If the compiler correctly identifies the use of HAVE_SO_TIMESTAMPNS but in runtime SO_TIMESTAMPNS cannot be used, then SO_TIMESTAMP is tried to be used as fallback. Only if this also does not work, an error message is issued for both SO_TIMESTAMPNS and SO_TIMESTAMP.
If the compiler correctly identifies the use of HAVE_SO_TIMESTAMPNS but in runtime SO_TIMESTAMPNS cannot be used, then SO_TIMESTAMP is tried to be used as fallback. Only if this also does not work, an error message is issued for both SO_TIMESTAMPNS and SO_TIMESTAMP.
Fixed Issues #272 and #273