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

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