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dump.go
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dump.go
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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package httputil
import (
"bufio"
"bytes"
"errors"
"fmt"
"io"
"net"
"net/http"
"net/url"
"strings"
"time"
)
// drainBody reads all of b to memory and then returns two equivalent
// ReadClosers yielding the same bytes.
//
// It returns an error if the initial slurp of all bytes fails. It does not attempt
// to make the returned ReadClosers have identical error-matching behavior.
func drainBody(b io.ReadCloser) (r1, r2 io.ReadCloser, err error) {
if b == nil || b == http.NoBody {
// No copying needed. Preserve the magic sentinel meaning of NoBody.
return http.NoBody, http.NoBody, nil
}
var buf bytes.Buffer
if _, err = buf.ReadFrom(b); err != nil {
return nil, b, err
}
if err = b.Close(); err != nil {
return nil, b, err
}
return io.NopCloser(&buf), io.NopCloser(bytes.NewReader(buf.Bytes())), nil
}
// dumpConn is a net.Conn which writes to Writer and reads from Reader
type dumpConn struct {
io.Writer
io.Reader
}
func (c *dumpConn) Close() error { return nil }
func (c *dumpConn) LocalAddr() net.Addr { return nil }
func (c *dumpConn) RemoteAddr() net.Addr { return nil }
func (c *dumpConn) SetDeadline(t time.Time) error { return nil }
func (c *dumpConn) SetReadDeadline(t time.Time) error { return nil }
func (c *dumpConn) SetWriteDeadline(t time.Time) error { return nil }
type neverEnding byte
func (b neverEnding) Read(p []byte) (n int, err error) {
for i := range p {
p[i] = byte(b)
}
return len(p), nil
}
// outgoingLength is a copy of the unexported
// (*http.Request).outgoingLength method.
func outgoingLength(req *http.Request) int64 {
if req.Body == nil || req.Body == http.NoBody {
return 0
}
if req.ContentLength != 0 {
return req.ContentLength
}
return -1
}
// DumpRequestOut is like [DumpRequest] but for outgoing client requests. It
// includes any headers that the standard [http.Transport] adds, such as
// User-Agent.
func DumpRequestOut(req *http.Request, body bool) ([]byte, error) {
save := req.Body
dummyBody := false
if !body {
contentLength := outgoingLength(req)
if contentLength != 0 {
req.Body = io.NopCloser(io.LimitReader(neverEnding('x'), contentLength))
dummyBody = true
}
} else {
var err error
save, req.Body, err = drainBody(req.Body)
if err != nil {
return nil, err
}
}
// Since we're using the actual Transport code to write the request,
// switch to http so the Transport doesn't try to do an SSL
// negotiation with our dumpConn and its bytes.Buffer & pipe.
// The wire format for https and http are the same, anyway.
reqSend := req
if req.URL.Scheme == "https" {
reqSend = new(http.Request)
*reqSend = *req
reqSend.URL = new(url.URL)
*reqSend.URL = *req.URL
reqSend.URL.Scheme = "http"
}
// Use the actual Transport code to record what we would send
// on the wire, but not using TCP. Use a Transport with a
// custom dialer that returns a fake net.Conn that waits
// for the full input (and recording it), and then responds
// with a dummy response.
var buf bytes.Buffer // records the output
pr, pw := io.Pipe()
defer pr.Close()
defer pw.Close()
dr := &delegateReader{c: make(chan io.Reader)}
t := &http.Transport{
Dial: func(net, addr string) (net.Conn, error) {
return &dumpConn{io.MultiWriter(&buf, pw), dr}, nil
},
}
defer t.CloseIdleConnections()
// We need this channel to ensure that the reader
// goroutine exits if t.RoundTrip returns an error.
// See golang.org/issue/32571.
quitReadCh := make(chan struct{})
// Wait for the request before replying with a dummy response:
go func() {
req, err := http.ReadRequest(bufio.NewReader(pr))
if err == nil {
// Ensure all the body is read; otherwise
// we'll get a partial dump.
io.Copy(io.Discard, req.Body)
req.Body.Close()
}
select {
case dr.c <- strings.NewReader("HTTP/1.1 204 No Content\r\nConnection: close\r\n\r\n"):
case <-quitReadCh:
// Ensure delegateReader.Read doesn't block forever if we get an error.
close(dr.c)
}
}()
_, err := t.RoundTrip(reqSend)
req.Body = save
if err != nil {
pw.Close()
dr.err = err
close(quitReadCh)
return nil, err
}
dump := buf.Bytes()
// If we used a dummy body above, remove it now.
// TODO: if the req.ContentLength is large, we allocate memory
// unnecessarily just to slice it off here. But this is just
// a debug function, so this is acceptable for now. We could
// discard the body earlier if this matters.
if dummyBody {
if i := bytes.Index(dump, []byte("\r\n\r\n")); i >= 0 {
dump = dump[:i+4]
}
}
return dump, nil
}
// delegateReader is a reader that delegates to another reader,
// once it arrives on a channel.
type delegateReader struct {
c chan io.Reader
err error // only used if r is nil and c is closed.
r io.Reader // nil until received from c
}
func (r *delegateReader) Read(p []byte) (int, error) {
if r.r == nil {
var ok bool
if r.r, ok = <-r.c; !ok {
return 0, r.err
}
}
return r.r.Read(p)
}
// Return value if nonempty, def otherwise.
func valueOrDefault(value, def string) string {
if value != "" {
return value
}
return def
}
var reqWriteExcludeHeaderDump = map[string]bool{
"Host": true, // not in Header map anyway
"Transfer-Encoding": true,
"Trailer": true,
}
// DumpRequest returns the given request in its HTTP/1.x wire
// representation. It should only be used by servers to debug client
// requests. The returned representation is an approximation only;
// some details of the initial request are lost while parsing it into
// an [http.Request]. In particular, the order and case of header field
// names are lost. The order of values in multi-valued headers is kept
// intact. HTTP/2 requests are dumped in HTTP/1.x form, not in their
// original binary representations.
//
// If body is true, DumpRequest also returns the body. To do so, it
// consumes req.Body and then replaces it with a new [io.ReadCloser]
// that yields the same bytes. If DumpRequest returns an error,
// the state of req is undefined.
//
// The documentation for [http.Request.Write] details which fields
// of req are included in the dump.
func DumpRequest(req *http.Request, body bool) ([]byte, error) {
var err error
save := req.Body
if !body || req.Body == nil {
req.Body = nil
} else {
save, req.Body, err = drainBody(req.Body)
if err != nil {
return nil, err
}
}
var b bytes.Buffer
// By default, print out the unmodified req.RequestURI, which
// is always set for incoming server requests. But because we
// previously used req.URL.RequestURI and the docs weren't
// always so clear about when to use DumpRequest vs
// DumpRequestOut, fall back to the old way if the caller
// provides a non-server Request.
reqURI := req.RequestURI
if reqURI == "" {
reqURI = req.URL.RequestURI()
}
fmt.Fprintf(&b, "%s %s HTTP/%d.%d\r\n", valueOrDefault(req.Method, "GET"),
reqURI, req.ProtoMajor, req.ProtoMinor)
absRequestURI := strings.HasPrefix(req.RequestURI, "http://") || strings.HasPrefix(req.RequestURI, "https://")
if !absRequestURI {
host := req.Host
if host == "" && req.URL != nil {
host = req.URL.Host
}
if host != "" {
fmt.Fprintf(&b, "Host: %s\r\n", host)
}
}
chunked := len(req.TransferEncoding) > 0 && req.TransferEncoding[0] == "chunked"
if len(req.TransferEncoding) > 0 {
fmt.Fprintf(&b, "Transfer-Encoding: %s\r\n", strings.Join(req.TransferEncoding, ","))
}
err = req.Header.WriteSubset(&b, reqWriteExcludeHeaderDump)
if err != nil {
return nil, err
}
io.WriteString(&b, "\r\n")
if req.Body != nil {
var dest io.Writer = &b
if chunked {
dest = NewChunkedWriter(dest)
}
_, err = io.Copy(dest, req.Body)
if chunked {
dest.(io.Closer).Close()
io.WriteString(&b, "\r\n")
}
}
req.Body = save
if err != nil {
return nil, err
}
return b.Bytes(), nil
}
// errNoBody is a sentinel error value used by failureToReadBody so we
// can detect that the lack of body was intentional.
var errNoBody = errors.New("sentinel error value")
// failureToReadBody is an io.ReadCloser that just returns errNoBody on
// Read. It's swapped in when we don't actually want to consume
// the body, but need a non-nil one, and want to distinguish the
// error from reading the dummy body.
type failureToReadBody struct{}
func (failureToReadBody) Read([]byte) (int, error) { return 0, errNoBody }
func (failureToReadBody) Close() error { return nil }
// emptyBody is an instance of empty reader.
var emptyBody = io.NopCloser(strings.NewReader(""))
// DumpResponse is like DumpRequest but dumps a response.
func DumpResponse(resp *http.Response, body bool) ([]byte, error) {
var b bytes.Buffer
var err error
save := resp.Body
savecl := resp.ContentLength
if !body {
// For content length of zero. Make sure the body is an empty
// reader, instead of returning error through failureToReadBody{}.
if resp.ContentLength == 0 {
resp.Body = emptyBody
} else {
resp.Body = failureToReadBody{}
}
} else if resp.Body == nil {
resp.Body = emptyBody
} else {
save, resp.Body, err = drainBody(resp.Body)
if err != nil {
return nil, err
}
}
err = resp.Write(&b)
if err == errNoBody {
err = nil
}
resp.Body = save
resp.ContentLength = savecl
if err != nil {
return nil, err
}
return b.Bytes(), nil
}