rpc: avoid infinite loop on input error

Fixes #1828.
Fixes #2179.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5305084

src/pkg/rpc/jsonrpc/all_test.go

@@ -6,6 +6,7 @@ package jsonrpc
 
 import (
 	"fmt"
+	"io"
 	"json"
 	"net"
 	"os"
@@ -154,3 +155,67 @@ func TestClient(t *testing.T) {
 		t.Error("Div: expected divide by zero error; got", err)
 	}
 }
+
+func TestMalformedInput(t *testing.T) {
+	cli, srv := net.Pipe()
+	go cli.Write([]byte(`{id:1}`)) // invalid json
+	ServeConn(srv)                 // must return, not loop
+}
+
+func TestUnexpectedError(t *testing.T) {
+	cli, srv := myPipe()
+	go cli.PipeWriter.CloseWithError(os.NewError("unexpected error!")) // reader will get this error
+	ServeConn(srv)                                                     // must return, not loop
+}
+
+// Copied from package net.
+func myPipe() (*pipe, *pipe) {
+	r1, w1 := io.Pipe()
+	r2, w2 := io.Pipe()
+
+	return &pipe{r1, w2}, &pipe{r2, w1}
+}
+
+type pipe struct {
+	*io.PipeReader
+	*io.PipeWriter
+}
+
+type pipeAddr int
+
+func (pipeAddr) Network() string {
+	return "pipe"
+}
+
+func (pipeAddr) String() string {
+	return "pipe"
+}
+
+func (p *pipe) Close() os.Error {
+	err := p.PipeReader.Close()
+	err1 := p.PipeWriter.Close()
+	if err == nil {
+		err = err1
+	}
+	return err
+}
+
+func (p *pipe) LocalAddr() net.Addr {
+	return pipeAddr(0)
+}
+
+func (p *pipe) RemoteAddr() net.Addr {
+	return pipeAddr(0)
+}
+
+func (p *pipe) SetTimeout(nsec int64) os.Error {
+	return os.NewError("net.Pipe does not support timeouts")
+}
+
+func (p *pipe) SetReadTimeout(nsec int64) os.Error {
+	return os.NewError("net.Pipe does not support timeouts")
+}
+
+func (p *pipe) SetWriteTimeout(nsec int64) os.Error {
+	return os.NewError("net.Pipe does not support timeouts")
+}

src/pkg/rpc/server.go

@@ -394,12 +394,12 @@ func (server *Server) ServeConn(conn io.ReadWriteCloser) {
 func (server *Server) ServeCodec(codec ServerCodec) {
 	sending := new(sync.Mutex)
 	for {
-		service, mtype, req, argv, replyv, err := server.readRequest(codec)
+		service, mtype, req, argv, replyv, keepReading, err := server.readRequest(codec)
 		if err != nil {
 			if err != os.EOF {
 				log.Println("rpc:", err)
 			}
-			if err == os.EOF || err == io.ErrUnexpectedEOF {
+			if !keepReading {
 				break
 			}
 			// send a response if we actually managed to read a header.
@@ -418,9 +418,9 @@ func (server *Server) ServeCodec(codec ServerCodec) {
 // It does not close the codec upon completion.
 func (server *Server) ServeRequest(codec ServerCodec) os.Error {
 	sending := new(sync.Mutex)
-	service, mtype, req, argv, replyv, err := server.readRequest(codec)
+	service, mtype, req, argv, replyv, keepReading, err := server.readRequest(codec)
 	if err != nil {
-		if err == os.EOF || err == io.ErrUnexpectedEOF {
+		if !keepReading {
 			return err
 		}
 		// send a response if we actually managed to read a header.
@@ -474,10 +474,10 @@ func (server *Server) freeResponse(resp *Response) {
 	server.respLock.Unlock()
 }
 
-func (server *Server) readRequest(codec ServerCodec) (service *service, mtype *methodType, req *Request, argv, replyv reflect.Value, err os.Error) {
-	service, mtype, req, err = server.readRequestHeader(codec)
+func (server *Server) readRequest(codec ServerCodec) (service *service, mtype *methodType, req *Request, argv, replyv reflect.Value, keepReading bool, err os.Error) {
+	service, mtype, req, keepReading, err = server.readRequestHeader(codec)
 	if err != nil {
-		if err == os.EOF || err == io.ErrUnexpectedEOF {
+		if !keepReading {
 			return
 		}
 		// discard body
@@ -505,7 +505,7 @@ func (server *Server) readRequest(codec ServerCodec) (service *service, mtype *m
 	return
 }
 
-func (server *Server) readRequestHeader(codec ServerCodec) (service *service, mtype *methodType, req *Request, err os.Error) {
+func (server *Server) readRequestHeader(codec ServerCodec) (service *service, mtype *methodType, req *Request, keepReading bool, err os.Error) {
 	// Grab the request header.
 	req = server.getRequest()
 	err = codec.ReadRequestHeader(req)
@@ -518,6 +518,10 @@ func (server *Server) readRequestHeader(codec ServerCodec) (service *service, mt
 		return
 	}
 
+	// We read the header successfully.  If we see an error now,
+	// we can still recover and move on to the next request.
+	keepReading = true
+
 	serviceMethod := strings.Split(req.ServiceMethod, ".")
 	if len(serviceMethod) != 2 {
 		err = os.NewError("rpc: service/method request ill-formed: " + req.ServiceMethod)

src/pkg/rpc/server_test.go

@@ -311,8 +311,9 @@ func (codec *CodecEmulator) ReadRequestBody(argv interface{}) os.Error {
 func (codec *CodecEmulator) WriteResponse(resp *Response, reply interface{}) os.Error {
 	if resp.Error != "" {
 		codec.err = os.NewError(resp.Error)
+	} else {
+		*codec.reply = *(reply.(*Reply))
 	}
-	*codec.reply = *(reply.(*Reply))
 	return nil
 }