vm/bhyve: add support for the slirp network backend

bhyve recently grew support for using libslirp (from QEMU) as the
networking backend, which is useful for syzkaller since it requires no
configuration on the host.  This patch causes syz-manager to make use of
the slirp backend when no VM bridge is configured.

1 files changed, 63 insertions, 30 deletions

diff --git a/vm/bhyve/bhyve.go b/vm/bhyve/bhyve.go
index c3b53e053..1570b7939 100644
--- a/vm/bhyve/bhyve.go
+++ b/vm/bhyve/bhyve.go
@@ -25,7 +25,7 @@ func init() {
 }
 
 type Config struct {
-	Bridge  string `json:"bridge"`  // name of network bridge device
+	Bridge  string `json:"bridge"`  // name of network bridge device, optional
 	Count   int    `json:"count"`   // number of VMs to use
 	CPU     int    `json:"cpu"`     // number of VM vCPU
 	HostIP  string `json:"hostip"`  // VM host IP address
@@ -39,19 +39,21 @@ type Pool struct {
 }
 
 type instance struct {
-	cfg      *Config
-	snapshot string
-	tapdev   string
-	image    string
-	debug    bool
-	os       string
-	sshkey   string
-	sshuser  string
-	sshhost  string
-	merger   *vmimpl.OutputMerger
-	vmName   string
-	bhyve    *exec.Cmd
-	consolew io.WriteCloser
+	cfg         *Config
+	snapshot    string
+	tapdev      string
+	port        int
+	forwardPort int
+	image       string
+	debug       bool
+	os          string
+	sshkey      string
+	sshuser     string
+	sshhost     string
+	merger      *vmimpl.OutputMerger
+	vmName      string
+	bhyve       *exec.Cmd
+	consolew    io.WriteCloser
 }
 
 var ipRegex = regexp.MustCompile(`bound to (([0-9]+\.){3}[0-9]+) `)
@@ -129,15 +131,17 @@ func (pool *Pool) Create(workdir string, index int) (vmimpl.Instance, error) {
 		return nil, err
 	}
 
-	tapdev, err := osutil.RunCmd(time.Minute, "", "ifconfig", "tap", "create")
-	if err != nil {
-		inst.Close()
-		return nil, err
-	}
-	inst.tapdev = tapRegex.FindString(string(tapdev))
-	if _, err := osutil.RunCmd(time.Minute, "", "ifconfig", inst.cfg.Bridge, "addm", inst.tapdev); err != nil {
-		inst.Close()
-		return nil, err
+	if inst.cfg.Bridge != "" {
+		tapdev, err := osutil.RunCmd(time.Minute, "", "ifconfig", "tap", "create")
+		if err != nil {
+			inst.Close()
+			return nil, err
+		}
+		inst.tapdev = tapRegex.FindString(string(tapdev))
+		if _, err := osutil.RunCmd(time.Minute, "", "ifconfig", inst.cfg.Bridge, "addm", inst.tapdev); err != nil {
+			inst.Close()
+			return nil, err
+		}
 	}
 
 	if err := inst.Boot(); err != nil {
@@ -165,13 +169,22 @@ func (inst *instance) Boot() error {
 		return err
 	}
 
+	netdev := ""
+	if inst.tapdev != "" {
+		inst.port = 22
+		netdev = inst.tapdev
+	} else {
+		inst.port = vmimpl.UnusedTCPPort()
+		netdev = fmt.Sprintf("slirp,hostfwd=tcp:127.0.0.1:%v-:22", inst.port)
+	}
+
 	bhyveArgs := []string{
 		"-H", "-A", "-P",
 		"-c", fmt.Sprintf("%d", inst.cfg.CPU),
 		"-m", inst.cfg.Mem,
 		"-s", "0:0,hostbridge",
 		"-s", "1:0,lpc",
-		"-s", fmt.Sprintf("2:0,virtio-net,%v", inst.tapdev),
+		"-s", fmt.Sprintf("2:0,virtio-net,%v", netdev),
 		"-s", fmt.Sprintf("3:0,virtio-blk,%v", inst.image),
 		"-l", "com1,stdio",
 		inst.vmName,
@@ -238,7 +251,11 @@ func (inst *instance) Boot() error {
 
 	select {
 	case ip := <-ipch:
-		inst.sshhost = ip
+		if inst.tapdev != "" {
+			inst.sshhost = ip
+		} else {
+			inst.sshhost = "localhost"
+		}
 	case <-inst.merger.Err:
 		bootOutputStop <- true
 		<-bootOutputStop
@@ -250,7 +267,7 @@ func (inst *instance) Boot() error {
 	}
 
 	if err := vmimpl.WaitForSSH(inst.debug, 10*time.Minute, inst.sshhost,
-		inst.sshkey, inst.sshuser, inst.os, 22, nil, false); err != nil {
+		inst.sshkey, inst.sshuser, inst.os, inst.port, nil, false); err != nil {
 		bootOutputStop <- true
 		<-bootOutputStop
 		return vmimpl.MakeBootError(err, bootOutput)
@@ -280,12 +297,23 @@ func (inst *instance) Close() {
 }
 
 func (inst *instance) Forward(port int) (string, error) {
-	return fmt.Sprintf("%v:%v", inst.cfg.HostIP, port), nil
+	if inst.tapdev != "" {
+		return fmt.Sprintf("%v:%v", inst.cfg.HostIP, port), nil
+	} else {
+		if port == 0 {
+			return "", fmt.Errorf("vm/bhyve: forward port is zero")
+		}
+		if inst.forwardPort != 0 {
+			return "", fmt.Errorf("vm/bhyve: forward port is already set")
+		}
+		inst.forwardPort = port
+		return fmt.Sprintf("localhost:%v", port), nil
+	}
 }
 
 func (inst *instance) Copy(hostSrc string) (string, error) {
 	vmDst := filepath.Join("/root", filepath.Base(hostSrc))
-	args := append(vmimpl.SCPArgs(inst.debug, inst.sshkey, 22, false),
+	args := append(vmimpl.SCPArgs(inst.debug, inst.sshkey, inst.port, false),
 		hostSrc, inst.sshuser+"@"+inst.sshhost+":"+vmDst)
 	if inst.debug {
 		log.Logf(0, "running command: scp %#v", args)
@@ -305,8 +333,13 @@ func (inst *instance) Run(timeout time.Duration, stop <-chan bool, command strin
 	}
 	inst.merger.Add("ssh", rpipe)
 
-	args := append(vmimpl.SSHArgs(inst.debug, inst.sshkey, 22, false),
-		inst.sshuser+"@"+inst.sshhost, command)
+	sshargs := []string{}
+	if inst.forwardPort != 0 {
+		sshargs = vmimpl.SSHArgsForward(inst.debug, inst.sshkey, inst.port, inst.forwardPort, false)
+	} else {
+		sshargs = vmimpl.SSHArgs(inst.debug, inst.sshkey, inst.port, false)
+	}
+	args := append(sshargs, inst.sshuser+"@"+inst.sshhost, command)
 	if inst.debug {
 		log.Logf(0, "running command: ssh %#v", args)
 	}