[settings] Change "not-found" semantics of fetch_setting_copy()

fetch_settings_copy() currently returns success and a NULL data
pointer to indicate a non-existent setting.  This is intended to allow
the caller to differentiate between a non-existent setting and an
error in allocating memory for the copy of the setting.

The underlying settings blocks' fetch() methods provide no way to
perform an existence check separate from an attempt to fetch the
setting.  A "non-existent setting" therefore means simply a setting
for which an error was encountered when attempting to fetch from every
settings block within the subtree.

Since any underlying error within a settings block (e.g. a GuestRPC
failure when attempting to retrieve a VMware GuestInfo setting) will
produce the effect of a "non-existent setting", it seems somewhat
meaningless to give special treatment to memory allocation errors
within fetch_setting_copy().

Remove the special treatment and simplify the semantics of
fetch_setting_copy() by directly passing through any underlying error
(including non-existence) encountered while fetching the setting.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 2 insertions, 16 deletions

diff --git a/src/crypto/rootcert.c b/src/crypto/rootcert.c
index 30ca170f..2aa31334 100644
--- a/src/crypto/rootcert.c
+++ b/src/crypto/rootcert.c
@@ -91,7 +91,6 @@ struct x509_root root_certificates = {
 static void rootcert_init ( void ) {
 	void *external = NULL;
 	int len;
-	int rc;
 
 	/* Allow trusted root certificates to be overridden only if
 	 * not explicitly specified at build time.
@@ -101,21 +100,8 @@ static void rootcert_init ( void ) {
 		/* Fetch copy of "trust" setting, if it exists.  This
 		 * memory will never be freed.
 		 */
-		len = fetch_setting_copy ( NULL, &trust_setting, &external );
-		if ( len < 0 ) {
-			rc = len;
-			DBGC ( &root_certificates, "ROOTCERT cannot fetch "
-			       "trusted root certificate fingerprints: %s\n",
-			       strerror ( rc ) );
-			/* No way to prevent startup; fail safe by
-			 * trusting no certificates.
-			 */
-			root_certificates.count = 0;
-			return;
-		}
-
-		/* Use certificates from "trust" setting, if present */
-		if ( external ) {
+		if ( ( len = fetch_setting_copy ( NULL, &trust_setting,
+						  &external ) ) >= 0 ) {
 			root_certificates.fingerprints = external;
 			root_certificates.count = ( len / FINGERPRINT_LEN );
 		}