all: initial support for setup linux router

Wiring code to configure router when running ctrld. Future commits will
add implementation for each supported platforms.

internal/router/router.go

@@ -0,0 +1,86 @@
+package router
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"sync/atomic"
+
+	"github.com/Control-D-Inc/ctrld"
+)
+
+const (
+	OpenWrt = "openwrt"
+	DDWrt   = "ddwrt"
+	Merlin  = "merlin"
+	Ubios   = "ubios"
+)
+
+// ErrNotSupported reports the current router is not supported error.
+var ErrNotSupported = errors.New("unsupported platform")
+
+var routerAtomic atomic.Pointer[router]
+
+type router struct {
+	name string
+}
+
+// SupportedPlatforms return all platforms that can be configured to run with ctrld.
+func SupportedPlatforms() []string {
+	return []string{DDWrt, Merlin, OpenWrt, Ubios}
+}
+
+// Configure change the given *ctrld.Config for running on the router.
+func Configure(c *ctrld.Config) error {
+	name := Name()
+	switch name {
+	case DDWrt, Merlin, OpenWrt, Ubios:
+	default:
+		return ErrNotSupported
+	}
+	// TODO: implement all supported platforms.
+	fmt.Printf("Configuring router for: %s\n", name)
+	return nil
+}
+
+// Name returns name of the router platform.
+func Name() string {
+	if r := routerAtomic.Load(); r != nil {
+		return r.name
+	}
+	r := &router{}
+	r.name = distroName()
+	routerAtomic.Store(r)
+	return r.name
+}
+
+func distroName() string {
+	switch {
+	case bytes.HasPrefix(uname(), []byte("DD-WRT")):
+		return DDWrt
+	case bytes.HasPrefix(uname(), []byte("ASUSWRT-Merlin")):
+		return Merlin
+	case haveFile("/etc/openwrt_version"):
+		return OpenWrt
+	case haveDir("/data/unifi"):
+		return Ubios
+	}
+	return ""
+}
+
+func haveFile(file string) bool {
+	_, err := os.Stat(file)
+	return err == nil
+}
+
+func haveDir(dir string) bool {
+	fi, _ := os.Stat(dir)
+	return fi != nil && fi.IsDir()
+}
+
+func uname() []byte {
+	out, _ := exec.Command("uname", "-o").Output()
+	return out
+}