Movatterモバイル変換

keyctl_capabilities(3) — Linux manual page

KEYCTL_CAPABILITIES(3)  Linux Key Management CallsKEYCTL_CAPABILITIES(3)

NAME        top

       keyctl_capabilities - Query subsystem capabilities

SYNOPSIS        top

#include <keyutils.h>long keyctl_capabilities(unsigned char *buffer, size_tbuflen);

DESCRIPTION        top

keyctl_capabilities() queries the keyrings subsystem in the kernel       to ask about its capabilities and fills in the array in the buffer       with bits that indicate the presence or absence of specific       features in the keyrings subsystem.       The function returns the amount of data the kernel has available,       irrespective of the amount of buffer space available.  If the       buffer is shorter than the data, a short copy will be made; if the       buffer is larger than the data, the excess space will be cleared.       If this operation is not available in the kernel, the keyutils       library will emulate it as best it can and the capability bit that       indicates if the kernel operation is available will be cleared.       Inbuffer[0], the following capabilities exist:KEYCTL_CAPS0_CAPABILITIES              This is set if the kernel supports this operation and              cleared otherwise.  If it is cleared, the rest of the flags              are emulated.KEYCTL_CAPS0_PERSISTENT_KEYRINGS              This is set if the kernel supports persistent keyrings and              cleared otherwise.  Seekeyctl_get_persistent(3).KEYCTL_CAPS0_DIFFIE_HELLMAN              This is set if the kernel supports Diffie-Hellman              calculation and cleared otherwise.  Seekeyctl_dh_compute(3).KEYCTL_CAPS0_PUBLIC_KEY              This is set if the kernel supports public-key operations              and cleared otherwise.  Seekeyctl_pkey_query(3).KEYCTL_CAPS0_BIG_KEY              This is set if the kernel supports the big_key key type and              cleared otherwise.KEYCTL_CAPS0_INVALIDATE              This is set if the kernel supports key invalidation and              cleared otherwise.  Seekeyctl_invalidate(3).KEYCTL_CAPS0_RESTRICT_KEYRING              This is set if the kernel supports restrictions on keyrings              and cleared otherwise.  Seekeyctl_restrict_keyring(3).KEYCTL_CAPS0_MOVE              This is set if the kernel supports the move key operation              and cleared otherwise.  Seekeyctl_move(3).       Inbuffer[1], the following capabilities exist:KEYCTL_CAPS1_NS_KEYRING_NAME              This is set if the keyring names are segregated according              to the user-namespace in which a keyring is created.KEYCTL_CAPS1_NS_KEY_TAG              This is set if a key or keyring may get tagged with a              namespace, thereby allowing multiple keys with the same              type and description, but different namespace tags, to              coexist within the same keyring.  Tagging may be automatic              depending on the key type.  Only network-namespace tagging              is currently used.

RETURN VALUE        top

       On successkeyctl_capabilities() returns the size of the data it       has available, irrespective of the size of the buffer.  On error,       the value-1will be returned anderrno will have been set to an       appropriate error.

ERRORS        top

EFAULTThe buffer cannot be written to.

LINKING        top

       This is a library function that can be found inlibkeyutils.  When       linking,-lkeyutilsshould be specified to the linker.

SEE ALSO        top

keyctl(1),add_key(2),keyctl(2),request_key(2),keyctl(3),keyrings(7),keyutils(7)

COLOPHON        top

       This page is part of thekeyutils (key management utilities)       project.  Information about the project can be found at [unknown       -- if you know, please contact man-pages@man7.org] If you have a       bug report for this manual page, send it to       keyrings@linux-nfs.org.  This page was obtained from the project's       upstream Git repository       ⟨http://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git⟩       on 2025-08-11.  (At that time, the date of the most recent commit       that was found in the repository was 2023-03-20.)  If you discover       any rendering problems in this HTML version of the page, or you       believe there is a better or more up-to-date source for the page,       or you have corrections or improvements to the information in this       COLOPHON (which isnot part of the original manual page), send a       mail to man-pages@man7.orgLinux                          30 May 2019KEYCTL_CAPABILITIES(3)

Pages that refer to this page:keyctl(3)

HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH.