Add vendor to improve building speed.

This also adds ability to be built in network-constrained environment.

vendor/golang.org/x/net/http2/h2c/h2c.go

@@ -0,0 +1,240 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package h2c implements the unencrypted "h2c" form of HTTP/2.
+//
+// The h2c protocol is the non-TLS version of HTTP/2 which is not available from
+// net/http or golang.org/x/net/http2.
+package h2c
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"net/textproto"
+	"os"
+	"strings"
+
+	"golang.org/x/net/http/httpguts"
+	"golang.org/x/net/http2"
+)
+
+var (
+	http2VerboseLogs bool
+)
+
+func init() {
+	e := os.Getenv("GODEBUG")
+	if strings.Contains(e, "http2debug=1") || strings.Contains(e, "http2debug=2") {
+		http2VerboseLogs = true
+	}
+}
+
+// h2cHandler is a Handler which implements h2c by hijacking the HTTP/1 traffic
+// that should be h2c traffic. There are two ways to begin a h2c connection
+// (RFC 7540 Section 3.2 and 3.4): (1) Starting with Prior Knowledge - this
+// works by starting an h2c connection with a string of bytes that is valid
+// HTTP/1, but unlikely to occur in practice and (2) Upgrading from HTTP/1 to
+// h2c - this works by using the HTTP/1 Upgrade header to request an upgrade to
+// h2c. When either of those situations occur we hijack the HTTP/1 connection,
+// convert it to an HTTP/2 connection and pass the net.Conn to http2.ServeConn.
+type h2cHandler struct {
+	Handler http.Handler
+	s       *http2.Server
+}
+
+// NewHandler returns an http.Handler that wraps h, intercepting any h2c
+// traffic. If a request is an h2c connection, it's hijacked and redirected to
+// s.ServeConn. Otherwise the returned Handler just forwards requests to h. This
+// works because h2c is designed to be parseable as valid HTTP/1, but ignored by
+// any HTTP server that does not handle h2c. Therefore we leverage the HTTP/1
+// compatible parts of the Go http library to parse and recognize h2c requests.
+// Once a request is recognized as h2c, we hijack the connection and convert it
+// to an HTTP/2 connection which is understandable to s.ServeConn. (s.ServeConn
+// understands HTTP/2 except for the h2c part of it.)
+//
+// The first request on an h2c connection is read entirely into memory before
+// the Handler is called. To limit the memory consumed by this request, wrap
+// the result of NewHandler in an http.MaxBytesHandler.
+func NewHandler(h http.Handler, s *http2.Server) http.Handler {
+	return &h2cHandler{
+		Handler: h,
+		s:       s,
+	}
+}
+
+// extractServer extracts existing http.Server instance from http.Request or create an empty http.Server
+func extractServer(r *http.Request) *http.Server {
+	server, ok := r.Context().Value(http.ServerContextKey).(*http.Server)
+	if ok {
+		return server
+	}
+	return new(http.Server)
+}
+
+// ServeHTTP implement the h2c support that is enabled by h2c.GetH2CHandler.
+func (s h2cHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	// Handle h2c with prior knowledge (RFC 7540 Section 3.4)
+	if r.Method == "PRI" && len(r.Header) == 0 && r.URL.Path == "*" && r.Proto == "HTTP/2.0" {
+		if http2VerboseLogs {
+			log.Print("h2c: attempting h2c with prior knowledge.")
+		}
+		conn, err := initH2CWithPriorKnowledge(w)
+		if err != nil {
+			if http2VerboseLogs {
+				log.Printf("h2c: error h2c with prior knowledge: %v", err)
+			}
+			return
+		}
+		defer conn.Close()
+		s.s.ServeConn(conn, &http2.ServeConnOpts{
+			Context:          r.Context(),
+			BaseConfig:       extractServer(r),
+			Handler:          s.Handler,
+			SawClientPreface: true,
+		})
+		return
+	}
+	// Handle Upgrade to h2c (RFC 7540 Section 3.2)
+	if isH2CUpgrade(r.Header) {
+		conn, settings, err := h2cUpgrade(w, r)
+		if err != nil {
+			if http2VerboseLogs {
+				log.Printf("h2c: error h2c upgrade: %v", err)
+			}
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+		defer conn.Close()
+		s.s.ServeConn(conn, &http2.ServeConnOpts{
+			Context:        r.Context(),
+			BaseConfig:     extractServer(r),
+			Handler:        s.Handler,
+			UpgradeRequest: r,
+			Settings:       settings,
+		})
+		return
+	}
+	s.Handler.ServeHTTP(w, r)
+	return
+}
+
+// initH2CWithPriorKnowledge implements creating a h2c connection with prior
+// knowledge (Section 3.4) and creates a net.Conn suitable for http2.ServeConn.
+// All we have to do is look for the client preface that is suppose to be part
+// of the body, and reforward the client preface on the net.Conn this function
+// creates.
+func initH2CWithPriorKnowledge(w http.ResponseWriter) (net.Conn, error) {
+	hijacker, ok := w.(http.Hijacker)
+	if !ok {
+		return nil, errors.New("h2c: connection does not support Hijack")
+	}
+	conn, rw, err := hijacker.Hijack()
+	if err != nil {
+		return nil, err
+	}
+
+	const expectedBody = "SM\r\n\r\n"
+
+	buf := make([]byte, len(expectedBody))
+	n, err := io.ReadFull(rw, buf)
+	if err != nil {
+		return nil, fmt.Errorf("h2c: error reading client preface: %s", err)
+	}
+
+	if string(buf[:n]) == expectedBody {
+		return newBufConn(conn, rw), nil
+	}
+
+	conn.Close()
+	return nil, errors.New("h2c: invalid client preface")
+}
+
+// h2cUpgrade establishes a h2c connection using the HTTP/1 upgrade (Section 3.2).
+func h2cUpgrade(w http.ResponseWriter, r *http.Request) (_ net.Conn, settings []byte, err error) {
+	settings, err = getH2Settings(r.Header)
+	if err != nil {
+		return nil, nil, err
+	}
+	hijacker, ok := w.(http.Hijacker)
+	if !ok {
+		return nil, nil, errors.New("h2c: connection does not support Hijack")
+	}
+
+	body, err := io.ReadAll(r.Body)
+	if err != nil {
+		return nil, nil, err
+	}
+	r.Body = io.NopCloser(bytes.NewBuffer(body))
+
+	conn, rw, err := hijacker.Hijack()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	rw.Write([]byte("HTTP/1.1 101 Switching Protocols\r\n" +
+		"Connection: Upgrade\r\n" +
+		"Upgrade: h2c\r\n\r\n"))
+	return newBufConn(conn, rw), settings, nil
+}
+
+// isH2CUpgrade returns true if the header properly request an upgrade to h2c
+// as specified by Section 3.2.
+func isH2CUpgrade(h http.Header) bool {
+	return httpguts.HeaderValuesContainsToken(h[textproto.CanonicalMIMEHeaderKey("Upgrade")], "h2c") &&
+		httpguts.HeaderValuesContainsToken(h[textproto.CanonicalMIMEHeaderKey("Connection")], "HTTP2-Settings")
+}
+
+// getH2Settings returns the settings in the HTTP2-Settings header.
+func getH2Settings(h http.Header) ([]byte, error) {
+	vals, ok := h[textproto.CanonicalMIMEHeaderKey("HTTP2-Settings")]
+	if !ok {
+		return nil, errors.New("missing HTTP2-Settings header")
+	}
+	if len(vals) != 1 {
+		return nil, fmt.Errorf("expected 1 HTTP2-Settings. Got: %v", vals)
+	}
+	settings, err := base64.RawURLEncoding.DecodeString(vals[0])
+	if err != nil {
+		return nil, err
+	}
+	return settings, nil
+}
+
+func newBufConn(conn net.Conn, rw *bufio.ReadWriter) net.Conn {
+	rw.Flush()
+	if rw.Reader.Buffered() == 0 {
+		// If there's no buffered data to be read,
+		// we can just discard the bufio.ReadWriter.
+		return conn
+	}
+	return &bufConn{conn, rw.Reader}
+}
+
+// bufConn wraps a net.Conn, but reads drain the bufio.Reader first.
+type bufConn struct {
+	net.Conn
+	*bufio.Reader
+}
+
+func (c *bufConn) Read(p []byte) (int, error) {
+	if c.Reader == nil {
+		return c.Conn.Read(p)
+	}
+	n := c.Reader.Buffered()
+	if n == 0 {
+		c.Reader = nil
+		return c.Conn.Read(p)
+	}
+	if n < len(p) {
+		p = p[:n]
+	}
+	return c.Reader.Read(p)
+}