getPeerInfo(): Use cr_pid and cr_groups

Author: edolstra

src/nix/unix/daemon.cc

@@ -232,8 +232,12 @@ static PeerInfo getPeerInfo(int remote)
 
     xucred cred;
     socklen_t credLen = sizeof(cred);
-    if (getsockopt(remote, SOL_LOCAL, LOCAL_PEERCRED, &cred, &credLen) == 0)
+    if (getsockopt(remote, SOL_LOCAL, LOCAL_PEERCRED, &cred, &credLen) == 0) {
+        peer.pid = cred.cr_pid;
         peer.uid = cred.cr_uid;
+        if (cred.cr_ngroups)
+            peer.gid = cred.cr_groups[0];
+    }
 
 #endif