net/sched: flower: refactor control flag definitions

Redefine the flower control flags as an enum, so they are
included in BTF info.

Make the kernel-side enum a more explicit superset of
TCA_FLOWER_KEY_FLAGS_*, new flags still need to be added to
both enums, but at least the bit position only has to be
defined once.

FLOW_DIS_ENCAPSULATION is never set for mask, so it can't be
exposed to userspace in an unsupported flags mask error message,
so it will be placed one bit position above the last uAPI flag.
Suggested-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Davide Caratti <dcaratti@redhat.com>
Link: https://patch.msgid.link/20240713021911.1631517-2-ast@fiberby.netSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/flow_dissector.h

@@ -7,6 +7,7 @@
 #include <linux/siphash.h>
 #include <linux/string.h>
 #include <uapi/linux/if_ether.h>
+#include <uapi/linux/pkt_cls.h>
 
 struct bpf_prog;
 struct net;
@@ -24,9 +25,16 @@ struct flow_dissector_key_control {
 	u32	flags;
 };
 
-#define FLOW_DIS_IS_FRAGMENT	BIT(0)
-#define FLOW_DIS_FIRST_FRAG	BIT(1)
-#define FLOW_DIS_ENCAPSULATION	BIT(2)
+/* The control flags are kept in sync with TCA_FLOWER_KEY_FLAGS_*, as those
+ * flags are exposed to userspace in some error paths, ie. unsupported flags.
+ */
+enum flow_dissector_ctrl_flags {
+	FLOW_DIS_IS_FRAGMENT		= TCA_FLOWER_KEY_FLAGS_IS_FRAGMENT,
+	FLOW_DIS_FIRST_FRAG		= TCA_FLOWER_KEY_FLAGS_FRAG_IS_FIRST,
+
+	/* These flags are internal to the kernel */
+	FLOW_DIS_ENCAPSULATION		= (TCA_FLOWER_KEY_FLAGS_MAX << 1),
+};
 
 enum flow_dissect_ret {
 	FLOW_DISSECT_RET_OUT_GOOD,

include/uapi/linux/pkt_cls.h

@@ -677,8 +677,11 @@ enum {
 enum {
 	TCA_FLOWER_KEY_FLAGS_IS_FRAGMENT = (1 << 0),
 	TCA_FLOWER_KEY_FLAGS_FRAG_IS_FIRST = (1 << 1),
+	__TCA_FLOWER_KEY_FLAGS_MAX,
 };
 
+#define TCA_FLOWER_KEY_FLAGS_MAX (__TCA_FLOWER_KEY_FLAGS_MAX - 1)
+
 enum {
 	TCA_FLOWER_KEY_CFM_OPT_UNSPEC,
 	TCA_FLOWER_KEY_CFM_MD_LEVEL,