#define KEYCTL_INVALIDATE 21 /* invalidate a key */
#define KEYCTL_GET_PERSISTENT 22 /* get a user's persistent keyring */
#define KEYCTL_DH_COMPUTE 23 /* Compute Diffie-Hellman values */
+#define KEYCTL_RESTRICT_KEYRING 29 /* Restrict keys allowed to link to a keyring */
/* keyctl structures */
struct keyctl_dh_params {