Re: stateless reset in response to packet that is 43 bytes

Martin Thomson <mt@lowentropy.net> Mon, 01 June 2020 01:34 UTC

Return-Path: <mt@lowentropy.net>
X-Original-To: quic@ietfa.amsl.com
Delivered-To: quic@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 2415F3A0A3B for <quic@ietfa.amsl.com>; Sun, 31 May 2020 18:34:12 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.098
X-Spam-Level:
X-Spam-Status: No, score=-2.098 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=lowentropy.net header.b=e+MXt6An; dkim=pass (2048-bit key) header.d=messagingengine.com header.b=Ffobgecg
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id kpoYI4IclKm7 for <quic@ietfa.amsl.com>; Sun, 31 May 2020 18:34:10 -0700 (PDT)
Received: from out4-smtp.messagingengine.com (out4-smtp.messagingengine.com [66.111.4.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 759283A0A3A for <quic@ietf.org>; Sun, 31 May 2020 18:34:10 -0700 (PDT)
Received: from compute2.internal (compute2.nyi.internal [10.202.2.42]) by mailout.nyi.internal (Postfix) with ESMTP id A04325C00C5 for <quic@ietf.org>; Sun, 31 May 2020 21:34:09 -0400 (EDT)
Received: from imap2 ([10.202.2.52]) by compute2.internal (MEProxy); Sun, 31 May 2020 21:34:09 -0400
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lowentropy.net; h=mime-version:message-id:in-reply-to:references:date:from:to :subject:content-type; s=fm2; bh=d69e5+mZsKPQ+1iuvpNoLyHzdoNXCnk ryr2XZaX1A/w=; b=e+MXt6AnhwH243dRuWv/I34i/IbQ/CLTbZSyOkKvrqbixej NODGLtMXjrxCEzx1ICz0sCAoGvxm2DldnmbNq0FAI1jXhiTI+HX8mjNHG0mf7Cw3 jMQCleOEU4TdrZ7QoX2hGLlBuEhFw7x5osIjgwPqcegc9RpbqSPiy0aKIKKtixoF bcxvjJQslDjYKm16EFrK+fwUUxZoltJ7YdF4yZQB7yy3mOS5ReL69Gposj8YvW0A OcVL5h3A1WrDn6e5wsMEVZYVkrzd0elg04teYDubSOcUSMKOe24a+qPFTohJCJ9i OIWRnqqghu9mfVrcAszPjVi1zGJdMk7hpUQttZg==
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm2; bh=d69e5+ mZsKPQ+1iuvpNoLyHzdoNXCnkryr2XZaX1A/w=; b=FfobgecgojjbS7w5KgzZBt A9lo5KmbuZtm5jSOeHFFeN13yxHpfCkMpJgX/bi/2X05CuCfNjpstCcvc+Fi96Cw tBGSPXSQZoE7/maeJZjTpOOulz6qE7UpTMxv6zs3SZPg4eixJdg4+ZLFZqA+MYEU gNmH6FvyPkLlh4yUF7GpfYKBEtoV0dWH1fVAnJFaOGNfoMVnYW4TsiORRnZcxBUU jq9PmKNhFq/HGEgOdZU6XFuv9v/jVaNMO4/RvlouBVGAsPnHX/DQVLoeRh2DR18S rj/h4oI14cq1ojAQ9pCnZWBTd0CLONrAPiOnEd5/4eC5859jzHohbxL2FrH5M7tg ==
X-ME-Sender: <xms:EVvUXjoquJrMR4a4NONAQG6N--ssasBwon6kILukgySkiCiO5HUDAQ>
X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduhedrudefgedggeegucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucenucfjughrpefofgggkfgjfhffhffvufgtsehttd ertderredtnecuhfhrohhmpedfofgrrhhtihhnucfvhhhomhhsohhnfdcuoehmtheslhho figvnhhtrhhophihrdhnvghtqeenucggtffrrghtthgvrhhnpefhiedttdeviefhjeejgf evfeeuudfggfekveekheeugeegleevkeevkedthfeuieenucffohhmrghinhepihgvthhf rdhorhhgnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomh epmhhtsehlohifvghnthhrohhphidrnhgvth
X-ME-Proxy: <xmx:EVvUXtoyyNc5KDkMre8JTpMjSN2I7cqOH_7VR4uDqf4ZDuO2F8GEVw> <xmx:EVvUXgPbRaLr9nxREKAeZSFUbUVcXw7RIe0OY0xDO7SCyTyWQ_hbPA> <xmx:EVvUXm5eKqCMuopeWlYwyS5eYnhOLwNpRKXhJzAP17TKuROFDCslgQ> <xmx:EVvUXhLC78P_yA4WOfBDtTK-8tADXHBSo9gfIis9ysnnY7SKsXzi9A>
Received: by mailuser.nyi.internal (Postfix, from userid 501) id 4E775E00CD; Sun, 31 May 2020 21:34:09 -0400 (EDT)
X-Mailer: MessagingEngine.com Webmail Interface
User-Agent: Cyrus-JMAP/3.3.0-dev0-504-g204cd6f-fm-20200527.002-g204cd6f2
Mime-Version: 1.0
Message-Id: <755286bf-348d-4272-8905-ab71c8dd0cc0@www.fastmail.com>
In-Reply-To: <CAG9+TpZujQdj2OwJjnVOGQS942--wTuRN7n+MsHTjxYUhNtLdQ@mail.gmail.com>
References: <CAG9+TpZujQdj2OwJjnVOGQS942--wTuRN7n+MsHTjxYUhNtLdQ@mail.gmail.com>
Date: Mon, 01 Jun 2020 11:33:49 +1000
From: "Martin Thomson" <mt@lowentropy.net>
To: quic@ietf.org
Subject: Re: stateless reset in response to packet that is 43 bytes
Content-Type: text/plain
Archived-At: <https://mailarchive.ietf.org/arch/msg/quic/LzJFk6A5p69Qy3WdtF-NIPHB6Z0>
X-BeenThere: quic@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Main mailing list of the IETF QUIC working group <quic.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/quic>, <mailto:quic-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/quic/>
List-Post: <mailto:quic@ietf.org>
List-Help: <mailto:quic-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/quic>, <mailto:quic-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 01 Jun 2020 01:34:12 -0000

The packet with a short header that has the lowest length, but a maximum-length connection ID is 1 (type) + 20 (destination connection ID) + 4 (packet number + data) + 16 (aead expansion) = 41 bytes.

Hmm, maybe this should be 42 instead of 43.  I always get this bit wrong though.

On Mon, Jun 1, 2020, at 02:55, Jiuhai Zhang wrote:
> https://tools.ietf.org/html/draft-ietf-quic-transport-27#section-10.4
> An endpoint that sends a stateless reset in response to
>    packet that is 43 bytes or less in length SHOULD send a stateless
>    reset that is one byte shorter than the packet it responds to.
> Could someone explain why it is 43 bytes? thks