Merge pull request #38 from Snawoot/laddr_hint

allow use of $lAddr in ip hint template

README.md

@@ -194,8 +194,8 @@ Usage of /home/user/go/bin/dumbproxy:
     	colon-separated list of enabled ciphers
   -disable-http2
     	disable HTTP2
-  -ip-hints value
-    	a comma-separated list of source addresses to use on dial attempts. Example: "10.0.0.1,fe80::2,0.0.0.0,::"
+  -ip-hints string
+    	a comma-separated list of source addresses to use on dial attempts. "$lAddr" gets expanded to local address of connection. Example: "10.0.0.1,fe80::2,$lAddr,0.0.0.0,::"
   -key string
     	key for TLS certificate
   -list-ciphers

handler.go

@@ -31,7 +31,7 @@ func NewProxyHandler(timeout time.Duration, auth Auth, dialer HandlerDialer,
 	userIPHints bool, logger *CondLogger) *ProxyHandler {
 	httptransport := &http.Transport{
 		DialContext:       dialer.DialContext,
-		DisableKeepAlives: userIPHints,
+		DisableKeepAlives: true,
 	}
 	return &ProxyHandler{
 		timeout:       timeout,
@@ -134,29 +134,45 @@ func (s *ProxyHandler) ServeHTTP(wr http.ResponseWriter, req *http.Request) {
 	}
 
 	username, ok := s.auth.Validate(wr, req)
-	s.logger.Info("Request: %v %q %v %v %v", req.RemoteAddr, username, req.Proto, req.Method, req.URL)
+	localAddr := getLocalAddr(req.Context())
+	s.logger.Info("Request: %v => %v %q %v %v %v", req.RemoteAddr, localAddr, username, req.Proto, req.Method, req.URL)
 
 	if !ok {
 		return
 	}
+
+	var ipHints *string
 	if s.userIPHints {
 		hintValues := req.Header.Values(HintsHeaderName)
 		if len(hintValues) > 0 {
 			req.Header.Del(HintsHeaderName)
-			if hintIPs, err := parseIPList(hintValues[0]); err != nil {
-				s.logger.Info("Request: %v %q %v %v %v -- bad IP hint header: %q", req.RemoteAddr, username, req.Proto, req.Method, req.URL, hintValues[0])
-				http.Error(wr, BAD_REQ_MSG, http.StatusBadRequest)
-				return
-			} else {
-				newCtx := context.WithValue(req.Context(), BoundDialerContextKey{}, hintIPs)
-				req = req.WithContext(newCtx)
-			}
+			ipHints = &hintValues[0]
 		}
 	}
+	newCtx := context.WithValue(req.Context(), BoundDialerContextKey{}, BoundDialerContextValue{
+		Hints:     ipHints,
+		LocalAddr: trimAddrPort(localAddr),
+	})
+	req = req.WithContext(newCtx)
 	delHopHeaders(req.Header)
 	if isConnect {
 		s.HandleTunnel(wr, req)
 	} else {
 		s.HandleRequest(wr, req)
 	}
 }
+
+func trimAddrPort(addrPort string) string {
+	res, _, err := net.SplitHostPort(addrPort)
+	if err != nil {
+		return addrPort
+	}
+	return res
+}
+
+func getLocalAddr(ctx context.Context) string {
+	if addr, ok := ctx.Value(http.LocalAddrContextKey).(net.Addr); ok {
+		return addr.String()
+	}
+	return "<request context is missing address>"
+}

hintdialer.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"os"
 
 	"github.com/hashicorp/go-multierror"
 )
@@ -17,16 +18,21 @@ var (
 
 type BoundDialerContextKey struct{}
 
+type BoundDialerContextValue struct {
+	Hints     *string
+	LocalAddr string
+}
+
 type BoundDialerDefaultSink interface {
 	DialContext(ctx context.Context, network, address string) (net.Conn, error)
 }
 
 type BoundDialer struct {
 	defaultDialer BoundDialerDefaultSink
-	defaultHints  []net.IP
+	defaultHints  string
 }
 
-func NewBoundDialer(defaultDialer BoundDialerDefaultSink, defaultHints []net.IP) *BoundDialer {
+func NewBoundDialer(defaultDialer BoundDialerDefaultSink, defaultHints string) *BoundDialer {
 	if defaultDialer == nil {
 		defaultDialer = &net.Dialer{}
 	}
@@ -38,13 +44,22 @@ func NewBoundDialer(defaultDialer BoundDialerDefaultSink, defaultHints []net.IP)
 
 func (d *BoundDialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
 	hints := d.defaultHints
+	lAddr := ""
 	if hintsOverride := ctx.Value(BoundDialerContextKey{}); hintsOverride != nil {
-		if hintsOverrideValue, ok := hintsOverride.([]net.IP); ok {
-			hints = hintsOverrideValue
+		if hintsOverrideValue, ok := hintsOverride.(BoundDialerContextValue); ok {
+			if hintsOverrideValue.Hints != nil {
+				hints = *hintsOverrideValue.Hints
+			}
+			lAddr = hintsOverrideValue.LocalAddr
 		}
 	}
 
-	if len(hints) == 0 {
+	parsedHints, err := parseHints(hints, lAddr)
+	if err != nil {
+		return nil, fmt.Errorf("dial failed: %w", err)
+	}
+
+	if len(parsedHints) == 0 {
 		return d.defaultDialer.DialContext(ctx, network, address)
 	}
 
@@ -61,7 +76,7 @@ func (d *BoundDialer) DialContext(ctx context.Context, network, address string)
 	}
 
 	var resErr error
-	for _, lIP := range hints {
+	for _, lIP := range parsedHints {
 		lAddr, restrictedNetwork, err := ipToLAddr(netBase, lIP)
 		if err != nil {
 			resErr = multierror.Append(resErr, fmt.Errorf("ipToLAddr(%q) failed: %w", lIP.String(), err))
@@ -136,3 +151,19 @@ func ipToLAddr(network string, ip net.IP) (net.Addr, string, error) {
 
 	return lAddr, lNetwork, nil
 }
+
+func parseHints(hints, lAddr string) ([]net.IP, error) {
+	hints = os.Expand(hints, func(key string) string {
+		switch key {
+		case "lAddr":
+			return lAddr
+		default:
+			return fmt.Sprintf("<bad key:%q>", key)
+		}
+	})
+	res, err := parseIPList(hints)
+	if err != nil {
+		return nil, fmt.Errorf("unable to parse source IP hints %q: %w", hints, err)
+	}
+	return res, nil
+}

main.go

@@ -72,7 +72,7 @@ type CLIArgs struct {
 	passwdCost        int
 	positionalArgs    []string
 	proxy             []string
-	sourceIPHints     []net.IP
+	sourceIPHints     string
 	userIPHints       bool
 }
 
@@ -103,14 +103,7 @@ func parse_args() CLIArgs {
 		args.proxy = append(args.proxy, p)
 		return nil
 	})
-	flag.Func("ip-hints", "a comma-separated list of source addresses to use on dial attempts. Example: \"10.0.0.1,fe80::2,0.0.0.0,::\"", func(p string) error {
-		list, err := parseIPList(p)
-		if err != nil {
-			return err
-		}
-		args.sourceIPHints = list
-		return nil
-	})
+	flag.StringVar(&args.sourceIPHints, "ip-hints", "", "a comma-separated list of source addresses to use on dial attempts. \"$lAddr\" gets expanded to local address of connection. Example: \"10.0.0.1,fe80::2,$lAddr,0.0.0.0,::\"")
 	flag.BoolVar(&args.userIPHints, "user-ip-hints", false, "allow IP hints to be specified by user in X-Src-IP-Hints header")
 	flag.Parse()
 	args.positionalArgs = flag.Args()