Fix typos in comments

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Fix typos in variable names

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Fix typos in error message

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Fix typo in variable name

Signed-off-by: Stefan Weil <sw@weilnetz.de>