kernel: Add option to control DS field behavior

src/libcharon/kernel/kernel_ipsec.h

@@ -99,6 +99,8 @@ struct kernel_ipsec_add_sa_t {
 	bool copy_df;
 	/** TRUE to copy the ECN header field to/from the outer header */
 	bool copy_ecn;
+	/** Whether to copy the DSCP header field to/from the outer header */
+	dscp_copy_t copy_dscp;
 	/** TRUE if initiator of the exchange creating the SA */
 	bool initiator;
 	/** TRUE if this is an inbound SA */