flow_offload: add encapsulation control flag helpers

This patch adds two new helper functions:
  flow_rule_is_supp_enc_control_flags()
  flow_rule_has_enc_control_flags()

They are intended to be used for validating encapsulation control
flags, and compliment the similar helpers without "enc_" in the name.

The only difference is that they have their own error message,
to make it obvious if an unsupported flag error is related to
FLOW_DISSECTOR_KEY_CONTROL or FLOW_DISSECTOR_KEY_ENC_CONTROL.

flow_rule_has_enc_control_flags() is for drivers supporting
FLOW_DISSECTOR_KEY_ENC_CONTROL, but not supporting any
encapsulation control flags.
(Currently all 4 drivers fits this category)

flow_rule_is_supp_enc_control_flags() is currently only used
for the above helper, but should also be used by drivers once
they implement at least one encapsulation control flag.

There is AFAICT currently no need for an "enc_" variant of
flow_rule_match_has_control_flags(), as all drivers currently
supporting FLOW_DISSECTOR_KEY_ENC_CONTROL, are already calling
flow_rule_match_enc_control() directly.

Only compile tested.
Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Davide Caratti <dcaratti@redhat.com>
Link: https://lore.kernel.org/r/20240609173358.193178-2-ast@fiberby.netSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/flow_offload.h

@@ -471,6 +471,28 @@ static inline bool flow_rule_is_supp_control_flags(const u32 supp_flags,
 	return false;
 }
 
+/**
+ * flow_rule_is_supp_enc_control_flags() - check for supported control flags
+ * @supp_enc_flags: encapsulation control flags supported by driver
+ * @enc_ctrl_flags: encapsulation control flags present in rule
+ * @extack: The netlink extended ACK for reporting errors.
+ *
+ * Return: true if only supported control flags are set, false otherwise.
+ */
+static inline bool flow_rule_is_supp_enc_control_flags(const u32 supp_enc_flags,
+						       const u32 enc_ctrl_flags,
+						       struct netlink_ext_ack *extack)
+{
+	if (likely((enc_ctrl_flags & ~supp_enc_flags) == 0))
+		return true;
+
+	NL_SET_ERR_MSG_FMT_MOD(extack,
+			       "Unsupported match on enc_control.flags %#x",
+			       enc_ctrl_flags);
+
+	return false;
+}
+
 /**
  * flow_rule_has_control_flags() - check for presence of any control flags
  * @ctrl_flags: control flags present in rule
@@ -484,6 +506,19 @@ static inline bool flow_rule_has_control_flags(const u32 ctrl_flags,
 	return !flow_rule_is_supp_control_flags(0, ctrl_flags, extack);
 }
 
+/**
+ * flow_rule_has_enc_control_flags() - check for presence of any control flags
+ * @enc_ctrl_flags: encapsulation control flags present in rule
+ * @extack: The netlink extended ACK for reporting errors.
+ *
+ * Return: true if control flags are set, false otherwise.
+ */
+static inline bool flow_rule_has_enc_control_flags(const u32 enc_ctrl_flags,
+						   struct netlink_ext_ack *extack)
+{
+	return !flow_rule_is_supp_enc_control_flags(0, enc_ctrl_flags, extack);
+}
+
 /**
  * flow_rule_match_has_control_flags() - match and check for any control flags
  * @rule: The flow_rule under evaluation.