := io.ReadAll(res.Body)
   901  	if len(data) != 0 || err == nil {
   902  		t.Fatalf("ReadAll returned %q, %v; want error", data, err)
   903  	}
   904  }
   905  
   906  func TestConcurrentReadWriteReqBody(t *testing.T) { run(t, testConcurrentReadWriteReqBody) }
   907  func testConcurrentReadWriteReqBody(t *testing.T, mode testMode) {
   908  	const reqBody = "some request body"
   909  	const resBody = "some response body"
   910  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
   911  		var wg sync.WaitGroup
   912  		wg.Add(2)
   913  		didRead := make(chan bool, 1)
   914  		// Read in one goroutine.
   915  		go func() {
   916  			defer wg.Done()
   917  			data, err := io.ReadAll(r.Body)
   918  			if string(data) != reqBody {
   919  				t.Errorf("Handler read %q; want %q", data, reqBody)
   920  			}
   921  			if err != nil {
   922  				t.Errorf("Handler Read: %v", err)
   923  			}
   924  			didRead <- true
   925  		}()
   926  		// Write in another goroutine.
   927  		go func() {
   928  			defer wg.Done()
   929  			if mode != http2Mode {
   930  				// our HTTP/1 implementation intentionally
   931  				// doesn't permit writes during read (mostly
   932  				// due to it being undefined); if that is ever
   933  				// relaxed, change this.
   934  				<-didRead
   935  			}
   936  			io.WriteString(w, resBody)
   937  		}()
   938  		wg.Wait()
   939  	}))
   940  	req, _ := NewRequest("POST", cst.ts.URL, strings.NewReader(reqBody))
   941  	req.Header.Add("Expect", "100-continue") // just to complicate things
   942  	res, err := cst.c.Do(req)
   943  	if err != nil {
   944  		t.Fatal(err)
   945  	}
   946  	data, err := io.ReadAll(res.Body)
   947  	defer res.Body.Close()
   948  	if err != nil {
   949  		t.Fatal(err)
   950  	}
   951  	if string(data) != resBody {
   952  		t.Errorf("read %q; want %q", data, resBody)
   953  	}
   954  }
   955  
   956  func TestConnectRequest(t *testing.T) { run(t, testConnectRequest) }
   957  func testConnectRequest(t *testing.T, mode testMode) {
   958  	gotc := make(chan *Request, 1)
   959  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
   960  		gotc <- r
   961  	}))
   962  
   963  	u, err := url.Parse(cst.ts.URL)
   964  	if err != nil {
   965  		t.Fatal(err)
   966  	}
   967  
   968  	tests := []struct {
   969  		req  *Request
   970  		want string
   971  	}{
   972  		{
   973  			req: &Request{
   974  				Method: "CONNECT",
   975  				Header: Header{},
   976  				URL:    u,
   977  			},
   978  			want: u.Host,
   979  		},
   980  		{
   981  			req: &Request{
   982  				Method: "CONNECT",
   983  				Header: Header{},
   984  				URL:    u,
   985  				Host:   "example.com:123",
   986  			},
   987  			want: "example.com:123",
   988  		},
   989  	}
   990  
   991  	for i, tt := range tests {
   992  		res, err := cst.c.Do(tt.req)
   993  		if err != nil {
   994  			t.Errorf("%d. RoundTrip = %v", i, err)
   995  			continue
   996  		}
   997  		res.Body.Close()
   998  		req := <-gotc
   999  		if req.Method != "CONNECT" {
  1000  			t.Errorf("method = %q; want CONNECT", req.Method)
  1001  		}
  1002  		if req.Host != tt.want {
  1003  			t.Errorf("Host = %q; want %q", req.Host, tt.want)
  1004  		}
  1005  		if req.URL.Host != tt.want {
  1006  			t.Errorf("URL.Host = %q; want %q", req.URL.Host, tt.want)
  1007  		}
  1008  	}
  1009  }
  1010  
  1011  func TestTransportUserAgent(t *testing.T) { run(t, testTransportUserAgent) }
  1012  func testTransportUserAgent(t *testing.T, mode testMode) {
  1013  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1014  		fmt.Fprintf(w, "%q", r.Header["User-Agent"])
  1015  	}))
  1016  
  1017  	either := func(a, b string) string {
  1018  		if mode == http2Mode {
  1019  			return b
  1020  		}
  1021  		return a
  1022  	}
  1023  
  1024  	tests := []struct {
  1025  		setup func(*Request)
  1026  		want  string
  1027  	}{
  1028  		{
  1029  			func(r *Request) {},
  1030  			either(`["Go-http-client/1.1"]`, `["Go-http-client/2.0"]`),
  1031  		},
  1032  		{
  1033  			func(r *Request) { r.Header.Set("User-Agent", "foo/1.2.3") },
  1034  			`["foo/1.2.3"]`,
  1035  		},
  1036  		{
  1037  			func(r *Request) { r.Header["User-Agent"] = []string{"single", "or", "multiple"} },
  1038  			`["single"]`,
  1039  		},
  1040  		{
  1041  			func(r *Request) { r.Header.Set("User-Agent", "") },
  1042  			`[]`,
  1043  		},
  1044  		{
  1045  			func(r *Request) { r.Header["User-Agent"] = nil },
  1046  			`[]`,
  1047  		},
  1048  	}
  1049  	for i, tt := range tests {
  1050  		req, _ := NewRequest("GET", cst.ts.URL, nil)
  1051  		tt.setup(req)
  1052  		res, err := cst.c.Do(req)
  1053  		if err != nil {
  1054  			t.Errorf("%d. RoundTrip = %v", i, err)
  1055  			continue
  1056  		}
  1057  		slurp, err := io.ReadAll(res.Body)
  1058  		res.Body.Close()
  1059  		if err != nil {
  1060  			t.Errorf("%d. read body = %v", i, err)
  1061  			continue
  1062  		}
  1063  		if string(slurp) != tt.want {
  1064  			t.Errorf("%d. body mismatch.\n got: %s\nwant: %s\n", i, slurp, tt.want)
  1065  		}
  1066  	}
  1067  }
  1068  
  1069  func TestStarRequestMethod(t *testing.T) {
  1070  	for _, method := range []string{"FOO", "OPTIONS"} {
  1071  		t.Run(method, func(t *testing.T) {
  1072  			run(t, func(t *testing.T, mode testMode) {
  1073  				testStarRequest(t, method, mode)
  1074  			})
  1075  		})
  1076  	}
  1077  }
  1078  func testStarRequest(t *testing.T, method string, mode testMode) {
  1079  	gotc := make(chan *Request, 1)
  1080  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1081  		w.Header().Set("foo", "bar")
  1082  		gotc <- r
  1083  		w.(Flusher).Flush()
  1084  	}))
  1085  
  1086  	u, err := url.Parse(cst.ts.URL)
  1087  	if err != nil {
  1088  		t.Fatal(err)
  1089  	}
  1090  	u.Path = "*"
  1091  
  1092  	req := &Request{
  1093  		Method: method,
  1094  		Header: Header{},
  1095  		URL:    u,
  1096  	}
  1097  
  1098  	res, err := cst.c.Do(req)
  1099  	if err != nil {
  1100  		t.Fatalf("RoundTrip = %v", err)
  1101  	}
  1102  	res.Body.Close()
  1103  
  1104  	wantFoo := "bar"
  1105  	wantLen := int64(-1)
  1106  	if method == "OPTIONS" {
  1107  		wantFoo = ""
  1108  		wantLen = 0
  1109  	}
  1110  	if res.StatusCode != 200 {
  1111  		t.Errorf("status code = %v; want %d", res.Status, 200)
  1112  	}
  1113  	if res.ContentLength != wantLen {
  1114  		t.Errorf("content length = %v; want %d", res.ContentLength, wantLen)
  1115  	}
  1116  	if got := res.Header.Get("foo"); got != wantFoo {
  1117  		t.Errorf("response \"foo\" header = %q; want %q", got, wantFoo)
  1118  	}
  1119  	select {
  1120  	case req = <-gotc:
  1121  	default:
  1122  		req = nil
  1123  	}
  1124  	if req == nil {
  1125  		if method != "OPTIONS" {
  1126  			t.Fatalf("handler never got request")
  1127  		}
  1128  		return
  1129  	}
  1130  	if req.Method != method {
  1131  		t.Errorf("method = %q; want %q", req.Method, method)
  1132  	}
  1133  	if req.URL.Path != "*" {
  1134  		t.Errorf("URL.Path = %q; want *", req.URL.Path)
  1135  	}
  1136  	if req.RequestURI != "*" {
  1137  		t.Errorf("RequestURI = %q; want *", req.RequestURI)
  1138  	}
  1139  }
  1140  
  1141  // Issue 13957
  1142  func TestTransportDiscardsUnneededConns(t *testing.T) {
  1143  	run(t, testTransportDiscardsUnneededConns, []testMode{http2Mode})
  1144  }
  1145  func testTransportDiscardsUnneededConns(t *testing.T, mode testMode) {
  1146  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1147  		fmt.Fprintf(w, "Hello, %v", r.RemoteAddr)
  1148  	}))
  1149  	defer cst.close()
  1150  
  1151  	var numOpen, numClose int32 // atomic
  1152  
  1153  	tlsConfig := &tls.Config{InsecureSkipVerify: true}
  1154  	tr := &Transport{
  1155  		TLSClientConfig: tlsConfig,
  1156  		DialTLS: func(_, addr string) (net.Conn, error) {
  1157  			time.Sleep(10 * time.Millisecond)
  1158  			rc, err := net.Dial("tcp", addr)
  1159  			if err != nil {
  1160  				return nil, err
  1161  			}
  1162  			atomic.AddInt32(&numOpen, 1)
  1163  			c := noteCloseConn{rc, func() { atomic.AddInt32(&numClose, 1) }}
  1164  			return tls.Client(c, tlsConfig), nil
  1165  		},
  1166  	}
  1167  	if err := ExportHttp2ConfigureTransport(tr); err != nil {
  1168  		t.Fatal(err)
  1169  	}
  1170  	defer tr.CloseIdleConnections()
  1171  
  1172  	c := &Client{Transport: tr}
  1173  
  1174  	const N = 10
  1175  	gotBody := make(chan string, N)
  1176  	var wg sync.WaitGroup
  1177  	for i := 0; i < N; i++ {
  1178  		wg.Add(1)
  1179  		go func() {
  1180  			defer wg.Done()
  1181  			resp, err := c.Get(cst.ts.URL)
  1182  			if err != nil {
  1183  				// Try to work around spurious connection reset on loaded system.
  1184  				// See golang.org/issue/33585 and golang.org/issue/36797.
  1185  				time.Sleep(10 * time.Millisecond)
  1186  				resp, err = c.Get(cst.ts.URL)
  1187  				if err != nil {
  1188  					t.Errorf("Get: %v", err)
  1189  					return
  1190  				}
  1191  			}
  1192  			defer resp.Body.Close()
  1193  			slurp, err := io.ReadAll(resp.Body)
  1194  			if err != nil {
  1195  				t.Error(err)
  1196  			}
  1197  			gotBody <- string(slurp)
  1198  		}()
  1199  	}
  1200  	wg.Wait()
  1201  	close(gotBody)
  1202  
  1203  	var last string
  1204  	for got := range gotBody {
  1205  		if last == "" {
  1206  			last = got
  1207  			continue
  1208  		}
  1209  		if got != last {
  1210  			t.Errorf("Response body changed: %q -> %q", last, got)
  1211  		}
  1212  	}
  1213  
  1214  	var open, close int32
  1215  	for i := 0; i < 150; i++ {
  1216  		open, close = atomic.LoadInt32(&numOpen), atomic.LoadInt32(&numClose)
  1217  		if open < 1 {
  1218  			t.Fatalf("open = %d; want at least", open)
  1219  		}
  1220  		if close == open-1 {
  1221  			// Success
  1222  			return
  1223  		}
  1224  		time.Sleep(10 * time.Millisecond)
  1225  	}
  1226  	t.Errorf("%d connections opened, %d closed; want %d to close", open, close, open-1)
  1227  }
  1228  
  1229  // tests that Transport doesn't retain a pointer to the provided request.
  1230  func TestTransportGCRequest(t *testing.T) {
  1231  	run(t, func(t *testing.T, mode testMode) {
  1232  		t.Run("Body", func(t *testing.T) { testTransportGCRequest(t, mode, true) })
  1233  		t.Run("NoBody", func(t *testing.T) { testTransportGCRequest(t, mode, false) })
  1234  	})
  1235  }
  1236  func testTransportGCRequest(t *testing.T, mode testMode, body bool) {
  1237  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1238  		io.ReadAll(r.Body)
  1239  		if body {
  1240  			io.WriteString(w, "Hello.")
  1241  		}
  1242  	}))
  1243  
  1244  	didGC := make(chan struct{})
  1245  	(func() {
  1246  		body := strings.NewReader("some body")
  1247  		req, _ := NewRequest("POST", cst.ts.URL, body)
  1248  		runtime.AddCleanup(req, func(ch chan struct{}) { close(ch) }, didGC)
  1249  		res, err := cst.c.Do(req)
  1250  		if err != nil {
  1251  			t.Fatal(err)
  1252  		}
  1253  		if _, err := io.ReadAll(res.Body); err != nil {
  1254  			t.Fatal(err)
  1255  		}
  1256  		if err := res.Body.Close(); err != nil {
  1257  			t.Fatal(err)
  1258  		}
  1259  	})()
  1260  	for {
  1261  		select {
  1262  		case <-didGC:
  1263  			return
  1264  		case <-time.After(1 * time.Millisecond):
  1265  			runtime.GC()
  1266  		}
  1267  	}
  1268  }
  1269  
  1270  func TestTransportRejectsInvalidHeaders(t *testing.T) { run(t, testTransportRejectsInvalidHeaders) }
  1271  func testTransportRejectsInvalidHeaders(t *testing.T, mode testMode) {
  1272  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1273  		fmt.Fprintf(w, "Handler saw headers: %q", r.Header)
  1274  	}), optQuietLog)
  1275  	cst.tr.DisableKeepAlives = true
  1276  
  1277  	tests := []struct {
  1278  		key, val string
  1279  		ok       bool
  1280  	}{
  1281  		{"Foo", "capital-key", true}, // verify h2 allows capital keys
  1282  		{"Foo", "foo\x00bar", false}, // \x00 byte in value not allowed
  1283  		{"Foo", "two\nlines", false}, // \n byte in value not allowed
  1284  		{"bogus\nkey", "v", false},   // \n byte also not allowed in key
  1285  		{"A space", "v", false},      // spaces in keys not allowed
  1286  		{"имя", "v", false},          // key must be ascii
  1287  		{"name", "валю", true},       // value may be non-ascii
  1288  		{"", "v", false},             // key must be non-empty
  1289  		{"k", "", true},              // value may be empty
  1290  	}
  1291  	for _, tt := range tests {
  1292  		dialedc := make(chan bool, 1)
  1293  		cst.tr.Dial = func(netw, addr string) (net.Conn, error) {
  1294  			dialedc <- true
  1295  			return net.Dial(netw, addr)
  1296  		}
  1297  		req, _ := NewRequest("GET", cst.ts.URL, nil)
  1298  		req.Header[tt.key] = []string{tt.val}
  1299  		res, err := cst.c.Do(req)
  1300  		var body []byte
  1301  		if err == nil {
  1302  			body, _ = io.ReadAll(res.Body)
  1303  			res.Body.Close()
  1304  		}
  1305  		var dialed bool
  1306  		select {
  1307  		case <-dialedc:
  1308  			dialed = true
  1309  		default:
  1310  		}
  1311  
  1312  		if !tt.ok && dialed {
  1313  			t.Errorf("For key %q, value %q, transport dialed. Expected local failure. Response was: (%v, %v)\nServer replied with: %s", tt.key, tt.val, res, err, body)
  1314  		} else if (err == nil) != tt.ok {
  1315  			t.Errorf("For key %q, value %q; got err = %v; want ok=%v", tt.key, tt.val, err, tt.ok)
  1316  		}
  1317  	}
  1318  }
  1319  
  1320  func TestInterruptWithPanic(t *testing.T) {
  1321  	run(t, func(t *testing.T, mode testMode) {
  1322  		t.Run("boom", func(t *testing.T) { testInterruptWithPanic(t, mode, "boom") })
  1323  		t.Run("nil", func(t *testing.T) { t.Setenv("GODEBUG", "panicnil=1"); testInterruptWithPanic(t, mode, nil) })
  1324  		t.Run("ErrAbortHandler", func(t *testing.T) { testInterruptWithPanic(t, mode, ErrAbortHandler) })
  1325  	}, testNotParallel)
  1326  }
  1327  func testInterruptWithPanic(t *testing.T, mode testMode, panicValue any) {
  1328  	const msg = "hello"
  1329  
  1330  	testDone := make(chan struct{})
  1331  	defer close(testDone)
  1332  
  1333  	var errorLog lockedBytesBuffer
  1334  	gotHeaders := make(chan bool, 1)
  1335  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1336  		io.WriteString(w, msg)
  1337  		w.(Flusher).Flush()
  1338  
  1339  		select {
  1340  		case <-gotHeaders:
  1341  		case <-testDone:
  1342  		}
  1343  		panic(panicValue)
  1344  	}), func(ts *httptest.Server) {
  1345  		ts.Config.ErrorLog = log.New(&errorLog, "", 0)
  1346  	})
  1347  	res, err := cst.c.Get(cst.ts.URL)
  1348  	if err != nil {
  1349  		t.Fatal(err)
  1350  	}
  1351  	gotHeaders <- true
  1352  	defer res.Body.Close()
  1353  	slurp, err := io.ReadAll(res.Body)
  1354  	if string(slurp) != msg {
  1355  		t.Errorf("client read %q; want %q", slurp, msg)
  1356  	}
  1357  	if err == nil {
  1358  		t.Errorf("client read all successfully; want some error")
  1359  	}
  1360  	logOutput := func() string {
  1361  		errorLog.Lock()
  1362  		defer errorLog.Unlock()
  1363  		return errorLog.String()
  1364  	}
  1365  	wantStackLogged := panicValue != nil && panicValue != ErrAbortHandler
  1366  
  1367  	waitCondition(t, 10*time.Millisecond, func(d time.Duration) bool {
  1368  		gotLog := logOutput()
  1369  		if !wantStackLogged {
  1370  			if gotLog == "" {
  1371  				return true
  1372  			}
  1373  			t.Fatalf("want no log output; got: %s", gotLog)
  1374  		}
  1375  		if gotLog == "" {
  1376  			if d > 0 {
  1377  				t.Logf("wanted a stack trace logged; got nothing after %v", d)
  1378  			}
  1379  			return false
  1380  		}
  1381  		if !strings.Contains(gotLog, "created by ") && strings.Count(gotLog, "\n") < 6 {
  1382  			if d > 0 {
  1383  				t.Logf("output doesn't look like a panic stack trace after %v. Got: %s", d, gotLog)
  1384  			}
  1385  			return false
  1386  		}
  1387  		return true
  1388  	})
  1389  }
  1390  
  1391  type lockedBytesBuffer struct {
  1392  	sync.Mutex
  1393  	bytes.Buffer
  1394  }
  1395  
  1396  func (b *lockedBytesBuffer) Write(p []byte) (int, error) {
  1397  	b.Lock()
  1398  	defer b.Unlock()
  1399  	return b.Buffer.Write(p)
  1400  }
  1401  
  1402  // Issue 15366
  1403  func TestH12_AutoGzipWithDumpResponse(t *testing.T) {
  1404  	h12Compare{
  1405  		Handler: func(w ResponseWriter, r *Request) {
  1406  			h := w.Header()
  1407  			h.Set("Content-Encoding", "gzip")
  1408  			h.Set("Content-Length", "23")
  1409  			io.WriteString(w, "\x1f\x8b\b\x00\x00\x00\x00\x00\x00\x00s\xf3\xf7\a\x00\xab'\xd4\x1a\x03\x00\x00\x00")
  1410  		},
  1411  		EarlyCheckResponse: func(proto string, res *Response) {
  1412  			if !res.Uncompressed {
  1413  				t.Errorf("%s: expected Uncompressed to be set", proto)
  1414  			}
  1415  			dump, err := httputil.DumpResponse(res, true)
  1416  			if err != nil {
  1417  				t.Errorf("%s: DumpResponse: %v", proto, err)
  1418  				return
  1419  			}
  1420  			if strings.Contains(string(dump), "Connection: close") {
  1421  				t.Errorf("%s: should not see \"Connection: close\" in dump; got:\n%s", proto, dump)
  1422  			}
  1423  			if !strings.Contains(string(dump), "FOO") {
  1424  				t.Errorf("%s: should see \"FOO\" in response; got:\n%s", proto, dump)
  1425  			}
  1426  		},
  1427  	}.run(t)
  1428  }
  1429  
  1430  // Issue 14607
  1431  func TestCloseIdleConnections(t *testing.T) { run(t, testCloseIdleConnections) }
  1432  func testCloseIdleConnections(t *testing.T, mode testMode) {
  1433  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1434  		w.Header().Set("X-Addr", r.RemoteAddr)
  1435  	}))
  1436  	get := func() string {
  1437  		res, err := cst.c.Get(cst.ts.URL)
  1438  		if err != nil {
  1439  			t.Fatal(err)
  1440  		}
  1441  		res.Body.Close()
  1442  		v := res.Header.Get("X-Addr")
  1443  		if v == "" {
  1444  			t.Fatal("didn't get X-Addr")
  1445  		}
  1446  		return v
  1447  	}
  1448  	a1 := get()
  1449  	cst.tr.CloseIdleConnections()
  1450  	a2 := get()
  1451  	if a1 == a2 {
  1452  		t.Errorf("didn't close connection")
  1453  	}
  1454  }
  1455  
  1456  type noteCloseConn struct {
  1457  	net.Conn
  1458  	closeFunc func()
  1459  }
  1460  
  1461  func (x noteCloseConn) Close() error {
  1462  	x.closeFunc()
  1463  	return x.Conn.Close()
  1464  }
  1465  
  1466  type testErrorReader struct{ t *testing.T }
  1467  
  1468  func (r testErrorReader) Read(p []byte) (n int, err error) {
  1469  	r.t.Error("unexpected Read call")
  1470  	return 0, io.EOF
  1471  }
  1472  
  1473  func TestNoSniffExpectRequestBody(t *testing.T) { run(t, testNoSniffExpectRequestBody) }
  1474  func testNoSniffExpectRequestBody(t *testing.T, mode testMode) {
  1475  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1476  		w.WriteHeader(StatusUnauthorized)
  1477  	}))
  1478  
  1479  	// Set ExpectContinueTimeout non-zero so RoundTrip won't try to write it.
  1480  	cst.tr.ExpectContinueTimeout = 10 * time.Second
  1481  
  1482  	req, err := NewRequest("POST", cst.ts.URL, testErrorReader{t})
  1483  	if err != nil {
  1484  		t.Fatal(err)
  1485  	}
  1486  	req.ContentLength = 0 // so transport is tempted to sniff it
  1487  	req.Header.Set("Expect", "100-continue")
  1488  	res, err := cst.tr.RoundTrip(req)
  1489  	if err != nil {
  1490  		t.Fatal(err)
  1491  	}
  1492  	defer res.Body.Close()
  1493  	if res.StatusCode != StatusUnauthorized {
  1494  		t.Errorf("status code = %v; want %v", res.StatusCode, StatusUnauthorized)
  1495  	}
  1496  }
  1497  
  1498  func TestServerUndeclaredTrailers(t *testing.T) { run(t, testServerUndeclaredTrailers) }
  1499  func testServerUndeclaredTrailers(t *testing.T, mode testMode) {
  1500  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1501  		w.Header().Set("Foo", "Bar")
  1502  		w.Header().Set("Trailer:Foo", "Baz")
  1503  		w.(Flusher).Flush()
  1504  		w.Header().Add("Trailer:Foo", "Baz2")
  1505  		w.Header().Set("Trailer:Bar", "Quux")
  1506  	}))
  1507  	res, err := cst.c.Get(cst.ts.URL)
  1508  	if err != nil {
  1509  		t.Fatal(err)
  1510  	}
  1511  	if _, err := io.Copy(io.Discard, res.Body); err != nil {
  1512  		t.Fatal(err)
  1513  	}
  1514  	res.Body.Close()
  1515  	delete(res.Header, "Date")
  1516  	delete(res.Header, "Content-Type")
  1517  
  1518  	if want := (Header{"Foo": {"Bar"}}); !reflect.DeepEqual(res.Header, want) {
  1519  		t.Errorf("Header = %#v; want %#v", res.Header, want)
  1520  	}
  1521  	if want := (Header{"Foo": {"Baz", "Baz2"}, "Bar": {"Quux"}}); !reflect.DeepEqual(res.Trailer, want) {
  1522  		t.Errorf("Trailer = %#v; want %#v", res.Trailer, want)
  1523  	}
  1524  }
  1525  
  1526  func TestBadResponseAfterReadingBody(t *testing.T) {
  1527  	run(t, testBadResponseAfterReadingBody, []testMode{http1Mode})
  1528  }
  1529  func testBadResponseAfterReadingBody(t *testing.T, mode testMode) {
  1530  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1531  		_, err := io.Copy(io.Discard, r.Body)
  1532  		if err != nil {
  1533  			t.Fatal(err)
  1534  		}
  1535  		c, _, err := w.(Hijacker).Hijack()
  1536  		if err != nil {
  1537  			t.Fatal(err)
  1538  		}
  1539  		defer c.Close()
  1540  		fmt.Fprintln(c, "some bogus crap")
  1541  	}))
  1542  
  1543  	closes := 0
  1544  	res, err := cst.c.Post(cst.ts.URL, "text/plain", countCloseReader{&closes, strings.NewReader("hello")})
  1545  	if err == nil {
  1546  		res.Body.Close()
  1547  		t.Fatal("expected an error to be returned from Post")
  1548  	}
  1549  	if closes != 1 {
  1550  		t.Errorf("closes = %d; want 1", closes)
  1551  	}
  1552  }
  1553  
  1554  func TestWriteHeader0(t *testing.T) { run(t, testWriteHeader0) }
  1555  func testWriteHeader0(t *testing.T, mode testMode) {
  1556  	gotpanic := make(chan bool, 1)
  1557  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1558  		defer close(gotpanic)
  1559  		defer func() {
  1560  			if e := recover(); e != nil {
  1561  				got := fmt.Sprintf("%T, %v", e, e)
  1562  				want := "string, invalid WriteHeader code 0"
  1563  				if got != want {
  1564  					t.Errorf("unexpected panic value:\n got: %v\nwant: %v\n", got, want)
  1565  				}
  1566  				gotpanic <- true
  1567  
  1568  				// Set an explicit 503. This also tests that the WriteHeader call panics
  1569  				// before it recorded that an explicit value was set and that bogus
  1570  				// value wasn't stuck.
  1571  				w.WriteHeader(503)
  1572  			}
  1573  		}()
  1574  		w.WriteHeader(0)
  1575  	}))
  1576  	res, err := cst.c.Get(cst.ts.URL)
  1577  	if err != nil {
  1578  		t.Fatal(err)
  1579  	}
  1580  	if res.StatusCode != 503 {
  1581  		t.Errorf("Response: %v %q; want 503", res.StatusCode, res.Status)
  1582  	}
  1583  	if !<-gotpanic {
  1584  		t.Error("expected panic in handler")
  1585  	}
  1586  }
  1587  
  1588  // Issue 23010: don't be super strict checking WriteHeader's code if
  1589  // it's not even valid to call WriteHeader then anyway.
  1590  func TestWriteHeaderNoCodeCheck(t *testing.T) {
  1591  	run(t, func(t *testing.T, mode testMode) {
  1592  		testWriteHeaderAfterWrite(t, mode, false)
  1593  	})
  1594  }
  1595  func TestWriteHeaderNoCodeCheck_h1hijack(t *testing.T) {
  1596  	testWriteHeaderAfterWrite(t, http1Mode, true)
  1597  }
  1598  func testWriteHeaderAfterWrite(t *testing.T, mode testMode, hijack bool) {
  1599  	var errorLog lockedBytesBuffer
  1600  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1601  		if hijack {
  1602  			conn, _, _ := w.(Hijacker).Hijack()
  1603  			defer conn.Close()
  1604  			conn.Write([]byte("HTTP/1.1 200 OK\r\nContent-Length: 6\r\n\r\nfoo"))
  1605  			w.WriteHeader(0) // verify this doesn't panic if there's already output; Issue 23010
  1606  			conn.Write([]byte("bar"))
  1607  			return
  1608  		}
  1609  		io.WriteString(w, "foo")
  1610  		w.(Flusher).Flush()
  1611  		w.WriteHeader(0) // verify this doesn't panic if there's already output; Issue 23010
  1612  		io.WriteString(w, "bar")
  1613  	}), func(ts *httptest.Server) {
  1614  		ts.Config.ErrorLog = log.New(&errorLog, "", 0)
  1615  	})
  1616  	res, err := cst.c.Get(cst.ts.URL)
  1617  	if err != nil {
  1618  		t.Fatal(err)
  1619  	}
  1620  	defer res.Body.Close()
  1621  	body, err := io.ReadAll(res.Body)
  1622  	if err != nil {
  1623  		t.Fatal(err)
  1624  	}
  1625  	if got, want := string(body), "foobar"; got != want {
  1626  		t.Errorf("got = %q; want %q", got, want)
  1627  	}
  1628  
  1629  	// Also check the stderr output:
  1630  	if mode == http2Mode {
  1631  		// TODO: also emit this log message for HTTP/2?
  1632  		// We historically haven't, so don't check.
  1633  		return
  1634  	}
  1635  	gotLog := strings.TrimSpace(errorLog.String())
  1636  	wantLog := "http: superfluous response.WriteHeader call from net/http_test.testWriteHeaderAfterWrite.func1 (clientserver_test.go:"
  1637  	if hijack {
  1638  		wantLog = "http: response.WriteHeader on hijacked connection from net/http_test.testWriteHeaderAfterWrite.func1 (clientserver_test.go:"
  1639  	}
  1640  	if !strings.HasPrefix(gotLog, wantLog) {
  1641  		t.Errorf("stderr output = %q; want %q", gotLog, wantLog)
  1642  	}
  1643  }
  1644  
  1645  func TestBidiStreamReverseProxy(t *testing.T) {
  1646  	run(t, testBidiStreamReverseProxy, []testMode{http2Mode})
  1647  }
  1648  func testBidiStreamReverseProxy(t *testing.T, mode testMode) {
  1649  	backend := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1650  		if _, err := io.Copy(w, r.Body); err != nil {
  1651  			log.Printf("bidi backend copy: %v", err)
  1652  		}
  1653  	}))
  1654  
  1655  	backURL, err := url.Parse(backend.ts.URL)
  1656  	if err != nil {
  1657  		t.Fatal(err)
  1658  	}
  1659  	rp := httputil.NewSingleHostReverseProxy(backURL)
  1660  	rp.Transport = backend.tr
  1661  	proxy := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1662  		rp.ServeHTTP(w, r)
  1663  	}))
  1664  
  1665  	bodyRes := make(chan any, 1) // error or hash.Hash
  1666  	pr, pw := io.Pipe()
  1667  	req, _ := NewRequest("PUT", proxy.ts.URL, pr)
  1668  	const size = 4 << 20
  1669  	go func() {
  1670  		h := sha1.New()
  1671  		_, err := io.CopyN(io.MultiWriter(h, pw), rand.Reader, size)
  1672  		go pw.Close()
  1673  		if err != nil {
  1674  			t.Errorf("body copy: %v", err)
  1675  			bodyRes <- err
  1676  		} else {
  1677  			bodyRes <- h
  1678  		}
  1679  	}()
  1680  	res, err := backend.c.Do(req)
  1681  	if err != nil {
  1682  		t.Fatal(err)
  1683  	}
  1684  	defer res.Body.Close()
  1685  	hgot := sha1.New()
  1686  	n, err := io.Copy(hgot, res.Body)
  1687  	if err != nil {
  1688  		t.Fatal(err)
  1689  	}
  1690  	if n != size {
  1691  		t.Fatalf("got %d bytes; want %d", n, size)
  1692  	}
  1693  	select {
  1694  	case v := <-bodyRes:
  1695  		switch v := v.(type) {
  1696  		default:
  1697  			t.Fatalf("body copy: %v", err)
  1698  		case hash.Hash:
  1699  			if !bytes.Equal(v.Sum(nil), hgot.Sum(nil)) {
  1700  				t.Errorf("written bytes didn't match received bytes")
  1701  			}
  1702  		}
  1703  	case <-time.After(10 * time.Second):
  1704  		t.Fatal("timeout")
  1705  	}
  1706  
  1707  }
  1708  
  1709  // Always use HTTP/1.1 for WebSocket upgrades.
  1710  func TestH12_WebSocketUpgrade(t *testing.T) {
  1711  	h12Compare{
  1712  		Handler: func(w ResponseWriter, r *Request) {
  1713  			h := w.Header()
  1714  			h.Set("Foo", "bar")
  1715  		},
  1716  		ReqFunc: func(c *Client, url string) (*Response, error) {
  1717  			req, _ := NewRequest("GET", url, nil)
  1718  			req.Header.Set("Connection", "Upgrade")
  1719  			req.Header.Set("Upgrade", "WebSocket")
  1720  			return c.Do(req)
  1721  		},
  1722  		EarlyCheckResponse: func(proto string, res *Response) {
  1723  			if res.Proto != "HTTP/1.1" {
  1724  				t.Errorf("%s: expected HTTP/1.1, got %q", proto, res.Proto)
  1725  			}
  1726  			res.Proto = "HTTP/IGNORE" // skip later checks that Proto must be 1.1 vs 2.0
  1727  		},
  1728  	}.run(t)
  1729  }
  1730  
  1731  func TestIdentityTransferEncoding(t *testing.T) { run(t, testIdentityTransferEncoding) }
  1732  func testIdentityTransferEncoding(t *testing.T, mode testMode) {
  1733  	const body = "body"
  1734  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1735  		gotBody, _ := io.ReadAll(r.Body)
  1736  		if got, want := string(gotBody), body; got != want {
  1737  			t.Errorf("got request body = %q; want %q", got, want)
  1738  		}
  1739  		w.Header().Set("Transfer-Encoding", "identity")
  1740  		w.WriteHeader(StatusOK)
  1741  		w.(Flusher).Flush()
  1742  		io.WriteString(w, body)
  1743  	}))
  1744  	req, _ := NewRequest("GET", cst.ts.URL, strings.NewReader(body))
  1745  	res, err := cst.c.Do(req)
  1746  	if err != nil {
  1747  		t.Fatal(err)
  1748  	}
  1749  	defer res.Body.Close()
  1750  	gotBody, err := io.ReadAll(res.Body)
  1751  	if err != nil {
  1752  		t.Fatal(err)
  1753  	}
  1754  	if got, want := string(gotBody), body; got != want {
  1755  		t.Errorf("got response body = %q; want %q", got, want)
  1756  	}
  1757  }
  1758  
  1759  func TestEarlyHintsRequest(t *testing.T) { run(t, testEarlyHintsRequest) }
  1760  func testEarlyHintsRequest(t *testing.T, mode testMode) {
  1761  	var wg sync.WaitGroup
  1762  	wg.Add(1)
  1763  	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
  1764  		h := w.Header()
  1765  
  1766  		h.Add("Content-Length", "123") // must be ignored
  1767  		h.Add("Link", "</style.css>; rel=preload; as=style")
  1768  		h.Add("Link", "</script.js>; rel=preload; as=script")
  1769  		w.WriteHeader(StatusEarlyHints)
  1770  
  1771  		wg.Wait()
  1772  
  1773  		h.Add("Link", "</foo.js>; rel=preload; as=script")
  1774  		w.WriteHeader(StatusEarlyHints)
  1775  
  1776  		w.Write([]byte("Hello"))
  1777  	}))
  1778  
  1779  	checkLinkHeaders := func(t *testing.T, expected, got []string) {
  1780  		t.Helper()
  1781  
  1782  		if len(expected) != len(got) {
  1783  			t.Errorf("got %d expected %d", len(got), len(expected))
  1784  		}
  1785  
  1786  		for i := range expected {
  1787  			if expected[i] != got[i] {
  1788  				t.Errorf("got %q expected %q", got[i], expected[i])
  1789  			}
  1790  		}
  1791  	}
  1792  
  1793  	checkExcludedHeaders := func(t *testing.T, header textproto.MIMEHeader) {
  1794  		t.Helper()
  1795  
  1796  		for _, h := range []string{"Content-Length", "Transfer-Encoding"} {
  1797  			if v, ok := header[h]; ok {
  1798  				t.Errorf("%s is %q; must not be sent", h, v)
  1799  			}
  1800  		}
  1801  	}
  1802  
  1803  	var respCounter uint8
  1804  	trace := &httptrace.ClientTrace{
  1805  		Got1xxResponse: func(code int, header textproto.MIMEHeader) error {
  1806  			switch respCounter {
  1807  			case 0:
  1808  				checkLinkHeaders(t, []string{"</style.css>; rel=preload; as=style", "</script.js>; rel=preload; as=script"}, header["Link"])
  1809  				checkExcludedHeaders(t, header)
  1810  
  1811  				wg.Done()
  1812  			case 1:
  1813  				checkLinkHeaders(t, []string{"</style.css>; rel=preload; as=style", "</script.js>; rel=preload; as=script", "</foo.js>; rel=preload; as=script"}, header["Link"])
  1814  				checkExcludedHeaders(t, header)
  1815  
  1816  			default:
  1817  				t.Error("Unexpected 1xx response")
  1818  			}
  1819  
  1820  			respCounter++
  1821  
  1822  			return nil
  1823  		},
  1824  	}
  1825  	req, _ := NewRequestWithContext(httptrace.WithClientTrace(context.Background(), trace), "GET", cst.ts.URL, nil)
  1826  
  1827  	res, err := cst.c.Do(req)
  1828  	if err != nil {
  1829  		t.Fatal(err)
  1830  	}
  1831  	defer res.Body.Close()
  1832  
  1833  	checkLinkHeaders(t, []string{"</style.css>; rel=preload; as=style", "</script.js>; rel=preload; as=script", "</foo.js>; rel=preload; as=script"}, res.Header["Link"])
  1834  	if cl := res.Header.Get("Content-Length"); cl != "123" {
  1835  		t.Errorf("Content-Length is %q; want 123", cl)
  1836  	}
  1837  
  1838  	body, _ := io.ReadAll(res.Body)
  1839  	if string(body) != "Hello" {
  1840  		t.Errorf("Read body %q; want Hello", body)
  1841  	}
  1842  }
  1843  

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