hostinfo,distro: Identify Western Digital MyCloud devices.

root@WDMyCloud HD_a2 # ./tailscale debug hostinfo
{
  "IPNVersion": "1.25.0-dev20220605-t7fea52e02",
  "OS": "linux",
  "OSVersion": "5.22.113",
  "Desktop": false,
  "DeviceModel": "WD My Cloud Gen2: Marvell Armada 375",
  "Hostname": "WDMyCloud",
  "GoArch": "arm"
}

Updates https://github.com/tailscale/tailscale/issues/4622

Signed-off-by: Denton Gentry <dgentry@tailscale.com>

hostinfo/hostinfo_linux.go

@@ -37,6 +37,7 @@ func linuxDeviceModel() string {
 		// Otherwise, try the Devicetree model, usually set on
 		// ARM SBCs, etc.
 		// Example: "Raspberry Pi 4 Model B Rev 1.2"
+		// Example: "WD My Cloud Gen2: Marvell Armada 375"
 		"/sys/firmware/devicetree/base/model", // Raspberry Pi 4 Model B Rev 1.2"
 	} {
 		b, _ := os.ReadFile(path)
@@ -55,6 +56,9 @@ func osVersionLinux() string {
 		propFile = "/etc.defaults/VERSION"
 	case distro.OpenWrt:
 		propFile = "/etc/openwrt_release"
+	case distro.WDMyCloud:
+		slurp, _ := ioutil.ReadFile("/etc/version")
+		return fmt.Sprintf("%s", string(bytes.TrimSpace(slurp)))
 	}
 
 	m := map[string]string{}