Are appeal waivers in federal criminal plea agreements unconstitutional?

QUESTIONS PRESENTED IL Are appeal waivers presented in federal criminal plea agreements an unconstitutional overreach by the Government preventing review of constitutional questions [raised in the appeal] at the Appellate Division in violation of due process guaranteed by the Fifth and Fourteenth Amendments? Subpart A: Can a plea containing an appeal waiver ever be knowing and voluntary where the defendant is “bargaining” for prospective sentencing favor of a Government who is not bound to perform (thus illusory), and Subpart B: Where he is not counseled by a defense pursuing any constitutional protections or mitigation? I. Should [claims outside the waiver including IAC] be limited to “face of record” standard where that precludes review of failure to act or false inducement not appearing in the record, insulating failure by defense counsel to protect or fully advise, as well as illusory inducements, on direct review?