* kbx/backend.h (enum database_types): Add DB_TYPE_CACHE.
(struct db_request_part_s): Add seqno fields.
(struct db_request_s): Add infos for the cache backend.
* kbx/backend-support.c (struct backend_handle_s): Add 'backend_id'.
(strdbtype): Support DB_TYPE_CACHE.
(be_generic_release_backend): Ditto.
(be_find_request_part): New.
(be_return_pubkey): New arg UBID and chnage status name.
* kbx/backend-cache.c: New.
* kbx/backend-kbx.c (be_kbx_init_request_part): New.
(be_kbx_search): Factor some code out to a support function.
(be_kbx_seek): New.
* kbx/frontend.c (kbxd_add_resource): Support DB_TYPE_CACHE.
(kbxd_search): Support the NEXR operation with the cache.
* kbx/keybox-search-desc.h (KEYDB_SEARCH_MODE_UBID): New.
(struct keydb_search_desc): Add field u.ubid.
* kbx/keybox-search.c (has_ubid): New.
(keybox_search): Support the UBID search.
--
This adds a caching backend to the keyboxd. This tries to accommodate
for duplicate use of fingerprints and thus be correct in case a
fingerprint is used in several keys. It also turned out that we need
to have a unique identifier (UBID) to identify a keyblock or X.509
certificate. In particular with an OpenPGP keyblob we can't easily
use the primary fingerprint as an identifier because that fingerprint
may also be used as subkey in another key. Thus using a hash of the
entire keyblock is a better identifier to be used to address a
keyblock for restarting a search or for identifying the keyblock to be
updated. Note that this new UBID is not a permanent identifier
because it changes with all keyblock update; it should be viewed as a
handle to the keyblock or X509 cert.
