TUN-3863: Consolidate header handling logic in the connection package; move headers definitions from h2mux to packages that manage them; cleanup header conversions

All header transformation code from h2mux has been consolidated in the connection package since it's used by both h2mux and http2 logic.
Exported headers used by proxying between edge and cloudflared so then can be shared by tunnel service on the edge.
Moved access-related headers to corresponding packages that have the code that sets/uses these headers.
Removed tunnel hostname tracking from h2mux since it wasn't used by anything. We will continue to set the tunnel hostname header from the edge for backward compatibilty, but it's no longer used by cloudflared.
Move bastion-related logic into carrier package, untangled dependencies between carrier, origin, and websocket packages.

carrier/carrier.go

@@ -5,20 +5,25 @@ package carrier
 
 import (
 	"crypto/tls"
+	"fmt"
 	"io"
 	"net"
 	"net/http"
+	"net/url"
 	"os"
 	"strings"
 
 	"github.com/pkg/errors"
 	"github.com/rs/zerolog"
 
-	"github.com/cloudflare/cloudflared/h2mux"
 	"github.com/cloudflare/cloudflared/token"
 )
 
-const LogFieldOriginURL = "originURL"
+const (
+	LogFieldOriginURL       = "originURL"
+	CFAccessTokenHeader     = "Cf-Access-Token"
+	cfJumpDestinationHeader = "Cf-Access-Jump-Destination"
+)
 
 type StartOptions struct {
 	AppInfo         *token.AppInfo
@@ -32,15 +37,11 @@ type StartOptions struct {
 type Connection interface {
 	// ServeStream is used to forward data from the client to the edge
 	ServeStream(*StartOptions, io.ReadWriter) error
-
-	// StartServer is used to listen for incoming connections from the edge to the origin
-	StartServer(net.Listener, string, <-chan struct{}) error
 }
 
 // StdinoutStream is empty struct for wrapping stdin/stdout
 // into a single ReadWriter
-type StdinoutStream struct {
-}
+type StdinoutStream struct{}
 
 // Read will read from Stdin
 func (c *StdinoutStream) Read(p []byte) (int, error) {
@@ -149,7 +150,7 @@ func BuildAccessRequest(options *StartOptions, log *zerolog.Logger) (*http.Reque
 	if err != nil {
 		return nil, err
 	}
-	originRequest.Header.Set(h2mux.CFAccessTokenHeader, token)
+	originRequest.Header.Set(CFAccessTokenHeader, token)
 
 	for k, v := range options.Headers {
 		if len(v) >= 1 {
@@ -159,3 +160,26 @@ func BuildAccessRequest(options *StartOptions, log *zerolog.Logger) (*http.Reque
 
 	return originRequest, nil
 }
+
+func SetBastionDest(header http.Header, destination string) {
+	if destination != "" {
+		header.Set(cfJumpDestinationHeader, destination)
+	}
+}
+
+func ResolveBastionDest(r *http.Request) (string, error) {
+	jumpDestination := r.Header.Get(cfJumpDestinationHeader)
+	if jumpDestination == "" {
+		return "", fmt.Errorf("Did not receive final destination from client. The --destination flag is likely not set on the client side")
+	}
+	// Strip scheme and path set by client. Without a scheme
+	// Parsing a hostname and path without scheme might not return an error due to parsing ambiguities
+	if jumpURL, err := url.Parse(jumpDestination); err == nil && jumpURL.Host != "" {
+		return removePath(jumpURL.Host), nil
+	}
+	return removePath(jumpDestination), nil
+}
+
+func removePath(dest string) string {
+	return strings.SplitN(dest, "/", 2)[0]
+}