[qmp] Add RunWithFile to socket client (digitalocean#169)

* qmp/socket: Add capabilities tracking
* qmp/socket: Add new RunWithFile function

Signed-off-by: Stéphane Graber <[email protected]>

Author: stgraber

go.mod

@@ -5,4 +5,5 @@ go 1.15
 require (
 	github.com/digitalocean/go-libvirt v0.0.0-20201209184759-e2a69bcd5bd1
 	github.com/fatih/camelcase v1.0.0
+	golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4
 )

go.sum

@@ -22,7 +22,10 @@ golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20200625203802-6e8e738ad208/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd h1:xhmwyvizuTgC2qz7ZlMluP20uW+C3Rm0FD/WLDX8884=
 golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 h1:myAQVi0cGEoqQVR5POX+8RR2mrocKqNN1hmeMqhX27k=
+golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20200711155855-7342f9734a7d h1:F3OmlXCzYtG9YE6tXDnUOlJBzVzHF8EcmZ1yTJlcgIk=

qmp/socket.go

@@ -18,8 +18,10 @@ import (
 	"bufio"
 	"context"
 	"encoding/json"
+	"fmt"
 	"io"
 	"net"
+	"os"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -34,6 +36,9 @@ type SocketMonitor struct {
 	// QEMU version reported by a connected monitor socket.
 	Version *Version
 
+	// QEMU QMP capabiltiies reported by a connected monitor socket.
+	Capabilities []string
+
 	// Underlying connection
 	c net.Conn
 
@@ -119,6 +124,7 @@ func (mon *SocketMonitor) Connect() error {
 		return err
 	}
 	mon.Version = &ban.QMP.Version
+	mon.Capabilities = ban.QMP.Capabilities
 
 	// Issue capabilities handshake
 	cmd := Command{Execute: qmpCapabilities}
@@ -194,13 +200,45 @@ func (mon *SocketMonitor) listen(r io.Reader, events chan<- Event, stream chan<-
 // For a list of available QAPI commands, see:
 //	http://git.qemu.org/?p=qemu.git;a=blob;f=qapi-schema.json;hb=HEAD
 func (mon *SocketMonitor) Run(command []byte) ([]byte, error) {
+	// Just call RunWithFile with no file
+	return mon.RunWithFile(command, nil)
+}
+
+// RunWithFile behaves like Run but allows for passing a file through out-of-band data.
+func (mon *SocketMonitor) RunWithFile(command []byte, file *os.File) ([]byte, error) {
 	// Only allow a single command to be run at a time to ensure that responses
 	// to a command cannot be mixed with responses from another command
 	mon.mu.Lock()
 	defer mon.mu.Unlock()
 
-	if _, err := mon.c.Write(command); err != nil {
-		return nil, err
+	if file == nil {
+		// Just send a normal command through.
+		if _, err := mon.c.Write(command); err != nil {
+			return nil, err
+		}
+	} else {
+		unixConn, ok := mon.c.(*net.UnixConn)
+		if !ok {
+			return nil, fmt.Errorf("RunWithFile only works with unix monitor sockets")
+		}
+
+		oobSupported := false
+		for _, capability := range mon.Capabilities {
+			if capability == "oob" {
+				oobSupported = true
+				break
+			}
+		}
+
+		if !oobSupported {
+			return nil, fmt.Errorf("The QEMU server doesn't support oob (needed for RunWithFile)")
+		}
+
+		// Send the command along with the file descriptor.
+		oob := getUnixRights(file)
+		if _, _, err := unixConn.WriteMsgUnix(command, oob, nil); err != nil {
+			return nil, err
+		}
 	}
 
 	// Wait for a response or error to our command
@@ -224,6 +262,7 @@ func (mon *SocketMonitor) Run(command []byte) ([]byte, error) {
 // banner is a wrapper type around a Version.
 type banner struct {
 	QMP struct {
+		Capabilities []string `json:"capabilities"`
 		Version Version `json:"version"`
 	} `json:"QMP"`
 }

qmp/socket_unix.go

@@ -0,0 +1,27 @@
+// Copyright 2016 The go-qemu Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !windows
+
+package qmp
+
+import (
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+func getUnixRights(file *os.File) []byte {
+	return unix.UnixRights(int(file.Fd()))
+}

qmp/socket_windows.go

@@ -0,0 +1,25 @@
+// Copyright 2016 The go-qemu Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build windows
+
+package qmp
+
+import (
+	"os"
+)
+
+func getUnixRights(file *os.File) []byte {
+	return nil
+}