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Source file src/net/http/httputil/dump.go

Documentation: net/http/httputil

     1  // Copyright 2009 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  package httputil
     6  
     7  import (
     8  	"bufio"
     9  	"bytes"
    10  	"errors"
    11  	"fmt"
    12  	"io"
    13  	"io/ioutil"
    14  	"net"
    15  	"net/http"
    16  	"net/url"
    17  	"strings"
    18  	"time"
    19  )
    20  
    21  // drainBody reads all of b to memory and then returns two equivalent
    22  // ReadClosers yielding the same bytes.
    23  //
    24  // It returns an error if the initial slurp of all bytes fails. It does not attempt
    25  // to make the returned ReadClosers have identical error-matching behavior.
    26  func drainBody(b io.ReadCloser) (r1, r2 io.ReadCloser, err error) {
    27  	if b == nil || b == http.NoBody {
    28  		// No copying needed. Preserve the magic sentinel meaning of NoBody.
    29  		return http.NoBody, http.NoBody, nil
    30  	}
    31  	var buf bytes.Buffer
    32  	if _, err = buf.ReadFrom(b); err != nil {
    33  		return nil, b, err
    34  	}
    35  	if err = b.Close(); err != nil {
    36  		return nil, b, err
    37  	}
    38  	return ioutil.NopCloser(&buf), ioutil.NopCloser(bytes.NewReader(buf.Bytes())), nil
    39  }
    40  
    41  // dumpConn is a net.Conn which writes to Writer and reads from Reader
    42  type dumpConn struct {
    43  	io.Writer
    44  	io.Reader
    45  }
    46  
    47  func (c *dumpConn) Close() error                       { return nil }
    48  func (c *dumpConn) LocalAddr() net.Addr                { return nil }
    49  func (c *dumpConn) RemoteAddr() net.Addr               { return nil }
    50  func (c *dumpConn) SetDeadline(t time.Time) error      { return nil }
    51  func (c *dumpConn) SetReadDeadline(t time.Time) error  { return nil }
    52  func (c *dumpConn) SetWriteDeadline(t time.Time) error { return nil }
    53  
    54  type neverEnding byte
    55  
    56  func (b neverEnding) Read(p []byte) (n int, err error) {
    57  	for i := range p {
    58  		p[i] = byte(b)
    59  	}
    60  	return len(p), nil
    61  }
    62  
    63  // outGoingLength is a copy of the unexported
    64  // (*http.Request).outgoingLength method.
    65  func outgoingLength(req *http.Request) int64 {
    66  	if req.Body == nil || req.Body == http.NoBody {
    67  		return 0
    68  	}
    69  	if req.ContentLength != 0 {
    70  		return req.ContentLength
    71  	}
    72  	return -1
    73  }
    74  
    75  // DumpRequestOut is like DumpRequest but for outgoing client requests. It
    76  // includes any headers that the standard http.Transport adds, such as
    77  // User-Agent.
    78  func DumpRequestOut(req *http.Request, body bool) ([]byte, error) {
    79  	save := req.Body
    80  	dummyBody := false
    81  	if !body {
    82  		contentLength := outgoingLength(req)
    83  		if contentLength != 0 {
    84  			req.Body = ioutil.NopCloser(io.LimitReader(neverEnding('x'), contentLength))
    85  			dummyBody = true
    86  		}
    87  	} else {
    88  		var err error
    89  		save, req.Body, err = drainBody(req.Body)
    90  		if err != nil {
    91  			return nil, err
    92  		}
    93  	}
    94  
    95  	// Since we're using the actual Transport code to write the request,
    96  	// switch to http so the Transport doesn't try to do an SSL
    97  	// negotiation with our dumpConn and its bytes.Buffer & pipe.
    98  	// The wire format for https and http are the same, anyway.
    99  	reqSend := req
   100  	if req.URL.Scheme == "https" {
   101  		reqSend = new(http.Request)
   102  		*reqSend = *req
   103  		reqSend.URL = new(url.URL)
   104  		*reqSend.URL = *req.URL
   105  		reqSend.URL.Scheme = "http"
   106  	}
   107  
   108  	// Use the actual Transport code to record what we would send
   109  	// on the wire, but not using TCP.  Use a Transport with a
   110  	// custom dialer that returns a fake net.Conn that waits
   111  	// for the full input (and recording it), and then responds
   112  	// with a dummy response.
   113  	var buf bytes.Buffer // records the output
   114  	pr, pw := io.Pipe()
   115  	defer pr.Close()
   116  	defer pw.Close()
   117  	dr := &delegateReader{c: make(chan io.Reader)}
   118  
   119  	t := &http.Transport{
   120  		Dial: func(net, addr string) (net.Conn, error) {
   121  			return &dumpConn{io.MultiWriter(&buf, pw), dr}, nil
   122  		},
   123  	}
   124  	defer t.CloseIdleConnections()
   125  
   126  	// We need this channel to ensure that the reader
   127  	// goroutine exits if t.RoundTrip returns an error.
   128  	// See golang.org/issue/32571.
   129  	quitReadCh := make(chan struct{})
   130  	// Wait for the request before replying with a dummy response:
   131  	go func() {
   132  		req, err := http.ReadRequest(bufio.NewReader(pr))
   133  		if err == nil {
   134  			// Ensure all the body is read; otherwise
   135  			// we'll get a partial dump.
   136  			io.Copy(ioutil.Discard, req.Body)
   137  			req.Body.Close()
   138  		}
   139  		select {
   140  		case dr.c <- strings.NewReader("HTTP/1.1 204 No Content\r\nConnection: close\r\n\r\n"):
   141  		case <-quitReadCh:
   142  		}
   143  	}()
   144  
   145  	_, err := t.RoundTrip(reqSend)
   146  
   147  	req.Body = save
   148  	if err != nil {
   149  		pw.Close()
   150  		quitReadCh <- struct{}{}
   151  		return nil, err
   152  	}
   153  	dump := buf.Bytes()
   154  
   155  	// If we used a dummy body above, remove it now.
   156  	// TODO: if the req.ContentLength is large, we allocate memory
   157  	// unnecessarily just to slice it off here. But this is just
   158  	// a debug function, so this is acceptable for now. We could
   159  	// discard the body earlier if this matters.
   160  	if dummyBody {
   161  		if i := bytes.Index(dump, []byte("\r\n\r\n")); i >= 0 {
   162  			dump = dump[:i+4]
   163  		}
   164  	}
   165  	return dump, nil
   166  }
   167  
   168  // delegateReader is a reader that delegates to another reader,
   169  // once it arrives on a channel.
   170  type delegateReader struct {
   171  	c chan io.Reader
   172  	r io.Reader // nil until received from c
   173  }
   174  
   175  func (r *delegateReader) Read(p []byte) (int, error) {
   176  	if r.r == nil {
   177  		r.r = <-r.c
   178  	}
   179  	return r.r.Read(p)
   180  }
   181  
   182  // Return value if nonempty, def otherwise.
   183  func valueOrDefault(value, def string) string {
   184  	if value != "" {
   185  		return value
   186  	}
   187  	return def
   188  }
   189  
   190  var reqWriteExcludeHeaderDump = map[string]bool{
   191  	"Host":              true, // not in Header map anyway
   192  	"Transfer-Encoding": true,
   193  	"Trailer":           true,
   194  }
   195  
   196  // DumpRequest returns the given request in its HTTP/1.x wire
   197  // representation. It should only be used by servers to debug client
   198  // requests. The returned representation is an approximation only;
   199  // some details of the initial request are lost while parsing it into
   200  // an http.Request. In particular, the order and case of header field
   201  // names are lost. The order of values in multi-valued headers is kept
   202  // intact. HTTP/2 requests are dumped in HTTP/1.x form, not in their
   203  // original binary representations.
   204  //
   205  // If body is true, DumpRequest also returns the body. To do so, it
   206  // consumes req.Body and then replaces it with a new io.ReadCloser
   207  // that yields the same bytes. If DumpRequest returns an error,
   208  // the state of req is undefined.
   209  //
   210  // The documentation for http.Request.Write details which fields
   211  // of req are included in the dump.
   212  func DumpRequest(req *http.Request, body bool) ([]byte, error) {
   213  	var err error
   214  	save := req.Body
   215  	if !body || req.Body == nil {
   216  		req.Body = nil
   217  	} else {
   218  		save, req.Body, err = drainBody(req.Body)
   219  		if err != nil {
   220  			return nil, err
   221  		}
   222  	}
   223  
   224  	var b bytes.Buffer
   225  
   226  	// By default, print out the unmodified req.RequestURI, which
   227  	// is always set for incoming server requests. But because we
   228  	// previously used req.URL.RequestURI and the docs weren't
   229  	// always so clear about when to use DumpRequest vs
   230  	// DumpRequestOut, fall back to the old way if the caller
   231  	// provides a non-server Request.
   232  	reqURI := req.RequestURI
   233  	if reqURI == "" {
   234  		reqURI = req.URL.RequestURI()
   235  	}
   236  
   237  	fmt.Fprintf(&b, "%s %s HTTP/%d.%d\r\n", valueOrDefault(req.Method, "GET"),
   238  		reqURI, req.ProtoMajor, req.ProtoMinor)
   239  
   240  	absRequestURI := strings.HasPrefix(req.RequestURI, "http://") || strings.HasPrefix(req.RequestURI, "https://")
   241  	if !absRequestURI {
   242  		host := req.Host
   243  		if host == "" && req.URL != nil {
   244  			host = req.URL.Host
   245  		}
   246  		if host != "" {
   247  			fmt.Fprintf(&b, "Host: %s\r\n", host)
   248  		}
   249  	}
   250  
   251  	chunked := len(req.TransferEncoding) > 0 && req.TransferEncoding[0] == "chunked"
   252  	if len(req.TransferEncoding) > 0 {
   253  		fmt.Fprintf(&b, "Transfer-Encoding: %s\r\n", strings.Join(req.TransferEncoding, ","))
   254  	}
   255  	if req.Close {
   256  		fmt.Fprintf(&b, "Connection: close\r\n")
   257  	}
   258  
   259  	err = req.Header.WriteSubset(&b, reqWriteExcludeHeaderDump)
   260  	if err != nil {
   261  		return nil, err
   262  	}
   263  
   264  	io.WriteString(&b, "\r\n")
   265  
   266  	if req.Body != nil {
   267  		var dest io.Writer = &b
   268  		if chunked {
   269  			dest = NewChunkedWriter(dest)
   270  		}
   271  		_, err = io.Copy(dest, req.Body)
   272  		if chunked {
   273  			dest.(io.Closer).Close()
   274  			io.WriteString(&b, "\r\n")
   275  		}
   276  	}
   277  
   278  	req.Body = save
   279  	if err != nil {
   280  		return nil, err
   281  	}
   282  	return b.Bytes(), nil
   283  }
   284  
   285  // errNoBody is a sentinel error value used by failureToReadBody so we
   286  // can detect that the lack of body was intentional.
   287  var errNoBody = errors.New("sentinel error value")
   288  
   289  // failureToReadBody is a io.ReadCloser that just returns errNoBody on
   290  // Read. It's swapped in when we don't actually want to consume
   291  // the body, but need a non-nil one, and want to distinguish the
   292  // error from reading the dummy body.
   293  type failureToReadBody struct{}
   294  
   295  func (failureToReadBody) Read([]byte) (int, error) { return 0, errNoBody }
   296  func (failureToReadBody) Close() error             { return nil }
   297  
   298  // emptyBody is an instance of empty reader.
   299  var emptyBody = ioutil.NopCloser(strings.NewReader(""))
   300  
   301  // DumpResponse is like DumpRequest but dumps a response.
   302  func DumpResponse(resp *http.Response, body bool) ([]byte, error) {
   303  	var b bytes.Buffer
   304  	var err error
   305  	save := resp.Body
   306  	savecl := resp.ContentLength
   307  
   308  	if !body {
   309  		// For content length of zero. Make sure the body is an empty
   310  		// reader, instead of returning error through failureToReadBody{}.
   311  		if resp.ContentLength == 0 {
   312  			resp.Body = emptyBody
   313  		} else {
   314  			resp.Body = failureToReadBody{}
   315  		}
   316  	} else if resp.Body == nil {
   317  		resp.Body = emptyBody
   318  	} else {
   319  		save, resp.Body, err = drainBody(resp.Body)
   320  		if err != nil {
   321  			return nil, err
   322  		}
   323  	}
   324  	err = resp.Write(&b)
   325  	if err == errNoBody {
   326  		err = nil
   327  	}
   328  	resp.Body = save
   329  	resp.ContentLength = savecl
   330  	if err != nil {
   331  		return nil, err
   332  	}
   333  	return b.Bytes(), nil
   334  }
   335  

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