Add the dut command from linuxboot

It is much easier to bring dut into cpu than have 2 repos.
Further, dut is not a combined cpu and cpud; it is useful
to have this illustrative use of the cpu package.

Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>

Author: rminnich

dut/doc.go

@@ -0,0 +1,66 @@
+// dut manages Devices Under Test (a.k.a. DUT) from a host.
+// A primary goal is allowing multiple hosts with any architecture to connect.
+//
+// This program was designed to be used in u-root images, as the uinit,
+// or in other initramfs systems. It can not function as a standalone
+// init: it assumes network is set up, for example.
+//
+// In this document, dut refers to this program, and DUT refers to
+// Devices Under Test. Hopefully this is not too confusing, but it is
+// convenient. Also, please note: DUT is plural (Devices). We don't need
+// to say DUTs -- at least one is assumed.
+//
+// The same dut binary runs on host and DUT, in either device mode (i.e.
+// on the DUT), or in some host-specific mode. The mode is chosen by
+// the first non-flag argument. If there are flags specific to that mode,
+// they follow that argument.
+// E.g., when uinit is run on the host and we want it to enable cpu daemons
+// on the DUT, we run it as follows:
+// dut cpu -key ...
+// the -key switch is only valid following the cpu mode argument.
+//
+// modes
+// dut currently supports 3 modes.
+//
+// The first, default, mode, is "device". In device mode, dut makes an http connection
+// to a dut running on a host, then starts an  HTTP RPC server.
+//
+// The second mode is "tester". In this mode, dut calls the Welcome service, followed
+// by the Reboot service. Tester can be useful, run by a shell script in a for loop, for
+// ensure reboot is reliable.
+//
+// The third mode is "cpu". dut will direct the DUT to start a cpu service, and block until
+// it exits. Flags for this service:
+// pubkey: name of the public key file
+// hostkey: name of the host key file
+// cpuport: port on which to serve the cpu service
+//
+// Theory of Operation
+// dut runs on the host, accepting connections from DUT, and controlling them via
+// Go HTTP RPC commands. As each command is executed, its response is printed.
+// Commands are:
+//
+// Welcome -- get a welcome message
+// Argument: None
+// Return: a welcome message in cowsay format:
+// < welcome to DUT >
+//   --------------
+//          \   ^__^
+//           \  (oo)\_______
+//              (__)\       )\/\
+//                  ||----w |
+//                  ||     ||
+//
+// Die -- force dut on DUT to exit
+// Argument: time to sleep before exiting as a time.Duration
+// Return: no return; kills the program running on DUT
+//
+// Reboot
+// Argument: time to sleep before rebooting as a time.Duration
+//
+// CPU -- Start a CPU server on DUT
+// Arguments: public key and host key as a []byte, service port as a string
+// Returns: returns (possibly nil) error exit value of cpu server; blocks until it is done
+//
+//
+package main

dut/dut.go

@@ -0,0 +1,189 @@
+// This is a very simple dut program. It builds into one binary to implement
+// both client and server. It's just easier to see both sides of the code and test
+// that way.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net"
+	"net/rpc"
+	"os"
+	"time"
+
+	"github.com/u-root/u-root/pkg/ulog"
+	"golang.org/x/sys/unix"
+)
+
+var (
+	debug = flag.Bool("d", false, "Enable debug prints")
+	host  = flag.String("host", "192.168.0.1", "hostname")
+	klog  = flag.Bool("klog", false, "Direct all logging to klog -- depends on debug")
+	port  = flag.String("port", "8080", "port number")
+	dir   = flag.String("dir", ".", "directory to serve")
+
+	// for debug
+	v = func(string, ...interface{}) {}
+)
+
+func dutStart(t, host, port string) (net.Listener, error) {
+	ln, err := net.Listen(t, host+":"+port)
+	if err != nil {
+		log.Print(err)
+		return nil, err
+	}
+	log.Printf("Listening on %v at %v", ln.Addr(), time.Now())
+	return ln, nil
+}
+
+func dutAccept(l net.Listener) (net.Conn, error) {
+	if err := l.(*net.TCPListener).SetDeadline(time.Now().Add(3 * time.Minute)); err != nil {
+		return nil, err
+	}
+	c, err := l.Accept()
+	if err != nil {
+		log.Printf("Listen failed: %v at %v", err, time.Now())
+		log.Print(err)
+		return nil, err
+	}
+	log.Printf("Accepted %v", c)
+	return c, nil
+}
+
+func dutRPC(host, port string) error {
+	l, err := dutStart("tcp", host, port)
+	if err != nil {
+		return err
+	}
+	c, err := dutAccept(l)
+	if err != nil {
+		return err
+	}
+	cl := rpc.NewClient(c)
+	for _, cmd := range []struct {
+		call string
+		args interface{}
+	}{
+		{"Command.Welcome", &RPCWelcome{}},
+		{"Command.Reboot", &RPCReboot{}},
+	} {
+		var r RPCRes
+		if err := cl.Call(cmd.call, cmd.args, &r); err != nil {
+			return err
+		}
+		fmt.Printf("%v(%v): %v\n", cmd.call, cmd.args, string(r.C))
+	}
+
+	if c, err = dutAccept(l); err != nil {
+		return err
+	}
+	cl = rpc.NewClient(c)
+	var r RPCRes
+	if err := cl.Call("Command.Welcome", &RPCWelcome{}, &r); err != nil {
+		return err
+	}
+	fmt.Printf("%v(%v): %v\n", "Command.Welcome", nil, string(r.C))
+
+	return nil
+}
+
+func dutcpu(host, port, pubkey, hostkey, cpuport string) error {
+	var req = &RPCCPU{Port: cpuport}
+	var err error
+
+	// we send the pubkey and hostkey as the value of the key, not the
+	// name of the file.
+	// TODO: maybe use ssh_config to find keys? the cpu client can do that.
+	// Note: the public key is not optional. That said, we do not test
+	// for len(*pubKey) > 0; if it is set to ""< ReadFile will return
+	// an error.
+	if req.PubKey, err = ioutil.ReadFile(pubkey); err != nil {
+		return fmt.Errorf("Reading pubKey:%w", err)
+	}
+	if len(hostkey) > 0 {
+		if req.HostKey, err = ioutil.ReadFile(hostkey); err != nil {
+			return fmt.Errorf("Reading hostKey:%w", err)
+		}
+	}
+
+	l, err := dutStart("tcp", host, port)
+	if err != nil {
+		return err
+	}
+
+	c, err := dutAccept(l)
+	if err != nil {
+		return err
+	}
+
+	cl := rpc.NewClient(c)
+
+	for _, cmd := range []struct {
+		call string
+		args interface{}
+	}{
+		{"Command.Welcome", &RPCWelcome{}},
+		{"Command.Welcome", &RPCWelcome{}},
+		{"Command.CPU", req},
+	} {
+		var r RPCRes
+		if err := cl.Call(cmd.call, cmd.args, &r); err != nil {
+			return err
+		}
+		fmt.Printf("%v(%v): %v\n", cmd.call, cmd.args, string(r.C))
+	}
+	return err
+}
+
+func main() {
+	// for CPU
+	flag.Parse()
+
+	if *debug {
+		v = log.Printf
+		if *klog {
+			ulog.KernelLog.Reinit()
+			v = ulog.KernelLog.Printf
+		}
+	}
+	a := flag.Args()
+	if len(a) == 0 {
+		a = []string{"device"}
+	}
+
+	os.Args = a
+	var err error
+	v("Mode is %v", a[0])
+	switch a[0] {
+	case "tester":
+		err = dutRPC(*host, *port)
+	case "cpu":
+		var (
+			pubKey  = flag.String("pubkey", "key.pub", "public key file")
+			hostKey = flag.String("hostkey", "", "host key file -- usually empty")
+			cpuPort = flag.String("cpuport", "17010", "cpu port -- IANA value is ncpu tcp/17010")
+		)
+		v("Parse %v", os.Args)
+		flag.Parse()
+		v("pubkey %v", *pubKey)
+		if err := dutcpu(*host, *port, *pubKey, *hostKey, *cpuPort); err != nil {
+			log.Printf("cpu service: %v", err)
+		}
+	case "device":
+		err = uinit(*host, *port)
+		// What to do after a return? Reboot I suppose.
+		log.Printf("Device returns with error %v", err)
+		if err := unix.Reboot(int(unix.LINUX_REBOOT_CMD_RESTART)); err != nil {
+			log.Printf("Reboot failed, not sure what to do now.")
+		}
+	default:
+		log.Printf("Unknown mode %v", a[0])
+	}
+	log.Printf("We are now done ......................")
+	if err != nil {
+		log.Printf("%v", err)
+		os.Exit(2)
+	}
+}

dut/dut_test.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"net/rpc"
+	"testing"
+	"time"
+)
+
+func TestUinit(t *testing.T) {
+	var tests = []struct {
+		c   string
+		r   interface{}
+		err string
+	}{
+		{c: "Welcome", r: RPCWelcome{}},
+		{c: "Reboot", r: RPCReboot{}},
+	}
+	l, err := dutStart("tcp", "localhost", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	a := l.Addr()
+	t.Logf("listening on %v", a)
+	// Kick off our node.
+	go func() {
+		time.Sleep(1)
+		if err := uinit(a.Network(), a.String(), "17010"); err != nil {
+			t.Fatalf("starting uinit: got %v, want nil", err)
+		}
+	}()
+
+	c, err := dutAccept(l)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("Connected on %v", c)
+
+	cl := rpc.NewClient(c)
+	for _, tt := range tests {
+		t.Run(tt.c, func(t *testing.T) {
+			var r RPCRes
+			if err = cl.Call("Command."+tt.c, tt.r, &r); err != nil {
+				t.Fatalf("Call to %v: got %v, want nil", tt.c, err)
+			}
+			if r.Err != tt.err {
+				t.Errorf("%v: got %v, want %v", tt, r.Err, tt.err)
+			}
+		})
+	}
+}

dut/rpc.go

@@ -0,0 +1,79 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+type RPCRes struct {
+	C   []byte
+	Err string
+}
+
+type Command int
+
+type RPCWelcome struct {
+}
+
+func (*Command) Welcome(args *RPCWelcome, r *RPCRes) error {
+	r.C = []byte(welcome)
+	r.Err = ""
+	log.Printf("welcome")
+	return nil
+}
+
+type RPCExit struct {
+	When time.Duration
+}
+
+func (*Command) Die(args *RPCExit, r *RPCRes) error {
+	go func() {
+		time.Sleep(args.When)
+		log.Printf("die exits")
+		os.Exit(0)
+	}()
+	*r = RPCRes{}
+	log.Printf("die returns")
+	return nil
+}
+
+type RPCReboot struct {
+	When time.Duration
+}
+
+func (*Command) Reboot(args *RPCReboot, r *RPCRes) error {
+	go func() {
+		time.Sleep(args.When)
+		if err := unix.Reboot(unix.LINUX_REBOOT_CMD_RESTART); err != nil {
+			log.Printf("%v\n", err)
+		}
+	}()
+	*r = RPCRes{}
+	log.Printf("reboot returns")
+	return nil
+}
+
+type RPCCPU struct {
+	PubKey  []byte
+	HostKey []byte
+	Port    string
+}
+
+func (*Command) CPU(args *RPCCPU, r *RPCRes) error {
+	v("CPU")
+	res := make(chan error)
+	go func(pubKey, hostKey []byte, port string) {
+		v("cpu serve(%q,%q,%q)", pubKey, hostKey, port)
+		err := serve(pubKey, hostKey, port)
+		v("cpu serve returns")
+		res <- err
+	}(args.PubKey, args.HostKey, args.Port)
+	err := <-res
+	*r = RPCRes{Err: fmt.Sprintf("%v", err)}
+	v("cpud returns")
+	return nil
+}