From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id ED366C0051 for ; Sun, 23 Aug 2020 17:49:37 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id E84B487E34 for ; Sun, 23 Aug 2020 17:49:37 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id oinlFi5osVrK for ; Sun, 23 Aug 2020 17:49:37 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from mail-pl1-f173.google.com (mail-pl1-f173.google.com [209.85.214.173]) by hemlock.osuosl.org (Postfix) with ESMTPS id 484AF87DFF for ; Sun, 23 Aug 2020 17:49:37 +0000 (UTC) Received: by mail-pl1-f173.google.com with SMTP id b11so3108729pld.7 for ; Sun, 23 Aug 2020 10:49:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=voskuil-org.20150623.gappssmtp.com; s=20150623; h=content-transfer-encoding:from:mime-version:subject:date:message-id :references:cc:in-reply-to:to; bh=7oP0hQw2fscKNP4gXOXzMCDPxdZUaSf8gxP52ipKGMM=; b=SIkHtzcs9hAeNxWjdluKVjRUtKmEQSfd2cdnFnFSnOr+idhoEvTc13+CJosQ+fCPDy OcReE7G1Ax4NpUcHhOiruHZBmtoxqSALakfY29fzoIyKLd8KLdw3+i9AL+c6WSZs+BcN oCrkK2VWMyz11DP5f/dmGBlDMnUV8S/h8YEqwXZ8cuQaz4vGlc3Ek4z3GUuxKgId0tmt j3MCup7h1IiFFYrwfpgIDTSQHEgjhXJiEG7/F9znYgwvM3no0opoVI9xEibSLcW+yELL yY7aFfrdIchmgYvOYTy6wBE0LDEGXYhwtCJVI9zdU4jboBi9dC7MGLzOQMuXxgIjl72L K/xQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:content-transfer-encoding:from:mime-version :subject:date:message-id:references:cc:in-reply-to:to; bh=7oP0hQw2fscKNP4gXOXzMCDPxdZUaSf8gxP52ipKGMM=; b=Ku+/cU3oDgeb/r6DPUqRQAx+Qjx8kOCYjl6b2E13A4sGSnKtQjpgoFnZ8nFAmeQeBh ARl/HKPC6MYS8u6iarrQcFqWTo4R0L8zKAiSvupnHrHuPymcHM6wc9nH0eIq6+FtvREU E+33PNYz5Ief3pGDsTV0igrzYOZ5km0aUc98FvoquXIozifvXlvD3wI4pqIEnr0trSbZ QkJl31Pgtq4OBWmkBnoMMw/RlvAD2M3XhxRRjBhcKdNndPKecKzxyk1yF7RWbMmU3/cS iX/LBBxYLX/xtbfnZhEPdG/PbGUIklOCDfWipwfZ07ANKWxY+phIZSiX99EIotjOPXo/ WaJA== X-Gm-Message-State: AOAM532rvGiOmzuvjtTOKBv2airzkjJC0B2b0r/GqxSGndcMMXgflyQC sny+XmsRCFIX7h7PMG7N2oAXhg== X-Google-Smtp-Source: ABdhPJwzDDDBHQKy41NQsOUiORK17cp+w2lPntDssinbmXY7oKSlJVeGfKAAd6qTeu10GFcfSAAjXA== X-Received: by 2002:a17:90a:e781:: with SMTP id iz1mr1679520pjb.181.1598204976713; Sun, 23 Aug 2020 10:49:36 -0700 (PDT) Received: from ?IPv6:2600:380:7045:ddda:2dc5:cf82:3470:54a0? ([2600:380:7045:ddda:2dc5:cf82:3470:54a0]) by smtp.gmail.com with ESMTPSA id x12sm8507291pff.48.2020.08.23.10.49.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 23 Aug 2020 10:49:36 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Eric Voskuil Mime-Version: 1.0 (1.0) Date: Sun, 23 Aug 2020 10:49:35 -0700 Message-Id: <27FE83C7-0269-4DEB-82E4-486FAFFA0DE5@voskuil.org> References: In-Reply-To: To: Matt Corallo X-Mailer: iPhone Mail (17G80) X-Mailman-Approved-At: Sun, 23 Aug 2020 17:51:05 +0000 Cc: Bitcoin Protocol Discussion Subject: Re: [bitcoin-dev] Generalizing feature negotiation when new p2p connections are setup X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 23 Aug 2020 17:49:38 -0000 > On Aug 21, 2020, at 15:16, Matt Corallo wrote: >=20 > =EF=BB=BFHmm, could that not be accomplished by simply building this into n= ew messages? eg, send "betterprotocol", if you see a verack and no "betterpr= otocol" from your peer, send "worseprotocol" before you send a "verack". >=20 > Matt >=20 >> On 8/21/20 5:17 PM, Jeremy wrote: >> As for an example of where you'd want multi-round, you could imagine a sc= enario where you have a feature A which gets bugfixed by the introduction of= feature B, and you don't want to expose that you support A unless you first= negotiate B. Or if you can negotiate B you should never expose A, but for o= ld nodes you'll still do it if B is unknown to them. This seems to imply a security benefit (I can=E2=80=99t discern any other ra= tionale for this complexity). It should be clear that this is no more than t= rivially weak obfuscation and not worth complicating the protocol to achieve= . >> An example of this would be (were it not already out without a feature ne= gotiation existing) WTXID/TXID relay. >> The SYNC primitve simply codifies what order messages should be in and wh= en you're done for a phase of negotiation offering something. It can be done= without, but then you have to be more careful to broadcast in the correct o= rder and it's not clear when/if you should wait for more time before respond= ing. >> On Fri, Aug 21, 2020 at 2:08 PM Jeremy > wrote: >> Actually we already have service bits (which are sadly limited) which a= llow negotiation of non bilateral feature >> support, so this would supercede that. >> -- >> @JeremyRubin