def gen_veth_str(self, const_str, intf_str):
avl_len = constants.MAX_VETH_NAME - len(const_str)<EOL>if avl_len <= <NUM_LIT:0>:<EOL><INDENT>LOG.error("<STR_LIT>")<EOL>raise dfae.DfaAgentFailed(reason="<STR_LIT>")<EOL><DEDENT>start_pos = len(intf_str) - avl_len<EOL>veth_str = const_str + intf_str[start_pos:]<EOL>return veth_str<EOL>
Generate a veth string.

        Concatenates the constant string with remaining available length
        of interface string from trailing position.