Adding upstream version 1.20.14.upstream/1.20.14upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1024 insertions, 0 deletions

diff --git a/src/net/http/client.go b/src/net/http/client.go
new file mode 100644
index 0000000..122e8d0
--- /dev/null
+++ b/src/net/http/client.go
@@ -0,0 +1,1024 @@
+// 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.
+
+// HTTP client. See RFC 7230 through 7235.
+//
+// This is the high-level Client interface.
+// The low-level implementation is in transport.go.
+
+package http
+
+import (
+	"context"
+	"crypto/tls"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net/http/internal/ascii"
+	"net/url"
+	"reflect"
+	"sort"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// A Client is an HTTP client. Its zero value (DefaultClient) is a
+// usable client that uses DefaultTransport.
+//
+// The Client's Transport typically has internal state (cached TCP
+// connections), so Clients should be reused instead of created as
+// needed. Clients are safe for concurrent use by multiple goroutines.
+//
+// A Client is higher-level than a RoundTripper (such as Transport)
+// and additionally handles HTTP details such as cookies and
+// redirects.
+//
+// When following redirects, the Client will forward all headers set on the
+// initial Request except:
+//
+// • when forwarding sensitive headers like "Authorization",
+// "WWW-Authenticate", and "Cookie" to untrusted targets.
+// These headers will be ignored when following a redirect to a domain
+// that is not a subdomain match or exact match of the initial domain.
+// For example, a redirect from "foo.com" to either "foo.com" or "sub.foo.com"
+// will forward the sensitive headers, but a redirect to "bar.com" will not.
+//
+// • when forwarding the "Cookie" header with a non-nil cookie Jar.
+// Since each redirect may mutate the state of the cookie jar,
+// a redirect may possibly alter a cookie set in the initial request.
+// When forwarding the "Cookie" header, any mutated cookies will be omitted,
+// with the expectation that the Jar will insert those mutated cookies
+// with the updated values (assuming the origin matches).
+// If Jar is nil, the initial cookies are forwarded without change.
+type Client struct {
+	// Transport specifies the mechanism by which individual
+	// HTTP requests are made.
+	// If nil, DefaultTransport is used.
+	Transport RoundTripper
+
+	// CheckRedirect specifies the policy for handling redirects.
+	// If CheckRedirect is not nil, the client calls it before
+	// following an HTTP redirect. The arguments req and via are
+	// the upcoming request and the requests made already, oldest
+	// first. If CheckRedirect returns an error, the Client's Get
+	// method returns both the previous Response (with its Body
+	// closed) and CheckRedirect's error (wrapped in a url.Error)
+	// instead of issuing the Request req.
+	// As a special case, if CheckRedirect returns ErrUseLastResponse,
+	// then the most recent response is returned with its body
+	// unclosed, along with a nil error.
+	//
+	// If CheckRedirect is nil, the Client uses its default policy,
+	// which is to stop after 10 consecutive requests.
+	CheckRedirect func(req *Request, via []*Request) error
+
+	// Jar specifies the cookie jar.
+	//
+	// The Jar is used to insert relevant cookies into every
+	// outbound Request and is updated with the cookie values
+	// of every inbound Response. The Jar is consulted for every
+	// redirect that the Client follows.
+	//
+	// If Jar is nil, cookies are only sent if they are explicitly
+	// set on the Request.
+	Jar CookieJar
+
+	// Timeout specifies a time limit for requests made by this
+	// Client. The timeout includes connection time, any
+	// redirects, and reading the response body. The timer remains
+	// running after Get, Head, Post, or Do return and will
+	// interrupt reading of the Response.Body.
+	//
+	// A Timeout of zero means no timeout.
+	//
+	// The Client cancels requests to the underlying Transport
+	// as if the Request's Context ended.
+	//
+	// For compatibility, the Client will also use the deprecated
+	// CancelRequest method on Transport if found. New
+	// RoundTripper implementations should use the Request's Context
+	// for cancellation instead of implementing CancelRequest.
+	Timeout time.Duration
+}
+
+// DefaultClient is the default Client and is used by Get, Head, and Post.
+var DefaultClient = &Client{}
+
+// RoundTripper is an interface representing the ability to execute a
+// single HTTP transaction, obtaining the Response for a given Request.
+//
+// A RoundTripper must be safe for concurrent use by multiple
+// goroutines.
+type RoundTripper interface {
+	// RoundTrip executes a single HTTP transaction, returning
+	// a Response for the provided Request.
+	//
+	// RoundTrip should not attempt to interpret the response. In
+	// particular, RoundTrip must return err == nil if it obtained
+	// a response, regardless of the response's HTTP status code.
+	// A non-nil err should be reserved for failure to obtain a
+	// response. Similarly, RoundTrip should not attempt to
+	// handle higher-level protocol details such as redirects,
+	// authentication, or cookies.
+	//
+	// RoundTrip should not modify the request, except for
+	// consuming and closing the Request's Body. RoundTrip may
+	// read fields of the request in a separate goroutine. Callers
+	// should not mutate or reuse the request until the Response's
+	// Body has been closed.
+	//
+	// RoundTrip must always close the body, including on errors,
+	// but depending on the implementation may do so in a separate
+	// goroutine even after RoundTrip returns. This means that
+	// callers wanting to reuse the body for subsequent requests
+	// must arrange to wait for the Close call before doing so.
+	//
+	// The Request's URL and Header fields must be initialized.
+	RoundTrip(*Request) (*Response, error)
+}
+
+// refererForURL returns a referer without any authentication info or
+// an empty string if lastReq scheme is https and newReq scheme is http.
+func refererForURL(lastReq, newReq *url.URL) string {
+	// https://tools.ietf.org/html/rfc7231#section-5.5.2
+	//   "Clients SHOULD NOT include a Referer header field in a
+	//    (non-secure) HTTP request if the referring page was
+	//    transferred with a secure protocol."
+	if lastReq.Scheme == "https" && newReq.Scheme == "http" {
+		return ""
+	}
+	referer := lastReq.String()
+	if lastReq.User != nil {
+		// This is not very efficient, but is the best we can
+		// do without:
+		// - introducing a new method on URL
+		// - creating a race condition
+		// - copying the URL struct manually, which would cause
+		//   maintenance problems down the line
+		auth := lastReq.User.String() + "@"
+		referer = strings.Replace(referer, auth, "", 1)
+	}
+	return referer
+}
+
+// didTimeout is non-nil only if err != nil.
+func (c *Client) send(req *Request, deadline time.Time) (resp *Response, didTimeout func() bool, err error) {
+	if c.Jar != nil {
+		for _, cookie := range c.Jar.Cookies(req.URL) {
+			req.AddCookie(cookie)
+		}
+	}
+	resp, didTimeout, err = send(req, c.transport(), deadline)
+	if err != nil {
+		return nil, didTimeout, err
+	}
+	if c.Jar != nil {
+		if rc := resp.Cookies(); len(rc) > 0 {
+			c.Jar.SetCookies(req.URL, rc)
+		}
+	}
+	return resp, nil, nil
+}
+
+func (c *Client) deadline() time.Time {
+	if c.Timeout > 0 {
+		return time.Now().Add(c.Timeout)
+	}
+	return time.Time{}
+}
+
+func (c *Client) transport() RoundTripper {
+	if c.Transport != nil {
+		return c.Transport
+	}
+	return DefaultTransport
+}
+
+// send issues an HTTP request.
+// Caller should close resp.Body when done reading from it.
+func send(ireq *Request, rt RoundTripper, deadline time.Time) (resp *Response, didTimeout func() bool, err error) {
+	req := ireq // req is either the original request, or a modified fork
+
+	if rt == nil {
+		req.closeBody()
+		return nil, alwaysFalse, errors.New("http: no Client.Transport or DefaultTransport")
+	}
+
+	if req.URL == nil {
+		req.closeBody()
+		return nil, alwaysFalse, errors.New("http: nil Request.URL")
+	}
+
+	if req.RequestURI != "" {
+		req.closeBody()
+		return nil, alwaysFalse, errors.New("http: Request.RequestURI can't be set in client requests")
+	}
+
+	// forkReq forks req into a shallow clone of ireq the first
+	// time it's called.
+	forkReq := func() {
+		if ireq == req {
+			req = new(Request)
+			*req = *ireq // shallow clone
+		}
+	}
+
+	// Most the callers of send (Get, Post, et al) don't need
+	// Headers, leaving it uninitialized. We guarantee to the
+	// Transport that this has been initialized, though.
+	if req.Header == nil {
+		forkReq()
+		req.Header = make(Header)
+	}
+
+	if u := req.URL.User; u != nil && req.Header.Get("Authorization") == "" {
+		username := u.Username()
+		password, _ := u.Password()
+		forkReq()
+		req.Header = cloneOrMakeHeader(ireq.Header)
+		req.Header.Set("Authorization", "Basic "+basicAuth(username, password))
+	}
+
+	if !deadline.IsZero() {
+		forkReq()
+	}
+	stopTimer, didTimeout := setRequestCancel(req, rt, deadline)
+
+	resp, err = rt.RoundTrip(req)
+	if err != nil {
+		stopTimer()
+		if resp != nil {
+			log.Printf("RoundTripper returned a response & error; ignoring response")
+		}
+		if tlsErr, ok := err.(tls.RecordHeaderError); ok {
+			// If we get a bad TLS record header, check to see if the
+			// response looks like HTTP and give a more helpful error.
+			// See golang.org/issue/11111.
+			if string(tlsErr.RecordHeader[:]) == "HTTP/" {
+				err = errors.New("http: server gave HTTP response to HTTPS client")
+			}
+		}
+		return nil, didTimeout, err
+	}
+	if resp == nil {
+		return nil, didTimeout, fmt.Errorf("http: RoundTripper implementation (%T) returned a nil *Response with a nil error", rt)
+	}
+	if resp.Body == nil {
+		// The documentation on the Body field says “The http Client and Transport
+		// guarantee that Body is always non-nil, even on responses without a body
+		// or responses with a zero-length body.” Unfortunately, we didn't document
+		// that same constraint for arbitrary RoundTripper implementations, and
+		// RoundTripper implementations in the wild (mostly in tests) assume that
+		// they can use a nil Body to mean an empty one (similar to Request.Body).
+		// (See https://golang.org/issue/38095.)
+		//
+		// If the ContentLength allows the Body to be empty, fill in an empty one
+		// here to ensure that it is non-nil.
+		if resp.ContentLength > 0 && req.Method != "HEAD" {
+			return nil, didTimeout, fmt.Errorf("http: RoundTripper implementation (%T) returned a *Response with content length %d but a nil Body", rt, resp.ContentLength)
+		}
+		resp.Body = io.NopCloser(strings.NewReader(""))
+	}
+	if !deadline.IsZero() {
+		resp.Body = &cancelTimerBody{
+			stop:          stopTimer,
+			rc:            resp.Body,
+			reqDidTimeout: didTimeout,
+		}
+	}
+	return resp, nil, nil
+}
+
+// timeBeforeContextDeadline reports whether the non-zero Time t is
+// before ctx's deadline, if any. If ctx does not have a deadline, it
+// always reports true (the deadline is considered infinite).
+func timeBeforeContextDeadline(t time.Time, ctx context.Context) bool {
+	d, ok := ctx.Deadline()
+	if !ok {
+		return true
+	}
+	return t.Before(d)
+}
+
+// knownRoundTripperImpl reports whether rt is a RoundTripper that's
+// maintained by the Go team and known to implement the latest
+// optional semantics (notably contexts). The Request is used
+// to check whether this particular request is using an alternate protocol,
+// in which case we need to check the RoundTripper for that protocol.
+func knownRoundTripperImpl(rt RoundTripper, req *Request) bool {
+	switch t := rt.(type) {
+	case *Transport:
+		if altRT := t.alternateRoundTripper(req); altRT != nil {
+			return knownRoundTripperImpl(altRT, req)
+		}
+		return true
+	case *http2Transport, http2noDialH2RoundTripper:
+		return true
+	}
+	// There's a very minor chance of a false positive with this.
+	// Instead of detecting our golang.org/x/net/http2.Transport,
+	// it might detect a Transport type in a different http2
+	// package. But I know of none, and the only problem would be
+	// some temporarily leaked goroutines if the transport didn't
+	// support contexts. So this is a good enough heuristic:
+	if reflect.TypeOf(rt).String() == "*http2.Transport" {
+		return true
+	}
+	return false
+}
+
+// setRequestCancel sets req.Cancel and adds a deadline context to req
+// if deadline is non-zero. The RoundTripper's type is used to
+// determine whether the legacy CancelRequest behavior should be used.
+//
+// As background, there are three ways to cancel a request:
+// First was Transport.CancelRequest. (deprecated)
+// Second was Request.Cancel.
+// Third was Request.Context.
+// This function populates the second and third, and uses the first if it really needs to.
+func setRequestCancel(req *Request, rt RoundTripper, deadline time.Time) (stopTimer func(), didTimeout func() bool) {
+	if deadline.IsZero() {
+		return nop, alwaysFalse
+	}
+	knownTransport := knownRoundTripperImpl(rt, req)
+	oldCtx := req.Context()
+
+	if req.Cancel == nil && knownTransport {
+		// If they already had a Request.Context that's
+		// expiring sooner, do nothing:
+		if !timeBeforeContextDeadline(deadline, oldCtx) {
+			return nop, alwaysFalse
+		}
+
+		var cancelCtx func()
+		req.ctx, cancelCtx = context.WithDeadline(oldCtx, deadline)
+		return cancelCtx, func() bool { return time.Now().After(deadline) }
+	}
+	initialReqCancel := req.Cancel // the user's original Request.Cancel, if any
+
+	var cancelCtx func()
+	if timeBeforeContextDeadline(deadline, oldCtx) {
+		req.ctx, cancelCtx = context.WithDeadline(oldCtx, deadline)
+	}
+
+	cancel := make(chan struct{})
+	req.Cancel = cancel
+
+	doCancel := func() {
+		// The second way in the func comment above:
+		close(cancel)
+		// The first way, used only for RoundTripper
+		// implementations written before Go 1.5 or Go 1.6.
+		type canceler interface{ CancelRequest(*Request) }
+		if v, ok := rt.(canceler); ok {
+			v.CancelRequest(req)
+		}
+	}
+
+	stopTimerCh := make(chan struct{})
+	var once sync.Once
+	stopTimer = func() {
+		once.Do(func() {
+			close(stopTimerCh)
+			if cancelCtx != nil {
+				cancelCtx()
+			}
+		})
+	}
+
+	timer := time.NewTimer(time.Until(deadline))
+	var timedOut atomic.Bool
+
+	go func() {
+		select {
+		case <-initialReqCancel:
+			doCancel()
+			timer.Stop()
+		case <-timer.C:
+			timedOut.Store(true)
+			doCancel()
+		case <-stopTimerCh:
+			timer.Stop()
+		}
+	}()
+
+	return stopTimer, timedOut.Load
+}
+
+// See 2 (end of page 4) https://www.ietf.org/rfc/rfc2617.txt
+// "To receive authorization, the client sends the userid and password,
+// separated by a single colon (":") character, within a base64
+// encoded string in the credentials."
+// It is not meant to be urlencoded.
+func basicAuth(username, password string) string {
+	auth := username + ":" + password
+	return base64.StdEncoding.EncodeToString([]byte(auth))
+}
+
+// Get issues a GET to the specified URL. If the response is one of
+// the following redirect codes, Get follows the redirect, up to a
+// maximum of 10 redirects:
+//
+//	301 (Moved Permanently)
+//	302 (Found)
+//	303 (See Other)
+//	307 (Temporary Redirect)
+//	308 (Permanent Redirect)
+//
+// An error is returned if there were too many redirects or if there
+// was an HTTP protocol error. A non-2xx response doesn't cause an
+// error. Any returned error will be of type *url.Error. The url.Error
+// value's Timeout method will report true if the request timed out.
+//
+// When err is nil, resp always contains a non-nil resp.Body.
+// Caller should close resp.Body when done reading from it.
+//
+// Get is a wrapper around DefaultClient.Get.
+//
+// To make a request with custom headers, use NewRequest and
+// DefaultClient.Do.
+//
+// To make a request with a specified context.Context, use NewRequestWithContext
+// and DefaultClient.Do.
+func Get(url string) (resp *Response, err error) {
+	return DefaultClient.Get(url)
+}
+
+// Get issues a GET to the specified URL. If the response is one of the
+// following redirect codes, Get follows the redirect after calling the
+// Client's CheckRedirect function:
+//
+//	301 (Moved Permanently)
+//	302 (Found)
+//	303 (See Other)
+//	307 (Temporary Redirect)
+//	308 (Permanent Redirect)
+//
+// An error is returned if the Client's CheckRedirect function fails
+// or if there was an HTTP protocol error. A non-2xx response doesn't
+// cause an error. Any returned error will be of type *url.Error. The
+// url.Error value's Timeout method will report true if the request
+// timed out.
+//
+// When err is nil, resp always contains a non-nil resp.Body.
+// Caller should close resp.Body when done reading from it.
+//
+// To make a request with custom headers, use NewRequest and Client.Do.
+//
+// To make a request with a specified context.Context, use NewRequestWithContext
+// and Client.Do.
+func (c *Client) Get(url string) (resp *Response, err error) {
+	req, err := NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	return c.Do(req)
+}
+
+func alwaysFalse() bool { return false }
+
+// ErrUseLastResponse can be returned by Client.CheckRedirect hooks to
+// control how redirects are processed. If returned, the next request
+// is not sent and the most recent response is returned with its body
+// unclosed.
+var ErrUseLastResponse = errors.New("net/http: use last response")
+
+// checkRedirect calls either the user's configured CheckRedirect
+// function, or the default.
+func (c *Client) checkRedirect(req *Request, via []*Request) error {
+	fn := c.CheckRedirect
+	if fn == nil {
+		fn = defaultCheckRedirect
+	}
+	return fn(req, via)
+}
+
+// redirectBehavior describes what should happen when the
+// client encounters a 3xx status code from the server.
+func redirectBehavior(reqMethod string, resp *Response, ireq *Request) (redirectMethod string, shouldRedirect, includeBody bool) {
+	switch resp.StatusCode {
+	case 301, 302, 303:
+		redirectMethod = reqMethod
+		shouldRedirect = true
+		includeBody = false
+
+		// RFC 2616 allowed automatic redirection only with GET and
+		// HEAD requests. RFC 7231 lifts this restriction, but we still
+		// restrict other methods to GET to maintain compatibility.
+		// See Issue 18570.
+		if reqMethod != "GET" && reqMethod != "HEAD" {
+			redirectMethod = "GET"
+		}
+	case 307, 308:
+		redirectMethod = reqMethod
+		shouldRedirect = true
+		includeBody = true
+
+		if ireq.GetBody == nil && ireq.outgoingLength() != 0 {
+			// We had a request body, and 307/308 require
+			// re-sending it, but GetBody is not defined. So just
+			// return this response to the user instead of an
+			// error, like we did in Go 1.7 and earlier.
+			shouldRedirect = false
+		}
+	}
+	return redirectMethod, shouldRedirect, includeBody
+}
+
+// urlErrorOp returns the (*url.Error).Op value to use for the
+// provided (*Request).Method value.
+func urlErrorOp(method string) string {
+	if method == "" {
+		return "Get"
+	}
+	if lowerMethod, ok := ascii.ToLower(method); ok {
+		return method[:1] + lowerMethod[1:]
+	}
+	return method
+}
+
+// Do sends an HTTP request and returns an HTTP response, following
+// policy (such as redirects, cookies, auth) as configured on the
+// client.
+//
+// An error is returned if caused by client policy (such as
+// CheckRedirect), or failure to speak HTTP (such as a network
+// connectivity problem). A non-2xx status code doesn't cause an
+// error.
+//
+// If the returned error is nil, the Response will contain a non-nil
+// Body which the user is expected to close. If the Body is not both
+// read to EOF and closed, the Client's underlying RoundTripper
+// (typically Transport) may not be able to re-use a persistent TCP
+// connection to the server for a subsequent "keep-alive" request.
+//
+// The request Body, if non-nil, will be closed by the underlying
+// Transport, even on errors.
+//
+// On error, any Response can be ignored. A non-nil Response with a
+// non-nil error only occurs when CheckRedirect fails, and even then
+// the returned Response.Body is already closed.
+//
+// Generally Get, Post, or PostForm will be used instead of Do.
+//
+// If the server replies with a redirect, the Client first uses the
+// CheckRedirect function to determine whether the redirect should be
+// followed. If permitted, a 301, 302, or 303 redirect causes
+// subsequent requests to use HTTP method GET
+// (or HEAD if the original request was HEAD), with no body.
+// A 307 or 308 redirect preserves the original HTTP method and body,
+// provided that the Request.GetBody function is defined.
+// The NewRequest function automatically sets GetBody for common
+// standard library body types.
+//
+// Any returned error will be of type *url.Error. The url.Error
+// value's Timeout method will report true if the request timed out.
+func (c *Client) Do(req *Request) (*Response, error) {
+	return c.do(req)
+}
+
+var testHookClientDoResult func(retres *Response, reterr error)
+
+func (c *Client) do(req *Request) (retres *Response, reterr error) {
+	if testHookClientDoResult != nil {
+		defer func() { testHookClientDoResult(retres, reterr) }()
+	}
+	if req.URL == nil {
+		req.closeBody()
+		return nil, &url.Error{
+			Op:  urlErrorOp(req.Method),
+			Err: errors.New("http: nil Request.URL"),
+		}
+	}
+
+	var (
+		deadline      = c.deadline()
+		reqs          []*Request
+		resp          *Response
+		copyHeaders   = c.makeHeadersCopier(req)
+		reqBodyClosed = false // have we closed the current req.Body?
+
+		// Redirect behavior:
+		redirectMethod string
+		includeBody    bool
+	)
+	uerr := func(err error) error {
+		// the body may have been closed already by c.send()
+		if !reqBodyClosed {
+			req.closeBody()
+		}
+		var urlStr string
+		if resp != nil && resp.Request != nil {
+			urlStr = stripPassword(resp.Request.URL)
+		} else {
+			urlStr = stripPassword(req.URL)
+		}
+		return &url.Error{
+			Op:  urlErrorOp(reqs[0].Method),
+			URL: urlStr,
+			Err: err,
+		}
+	}
+	for {
+		// For all but the first request, create the next
+		// request hop and replace req.
+		if len(reqs) > 0 {
+			loc := resp.Header.Get("Location")
+			if loc == "" {
+				// While most 3xx responses include a Location, it is not
+				// required and 3xx responses without a Location have been
+				// observed in the wild. See issues #17773 and #49281.
+				return resp, nil
+			}
+			u, err := req.URL.Parse(loc)
+			if err != nil {
+				resp.closeBody()
+				return nil, uerr(fmt.Errorf("failed to parse Location header %q: %v", loc, err))
+			}
+			host := ""
+			if req.Host != "" && req.Host != req.URL.Host {
+				// If the caller specified a custom Host header and the
+				// redirect location is relative, preserve the Host header
+				// through the redirect. See issue #22233.
+				if u, _ := url.Parse(loc); u != nil && !u.IsAbs() {
+					host = req.Host
+				}
+			}
+			ireq := reqs[0]
+			req = &Request{
+				Method:   redirectMethod,
+				Response: resp,
+				URL:      u,
+				Header:   make(Header),
+				Host:     host,
+				Cancel:   ireq.Cancel,
+				ctx:      ireq.ctx,
+			}
+			if includeBody && ireq.GetBody != nil {
+				req.Body, err = ireq.GetBody()
+				if err != nil {
+					resp.closeBody()
+					return nil, uerr(err)
+				}
+				req.ContentLength = ireq.ContentLength
+			}
+
+			// Copy original headers before setting the Referer,
+			// in case the user set Referer on their first request.
+			// If they really want to override, they can do it in
+			// their CheckRedirect func.
+			copyHeaders(req)
+
+			// Add the Referer header from the most recent
+			// request URL to the new one, if it's not https->http:
+			if ref := refererForURL(reqs[len(reqs)-1].URL, req.URL); ref != "" {
+				req.Header.Set("Referer", ref)
+			}
+			err = c.checkRedirect(req, reqs)
+
+			// Sentinel error to let users select the
+			// previous response, without closing its
+			// body. See Issue 10069.
+			if err == ErrUseLastResponse {
+				return resp, nil
+			}
+
+			// Close the previous response's body. But
+			// read at least some of the body so if it's
+			// small the underlying TCP connection will be
+			// re-used. No need to check for errors: if it
+			// fails, the Transport won't reuse it anyway.
+			const maxBodySlurpSize = 2 << 10
+			if resp.ContentLength == -1 || resp.ContentLength <= maxBodySlurpSize {
+				io.CopyN(io.Discard, resp.Body, maxBodySlurpSize)
+			}
+			resp.Body.Close()
+
+			if err != nil {
+				// Special case for Go 1 compatibility: return both the response
+				// and an error if the CheckRedirect function failed.
+				// See https://golang.org/issue/3795
+				// The resp.Body has already been closed.
+				ue := uerr(err)
+				ue.(*url.Error).URL = loc
+				return resp, ue
+			}
+		}
+
+		reqs = append(reqs, req)
+		var err error
+		var didTimeout func() bool
+		if resp, didTimeout, err = c.send(req, deadline); err != nil {
+			// c.send() always closes req.Body
+			reqBodyClosed = true
+			if !deadline.IsZero() && didTimeout() {
+				err = &httpError{
+					err:     err.Error() + " (Client.Timeout exceeded while awaiting headers)",
+					timeout: true,
+				}
+			}
+			return nil, uerr(err)
+		}
+
+		var shouldRedirect bool
+		redirectMethod, shouldRedirect, includeBody = redirectBehavior(req.Method, resp, reqs[0])
+		if !shouldRedirect {
+			return resp, nil
+		}
+
+		req.closeBody()
+	}
+}
+
+// makeHeadersCopier makes a function that copies headers from the
+// initial Request, ireq. For every redirect, this function must be called
+// so that it can copy headers into the upcoming Request.
+func (c *Client) makeHeadersCopier(ireq *Request) func(*Request) {
+	// The headers to copy are from the very initial request.
+	// We use a closured callback to keep a reference to these original headers.
+	var (
+		ireqhdr  = cloneOrMakeHeader(ireq.Header)
+		icookies map[string][]*Cookie
+	)
+	if c.Jar != nil && ireq.Header.Get("Cookie") != "" {
+		icookies = make(map[string][]*Cookie)
+		for _, c := range ireq.Cookies() {
+			icookies[c.Name] = append(icookies[c.Name], c)
+		}
+	}
+
+	preq := ireq // The previous request
+	return func(req *Request) {
+		// If Jar is present and there was some initial cookies provided
+		// via the request header, then we may need to alter the initial
+		// cookies as we follow redirects since each redirect may end up
+		// modifying a pre-existing cookie.
+		//
+		// Since cookies already set in the request header do not contain
+		// information about the original domain and path, the logic below
+		// assumes any new set cookies override the original cookie
+		// regardless of domain or path.
+		//
+		// See https://golang.org/issue/17494
+		if c.Jar != nil && icookies != nil {
+			var changed bool
+			resp := req.Response // The response that caused the upcoming redirect
+			for _, c := range resp.Cookies() {
+				if _, ok := icookies[c.Name]; ok {
+					delete(icookies, c.Name)
+					changed = true
+				}
+			}
+			if changed {
+				ireqhdr.Del("Cookie")
+				var ss []string
+				for _, cs := range icookies {
+					for _, c := range cs {
+						ss = append(ss, c.Name+"="+c.Value)
+					}
+				}
+				sort.Strings(ss) // Ensure deterministic headers
+				ireqhdr.Set("Cookie", strings.Join(ss, "; "))
+			}
+		}
+
+		// Copy the initial request's Header values
+		// (at least the safe ones).
+		for k, vv := range ireqhdr {
+			if shouldCopyHeaderOnRedirect(k, preq.URL, req.URL) {
+				req.Header[k] = vv
+			}
+		}
+
+		preq = req // Update previous Request with the current request
+	}
+}
+
+func defaultCheckRedirect(req *Request, via []*Request) error {
+	if len(via) >= 10 {
+		return errors.New("stopped after 10 redirects")
+	}
+	return nil
+}
+
+// Post issues a POST to the specified URL.
+//
+// Caller should close resp.Body when done reading from it.
+//
+// If the provided body is an io.Closer, it is closed after the
+// request.
+//
+// Post is a wrapper around DefaultClient.Post.
+//
+// To set custom headers, use NewRequest and DefaultClient.Do.
+//
+// See the Client.Do method documentation for details on how redirects
+// are handled.
+//
+// To make a request with a specified context.Context, use NewRequestWithContext
+// and DefaultClient.Do.
+func Post(url, contentType string, body io.Reader) (resp *Response, err error) {
+	return DefaultClient.Post(url, contentType, body)
+}
+
+// Post issues a POST to the specified URL.
+//
+// Caller should close resp.Body when done reading from it.
+//
+// If the provided body is an io.Closer, it is closed after the
+// request.
+//
+// To set custom headers, use NewRequest and Client.Do.
+//
+// To make a request with a specified context.Context, use NewRequestWithContext
+// and Client.Do.
+//
+// See the Client.Do method documentation for details on how redirects
+// are handled.
+func (c *Client) Post(url, contentType string, body io.Reader) (resp *Response, err error) {
+	req, err := NewRequest("POST", url, body)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", contentType)
+	return c.Do(req)
+}
+
+// PostForm issues a POST to the specified URL, with data's keys and
+// values URL-encoded as the request body.
+//
+// The Content-Type header is set to application/x-www-form-urlencoded.
+// To set other headers, use NewRequest and DefaultClient.Do.
+//
+// When err is nil, resp always contains a non-nil resp.Body.
+// Caller should close resp.Body when done reading from it.
+//
+// PostForm is a wrapper around DefaultClient.PostForm.
+//
+// See the Client.Do method documentation for details on how redirects
+// are handled.
+//
+// To make a request with a specified context.Context, use NewRequestWithContext
+// and DefaultClient.Do.
+func PostForm(url string, data url.Values) (resp *Response, err error) {
+	return DefaultClient.PostForm(url, data)
+}
+
+// PostForm issues a POST to the specified URL,
+// with data's keys and values URL-encoded as the request body.
+//
+// The Content-Type header is set to application/x-www-form-urlencoded.
+// To set other headers, use NewRequest and Client.Do.
+//
+// When err is nil, resp always contains a non-nil resp.Body.
+// Caller should close resp.Body when done reading from it.
+//
+// See the Client.Do method documentation for details on how redirects
+// are handled.
+//
+// To make a request with a specified context.Context, use NewRequestWithContext
+// and Client.Do.
+func (c *Client) PostForm(url string, data url.Values) (resp *Response, err error) {
+	return c.Post(url, "application/x-www-form-urlencoded", strings.NewReader(data.Encode()))
+}
+
+// Head issues a HEAD to the specified URL. If the response is one of
+// the following redirect codes, Head follows the redirect, up to a
+// maximum of 10 redirects:
+//
+//	301 (Moved Permanently)
+//	302 (Found)
+//	303 (See Other)
+//	307 (Temporary Redirect)
+//	308 (Permanent Redirect)
+//
+// Head is a wrapper around DefaultClient.Head.
+//
+// To make a request with a specified context.Context, use NewRequestWithContext
+// and DefaultClient.Do.
+func Head(url string) (resp *Response, err error) {
+	return DefaultClient.Head(url)
+}
+
+// Head issues a HEAD to the specified URL. If the response is one of the
+// following redirect codes, Head follows the redirect after calling the
+// Client's CheckRedirect function:
+//
+//	301 (Moved Permanently)
+//	302 (Found)
+//	303 (See Other)
+//	307 (Temporary Redirect)
+//	308 (Permanent Redirect)
+//
+// To make a request with a specified context.Context, use NewRequestWithContext
+// and Client.Do.
+func (c *Client) Head(url string) (resp *Response, err error) {
+	req, err := NewRequest("HEAD", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	return c.Do(req)
+}
+
+// CloseIdleConnections closes any connections on its Transport which
+// were previously connected from previous requests but are now
+// sitting idle in a "keep-alive" state. It does not interrupt any
+// connections currently in use.
+//
+// If the Client's Transport does not have a CloseIdleConnections method
+// then this method does nothing.
+func (c *Client) CloseIdleConnections() {
+	type closeIdler interface {
+		CloseIdleConnections()
+	}
+	if tr, ok := c.transport().(closeIdler); ok {
+		tr.CloseIdleConnections()
+	}
+}
+
+// cancelTimerBody is an io.ReadCloser that wraps rc with two features:
+//  1. On Read error or close, the stop func is called.
+//  2. On Read failure, if reqDidTimeout is true, the error is wrapped and
+//     marked as net.Error that hit its timeout.
+type cancelTimerBody struct {
+	stop          func() // stops the time.Timer waiting to cancel the request
+	rc            io.ReadCloser
+	reqDidTimeout func() bool
+}
+
+func (b *cancelTimerBody) Read(p []byte) (n int, err error) {
+	n, err = b.rc.Read(p)
+	if err == nil {
+		return n, nil
+	}
+	if err == io.EOF {
+		return n, err
+	}
+	if b.reqDidTimeout() {
+		err = &httpError{
+			err:     err.Error() + " (Client.Timeout or context cancellation while reading body)",
+			timeout: true,
+		}
+	}
+	return n, err
+}
+
+func (b *cancelTimerBody) Close() error {
+	err := b.rc.Close()
+	b.stop()
+	return err
+}
+
+func shouldCopyHeaderOnRedirect(headerKey string, initial, dest *url.URL) bool {
+	switch CanonicalHeaderKey(headerKey) {
+	case "Authorization", "Www-Authenticate", "Cookie", "Cookie2":
+		// Permit sending auth/cookie headers from "foo.com"
+		// to "sub.foo.com".
+
+		// Note that we don't send all cookies to subdomains
+		// automatically. This function is only used for
+		// Cookies set explicitly on the initial outgoing
+		// client request. Cookies automatically added via the
+		// CookieJar mechanism continue to follow each
+		// cookie's scope as set by Set-Cookie. But for
+		// outgoing requests with the Cookie header set
+		// directly, we don't know their scope, so we assume
+		// it's for *.domain.com.
+
+		ihost := canonicalAddr(initial)
+		dhost := canonicalAddr(dest)
+		return isDomainOrSubdomain(dhost, ihost)
+	}
+	// All other headers are copied:
+	return true
+}
+
+// isDomainOrSubdomain reports whether sub is a subdomain (or exact
+// match) of the parent domain.
+//
+// Both domains must already be in canonical form.
+func isDomainOrSubdomain(sub, parent string) bool {
+	if sub == parent {
+		return true
+	}
+	// If sub is "foo.example.com" and parent is "example.com",
+	// that means sub must end in "."+parent.
+	// Do it without allocating.
+	if !strings.HasSuffix(sub, parent) {
+		return false
+	}
+	return sub[len(sub)-len(parent)-1] == '.'
+}
+
+func stripPassword(u *url.URL) string {
+	_, passSet := u.User.Password()
+	if passSet {
+		return strings.Replace(u.String(), u.User.String()+"@", u.User.Username()+":***@", 1)
+	}
+	return u.String()
+}