feature/portmapper: make the portmapper & its debugging tools modular

Starting at a minimal binary and adding one feature back...
    tailscaled tailscale combined (linux/amd64)
     30073135  17451704  31543692 omitting everything
    +  480302 +   10258 +  493896 .. add debugportmapper
    +  475317 +  151943 +  467660 .. add portmapper
    +  500086 +  162873 +  510511 .. add portmapper+debugportmapper

Fixes #17148

Change-Id: I90bd0e9d1bd8cbe64fa2e885e9afef8fb5ee74b1
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscale/cli/debug.go

@@ -30,7 +30,6 @@ import (
 	"github.com/peterbourgon/ff/v3/ffcli"
 	"golang.org/x/net/http/httpproxy"
 	"golang.org/x/net/http2"
-	"tailscale.com/client/local"
 	"tailscale.com/client/tailscale/apitype"
 	"tailscale.com/control/controlhttp"
 	"tailscale.com/hostinfo"
@@ -50,6 +49,7 @@ import (
 
 var (
 	debugCaptureCmd func() *ffcli.Command // or nil
+	debugPortmapCmd func() *ffcli.Command // or nil
 )
 
 func debugCmd() *ffcli.Command {
@@ -319,21 +319,7 @@ func debugCmd() *ffcli.Command {
 				ShortHelp:  "Test a DERP configuration",
 			},
 			ccall(debugCaptureCmd),
-			{
-				Name:       "portmap",
-				ShortUsage: "tailscale debug portmap",
-				Exec:       debugPortmap,
-				ShortHelp:  "Run portmap debugging",
-				FlagSet: (func() *flag.FlagSet {
-					fs := newFlagSet("portmap")
-					fs.DurationVar(&debugPortmapArgs.duration, "duration", 5*time.Second, "timeout for port mapping")
-					fs.StringVar(&debugPortmapArgs.ty, "type", "", `portmap debug type (one of "", "pmp", "pcp", or "upnp")`)
-					fs.StringVar(&debugPortmapArgs.gatewayAddr, "gateway-addr", "", `override gateway IP (must also pass --self-addr)`)
-					fs.StringVar(&debugPortmapArgs.selfAddr, "self-addr", "", `override self IP (must also pass --gateway-addr)`)
-					fs.BoolVar(&debugPortmapArgs.logHTTP, "log-http", false, `print all HTTP requests and responses to the log`)
-					return fs
-				})(),
-			},
+			ccall(debugPortmapCmd),
 			{
 				Name:       "peer-endpoint-changes",
 				ShortUsage: "tailscale debug peer-endpoint-changes <hostname-or-IP>",
@@ -1210,44 +1196,6 @@ func runSetExpire(ctx context.Context, args []string) error {
 	return localClient.DebugSetExpireIn(ctx, setExpireArgs.in)
 }
 
-var debugPortmapArgs struct {
-	duration    time.Duration
-	gatewayAddr string
-	selfAddr    string
-	ty          string
-	logHTTP     bool
-}
-
-func debugPortmap(ctx context.Context, args []string) error {
-	opts := &local.DebugPortmapOpts{
-		Duration: debugPortmapArgs.duration,
-		Type:     debugPortmapArgs.ty,
-		LogHTTP:  debugPortmapArgs.logHTTP,
-	}
-	if (debugPortmapArgs.gatewayAddr != "") != (debugPortmapArgs.selfAddr != "") {
-		return fmt.Errorf("if one of --gateway-addr and --self-addr is provided, the other must be as well")
-	}
-	if debugPortmapArgs.gatewayAddr != "" {
-		var err error
-		opts.GatewayAddr, err = netip.ParseAddr(debugPortmapArgs.gatewayAddr)
-		if err != nil {
-			return fmt.Errorf("invalid --gateway-addr: %w", err)
-		}
-		opts.SelfAddr, err = netip.ParseAddr(debugPortmapArgs.selfAddr)
-		if err != nil {
-			return fmt.Errorf("invalid --self-addr: %w", err)
-		}
-	}
-	rc, err := localClient.DebugPortmap(ctx, opts)
-	if err != nil {
-		return err
-	}
-	defer rc.Close()
-
-	_, err = io.Copy(os.Stdout, rc)
-	return err
-}
-
 func runPeerEndpointChanges(ctx context.Context, args []string) error {
 	st, err := localClient.Status(ctx)
 	if err != nil {