Merge pull request #4 from digitalocean/qemu-errors

check for QEMU response errors

libvirt.go

@@ -19,6 +19,7 @@ package libvirt
 import (
 	"bufio"
 	"bytes"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"net"
@@ -68,6 +69,14 @@ type DomainEvent struct {
 	Details      []byte
 }
 
+// qemuError represents a QEMU process error.
+type qemuError struct {
+	Error struct {
+		Class       string `json:"class"`
+		Description string `json:"desc"`
+	} `json:"error"`
+}
+
 // Connect establishes communication with the libvirt server.
 // The underlying libvirt socket connection must be previously established.
 func (l *Libvirt) Connect() error {
@@ -225,10 +234,16 @@ func (l *Libvirt) Run(dom string, cmd []byte) ([]byte, error) {
 	}
 
 	res := <-resp
+	// check for libvirt errors
 	if res.Status != StatusOK {
 		return nil, decodeError(res.Payload)
 	}
 
+	// check for QEMU process errors
+	if err = getQEMUError(res); err != nil {
+		return nil, err
+	}
+
 	r := bytes.NewReader(res.Payload)
 	dec := xdr.NewDecoder(r)
 	data, _, err := dec.DecodeFixedOpaque(int32(r.Len()))
@@ -238,7 +253,7 @@ func (l *Libvirt) Run(dom string, cmd []byte) ([]byte, error) {
 
 	// drop QMP control characters from start of line, and drop
 	// any trailing NULL characters from the end
-	return bytes.TrimRight(data[4:], "\x00"), err
+	return bytes.TrimRight(data[4:], "\x00"), nil
 }
 
 // Version returns the version of the libvirt daemon.
@@ -308,6 +323,29 @@ func (l *Libvirt) lookup(name string) (*Domain, error) {
 	return &d, nil
 }
 
+// getQEMUError checks the provided response for QEMU process errors.
+// If an error is found, it is extracted an returned, otherwise nil.
+func getQEMUError(r response) error {
+	pl := bytes.NewReader(r.Payload)
+	dec := xdr.NewDecoder(pl)
+
+	s, _, err := dec.DecodeString()
+	if err != nil {
+		return err
+	}
+
+	var e qemuError
+	if err = json.Unmarshal([]byte(s), &e); err != nil {
+		return err
+	}
+
+	if e.Error.Description != "" {
+		return errors.New(e.Error.Description)
+	}
+
+	return nil
+}
+
 // New configures a new Libvirt RPC connection.
 func New(conn net.Conn) *Libvirt {
 	l := &Libvirt{

libvirt_test.go

@@ -148,6 +148,17 @@ func TestRun(t *testing.T) {
 	}
 }
 
+func TestRunFail(t *testing.T) {
+	conn := libvirttest.New()
+	conn.Fail = true
+	l := New(conn)
+
+	_, err := l.Run("test", []byte(`{"drive-foo"}`))
+	if err == nil {
+		t.Error("expected qemu error")
+	}
+}
+
 func TestVersion(t *testing.T) {
 	conn := libvirttest.New()
 	l := New(conn)

libvirttest/libvirt.go

@@ -120,6 +120,32 @@ var testRunReply = []byte{
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 }
 
+var testRunReplyFail = []byte{
+	0x00, 0x00, 0x00, 0x8c, // length
+	0x20, 0x00, 0x80, 0x87, // program
+	0x00, 0x00, 0x00, 0x01, // version
+	0x00, 0x00, 0x00, 0x01, // procedure
+	0x00, 0x00, 0x00, 0x01, // type
+	0x00, 0x00, 0x00, 0x0a, // serial
+	0x00, 0x00, 0x00, 0x00, // status
+
+	// {"id":"libvirt-68","error":{"class":"CommandNotFound","desc":"The command drive-foo has not been found"}}`
+	0x00, 0x00, 0x00, 0x69, 0x7b, 0x22, 0x69, 0x64,
+	0x22, 0x3a, 0x22, 0x6c, 0x69, 0x62, 0x76, 0x69,
+	0x72, 0x74, 0x2d, 0x36, 0x38, 0x22, 0x2c, 0x22,
+	0x65, 0x72, 0x72, 0x6f, 0x72, 0x22, 0x3a, 0x7b,
+	0x22, 0x63, 0x6c, 0x61, 0x73, 0x73, 0x22, 0x3a,
+	0x22, 0x43, 0x6f, 0x6d, 0x6d, 0x61, 0x6e, 0x64,
+	0x4e, 0x6f, 0x74, 0x46, 0x6f, 0x75, 0x6e, 0x64,
+	0x22, 0x2c, 0x22, 0x64, 0x65, 0x73, 0x63, 0x22,
+	0x3a, 0x22, 0x54, 0x68, 0x65, 0x20, 0x63, 0x6f,
+	0x6d, 0x6d, 0x61, 0x6e, 0x64, 0x20, 0x64, 0x72,
+	0x69, 0x76, 0x65, 0x2d, 0x66, 0x6f, 0x6f, 0x20,
+	0x68, 0x61, 0x73, 0x20, 0x6e, 0x6f, 0x74, 0x20,
+	0x62, 0x65, 0x65, 0x6e, 0x20, 0x66, 0x6f, 0x75,
+	0x6e, 0x64, 0x22, 0x7d, 0x7d, 0x00, 0x00, 0x00,
+}
+
 var testDomainsReply = []byte{
 	0x00, 0x00, 0x00, 0x6c, // length
 	0x20, 0x00, 0x80, 0x86, // program
@@ -171,6 +197,7 @@ var testVersionReply = []byte{
 type MockLibvirt struct {
 	net.Conn
 	Test   net.Conn
+	Fail   bool
 	serial uint32
 }
 
@@ -233,9 +260,13 @@ func (m *MockLibvirt) handleQEMU(procedure uint32, conn net.Conn) {
 	case constants.QEMUConnectDomainMonitorEventDeregister:
 		conn.Write(m.reply(testDeregisterEvent))
 	case constants.QEMUDomainMonitor:
+		if m.Fail {
+			conn.Write(m.reply(testRunReplyFail))
+		} else {
 			conn.Write(m.reply(testRunReply))
 		}
 	}
+}
 
 // reply automatically injects the correct serial
 // number into the provided response buffer.