enclave-server: set a write deadline and check deadline errors on vsock conns

cmd/enclave-server/main.go

@@ -25,10 +25,17 @@ import (
 
 const (
 	vsockPort            = 5000
-	readDeadline         = 30 * time.Second
 	defaultMaxWorkersEnv = "ENCLAVE_MAX_WORKERS"
 )
 
+// Connection deadlines. The write deadline starts once the request is handled,
+// so a peer that stops reading releases its worker slot. Variables so tests can
+// shorten them.
+var (
+	readDeadline  = 30 * time.Second
+	writeDeadline = 30 * time.Second
+)
+
 func main() {
 	km, err := enclave.NewKeyManager()
 	if err != nil {
@@ -96,7 +103,10 @@ func handleConnection(conn net.Conn, km *enclave.KeyManager) {
 		}
 	}()
 
-	_ = conn.SetReadDeadline(time.Now().Add(readDeadline))
+	if err := conn.SetReadDeadline(time.Now().Add(readDeadline)); err != nil {
+		log.Printf("ERROR: set read deadline: %v", err)
+		return
+	}
 
 	var buf bytes.Buffer
 	if _, err := io.Copy(&buf, conn); err != nil {
@@ -114,6 +124,10 @@ func handleConnection(conn net.Conn, km *enclave.KeyManager) {
 	log.Printf("INFO: received request type: %s", base.Type)
 
 	response := dispatch(base.Type, buf.Bytes(), km)
+	if err := conn.SetWriteDeadline(time.Now().Add(writeDeadline)); err != nil {
+		log.Printf("ERROR: set write deadline: %v", err)
+		return
+	}
 	if err := json.NewEncoder(conn).Encode(response); err != nil {
 		log.Printf("ERROR: encode response: %v", err)
 	} else {

cmd/enclave-server/main_test.go

@@ -0,0 +1,72 @@
+package main
+
+import (
+	"errors"
+	"io"
+	"net"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// requestConn serves a fixed request on Read and passes writes and deadlines
+// through to the embedded conn.
+type requestConn struct {
+	net.Conn
+	req io.Reader
+}
+
+func (c *requestConn) Read(p []byte) (int, error) { return c.req.Read(p) }
+
+// readDeadlineFailConn fails SetReadDeadline and records any Read.
+type readDeadlineFailConn struct {
+	net.Conn
+	read bool
+}
+
+func (*readDeadlineFailConn) SetReadDeadline(time.Time) error {
+	return errors.New("set read deadline failed")
+}
+
+func (c *readDeadlineFailConn) Read([]byte) (int, error) {
+	c.read = true
+	return 0, io.EOF
+}
+
+func TestHandleConnection_WriteDeadlineReleasesStalledPeer(t *testing.T) {
+	orig := writeDeadline
+	writeDeadline = 50 * time.Millisecond
+	t.Cleanup(func() { writeDeadline = orig })
+
+	// net.Pipe is unbuffered, so the response write blocks until the peer reads.
+	// The peer never reads.
+	server, peer := net.Pipe()
+	t.Cleanup(func() { _ = peer.Close() })
+	conn := &requestConn{Conn: server, req: strings.NewReader(`{"type":"ping"}`)}
+
+	done := make(chan struct{})
+	go func() {
+		handleConnection(conn, nil)
+		close(done)
+	}()
+
+	select {
+	case <-done:
+	case <-time.After(5 * time.Second):
+		t.Fatal("handleConnection still blocked writing to a peer that never reads")
+	}
+}
+
+func TestHandleConnection_ClosesWithoutReadingWhenReadDeadlineFails(t *testing.T) {
+	server, peer := net.Pipe()
+	t.Cleanup(func() { _ = peer.Close() })
+	conn := &readDeadlineFailConn{Conn: server}
+
+	handleConnection(conn, nil)
+
+	assert.False(t, conn.read)
+	_, err := server.Write([]byte("x"))
+	assert.Error(t, err)
+}