net/tls: Add TLS Alert definitions

I'm about to add support for kernel handshake API consumers to send
TLS Alerts, so introduce the needed protocol definitions in the new
header tls_prot.h.

This presages support for Closure alerts. Also, support for alerts
is a pre-requite for handling session re-keying, where one peer will
signal the need for a re-key by sending a TLS Alert.

Reviewed-by: Hannes Reinecke <[e-mail]>
Signed-off-by: Chuck Lever <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

include/net/tls_prot.h

···
 	TLS_RECORD_TYPE_ACK = 26,
 };
 
+/*
+ * TLS Alert protocol: AlertLevel
+ */
+enum {
+	TLS_ALERT_LEVEL_WARNING = 1,
+	TLS_ALERT_LEVEL_FATAL = 2,
+};
+
+/*
+ * TLS Alert protocol: AlertDescription
+ */
+enum {
+	TLS_ALERT_DESC_CLOSE_NOTIFY = 0,
+	TLS_ALERT_DESC_UNEXPECTED_MESSAGE = 10,
+	TLS_ALERT_DESC_BAD_RECORD_MAC = 20,
+	TLS_ALERT_DESC_RECORD_OVERFLOW = 22,
+	TLS_ALERT_DESC_HANDSHAKE_FAILURE = 40,
+	TLS_ALERT_DESC_BAD_CERTIFICATE = 42,
+	TLS_ALERT_DESC_UNSUPPORTED_CERTIFICATE = 43,
+	TLS_ALERT_DESC_CERTIFICATE_REVOKED = 44,
+	TLS_ALERT_DESC_CERTIFICATE_EXPIRED = 45,
+	TLS_ALERT_DESC_CERTIFICATE_UNKNOWN = 46,
+	TLS_ALERT_DESC_ILLEGAL_PARAMETER = 47,
+	TLS_ALERT_DESC_UNKNOWN_CA = 48,
+	TLS_ALERT_DESC_ACCESS_DENIED = 49,
+	TLS_ALERT_DESC_DECODE_ERROR = 50,
+	TLS_ALERT_DESC_DECRYPT_ERROR = 51,
+	TLS_ALERT_DESC_TOO_MANY_CIDS_REQUESTED	= 52,
+	TLS_ALERT_DESC_PROTOCOL_VERSION = 70,
+	TLS_ALERT_DESC_INSUFFICIENT_SECURITY = 71,
+	TLS_ALERT_DESC_INTERNAL_ERROR = 80,
+	TLS_ALERT_DESC_INAPPROPRIATE_FALLBACK = 86,
+	TLS_ALERT_DESC_USER_CANCELED = 90,
+	TLS_ALERT_DESC_MISSING_EXTENSION = 109,
+	TLS_ALERT_DESC_UNSUPPORTED_EXTENSION = 110,
+	TLS_ALERT_DESC_UNRECOGNIZED_NAME = 112,
+	TLS_ALERT_DESC_BAD_CERTIFICATE_STATUS_RESPONSE = 113,
+	TLS_ALERT_DESC_UNKNOWN_PSK_IDENTITY = 115,
+	TLS_ALERT_DESC_CERTIFICATE_REQUIRED = 116,
+	TLS_ALERT_DESC_NO_APPLICATION_PROTOCOL = 120,
+};
+
 #endif /* _TLS_PROT_H */