Add krb5_storage_fsync().

We add a function to cause krb5_storage's to be sync'd to their backing
store.  For memory backed storages, this is a NOP.  For files, it calls
fsync on the file descriptor.

lib/krb5/store-int.h

@@ -40,6 +40,7 @@ struct krb5_storage_data {
     ssize_t (*store)(struct krb5_storage_data*, const void*, size_t);
     off_t (*seek)(struct krb5_storage_data*, off_t, int);
     int (*trunc)(struct krb5_storage_data*, off_t);
+    int (*fsync)(struct krb5_storage_data*);
     void (*free)(struct krb5_storage_data*);
     krb5_flags flags;
     int eof_code;

lib/krb5/store.c

@@ -190,6 +190,25 @@ krb5_storage_truncate(krb5_storage *sp, off_t offset)
     return (*sp->trunc)(sp, offset);
 }
 
+/**
+ * Sync the storage buffer to its backing store.  If there is no
+ * backing store this function will return success.
+ *
+ * @param sp the storage buffer to sync
+ *
+ * @return A Kerberos 5 error code
+ *
+ * @ingroup krb5_storage
+ */
+
+KRB5_LIB_FUNCTION int KRB5_LIB_CALL
+krb5_storage_fsync(krb5_storage *sp)
+{
+    if (sp->fsync != NULL)
+	return sp->fsync(sp);
+    return 0;
+}
+
 /**
  * Read to the storage buffer.
  *

lib/krb5/store_emem.c

@@ -189,6 +189,7 @@ krb5_storage_emem(void)
     sp->store = emem_store;
     sp->seek = emem_seek;
     sp->trunc = emem_trunc;
+    sp->fsync = NULL;
     sp->free = emem_free;
     sp->max_alloc = UINT_MAX/8;
     return sp;

lib/krb5/store_fd.c

@@ -66,6 +66,14 @@ fd_trunc(krb5_storage * sp, off_t offset)
     return 0;
 }
 
+static int
+fd_sync(krb5_storage * sp)
+{
+    if (fsync(FD(sp)) == -1)
+	return errno;
+    return 0;
+}
+
 static void
 fd_free(krb5_storage * sp)
 {
@@ -134,6 +142,7 @@ krb5_storage_from_fd(krb5_socket_t fd_in)
     sp->store = fd_store;
     sp->seek = fd_seek;
     sp->trunc = fd_trunc;
+    sp->fsync = fd_sync;
     sp->free = fd_free;
     sp->max_alloc = UINT_MAX/8;
     return sp;

lib/krb5/store_mem.c

@@ -144,6 +144,7 @@ krb5_storage_from_mem(void *buf, size_t len)
     sp->store = mem_store;
     sp->seek = mem_seek;
     sp->trunc = mem_trunc;
+    sp->fsync = NULL;
     sp->free = NULL;
     sp->max_alloc = UINT_MAX/8;
     return sp;
@@ -203,6 +204,7 @@ krb5_storage_from_readonly_mem(const void *buf, size_t len)
     sp->store = mem_no_store;
     sp->seek = mem_seek;
     sp->trunc = mem_no_trunc;
+    sp->fsync = NULL;
     sp->free = NULL;
     sp->max_alloc = UINT_MAX/8;
     return sp;

lib/krb5/version-script.map

@@ -600,6 +600,7 @@ HEIMDAL_KRB5_2.0 {
 		krb5_storage_from_fd;
 		krb5_storage_from_mem;
 		krb5_storage_from_readonly_mem;
+		krb5_storage_fsync;
 		krb5_storage_get_byteorder;
 		krb5_storage_get_eof_code;
 		krb5_storage_is_flags;