cosmetic: clarify session active / partially active semantics

Change-Id: I2db85b3ffd61cbf8fb404b17ee3b6593d1d189c4

src/osmo-upf/up_session.c

@@ -1529,11 +1529,16 @@ static enum osmo_pfcp_cause up_session_setup_gtp(struct up_session *session)
 	return cause;
 }
 
+/* Return true when the session is in Established state and has active GTP actions. */
 bool up_session_is_active(struct up_session *session)
 {
 	return session && (session->fi->state == UP_SESSION_ST_ESTABLISHED) && !llist_empty(&session->active_gtp_actions);
 }
 
+/* Return true when up_session_is_active() == true *and* it has only active PDR/FAR pairs.
+ * A PDR/FAR is inactive when it is not part of an active GTP action. Reasons may be that it has no PDR-to-FAR relation,
+ * there is no matching reverse PDR/FAR, that a FAR is not set to FORW, an ignored Source/Destination Interface, ...
+ */
 bool up_session_is_fully_active(struct up_session *session, int *active_p, int *inactive_p)
 {
 	struct pdr *pdr;

src/osmo-upf/upf_vty.c

@@ -481,7 +481,7 @@ DEFUN(show_session, show_session_cmd,
 			}
 		}
 	}
-	vty_out(vty, "(%d fully-active + %d partially active + %d inactive)%s",
+	vty_out(vty, "(%d fully-active + %d active with some PDR/FAR ignored + %d inactive)%s",
 		fully_active_count, active_count, inactive_count, VTY_NEWLINE);
 	return CMD_SUCCESS;
 }