Update golang.org/x/net to not panic

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

vendor.conf

@@ -67,7 +67,7 @@ github.com/xeipuuv/gojsonpointer e0fe6f68307607d540ed8eac07a342c33fa1b54a
 github.com/xeipuuv/gojsonreference e02fc20de94c78484cd5ffb007f8af96be030a45
 github.com/xeipuuv/gojsonschema 93e72a773fade158921402d6a24c819b48aba29d
 golang.org/x/crypto 558b6879de74bc843225cde5686419267ff707ca
-golang.org/x/net 7dcfb8076726a3fdd9353b6b8a1f1b6be6811bd6
+golang.org/x/net a8b9294777976932365dabb6640cf1468d95c70f
 golang.org/x/sys 95c6576299259db960f6c5b9b69ea52422860fce
 golang.org/x/text f72d8390a633d5dfb0cc84043294db9f6c935756
 golang.org/x/time a4bde12657593d5e90d0533a3e4fd95e635124cb

vendor/golang.org/x/net/README

@@ -1,3 +0,0 @@
-This repository holds supplementary Go networking libraries.
-
-To submit changes to this repository, see http://golang.org/doc/contribute.html.

vendor/golang.org/x/net/README.md

@@ -0,0 +1,16 @@
+# Go Networking
+
+This repository holds supplementary Go networking libraries.
+
+## Download/Install
+
+The easiest way to install is to run `go get -u golang.org/x/net`. You can
+also manually git clone the repository to `$GOPATH/src/golang.org/x/net`.
+
+## Report Issues / Send Patches
+
+This repository uses Gerrit for code changes. To learn how to submit
+changes to this repository, see https://golang.org/doc/contribute.html.
+The main issue tracker for the net repository is located at
+https://github.com/golang/go/issues. Prefix your issue with "x/net:" in the
+subject line, so it is easy to find.

vendor/golang.org/x/net/context/context.go

@@ -5,6 +5,8 @@
 // Package context defines the Context type, which carries deadlines,
 // cancelation signals, and other request-scoped values across API boundaries
 // and between processes.
+// As of Go 1.7 this package is available in the standard library under the
+// name context.  https://golang.org/pkg/context.
 //
 // Incoming requests to a server should create a Context, and outgoing calls to
 // servers should accept a Context. The chain of function calls between must
@@ -36,103 +38,6 @@
 // Contexts.
 package context // import "golang.org/x/net/context"
 
-import "time"
-
-// A Context carries a deadline, a cancelation signal, and other values across
-// API boundaries.
-//
-// Context's methods may be called by multiple goroutines simultaneously.
-type Context interface {
-	// Deadline returns the time when work done on behalf of this context
-	// should be canceled. Deadline returns ok==false when no deadline is
-	// set. Successive calls to Deadline return the same results.
-	Deadline() (deadline time.Time, ok bool)
-
-	// Done returns a channel that's closed when work done on behalf of this
-	// context should be canceled. Done may return nil if this context can
-	// never be canceled. Successive calls to Done return the same value.
-	//
-	// WithCancel arranges for Done to be closed when cancel is called;
-	// WithDeadline arranges for Done to be closed when the deadline
-	// expires; WithTimeout arranges for Done to be closed when the timeout
-	// elapses.
-	//
-	// Done is provided for use in select statements:
-	//
-	//  // Stream generates values with DoSomething and sends them to out
-	//  // until DoSomething returns an error or ctx.Done is closed.
-	//  func Stream(ctx context.Context, out chan<- Value) error {
-	//  	for {
-	//  		v, err := DoSomething(ctx)
-	//  		if err != nil {
-	//  			return err
-	//  		}
-	//  		select {
-	//  		case <-ctx.Done():
-	//  			return ctx.Err()
-	//  		case out <- v:
-	//  		}
-	//  	}
-	//  }
-	//
-	// See http://blog.golang.org/pipelines for more examples of how to use
-	// a Done channel for cancelation.
-	Done() <-chan struct{}
-
-	// Err returns a non-nil error value after Done is closed. Err returns
-	// Canceled if the context was canceled or DeadlineExceeded if the
-	// context's deadline passed. No other values for Err are defined.
-	// After Done is closed, successive calls to Err return the same value.
-	Err() error
-
-	// Value returns the value associated with this context for key, or nil
-	// if no value is associated with key. Successive calls to Value with
-	// the same key returns the same result.
-	//
-	// Use context values only for request-scoped data that transits
-	// processes and API boundaries, not for passing optional parameters to
-	// functions.
-	//
-	// A key identifies a specific value in a Context. Functions that wish
-	// to store values in Context typically allocate a key in a global
-	// variable then use that key as the argument to context.WithValue and
-	// Context.Value. A key can be any type that supports equality;
-	// packages should define keys as an unexported type to avoid
-	// collisions.
-	//
-	// Packages that define a Context key should provide type-safe accessors
-	// for the values stores using that key:
-	//
-	// 	// Package user defines a User type that's stored in Contexts.
-	// 	package user
-	//
-	// 	import "golang.org/x/net/context"
-	//
-	// 	// User is the type of value stored in the Contexts.
-	// 	type User struct {...}
-	//
-	// 	// key is an unexported type for keys defined in this package.
-	// 	// This prevents collisions with keys defined in other packages.
-	// 	type key int
-	//
-	// 	// userKey is the key for user.User values in Contexts. It is
-	// 	// unexported; clients use user.NewContext and user.FromContext
-	// 	// instead of using this key directly.
-	// 	var userKey key = 0
-	//
-	// 	// NewContext returns a new Context that carries value u.
-	// 	func NewContext(ctx context.Context, u *User) context.Context {
-	// 		return context.WithValue(ctx, userKey, u)
-	// 	}
-	//
-	// 	// FromContext returns the User value stored in ctx, if any.
-	// 	func FromContext(ctx context.Context) (*User, bool) {
-	// 		u, ok := ctx.Value(userKey).(*User)
-	// 		return u, ok
-	// 	}
-	Value(key interface{}) interface{}
-}
-
 // Background returns a non-nil, empty Context. It is never canceled, has no
 // values, and has no deadline. It is typically used by the main function,
 // initialization, and tests, and as the top-level Context for incoming
@@ -149,8 +54,3 @@ func Background() Context {
 func TODO() Context {
 	return todo
 }
-
-// A CancelFunc tells an operation to abandon its work.
-// A CancelFunc does not wait for the work to stop.
-// After the first call, subsequent calls to a CancelFunc do nothing.
-type CancelFunc func()

vendor/golang.org/x/net/context/go19.go

@@ -0,0 +1,20 @@
+// Copyright 2017 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.
+
+// +build go1.9
+
+package context
+
+import "context" // standard library's context, as of Go 1.7
+
+// A Context carries a deadline, a cancelation signal, and other values across
+// API boundaries.
+//
+// Context's methods may be called by multiple goroutines simultaneously.
+type Context = context.Context
+
+// A CancelFunc tells an operation to abandon its work.
+// A CancelFunc does not wait for the work to stop.
+// After the first call, subsequent calls to a CancelFunc do nothing.
+type CancelFunc = context.CancelFunc

vendor/golang.org/x/net/context/pre_go19.go

@@ -0,0 +1,109 @@
+// Copyright 2014 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.
+
+// +build !go1.9
+
+package context
+
+import "time"
+
+// A Context carries a deadline, a cancelation signal, and other values across
+// API boundaries.
+//
+// Context's methods may be called by multiple goroutines simultaneously.
+type Context interface {
+	// Deadline returns the time when work done on behalf of this context
+	// should be canceled. Deadline returns ok==false when no deadline is
+	// set. Successive calls to Deadline return the same results.
+	Deadline() (deadline time.Time, ok bool)
+
+	// Done returns a channel that's closed when work done on behalf of this
+	// context should be canceled. Done may return nil if this context can
+	// never be canceled. Successive calls to Done return the same value.
+	//
+	// WithCancel arranges for Done to be closed when cancel is called;
+	// WithDeadline arranges for Done to be closed when the deadline
+	// expires; WithTimeout arranges for Done to be closed when the timeout
+	// elapses.
+	//
+	// Done is provided for use in select statements:
+	//
+	//  // Stream generates values with DoSomething and sends them to out
+	//  // until DoSomething returns an error or ctx.Done is closed.
+	//  func Stream(ctx context.Context, out chan<- Value) error {
+	//  	for {
+	//  		v, err := DoSomething(ctx)
+	//  		if err != nil {
+	//  			return err
+	//  		}
+	//  		select {
+	//  		case <-ctx.Done():
+	//  			return ctx.Err()
+	//  		case out <- v:
+	//  		}
+	//  	}
+	//  }
+	//
+	// See http://blog.golang.org/pipelines for more examples of how to use
+	// a Done channel for cancelation.
+	Done() <-chan struct{}
+
+	// Err returns a non-nil error value after Done is closed. Err returns
+	// Canceled if the context was canceled or DeadlineExceeded if the
+	// context's deadline passed. No other values for Err are defined.
+	// After Done is closed, successive calls to Err return the same value.
+	Err() error
+
+	// Value returns the value associated with this context for key, or nil
+	// if no value is associated with key. Successive calls to Value with
+	// the same key returns the same result.
+	//
+	// Use context values only for request-scoped data that transits
+	// processes and API boundaries, not for passing optional parameters to
+	// functions.
+	//
+	// A key identifies a specific value in a Context. Functions that wish
+	// to store values in Context typically allocate a key in a global
+	// variable then use that key as the argument to context.WithValue and
+	// Context.Value. A key can be any type that supports equality;
+	// packages should define keys as an unexported type to avoid
+	// collisions.
+	//
+	// Packages that define a Context key should provide type-safe accessors
+	// for the values stores using that key:
+	//
+	// 	// Package user defines a User type that's stored in Contexts.
+	// 	package user
+	//
+	// 	import "golang.org/x/net/context"
+	//
+	// 	// User is the type of value stored in the Contexts.
+	// 	type User struct {...}
+	//
+	// 	// key is an unexported type for keys defined in this package.
+	// 	// This prevents collisions with keys defined in other packages.
+	// 	type key int
+	//
+	// 	// userKey is the key for user.User values in Contexts. It is
+	// 	// unexported; clients use user.NewContext and user.FromContext
+	// 	// instead of using this key directly.
+	// 	var userKey key = 0
+	//
+	// 	// NewContext returns a new Context that carries value u.
+	// 	func NewContext(ctx context.Context, u *User) context.Context {
+	// 		return context.WithValue(ctx, userKey, u)
+	// 	}
+	//
+	// 	// FromContext returns the User value stored in ctx, if any.
+	// 	func FromContext(ctx context.Context) (*User, bool) {
+	// 		u, ok := ctx.Value(userKey).(*User)
+	// 		return u, ok
+	// 	}
+	Value(key interface{}) interface{}
+}
+
+// A CancelFunc tells an operation to abandon its work.
+// A CancelFunc does not wait for the work to stop.
+// After the first call, subsequent calls to a CancelFunc do nothing.
+type CancelFunc func()

vendor/golang.org/x/net/http2/configure_transport.go

@@ -56,7 +56,7 @@ func configureTransport(t1 *http.Transport) (*Transport, error) {
 }
 
 // registerHTTPSProtocol calls Transport.RegisterProtocol but
-// convering panics into errors.
+// converting panics into errors.
 func registerHTTPSProtocol(t *http.Transport, rt http.RoundTripper) (err error) {
 	defer func() {
 		if e := recover(); e != nil {

vendor/golang.org/x/net/http2/errors.go

@@ -87,13 +87,16 @@ type goAwayFlowError struct{}
 
 func (goAwayFlowError) Error() string { return "connection exceeded flow control window size" }
 
-// connErrorReason wraps a ConnectionError with an informative error about why it occurs.
+// connError represents an HTTP/2 ConnectionError error code, along
-
+// with a string (for debugging) explaining why.
+//
 // Errors of this type are only returned by the frame parser functions
-// and converted into ConnectionError(ErrCodeProtocol).
+// and converted into ConnectionError(Code), after stashing away
+// the Reason into the Framer's errDetail field, accessible via
+// the (*Framer).ErrorDetail method.
 type connError struct {
-	Code   ErrCode
+	Code   ErrCode // the ConnectionError error code
-	Reason string
+	Reason string  // additional reason
 }
 
 func (e connError) Error() string {

vendor/golang.org/x/net/http2/go18.go

@@ -52,3 +52,5 @@ func reqGetBody(req *http.Request) func() (io.ReadCloser, error) {
 func reqBodyIsNoBody(body io.ReadCloser) bool {
 	return body == http.NoBody
 }
+
+func go18httpNoBody() io.ReadCloser { return http.NoBody } // for tests only

vendor/golang.org/x/net/http2/http2.go

@@ -376,12 +376,16 @@ func (s *sorter) SortStrings(ss []string) {
 // validPseudoPath reports whether v is a valid :path pseudo-header
 // value. It must be either:
 //
-//     *) a non-empty string starting with '/', but not with with "//",
+//     *) a non-empty string starting with '/'
 //     *) the string '*', for OPTIONS requests.
 //
 // For now this is only used a quick check for deciding when to clean
 // up Opaque URLs before sending requests from the Transport.
 // See golang.org/issue/16847
+//
+// We used to enforce that the path also didn't start with "//", but
+// Google's GFE accepts such paths and Chrome sends them, so ignore
+// that part of the spec. See golang.org/issue/19103.
 func validPseudoPath(v string) bool {
-	return (len(v) > 0 && v[0] == '/' && (len(v) == 1 || v[1] != '/')) || v == "*"
+	return (len(v) > 0 && v[0] == '/') || v == "*"
 }

vendor/golang.org/x/net/http2/not_go18.go

@@ -25,3 +25,5 @@ func reqGetBody(req *http.Request) func() (io.ReadCloser, error) {
 }
 
 func reqBodyIsNoBody(io.ReadCloser) bool { return false }
+
+func go18httpNoBody() io.ReadCloser { return nil } // for tests only

vendor/golang.org/x/net/http2/pipe.go

@@ -50,7 +50,7 @@ func (p *pipe) Read(d []byte) (n int, err error) {
 		if p.breakErr != nil {
 			return 0, p.breakErr
 		}
-		if p.b.Len() > 0 {
+		if p.b != nil && p.b.Len() > 0 {
 			return p.b.Read(d)
 		}
 		if p.err != nil {

vendor/golang.org/x/net/http2/server.go

@@ -220,12 +220,15 @@ func ConfigureServer(s *http.Server, conf *Server) error {
 	} else if s.TLSConfig.CipherSuites != nil {
 		// If they already provided a CipherSuite list, return
 		// an error if it has a bad order or is missing
-		// ECDHE_RSA_WITH_AES_128_GCM_SHA256.
+		// ECDHE_RSA_WITH_AES_128_GCM_SHA256 or ECDHE_ECDSA_WITH_AES_128_GCM_SHA256.
-		const requiredCipher = tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
 		haveRequired := false
 		sawBad := false
 		for i, cs := range s.TLSConfig.CipherSuites {
-			if cs == requiredCipher {
+			switch cs {
+			case tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
+				// Alternative MTI cipher to not discourage ECDSA-only servers.
+				// See http://golang.org/cl/30721 for further information.
+				tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256:
 				haveRequired = true
 			}
 			if isBadCipher(cs) {
@@ -235,7 +238,7 @@ func ConfigureServer(s *http.Server, conf *Server) error {
 			}
 		}
 		if !haveRequired {
-			return fmt.Errorf("http2: TLSConfig.CipherSuites is missing HTTP/2-required TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256")
+			return fmt.Errorf("http2: TLSConfig.CipherSuites is missing an HTTP/2-required AES_128_GCM_SHA256 cipher.")
 		}
 	}
 
@@ -649,7 +652,7 @@ func (sc *serverConn) condlogf(err error, format string, args ...interface{}) {
 	if err == nil {
 		return
 	}
-	if err == io.EOF || err == io.ErrUnexpectedEOF || isClosedConnError(err) {
+	if err == io.EOF || err == io.ErrUnexpectedEOF || isClosedConnError(err) || err == errPrefaceTimeout {
 		// Boring, expected errors.
 		sc.vlogf(format, args...)
 	} else {
@@ -853,8 +856,13 @@ func (sc *serverConn) serve() {
 			}
 		}
 
-		if sc.inGoAway && sc.curOpenStreams() == 0 && !sc.needToSendGoAway && !sc.writingFrame {
+		// Start the shutdown timer after sending a GOAWAY. When sending GOAWAY
-			return
+		// with no error code (graceful shutdown), don't start the timer until
+		// all open streams have been completed.
+		sentGoAway := sc.inGoAway && !sc.needToSendGoAway && !sc.writingFrame
+		gracefulShutdownComplete := sc.goAwayCode == ErrCodeNo && sc.curOpenStreams() == 0
+		if sentGoAway && sc.shutdownTimer == nil && (sc.goAwayCode != ErrCodeNo || gracefulShutdownComplete) {
+			sc.shutDownIn(goAwayTimeout)
 		}
 	}
 }
@@ -889,8 +897,11 @@ func (sc *serverConn) sendServeMsg(msg interface{}) {
 	}
 }
 
-// readPreface reads the ClientPreface greeting from the peer
+var errPrefaceTimeout = errors.New("timeout waiting for client preface")
-// or returns an error on timeout or an invalid greeting.
+
+// readPreface reads the ClientPreface greeting from the peer or
+// returns errPrefaceTimeout on timeout, or an error if the greeting
+// is invalid.
 func (sc *serverConn) readPreface() error {
 	errc := make(chan error, 1)
 	go func() {
@@ -908,7 +919,7 @@ func (sc *serverConn) readPreface() error {
 	defer timer.Stop()
 	select {
 	case <-timer.C:
-		return errors.New("timeout waiting for client preface")
+		return errPrefaceTimeout
 	case err := <-errc:
 		if err == nil {
 			if VerboseLogs {
@@ -1218,30 +1229,31 @@ func (sc *serverConn) startGracefulShutdown() {
 	sc.shutdownOnce.Do(func() { sc.sendServeMsg(gracefulShutdownMsg) })
 }
 
+// After sending GOAWAY, the connection will close after goAwayTimeout.
+// If we close the connection immediately after sending GOAWAY, there may
+// be unsent data in our kernel receive buffer, which will cause the kernel
+// to send a TCP RST on close() instead of a FIN. This RST will abort the
+// connection immediately, whether or not the client had received the GOAWAY.
+//
+// Ideally we should delay for at least 1 RTT + epsilon so the client has
+// a chance to read the GOAWAY and stop sending messages. Measuring RTT
+// is hard, so we approximate with 1 second. See golang.org/issue/18701.
+//
+// This is a var so it can be shorter in tests, where all requests uses the
+// loopback interface making the expected RTT very small.
+//
+// TODO: configurable?
+var goAwayTimeout = 1 * time.Second
+
 func (sc *serverConn) startGracefulShutdownInternal() {
-	sc.goAwayIn(ErrCodeNo, 0)
+	sc.goAway(ErrCodeNo)
 }
 
 func (sc *serverConn) goAway(code ErrCode) {
-	sc.serveG.check()
-	var forceCloseIn time.Duration
-	if code != ErrCodeNo {
-		forceCloseIn = 250 * time.Millisecond
-	} else {
-		// TODO: configurable
-		forceCloseIn = 1 * time.Second
-	}
-	sc.goAwayIn(code, forceCloseIn)
-}
-
-func (sc *serverConn) goAwayIn(code ErrCode, forceCloseIn time.Duration) {
 	sc.serveG.check()
 	if sc.inGoAway {
 		return
 	}
-	if forceCloseIn != 0 {
-		sc.shutDownIn(forceCloseIn)
-	}
 	sc.inGoAway = true
 	sc.needToSendGoAway = true
 	sc.goAwayCode = code
@@ -2252,6 +2264,7 @@ type responseWriterState struct {
 	wroteHeader   bool        // WriteHeader called (explicitly or implicitly). Not necessarily sent to user yet.
 	sentHeader    bool        // have we sent the header frame?
 	handlerDone   bool        // handler has finished
+	dirty         bool        // a Write failed; don't reuse this responseWriterState
 
 	sentContentLen int64 // non-zero if handler set a Content-Length header
 	wroteBytes     int64
@@ -2309,7 +2322,7 @@ func (rws *responseWriterState) writeChunk(p []byte) (n int, err error) {
 			clen = strconv.Itoa(len(p))
 		}
 		_, hasContentType := rws.snapHeader["Content-Type"]
-		if !hasContentType && bodyAllowedForStatus(rws.status) {
+		if !hasContentType && bodyAllowedForStatus(rws.status) && len(p) > 0 {
 			ctype = http.DetectContentType(p)
 		}
 		var date string
@@ -2333,6 +2346,7 @@ func (rws *responseWriterState) writeChunk(p []byte) (n int, err error) {
 			date:          date,
 		})
 		if err != nil {
+			rws.dirty = true
 			return 0, err
 		}
 		if endStream {
@@ -2354,6 +2368,7 @@ func (rws *responseWriterState) writeChunk(p []byte) (n int, err error) {
 	if len(p) > 0 || endStream {
 		// only send a 0 byte DATA frame if we're ending the stream.
 		if err := rws.conn.writeDataFromHandler(rws.stream, p, endStream); err != nil {
+			rws.dirty = true
 			return 0, err
 		}
 	}
@@ -2365,6 +2380,9 @@ func (rws *responseWriterState) writeChunk(p []byte) (n int, err error) {
 			trailers:  rws.trailers,
 			endStream: true,
 		})
+		if err != nil {
+			rws.dirty = true
+		}
 		return len(p), err
 	}
 	return len(p), nil
@@ -2472,7 +2490,26 @@ func (w *responseWriter) Header() http.Header {
 	return rws.handlerHeader
 }
 
+// checkWriteHeaderCode is a copy of net/http's checkWriteHeaderCode.
+func checkWriteHeaderCode(code int) {
+	// Issue 22880: require valid WriteHeader status codes.
+	// For now we only enforce that it's three digits.
+	// In the future we might block things over 599 (600 and above aren't defined
+	// at http://httpwg.org/specs/rfc7231.html#status.codes)
+	// and we might block under 200 (once we have more mature 1xx support).
+	// But for now any three digits.
+	//
+	// We used to send "HTTP/1.1 000 0" on the wire in responses but there's
+	// no equivalent bogus thing we can realistically send in HTTP/2,
+	// so we'll consistently panic instead and help people find their bugs
+	// early. (We can't return an error from WriteHeader even if we wanted to.)
+	if code < 100 || code > 999 {
+		panic(fmt.Sprintf("invalid WriteHeader code %v", code))
+	}
+}
+
 func (w *responseWriter) WriteHeader(code int) {
+	checkWriteHeaderCode(code)
 	rws := w.rws
 	if rws == nil {
 		panic("WriteHeader called after Handler finished")
@@ -2504,7 +2541,7 @@ func cloneHeader(h http.Header) http.Header {
 //
 // * Handler calls w.Write or w.WriteString ->
 // * -> rws.bw (*bufio.Writer) ->
-// * (Handler migth call Flush)
+// * (Handler might call Flush)
 // * -> chunkWriter{rws}
 // * -> responseWriterState.writeChunk(p []byte)
 // * -> responseWriterState.writeChunk (most of the magic; see comment there)
@@ -2543,10 +2580,19 @@ func (w *responseWriter) write(lenData int, dataB []byte, dataS string) (n int,
 
 func (w *responseWriter) handlerDone() {
 	rws := w.rws
+	dirty := rws.dirty
 	rws.handlerDone = true
 	w.Flush()
 	w.rws = nil
-	responseWriterStatePool.Put(rws)
+	if !dirty {
+		// Only recycle the pool if all prior Write calls to
+		// the serverConn goroutine completed successfully. If
+		// they returned earlier due to resets from the peer
+		// there might still be write goroutines outstanding
+		// from the serverConn referencing the rws memory. See
+		// issue 20704.
+		responseWriterStatePool.Put(rws)
+	}
 }
 
 // Push errors.

vendor/golang.org/x/net/http2/transport.go

@@ -18,6 +18,7 @@ import (
 	"io/ioutil"
 	"log"
 	"math"
+	mathrand "math/rand"
 	"net"
 	"net/http"
 	"sort"
@@ -86,7 +87,7 @@ type Transport struct {
 
 	// MaxHeaderListSize is the http2 SETTINGS_MAX_HEADER_LIST_SIZE to
 	// send in the initial settings frame. It is how many bytes
-	// of response headers are allow. Unlike the http2 spec, zero here
+	// of response headers are allowed. Unlike the http2 spec, zero here
 	// means to use a default limit (currently 10MB). If you actually
 	// want to advertise an ulimited value to the peer, Transport
 	// interprets the highest possible value here (0xffffffff or 1<<32-1)
@@ -164,15 +165,17 @@ type ClientConn struct {
 	goAwayDebug     string                   // goAway frame's debug data, retained as a string
 	streams         map[uint32]*clientStream // client-initiated
 	nextStreamID    uint32
+	pendingRequests int                       // requests blocked and waiting to be sent because len(streams) == maxConcurrentStreams
 	pings           map[[8]byte]chan struct{} // in flight ping data to notification channel
 	bw              *bufio.Writer
 	br              *bufio.Reader
 	fr              *Framer
 	lastActive      time.Time
 	// Settings from peer: (also guarded by mu)
-	maxFrameSize         uint32
+	maxFrameSize          uint32
-	maxConcurrentStreams uint32
+	maxConcurrentStreams  uint32
-	initialWindowSize    uint32
+	peerMaxHeaderListSize uint64
+	initialWindowSize     uint32
 
 	hbuf    bytes.Buffer // HPACK encoder writes into this
 	henc    *hpack.Encoder
@@ -216,35 +219,45 @@ type clientStream struct {
 	resTrailer *http.Header // client's Response.Trailer
 }
 
-// awaitRequestCancel runs in its own goroutine and waits for the user
+// awaitRequestCancel waits for the user to cancel a request or for the done
-// to cancel a RoundTrip request, its context to expire, or for the
+// channel to be signaled. A non-nil error is returned only if the request was
-// request to be done (any way it might be removed from the cc.streams
+// canceled.
-// map: peer reset, successful completion, TCP connection breakage,
+func awaitRequestCancel(req *http.Request, done <-chan struct{}) error {
-// etc)
-func (cs *clientStream) awaitRequestCancel(req *http.Request) {
 	ctx := reqContext(req)
 	if req.Cancel == nil && ctx.Done() == nil {
-		return
+		return nil
 	}
 	select {
 	case <-req.Cancel:
-		cs.cancelStream()
+		return errRequestCanceled
-		cs.bufPipe.CloseWithError(errRequestCanceled)
 	case <-ctx.Done():
+		return ctx.Err()
+	case <-done:
+		return nil
+	}
+}
+
+// awaitRequestCancel waits for the user to cancel a request, its context to
+// expire, or for the request to be done (any way it might be removed from the
+// cc.streams map: peer reset, successful completion, TCP connection breakage,
+// etc). If the request is canceled, then cs will be canceled and closed.
+func (cs *clientStream) awaitRequestCancel(req *http.Request) {
+	if err := awaitRequestCancel(req, cs.done); err != nil {
 		cs.cancelStream()
-		cs.bufPipe.CloseWithError(ctx.Err())
+		cs.bufPipe.CloseWithError(err)
-	case <-cs.done:
 	}
 }
 
 func (cs *clientStream) cancelStream() {
-	cs.cc.mu.Lock()
+	cc := cs.cc
+	cc.mu.Lock()
 	didReset := cs.didReset
 	cs.didReset = true
-	cs.cc.mu.Unlock()
+	cc.mu.Unlock()
 
 	if !didReset {
-		cs.cc.writeStreamReset(cs.ID, ErrCodeCancel, nil)
+		cc.writeStreamReset(cs.ID, ErrCodeCancel, nil)
+		cc.forgetStreamID(cs.ID)
 	}
 }
 
@@ -261,6 +274,13 @@ func (cs *clientStream) checkResetOrDone() error {
 	}
 }
 
+func (cs *clientStream) getStartedWrite() bool {
+	cc := cs.cc
+	cc.mu.Lock()
+	defer cc.mu.Unlock()
+	return cs.startedWrite
+}
+
 func (cs *clientStream) abortRequestBodyWrite(err error) {
 	if err == nil {
 		panic("nil error")
@@ -329,17 +349,28 @@ func (t *Transport) RoundTripOpt(req *http.Request, opt RoundTripOpt) (*http.Res
 	}
 
 	addr := authorityAddr(req.URL.Scheme, req.URL.Host)
-	for {
+	for retry := 0; ; retry++ {
 		cc, err := t.connPool().GetClientConn(req, addr)
 		if err != nil {
 			t.vlogf("http2: Transport failed to get client conn for %s: %v", addr, err)
 			return nil, err
 		}
 		traceGotConn(req, cc)
-		res, err := cc.RoundTrip(req)
+		res, gotErrAfterReqBodyWrite, err := cc.roundTrip(req)
-		if err != nil {
+		if err != nil && retry <= 6 {
-			if req, err = shouldRetryRequest(req, err); err == nil {
+			if req, err = shouldRetryRequest(req, err, gotErrAfterReqBodyWrite); err == nil {
-				continue
+				// After the first retry, do exponential backoff with 10% jitter.
+				if retry == 0 {
+					continue
+				}
+				backoff := float64(uint(1) << (uint(retry) - 1))
+				backoff += backoff * (0.1 * mathrand.Float64())
+				select {
+				case <-time.After(time.Second * time.Duration(backoff)):
+					continue
+				case <-reqContext(req).Done():
+					return nil, reqContext(req).Err()
+				}
 			}
 		}
 		if err != nil {
@@ -360,43 +391,50 @@ func (t *Transport) CloseIdleConnections() {
 }
 
 var (
-	errClientConnClosed   = errors.New("http2: client conn is closed")
+	errClientConnClosed    = errors.New("http2: client conn is closed")
-	errClientConnUnusable = errors.New("http2: client conn not usable")
+	errClientConnUnusable  = errors.New("http2: client conn not usable")
-
+	errClientConnGotGoAway = errors.New("http2: Transport received Server's graceful shutdown GOAWAY")
-	errClientConnGotGoAway                 = errors.New("http2: Transport received Server's graceful shutdown GOAWAY")
-	errClientConnGotGoAwayAfterSomeReqBody = errors.New("http2: Transport received Server's graceful shutdown GOAWAY; some request body already written")
 )
 
 // shouldRetryRequest is called by RoundTrip when a request fails to get
 // response headers. It is always called with a non-nil error.
 // It returns either a request to retry (either the same request, or a
 // modified clone), or an error if the request can't be replayed.
-func shouldRetryRequest(req *http.Request, err error) (*http.Request, error) {
+func shouldRetryRequest(req *http.Request, err error, afterBodyWrite bool) (*http.Request, error) {
-	switch err {
+	if !canRetryError(err) {
-	default:
 		return nil, err
-	case errClientConnUnusable, errClientConnGotGoAway:
-		return req, nil
-	case errClientConnGotGoAwayAfterSomeReqBody:
-		// If the Body is nil (or http.NoBody), it's safe to reuse
-		// this request and its Body.
-		if req.Body == nil || reqBodyIsNoBody(req.Body) {
-			return req, nil
-		}
-		// Otherwise we depend on the Request having its GetBody
-		// func defined.
-		getBody := reqGetBody(req) // Go 1.8: getBody = req.GetBody
-		if getBody == nil {
-			return nil, errors.New("http2: Transport: peer server initiated graceful shutdown after some of Request.Body was written; define Request.GetBody to avoid this error")
-		}
-		body, err := getBody()
-		if err != nil {
-			return nil, err
-		}
-		newReq := *req
-		newReq.Body = body
-		return &newReq, nil
 	}
+	if !afterBodyWrite {
+		return req, nil
+	}
+	// If the Body is nil (or http.NoBody), it's safe to reuse
+	// this request and its Body.
+	if req.Body == nil || reqBodyIsNoBody(req.Body) {
+		return req, nil
+	}
+	// Otherwise we depend on the Request having its GetBody
+	// func defined.
+	getBody := reqGetBody(req) // Go 1.8: getBody = req.GetBody
+	if getBody == nil {
+		return nil, fmt.Errorf("http2: Transport: cannot retry err [%v] after Request.Body was written; define Request.GetBody to avoid this error", err)
+	}
+	body, err := getBody()
+	if err != nil {
+		return nil, err
+	}
+	newReq := *req
+	newReq.Body = body
+	return &newReq, nil
+}
+
+func canRetryError(err error) bool {
+	if err == errClientConnUnusable || err == errClientConnGotGoAway {
+		return true
+	}
+	if se, ok := err.(StreamError); ok {
+		return se.Code == ErrCodeRefusedStream
+	}
+	return false
 }
 
 func (t *Transport) dialClientConn(addr string, singleUse bool) (*ClientConn, error) {
@@ -474,17 +512,18 @@ func (t *Transport) NewClientConn(c net.Conn) (*ClientConn, error) {
 
 func (t *Transport) newClientConn(c net.Conn, singleUse bool) (*ClientConn, error) {
 	cc := &ClientConn{
-		t:                    t,
+		t:                     t,
-		tconn:                c,
+		tconn:                 c,
-		readerDone:           make(chan struct{}),
+		readerDone:            make(chan struct{}),
-		nextStreamID:         1,
+		nextStreamID:          1,
-		maxFrameSize:         16 << 10, // spec default
+		maxFrameSize:          16 << 10,           // spec default
-		initialWindowSize:    65535,    // spec default
+		initialWindowSize:     65535,              // spec default
-		maxConcurrentStreams: 1000,     // "infinite", per spec. 1000 seems good enough.
+		maxConcurrentStreams:  1000,               // "infinite", per spec. 1000 seems good enough.
-		streams:              make(map[uint32]*clientStream),
+		peerMaxHeaderListSize: 0xffffffffffffffff, // "infinite", per spec. Use 2^64-1 instead.
-		singleUse:            singleUse,
+		streams:               make(map[uint32]*clientStream),
-		wantSettingsAck:      true,
+		singleUse:             singleUse,
-		pings:                make(map[[8]byte]chan struct{}),
+		wantSettingsAck:       true,
+		pings:                 make(map[[8]byte]chan struct{}),
 	}
 	if d := t.idleConnTimeout(); d != 0 {
 		cc.idleTimeout = d
@@ -560,6 +599,8 @@ func (cc *ClientConn) setGoAway(f *GoAwayFrame) {
 	}
 }
 
+// CanTakeNewRequest reports whether the connection can take a new request,
+// meaning it has not been closed or received or sent a GOAWAY.
 func (cc *ClientConn) CanTakeNewRequest() bool {
 	cc.mu.Lock()
 	defer cc.mu.Unlock()
@@ -571,8 +612,7 @@ func (cc *ClientConn) canTakeNewRequestLocked() bool {
 		return false
 	}
 	return cc.goAway == nil && !cc.closed &&
-		int64(len(cc.streams)+1) < int64(cc.maxConcurrentStreams) &&
+		int64(cc.nextStreamID)+int64(cc.pendingRequests) < math.MaxInt32
-		cc.nextStreamID < math.MaxInt32
 }
 
 // onIdleTimeout is called from a time.AfterFunc goroutine. It will
@@ -694,7 +734,7 @@ func checkConnHeaders(req *http.Request) error {
 // req.ContentLength, where 0 actually means zero (not unknown) and -1
 // means unknown.
 func actualContentLength(req *http.Request) int64 {
-	if req.Body == nil {
+	if req.Body == nil || reqBodyIsNoBody(req.Body) {
 		return 0
 	}
 	if req.ContentLength != 0 {
@@ -704,8 +744,13 @@ func actualContentLength(req *http.Request) int64 {
 }
 
 func (cc *ClientConn) RoundTrip(req *http.Request) (*http.Response, error) {
+	resp, _, err := cc.roundTrip(req)
+	return resp, err
+}
+
+func (cc *ClientConn) roundTrip(req *http.Request) (res *http.Response, gotErrAfterReqBodyWrite bool, err error) {
 	if err := checkConnHeaders(req); err != nil {
-		return nil, err
+		return nil, false, err
 	}
 	if cc.idleTimer != nil {
 		cc.idleTimer.Stop()
@@ -713,20 +758,19 @@ func (cc *ClientConn) RoundTrip(req *http.Request) (*http.Response, error) {
 
 	trailers, err := commaSeparatedTrailers(req)
 	if err != nil {
-		return nil, err
+		return nil, false, err
 	}
 	hasTrailers := trailers != ""
 
 	cc.mu.Lock()
-	cc.lastActive = time.Now()
+	if err := cc.awaitOpenSlotForRequest(req); err != nil {
-	if cc.closed || !cc.canTakeNewRequestLocked() {
 		cc.mu.Unlock()
-		return nil, errClientConnUnusable
+		return nil, false, err
 	}
 
 	body := req.Body
-	hasBody := body != nil
 	contentLen := actualContentLength(req)
+	hasBody := contentLen != 0
 
 	// TODO(bradfitz): this is a copy of the logic in net/http. Unify somewhere?
 	var requestedGzip bool
@@ -755,7 +799,7 @@ func (cc *ClientConn) RoundTrip(req *http.Request) (*http.Response, error) {
 	hdrs, err := cc.encodeHeaders(req, requestedGzip, trailers, contentLen)
 	if err != nil {
 		cc.mu.Unlock()
-		return nil, err
+		return nil, false, err
 	}
 
 	cs := cc.newStream()
@@ -767,7 +811,7 @@ func (cc *ClientConn) RoundTrip(req *http.Request) (*http.Response, error) {
 
 	cc.wmu.Lock()
 	endStream := !hasBody && !hasTrailers
-	werr := cc.writeHeaders(cs.ID, endStream, hdrs)
+	werr := cc.writeHeaders(cs.ID, endStream, int(cc.maxFrameSize), hdrs)
 	cc.wmu.Unlock()
 	traceWroteHeaders(cs.trace)
 	cc.mu.Unlock()
@@ -781,7 +825,7 @@ func (cc *ClientConn) RoundTrip(req *http.Request) (*http.Response, error) {
 		// Don't bother sending a RST_STREAM (our write already failed;
 		// no need to keep writing)
 		traceWroteRequest(cs.trace, werr)
-		return nil, werr
+		return nil, false, werr
 	}
 
 	var respHeaderTimer <-chan time.Time
@@ -800,7 +844,7 @@ func (cc *ClientConn) RoundTrip(req *http.Request) (*http.Response, error) {
 	bodyWritten := false
 	ctx := reqContext(req)
 
-	handleReadLoopResponse := func(re resAndError) (*http.Response, error) {
+	handleReadLoopResponse := func(re resAndError) (*http.Response, bool, error) {
 		res := re.res
 		if re.err != nil || res.StatusCode > 299 {
 			// On error or status code 3xx, 4xx, 5xx, etc abort any
@@ -816,19 +860,12 @@ func (cc *ClientConn) RoundTrip(req *http.Request) (*http.Response, error) {
 			cs.abortRequestBodyWrite(errStopReqBodyWrite)
 		}
 		if re.err != nil {
-			if re.err == errClientConnGotGoAway {
-				cc.mu.Lock()
-				if cs.startedWrite {
-					re.err = errClientConnGotGoAwayAfterSomeReqBody
-				}
-				cc.mu.Unlock()
-			}
 			cc.forgetStreamID(cs.ID)
-			return nil, re.err
+			return nil, cs.getStartedWrite(), re.err
 		}
 		res.Request = req
 		res.TLS = cc.tlsState
-		return res, nil
+		return res, false, nil
 	}
 
 	for {
@@ -836,37 +873,37 @@ func (cc *ClientConn) RoundTrip(req *http.Request) (*http.Response, error) {
 		case re := <-readLoopResCh:
 			return handleReadLoopResponse(re)
 		case <-respHeaderTimer:
-			cc.forgetStreamID(cs.ID)
 			if !hasBody || bodyWritten {
 				cc.writeStreamReset(cs.ID, ErrCodeCancel, nil)
 			} else {
 				bodyWriter.cancel()
 				cs.abortRequestBodyWrite(errStopReqBodyWriteAndCancel)
 			}
-			return nil, errTimeout
+			cc.forgetStreamID(cs.ID)
+			return nil, cs.getStartedWrite(), errTimeout
 		case <-ctx.Done():
-			cc.forgetStreamID(cs.ID)
 			if !hasBody || bodyWritten {
 				cc.writeStreamReset(cs.ID, ErrCodeCancel, nil)
 			} else {
 				bodyWriter.cancel()
 				cs.abortRequestBodyWrite(errStopReqBodyWriteAndCancel)
 			}
-			return nil, ctx.Err()
+			cc.forgetStreamID(cs.ID)
+			return nil, cs.getStartedWrite(), ctx.Err()
 		case <-req.Cancel:
-			cc.forgetStreamID(cs.ID)
 			if !hasBody || bodyWritten {
 				cc.writeStreamReset(cs.ID, ErrCodeCancel, nil)
 			} else {
 				bodyWriter.cancel()
 				cs.abortRequestBodyWrite(errStopReqBodyWriteAndCancel)
 			}
-			return nil, errRequestCanceled
+			cc.forgetStreamID(cs.ID)
+			return nil, cs.getStartedWrite(), errRequestCanceled
 		case <-cs.peerReset:
 			// processResetStream already removed the
 			// stream from the streams map; no need for
 			// forgetStreamID.
-			return nil, cs.resetErr
+			return nil, cs.getStartedWrite(), cs.resetErr
 		case err := <-bodyWriter.resc:
 			// Prefer the read loop's response, if available. Issue 16102.
 			select {
@@ -875,7 +912,7 @@ func (cc *ClientConn) RoundTrip(req *http.Request) (*http.Response, error) {
 			default:
 			}
 			if err != nil {
-				return nil, err
+				return nil, cs.getStartedWrite(), err
 			}
 			bodyWritten = true
 			if d := cc.responseHeaderTimeout(); d != 0 {
@@ -887,14 +924,52 @@ func (cc *ClientConn) RoundTrip(req *http.Request) (*http.Response, error) {
 	}
 }
 
+// awaitOpenSlotForRequest waits until len(streams) < maxConcurrentStreams.
+// Must hold cc.mu.
+func (cc *ClientConn) awaitOpenSlotForRequest(req *http.Request) error {
+	var waitingForConn chan struct{}
+	var waitingForConnErr error // guarded by cc.mu
+	for {
+		cc.lastActive = time.Now()
+		if cc.closed || !cc.canTakeNewRequestLocked() {
+			return errClientConnUnusable
+		}
+		if int64(len(cc.streams))+1 <= int64(cc.maxConcurrentStreams) {
+			if waitingForConn != nil {
+				close(waitingForConn)
+			}
+			return nil
+		}
+		// Unfortunately, we cannot wait on a condition variable and channel at
+		// the same time, so instead, we spin up a goroutine to check if the
+		// request is canceled while we wait for a slot to open in the connection.
+		if waitingForConn == nil {
+			waitingForConn = make(chan struct{})
+			go func() {
+				if err := awaitRequestCancel(req, waitingForConn); err != nil {
+					cc.mu.Lock()
+					waitingForConnErr = err
+					cc.cond.Broadcast()
+					cc.mu.Unlock()
+				}
+			}()
+		}
+		cc.pendingRequests++
+		cc.cond.Wait()
+		cc.pendingRequests--
+		if waitingForConnErr != nil {
+			return waitingForConnErr
+		}
+	}
+}
+
 // requires cc.wmu be held
-func (cc *ClientConn) writeHeaders(streamID uint32, endStream bool, hdrs []byte) error {
+func (cc *ClientConn) writeHeaders(streamID uint32, endStream bool, maxFrameSize int, hdrs []byte) error {
 	first := true // first frame written (HEADERS is first, then CONTINUATION)
-	frameSize := int(cc.maxFrameSize)
 	for len(hdrs) > 0 && cc.werr == nil {
 		chunk := hdrs
-		if len(chunk) > frameSize {
+		if len(chunk) > maxFrameSize {
-			chunk = chunk[:frameSize]
+			chunk = chunk[:maxFrameSize]
 		}
 		hdrs = hdrs[len(chunk):]
 		endHeaders := len(hdrs) == 0
@@ -1002,17 +1077,26 @@ func (cs *clientStream) writeRequestBody(body io.Reader, bodyCloser io.Closer) (
 	var trls []byte
 	if hasTrailers {
 		cc.mu.Lock()
-		defer cc.mu.Unlock()
+		trls, err = cc.encodeTrailers(req)
-		trls = cc.encodeTrailers(req)
+		cc.mu.Unlock()
+		if err != nil {
+			cc.writeStreamReset(cs.ID, ErrCodeInternal, err)
+			cc.forgetStreamID(cs.ID)
+			return err
+		}
 	}
 
+	cc.mu.Lock()
+	maxFrameSize := int(cc.maxFrameSize)
+	cc.mu.Unlock()
+
 	cc.wmu.Lock()
 	defer cc.wmu.Unlock()
 
 	// Two ways to send END_STREAM: either with trailers, or
 	// with an empty DATA frame.
 	if len(trls) > 0 {
-		err = cc.writeHeaders(cs.ID, true, trls)
+		err = cc.writeHeaders(cs.ID, true, maxFrameSize, trls)
 	} else {
 		err = cc.fr.WriteData(cs.ID, true, nil)
 	}
@@ -1106,62 +1190,86 @@ func (cc *ClientConn) encodeHeaders(req *http.Request, addGzipHeader bool, trail
 		}
 	}
 
-	// 8.1.2.3 Request Pseudo-Header Fields
+	enumerateHeaders := func(f func(name, value string)) {
-	// The :path pseudo-header field includes the path and query parts of the
+		// 8.1.2.3 Request Pseudo-Header Fields
-	// target URI (the path-absolute production and optionally a '?' character
+		// The :path pseudo-header field includes the path and query parts of the
-	// followed by the query production (see Sections 3.3 and 3.4 of
+		// target URI (the path-absolute production and optionally a '?' character
-	// [RFC3986]).
+		// followed by the query production (see Sections 3.3 and 3.4 of
-	cc.writeHeader(":authority", host)
+		// [RFC3986]).
-	cc.writeHeader(":method", req.Method)
+		f(":authority", host)
-	if req.Method != "CONNECT" {
+		f(":method", req.Method)
-		cc.writeHeader(":path", path)
+		if req.Method != "CONNECT" {
-		cc.writeHeader(":scheme", req.URL.Scheme)
+			f(":path", path)
-	}
+			f(":scheme", req.URL.Scheme)
-	if trailers != "" {
+		}
-		cc.writeHeader("trailer", trailers)
+		if trailers != "" {
+			f("trailer", trailers)
+		}
+
+		var didUA bool
+		for k, vv := range req.Header {
+			if strings.EqualFold(k, "host") || strings.EqualFold(k, "content-length") {
+				// Host is :authority, already sent.
+				// Content-Length is automatic, set below.
+				continue
+			} else if strings.EqualFold(k, "connection") || strings.EqualFold(k, "proxy-connection") ||
+				strings.EqualFold(k, "transfer-encoding") || strings.EqualFold(k, "upgrade") ||
+				strings.EqualFold(k, "keep-alive") {
+				// Per 8.1.2.2 Connection-Specific Header
+				// Fields, don't send connection-specific
+				// fields. We have already checked if any
+				// are error-worthy so just ignore the rest.
+				continue
+			} else if strings.EqualFold(k, "user-agent") {
+				// Match Go's http1 behavior: at most one
+				// User-Agent. If set to nil or empty string,
+				// then omit it. Otherwise if not mentioned,
+				// include the default (below).
+				didUA = true
+				if len(vv) < 1 {
+					continue
+				}
+				vv = vv[:1]
+				if vv[0] == "" {
+					continue
+				}
+
+			}
+
+			for _, v := range vv {
+				f(k, v)
+			}
+		}
+		if shouldSendReqContentLength(req.Method, contentLength) {
+			f("content-length", strconv.FormatInt(contentLength, 10))
+		}
+		if addGzipHeader {
+			f("accept-encoding", "gzip")
+		}
+		if !didUA {
+			f("user-agent", defaultUserAgent)
+		}
 	}
 
-	var didUA bool
+	// Do a first pass over the headers counting bytes to ensure
-	for k, vv := range req.Header {
+	// we don't exceed cc.peerMaxHeaderListSize. This is done as a
-		lowKey := strings.ToLower(k)
+	// separate pass before encoding the headers to prevent
-		switch lowKey {
+	// modifying the hpack state.
-		case "host", "content-length":
+	hlSize := uint64(0)
-			// Host is :authority, already sent.
+	enumerateHeaders(func(name, value string) {
-			// Content-Length is automatic, set below.
+		hf := hpack.HeaderField{Name: name, Value: value}
-			continue
+		hlSize += uint64(hf.Size())
-		case "connection", "proxy-connection", "transfer-encoding", "upgrade", "keep-alive":
+	})
-			// Per 8.1.2.2 Connection-Specific Header
+
-			// Fields, don't send connection-specific
+	if hlSize > cc.peerMaxHeaderListSize {
-			// fields. We have already checked if any
+		return nil, errRequestHeaderListSize
-			// are error-worthy so just ignore the rest.
-			continue
-		case "user-agent":
-			// Match Go's http1 behavior: at most one
-			// User-Agent. If set to nil or empty string,
-			// then omit it. Otherwise if not mentioned,
-			// include the default (below).
-			didUA = true
-			if len(vv) < 1 {
-				continue
-			}
-			vv = vv[:1]
-			if vv[0] == "" {
-				continue
-			}
-		}
-		for _, v := range vv {
-			cc.writeHeader(lowKey, v)
-		}
-	}
-	if shouldSendReqContentLength(req.Method, contentLength) {
-		cc.writeHeader("content-length", strconv.FormatInt(contentLength, 10))
-	}
-	if addGzipHeader {
-		cc.writeHeader("accept-encoding", "gzip")
-	}
-	if !didUA {
-		cc.writeHeader("user-agent", defaultUserAgent)
 	}
+
+	// Header list size is ok. Write the headers.
+	enumerateHeaders(func(name, value string) {
+		cc.writeHeader(strings.ToLower(name), value)
+	})
+
 	return cc.hbuf.Bytes(), nil
 }
 
@@ -1188,17 +1296,29 @@ func shouldSendReqContentLength(method string, contentLength int64) bool {
 }
 
 // requires cc.mu be held.
-func (cc *ClientConn) encodeTrailers(req *http.Request) []byte {
+func (cc *ClientConn) encodeTrailers(req *http.Request) ([]byte, error) {
 	cc.hbuf.Reset()
+
+	hlSize := uint64(0)
 	for k, vv := range req.Trailer {
-		// Transfer-Encoding, etc.. have already been filter at the
+		for _, v := range vv {
+			hf := hpack.HeaderField{Name: k, Value: v}
+			hlSize += uint64(hf.Size())
+		}
+	}
+	if hlSize > cc.peerMaxHeaderListSize {
+		return nil, errRequestHeaderListSize
+	}
+
+	for k, vv := range req.Trailer {
+		// Transfer-Encoding, etc.. have already been filtered at the
 		// start of RoundTrip
 		lowKey := strings.ToLower(k)
 		for _, v := range vv {
 			cc.writeHeader(lowKey, v)
 		}
 	}
-	return cc.hbuf.Bytes()
+	return cc.hbuf.Bytes(), nil
 }
 
 func (cc *ClientConn) writeHeader(name, value string) {
@@ -1246,7 +1366,9 @@ func (cc *ClientConn) streamByID(id uint32, andRemove bool) *clientStream {
 			cc.idleTimer.Reset(cc.idleTimeout)
 		}
 		close(cs.done)
-		cc.cond.Broadcast() // wake up checkResetOrDone via clientStream.awaitFlowControl
+		// Wake up checkResetOrDone via clientStream.awaitFlowControl and
+		// wake up RoundTrip if there is a pending request.
+		cc.cond.Broadcast()
 	}
 	return cs
 }
@@ -1254,17 +1376,12 @@ func (cc *ClientConn) streamByID(id uint32, andRemove bool) *clientStream {
 // clientConnReadLoop is the state owned by the clientConn's frame-reading readLoop.
 type clientConnReadLoop struct {
 	cc            *ClientConn
-	activeRes     map[uint32]*clientStream // keyed by streamID
 	closeWhenIdle bool
 }
 
 // readLoop runs in its own goroutine and reads and dispatches frames.
 func (cc *ClientConn) readLoop() {
-	rl := &clientConnReadLoop{
+	rl := &clientConnReadLoop{cc: cc}
-		cc:        cc,
-		activeRes: make(map[uint32]*clientStream),
-	}
-
 	defer rl.cleanup()
 	cc.readerErr = rl.run()
 	if ce, ok := cc.readerErr.(ConnectionError); ok {
@@ -1319,10 +1436,8 @@ func (rl *clientConnReadLoop) cleanup() {
 	} else if err == io.EOF {
 		err = io.ErrUnexpectedEOF
 	}
-	for _, cs := range rl.activeRes {
-		cs.bufPipe.CloseWithError(err)
-	}
 	for _, cs := range cc.streams {
+		cs.bufPipe.CloseWithError(err) // no-op if already closed
 		select {
 		case cs.resc <- resAndError{err: err}:
 		default:
@@ -1345,8 +1460,9 @@ func (rl *clientConnReadLoop) run() error {
 			cc.vlogf("http2: Transport readFrame error on conn %p: (%T) %v", cc, err, err)
 		}
 		if se, ok := err.(StreamError); ok {
-			if cs := cc.streamByID(se.StreamID, true /*ended; remove it*/); cs != nil {
+			if cs := cc.streamByID(se.StreamID, false); cs != nil {
 				cs.cc.writeStreamReset(cs.ID, se.Code, err)
+				cs.cc.forgetStreamID(cs.ID)
 				if se.Cause == nil {
 					se.Cause = cc.fr.errDetail
 				}
@@ -1399,7 +1515,7 @@ func (rl *clientConnReadLoop) run() error {
 			}
 			return err
 		}
-		if rl.closeWhenIdle && gotReply && maybeIdle && len(rl.activeRes) == 0 {
+		if rl.closeWhenIdle && gotReply && maybeIdle {
 			cc.closeIfIdle()
 		}
 	}
@@ -1407,13 +1523,31 @@ func (rl *clientConnReadLoop) run() error {
 
 func (rl *clientConnReadLoop) processHeaders(f *MetaHeadersFrame) error {
 	cc := rl.cc
-	cs := cc.streamByID(f.StreamID, f.StreamEnded())
+	cs := cc.streamByID(f.StreamID, false)
 	if cs == nil {
 		// We'd get here if we canceled a request while the
 		// server had its response still in flight. So if this
 		// was just something we canceled, ignore it.
 		return nil
 	}
+	if f.StreamEnded() {
+		// Issue 20521: If the stream has ended, streamByID() causes
+		// clientStream.done to be closed, which causes the request's bodyWriter
+		// to be closed with an errStreamClosed, which may be received by
+		// clientConn.RoundTrip before the result of processing these headers.
+		// Deferring stream closure allows the header processing to occur first.
+		// clientConn.RoundTrip may still receive the bodyWriter error first, but
+		// the fix for issue 16102 prioritises any response.
+		//
+		// Issue 22413: If there is no request body, we should close the
+		// stream before writing to cs.resc so that the stream is closed
+		// immediately once RoundTrip returns.
+		if cs.req.Body != nil {
+			defer cc.forgetStreamID(f.StreamID)
+		} else {
+			cc.forgetStreamID(f.StreamID)
+		}
+	}
 	if !cs.firstByte {
 		if cs.trace != nil {
 			// TODO(bradfitz): move first response byte earlier,
@@ -1437,6 +1571,7 @@ func (rl *clientConnReadLoop) processHeaders(f *MetaHeadersFrame) error {
 		}
 		// Any other error type is a stream error.
 		cs.cc.writeStreamReset(f.StreamID, ErrCodeProtocol, err)
+		cc.forgetStreamID(cs.ID)
 		cs.resc <- resAndError{err: err}
 		return nil // return nil from process* funcs to keep conn alive
 	}
@@ -1444,9 +1579,6 @@ func (rl *clientConnReadLoop) processHeaders(f *MetaHeadersFrame) error {
 		// (nil, nil) special case. See handleResponse docs.
 		return nil
 	}
-	if res.Body != noBody {
-		rl.activeRes[cs.ID] = cs
-	}
 	cs.resTrailer = &res.Trailer
 	cs.resc <- resAndError{res: res}
 	return nil
@@ -1466,11 +1598,11 @@ func (rl *clientConnReadLoop) handleResponse(cs *clientStream, f *MetaHeadersFra
 
 	status := f.PseudoValue("status")
 	if status == "" {
-		return nil, errors.New("missing status pseudo header")
+		return nil, errors.New("malformed response from server: missing status pseudo header")
 	}
 	statusCode, err := strconv.Atoi(status)
 	if err != nil {
-		return nil, errors.New("malformed non-numeric status pseudo header")
+		return nil, errors.New("malformed response from server: malformed non-numeric status pseudo header")
 	}
 
 	if statusCode == 100 {
@@ -1668,6 +1800,7 @@ func (b transportResponseBody) Close() error {
 	}
 
 	cs.bufPipe.BreakWithError(errClosedResponseBody)
+	cc.forgetStreamID(cs.ID)
 	return nil
 }
 
@@ -1702,7 +1835,23 @@ func (rl *clientConnReadLoop) processData(f *DataFrame) error {
 		}
 		return nil
 	}
+	if !cs.firstByte {
+		cc.logf("protocol error: received DATA before a HEADERS frame")
+		rl.endStreamError(cs, StreamError{
+			StreamID: f.StreamID,
+			Code:     ErrCodeProtocol,
+		})
+		return nil
+	}
 	if f.Length > 0 {
+		if cs.req.Method == "HEAD" && len(data) > 0 {
+			cc.logf("protocol error: received DATA on a HEAD request")
+			rl.endStreamError(cs, StreamError{
+				StreamID: f.StreamID,
+				Code:     ErrCodeProtocol,
+			})
+			return nil
+		}
 		// Check connection-level flow control.
 		cc.mu.Lock()
 		if cs.inflow.available() >= int32(f.Length) {
@@ -1713,16 +1862,27 @@ func (rl *clientConnReadLoop) processData(f *DataFrame) error {
 		}
 		// Return any padded flow control now, since we won't
 		// refund it later on body reads.
-		if pad := int32(f.Length) - int32(len(data)); pad > 0 {
+		var refund int
-			cs.inflow.add(pad)
+		if pad := int(f.Length) - len(data); pad > 0 {
-			cc.inflow.add(pad)
+			refund += pad
+		}
+		// Return len(data) now if the stream is already closed,
+		// since data will never be read.
+		didReset := cs.didReset
+		if didReset {
+			refund += len(data)
+		}
+		if refund > 0 {
+			cc.inflow.add(int32(refund))
 			cc.wmu.Lock()
-			cc.fr.WriteWindowUpdate(0, uint32(pad))
+			cc.fr.WriteWindowUpdate(0, uint32(refund))
-			cc.fr.WriteWindowUpdate(cs.ID, uint32(pad))
+			if !didReset {
+				cs.inflow.add(int32(refund))
+				cc.fr.WriteWindowUpdate(cs.ID, uint32(refund))
+			}
 			cc.bw.Flush()
 			cc.wmu.Unlock()
 		}
-		didReset := cs.didReset
 		cc.mu.Unlock()
 
 		if len(data) > 0 && !didReset {
@@ -1753,11 +1913,10 @@ func (rl *clientConnReadLoop) endStreamError(cs *clientStream, err error) {
 		err = io.EOF
 		code = cs.copyTrailers
 	}
-	cs.bufPipe.closeWithErrorAndCode(err, code)
-	delete(rl.activeRes, cs.ID)
 	if isConnectionCloseRequest(cs.req) {
 		rl.closeWhenIdle = true
 	}
+	cs.bufPipe.closeWithErrorAndCode(err, code)
 
 	select {
 	case cs.resc <- resAndError{err: err}:
@@ -1805,6 +1964,8 @@ func (rl *clientConnReadLoop) processSettings(f *SettingsFrame) error {
 			cc.maxFrameSize = s.Val
 		case SettingMaxConcurrentStreams:
 			cc.maxConcurrentStreams = s.Val
+		case SettingMaxHeaderListSize:
+			cc.peerMaxHeaderListSize = uint64(s.Val)
 		case SettingInitialWindowSize:
 			// Values above the maximum flow-control
 			// window size of 2^31-1 MUST be treated as a
@@ -1882,7 +2043,6 @@ func (rl *clientConnReadLoop) processResetStream(f *RSTStreamFrame) error {
 		cs.bufPipe.CloseWithError(err)
 		cs.cc.cond.Broadcast() // wake up checkResetOrDone via clientStream.awaitFlowControl
 	}
-	delete(rl.activeRes, cs.ID)
 	return nil
 }
 
@@ -1971,6 +2131,7 @@ func (cc *ClientConn) writeStreamReset(streamID uint32, code ErrCode, err error)
 
 var (
 	errResponseHeaderListSize = errors.New("http2: response header list larger than advertised limit")
+	errRequestHeaderListSize  = errors.New("http2: request header list larger than peer's advertised limit")
 	errPseudoTrailers         = errors.New("http2: invalid pseudo header in trailers")
 )
 

vendor/golang.org/x/net/http2/write.go

@@ -10,7 +10,6 @@ import (
 	"log"
 	"net/http"
 	"net/url"
-	"time"
 
 	"golang.org/x/net/http2/hpack"
 	"golang.org/x/net/lex/httplex"
@@ -90,11 +89,7 @@ type writeGoAway struct {
 
 func (p *writeGoAway) writeFrame(ctx writeContext) error {
 	err := ctx.Framer().WriteGoAway(p.maxStreamID, p.code, nil)
-	if p.code != 0 {
+	ctx.Flush() // ignore error: we're hanging up on them anyway
-		ctx.Flush() // ignore error: we're hanging up on them anyway
-		time.Sleep(50 * time.Millisecond)
-		ctx.CloseConn()
-	}
 	return err
 }
 

vendor/golang.org/x/net/idna/idna.go

@@ -21,6 +21,7 @@ import (
 	"unicode/utf8"
 
 	"golang.org/x/text/secure/bidirule"
+	"golang.org/x/text/unicode/bidi"
 	"golang.org/x/text/unicode/norm"
 )
 
@@ -67,6 +68,15 @@ func VerifyDNSLength(verify bool) Option {
 	return func(o *options) { o.verifyDNSLength = verify }
 }
 
+// RemoveLeadingDots removes leading label separators. Leading runes that map to
+// dots, such as U+3002 IDEOGRAPHIC FULL STOP, are removed as well.
+//
+// This is the behavior suggested by the UTS #46 and is adopted by some
+// browsers.
+func RemoveLeadingDots(remove bool) Option {
+	return func(o *options) { o.removeLeadingDots = remove }
+}
+
 // ValidateLabels sets whether to check the mandatory label validation criteria
 // as defined in Section 5.4 of RFC 5891. This includes testing for correct use
 // of hyphens ('-'), normalization, validity of runes, and the context rules.
@@ -83,7 +93,7 @@ func ValidateLabels(enable bool) Option {
 	}
 }
 
-// StrictDomainName limits the set of permissable ASCII characters to those
+// StrictDomainName limits the set of permissible ASCII characters to those
 // allowed in domain names as defined in RFC 1034 (A-Z, a-z, 0-9 and the
 // hyphen). This is set by default for MapForLookup and ValidateForRegistration.
 //
@@ -137,10 +147,11 @@ func MapForLookup() Option {
 }
 
 type options struct {
-	transitional    bool
+	transitional      bool
-	useSTD3Rules    bool
+	useSTD3Rules      bool
-	validateLabels  bool
+	validateLabels    bool
-	verifyDNSLength bool
+	verifyDNSLength   bool
+	removeLeadingDots bool
 
 	trie *idnaTrie
 
@@ -149,14 +160,14 @@ type options struct {
 
 	// mapping implements a validation and mapping step as defined in RFC 5895
 	// or UTS 46, tailored to, for example, domain registration or lookup.
-	mapping func(p *Profile, s string) (string, error)
+	mapping func(p *Profile, s string) (mapped string, isBidi bool, err error)
 
 	// bidirule, if specified, checks whether s conforms to the Bidi Rule
 	// defined in RFC 5893.
 	bidirule func(s string) bool
 }
 
-// A Profile defines the configuration of a IDNA mapper.
+// A Profile defines the configuration of an IDNA mapper.
 type Profile struct {
 	options
 }
@@ -289,12 +300,16 @@ func (e runeError) Error() string {
 // see http://www.unicode.org/reports/tr46.
 func (p *Profile) process(s string, toASCII bool) (string, error) {
 	var err error
+	var isBidi bool
 	if p.mapping != nil {
-		s, err = p.mapping(p, s)
+		s, isBidi, err = p.mapping(p, s)
 	}
 	// Remove leading empty labels.
-	for ; len(s) > 0 && s[0] == '.'; s = s[1:] {
+	if p.removeLeadingDots {
+		for ; len(s) > 0 && s[0] == '.'; s = s[1:] {
+		}
 	}
+	// TODO: allow for a quick check of the tables data.
 	// It seems like we should only create this error on ToASCII, but the
 	// UTS 46 conformance tests suggests we should always check this.
 	if err == nil && p.verifyDNSLength && s == "" {
@@ -320,6 +335,7 @@ func (p *Profile) process(s string, toASCII bool) (string, error) {
 				// Spec says keep the old label.
 				continue
 			}
+			isBidi = isBidi || bidirule.DirectionString(u) != bidi.LeftToRight
 			labels.set(u)
 			if err == nil && p.validateLabels {
 				err = p.fromPuny(p, u)
@@ -334,6 +350,14 @@ func (p *Profile) process(s string, toASCII bool) (string, error) {
 			err = p.validateLabel(label)
 		}
 	}
+	if isBidi && p.bidirule != nil && err == nil {
+		for labels.reset(); !labels.done(); labels.next() {
+			if !p.bidirule(labels.label()) {
+				err = &labelError{s, "B"}
+				break
+			}
+		}
+	}
 	if toASCII {
 		for labels.reset(); !labels.done(); labels.next() {
 			label := labels.label()
@@ -365,41 +389,77 @@ func (p *Profile) process(s string, toASCII bool) (string, error) {
 	return s, err
 }
 
-func normalize(p *Profile, s string) (string, error) {
+func normalize(p *Profile, s string) (mapped string, isBidi bool, err error) {
-	return norm.NFC.String(s), nil
+	// TODO: consider first doing a quick check to see if any of these checks
+	// need to be done. This will make it slower in the general case, but
+	// faster in the common case.
+	mapped = norm.NFC.String(s)
+	isBidi = bidirule.DirectionString(mapped) == bidi.RightToLeft
+	return mapped, isBidi, nil
 }
 
-func validateRegistration(p *Profile, s string) (string, error) {
+func validateRegistration(p *Profile, s string) (idem string, bidi bool, err error) {
+	// TODO: filter need for normalization in loop below.
 	if !norm.NFC.IsNormalString(s) {
-		return s, &labelError{s, "V1"}
+		return s, false, &labelError{s, "V1"}
 	}
-	var err error
 	for i := 0; i < len(s); {
 		v, sz := trie.lookupString(s[i:])
-		i += sz
+		if sz == 0 {
+			return s, bidi, runeError(utf8.RuneError)
+		}
+		bidi = bidi || info(v).isBidi(s[i:])
 		// Copy bytes not copied so far.
 		switch p.simplify(info(v).category()) {
 		// TODO: handle the NV8 defined in the Unicode idna data set to allow
 		// for strict conformance to IDNA2008.
 		case valid, deviation:
 		case disallowed, mapped, unknown, ignored:
-			if err == nil {
+			r, _ := utf8.DecodeRuneInString(s[i:])
-				r, _ := utf8.DecodeRuneInString(s[i:])
+			return s, bidi, runeError(r)
-				err = runeError(r)
-			}
 		}
+		i += sz
 	}
-	return s, err
+	return s, bidi, nil
 }
 
-func validateAndMap(p *Profile, s string) (string, error) {
+func (c info) isBidi(s string) bool {
+	if !c.isMapped() {
+		return c&attributesMask == rtl
+	}
+	// TODO: also store bidi info for mapped data. This is possible, but a bit
+	// cumbersome and not for the common case.
+	p, _ := bidi.LookupString(s)
+	switch p.Class() {
+	case bidi.R, bidi.AL, bidi.AN:
+		return true
+	}
+	return false
+}
+
+func validateAndMap(p *Profile, s string) (vm string, bidi bool, err error) {
 	var (
-		err error
+		b []byte
-		b   []byte
+		k int
-		k   int
 	)
+	// combinedInfoBits contains the or-ed bits of all runes. We use this
+	// to derive the mayNeedNorm bit later. This may trigger normalization
+	// overeagerly, but it will not do so in the common case. The end result
+	// is another 10% saving on BenchmarkProfile for the common case.
+	var combinedInfoBits info
 	for i := 0; i < len(s); {
 		v, sz := trie.lookupString(s[i:])
+		if sz == 0 {
+			b = append(b, s[k:i]...)
+			b = append(b, "\ufffd"...)
+			k = len(s)
+			if err == nil {
+				err = runeError(utf8.RuneError)
+			}
+			break
+		}
+		combinedInfoBits |= info(v)
+		bidi = bidi || info(v).isBidi(s[i:])
 		start := i
 		i += sz
 		// Copy bytes not copied so far.
@@ -408,7 +468,7 @@ func validateAndMap(p *Profile, s string) (string, error) {
 			continue
 		case disallowed:
 			if err == nil {
-				r, _ := utf8.DecodeRuneInString(s[i:])
+				r, _ := utf8.DecodeRuneInString(s[start:])
 				err = runeError(r)
 			}
 			continue
@@ -426,7 +486,9 @@ func validateAndMap(p *Profile, s string) (string, error) {
 	}
 	if k == 0 {
 		// No changes so far.
-		s = norm.NFC.String(s)
+		if combinedInfoBits&mayNeedNorm != 0 {
+			s = norm.NFC.String(s)
+		}
 	} else {
 		b = append(b, s[k:]...)
 		if norm.NFC.QuickSpan(b) != len(b) {
@@ -435,7 +497,7 @@ func validateAndMap(p *Profile, s string) (string, error) {
 		// TODO: the punycode converters require strings as input.
 		s = string(b)
 	}
-	return s, err
+	return s, bidi, err
 }
 
 // A labelIter allows iterating over domain name labels.
@@ -530,8 +592,13 @@ func validateFromPunycode(p *Profile, s string) error {
 	if !norm.NFC.IsNormalString(s) {
 		return &labelError{s, "V1"}
 	}
+	// TODO: detect whether string may have to be normalized in the following
+	// loop.
 	for i := 0; i < len(s); {
 		v, sz := trie.lookupString(s[i:])
+		if sz == 0 {
+			return runeError(utf8.RuneError)
+		}
 		if c := p.simplify(info(v).category()); c != valid && c != deviation {
 			return &labelError{s, "V6"}
 		}
@@ -604,16 +671,13 @@ var joinStates = [][numJoinTypes]joinState{
 
 // validateLabel validates the criteria from Section 4.1. Item 1, 4, and 6 are
 // already implicitly satisfied by the overall implementation.
-func (p *Profile) validateLabel(s string) error {
+func (p *Profile) validateLabel(s string) (err error) {
 	if s == "" {
 		if p.verifyDNSLength {
 			return &labelError{s, "A4"}
 		}
 		return nil
 	}
-	if p.bidirule != nil && !p.bidirule(s) {
-		return &labelError{s, "B"}
-	}
 	if !p.validateLabels {
 		return nil
 	}

vendor/golang.org/x/net/idna/trieval.go

@@ -26,9 +26,9 @@ package idna
 //       15..3  index into xor or mapping table
 //     }
 //   } else {
-//       15..13 unused
+//       15..14 unused
-//           12 modifier (including virama)
+//       13     mayNeedNorm
-//           11 virama modifier
+//       12..11 attributes
 //       10..8  joining type
 //        7..3  category type
 //   }
@@ -49,15 +49,20 @@ const (
 	joinShift = 8
 	joinMask  = 0x07
 
-	viramaModifier = 0x0800
+	// Attributes
+	attributesMask = 0x1800
+	viramaModifier = 0x1800
 	modifier       = 0x1000
+	rtl            = 0x0800
+
+	mayNeedNorm = 0x2000
 )
 
 // A category corresponds to a category defined in the IDNA mapping table.
 type category uint16
 
 const (
-	unknown              category = 0 // not defined currently in unicode.
+	unknown              category = 0 // not currently defined in unicode.
 	mapped               category = 1
 	disallowedSTD3Mapped category = 2
 	deviation            category = 3
@@ -110,5 +115,5 @@ func (c info) isModifier() bool {
 }
 
 func (c info) isViramaModifier() bool {
-	return c&(viramaModifier|catSmallMask) == viramaModifier
+	return c&(attributesMask|catSmallMask) == viramaModifier
 }

vendor/golang.org/x/net/proxy/per_host.go

@@ -9,7 +9,7 @@ import (
 	"strings"
 )
 
-// A PerHost directs connections to a default Dialer unless the hostname
+// A PerHost directs connections to a default Dialer unless the host name
 // requested matches one of a number of exceptions.
 type PerHost struct {
 	def, bypass Dialer
@@ -61,7 +61,7 @@ func (p *PerHost) dialerForRequest(host string) Dialer {
 			return p.bypass
 		}
 		if host == zone[1:] {
-			// For a zone "example.com", we match "example.com"
+			// For a zone ".example.com", we match "example.com"
 			// too.
 			return p.bypass
 		}
@@ -76,7 +76,7 @@ func (p *PerHost) dialerForRequest(host string) Dialer {
 
 // AddFromString parses a string that contains comma-separated values
 // specifying hosts that should use the bypass proxy. Each value is either an
-// IP address, a CIDR range, a zone (*.example.com) or a hostname
+// IP address, a CIDR range, a zone (*.example.com) or a host name
 // (localhost). A best effort is made to parse the string and errors are
 // ignored.
 func (p *PerHost) AddFromString(s string) {
@@ -131,7 +131,7 @@ func (p *PerHost) AddZone(zone string) {
 	p.bypassZones = append(p.bypassZones, zone)
 }
 
-// AddHost specifies a hostname that will use the bypass proxy.
+// AddHost specifies a host name that will use the bypass proxy.
 func (p *PerHost) AddHost(host string) {
 	if strings.HasSuffix(host, ".") {
 		host = host[:len(host)-1]

vendor/golang.org/x/net/proxy/proxy.go

@@ -11,6 +11,7 @@ import (
 	"net"
 	"net/url"
 	"os"
+	"sync"
 )
 
 // A Dialer is a means to establish a connection.
@@ -27,7 +28,7 @@ type Auth struct {
 // FromEnvironment returns the dialer specified by the proxy related variables in
 // the environment.
 func FromEnvironment() Dialer {
-	allProxy := os.Getenv("all_proxy")
+	allProxy := allProxyEnv.Get()
 	if len(allProxy) == 0 {
 		return Direct
 	}
@@ -41,7 +42,7 @@ func FromEnvironment() Dialer {
 		return Direct
 	}
 
-	noProxy := os.Getenv("no_proxy")
+	noProxy := noProxyEnv.Get()
 	if len(noProxy) == 0 {
 		return proxy
 	}
@@ -92,3 +93,42 @@ func FromURL(u *url.URL, forward Dialer) (Dialer, error) {
 
 	return nil, errors.New("proxy: unknown scheme: " + u.Scheme)
 }
+
+var (
+	allProxyEnv = &envOnce{
+		names: []string{"ALL_PROXY", "all_proxy"},
+	}
+	noProxyEnv = &envOnce{
+		names: []string{"NO_PROXY", "no_proxy"},
+	}
+)
+
+// envOnce looks up an environment variable (optionally by multiple
+// names) once. It mitigates expensive lookups on some platforms
+// (e.g. Windows).
+// (Borrowed from net/http/transport.go)
+type envOnce struct {
+	names []string
+	once  sync.Once
+	val   string
+}
+
+func (e *envOnce) Get() string {
+	e.once.Do(e.init)
+	return e.val
+}
+
+func (e *envOnce) init() {
+	for _, n := range e.names {
+		e.val = os.Getenv(n)
+		if e.val != "" {
+			return
+		}
+	}
+}
+
+// reset is used by tests
+func (e *envOnce) reset() {
+	e.once = sync.Once{}
+	e.val = ""
+}

vendor/golang.org/x/net/proxy/socks5.go

@@ -12,7 +12,7 @@ import (
 )
 
 // SOCKS5 returns a Dialer that makes SOCKSv5 connections to the given address
-// with an optional username and password. See RFC 1928.
+// with an optional username and password. See RFC 1928 and RFC 1929.
 func SOCKS5(network, addr string, auth *Auth, forward Dialer) (Dialer, error) {
 	s := &socks5{
 		network: network,
@@ -60,7 +60,7 @@ var socks5Errors = []string{
 	"address type not supported",
 }
 
-// Dial connects to the address addr on the network net via the SOCKS5 proxy.
+// Dial connects to the address addr on the given network via the SOCKS5 proxy.
 func (s *socks5) Dial(network, addr string) (net.Conn, error) {
 	switch network {
 	case "tcp", "tcp6", "tcp4":
@@ -120,6 +120,7 @@ func (s *socks5) connect(conn net.Conn, target string) error {
 		return errors.New("proxy: SOCKS5 proxy at " + s.addr + " requires authentication")
 	}
 
+	// See RFC 1929
 	if buf[1] == socks5AuthPassword {
 		buf = buf[:0]
 		buf = append(buf, 1 /* password protocol version */)
@@ -154,7 +155,7 @@ func (s *socks5) connect(conn net.Conn, target string) error {
 		buf = append(buf, ip...)
 	} else {
 		if len(host) > 255 {
-			return errors.New("proxy: destination hostname too long: " + host)
+			return errors.New("proxy: destination host name too long: " + host)
 		}
 		buf = append(buf, socks5Domain)
 		buf = append(buf, byte(len(host)))

vendor/golang.org/x/net/trace/events.go

@@ -39,9 +39,9 @@ var buckets = []bucket{
 }
 
 // RenderEvents renders the HTML page typically served at /debug/events.
-// It does not do any auth checking; see AuthRequest for the default auth check
+// It does not do any auth checking. The request may be nil.
-// used by the handler registered on http.DefaultServeMux.
+//
-// req may be nil.
+// Most users will use the Events handler.
 func RenderEvents(w http.ResponseWriter, req *http.Request, sensitive bool) {
 	now := time.Now()
 	data := &struct {

vendor/golang.org/x/net/trace/trace.go

@@ -110,30 +110,46 @@ var AuthRequest = func(req *http.Request) (any, sensitive bool) {
 }
 
 func init() {
-	http.HandleFunc("/debug/requests", func(w http.ResponseWriter, req *http.Request) {
+	// TODO(jbd): Serve Traces from /debug/traces in the future?
-		any, sensitive := AuthRequest(req)
+	// There is no requirement for a request to be present to have traces.
-		if !any {
+	http.HandleFunc("/debug/requests", Traces)
-			http.Error(w, "not allowed", http.StatusUnauthorized)
+	http.HandleFunc("/debug/events", Events)
-			return
+}
-		}
+
-		w.Header().Set("Content-Type", "text/html; charset=utf-8")
+// Traces responds with traces from the program.
-		Render(w, req, sensitive)
+// The package initialization registers it in http.DefaultServeMux
-	})
+// at /debug/requests.
-	http.HandleFunc("/debug/events", func(w http.ResponseWriter, req *http.Request) {
+//
-		any, sensitive := AuthRequest(req)
+// It performs authorization by running AuthRequest.
-		if !any {
+func Traces(w http.ResponseWriter, req *http.Request) {
-			http.Error(w, "not allowed", http.StatusUnauthorized)
+	any, sensitive := AuthRequest(req)
-			return
+	if !any {
-		}
+		http.Error(w, "not allowed", http.StatusUnauthorized)
-		w.Header().Set("Content-Type", "text/html; charset=utf-8")
+		return
-		RenderEvents(w, req, sensitive)
+	}
-	})
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	Render(w, req, sensitive)
+}
+
+// Events responds with a page of events collected by EventLogs.
+// The package initialization registers it in http.DefaultServeMux
+// at /debug/events.
+//
+// It performs authorization by running AuthRequest.
+func Events(w http.ResponseWriter, req *http.Request) {
+	any, sensitive := AuthRequest(req)
+	if !any {
+		http.Error(w, "not allowed", http.StatusUnauthorized)
+		return
+	}
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	RenderEvents(w, req, sensitive)
 }
 
 // Render renders the HTML page typically served at /debug/requests.
-// It does not do any auth checking; see AuthRequest for the default auth check
+// It does not do any auth checking. The request may be nil.
-// used by the handler registered on http.DefaultServeMux.
+//
-// req may be nil.
+// Most users will use the Traces handler.
 func Render(w io.Writer, req *http.Request, sensitive bool) {
 	data := &struct {
 		Families         []string