clatd: drop AID_INET and AID_VPN supplementary groups am: 7c87aaa50a am: 9c78a85b21 am: 6f9bd72b59

Original change: https://android-review.googlesource.com/c/platform/external/android-clat/+/1895706

Change-Id: Ic34a3218ff695c46dce259505112c75700de5822
diff --git a/clatd.c b/clatd.c
index 86850b0..bd2bf62 100644
--- a/clatd.c
+++ b/clatd.c
@@ -159,8 +159,8 @@
  * drops root privs but keeps the needed capabilities
  */
 void drop_root_but_keep_caps() {
-  gid_t groups[] = { AID_INET, AID_VPN };
-  if (setgroups(sizeof(groups) / sizeof(groups[0]), groups) < 0) {
+  // see man setgroups: this drops all supplementary groups
+  if (setgroups(0, NULL) < 0) {
     logmsg(ANDROID_LOG_FATAL, "setgroups failed: %s", strerror(errno));
     exit(1);
   }