From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7E445C61DBD for ; Fri, 28 Aug 2026 17:38:59 +0000 (UTC) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id A66F34025A; Fri, 28 Aug 2026 19:38:58 +0200 (CEST) Received: from inbox.dpdk.org (inbox.dpdk.org [95.142.172.178]) by mails.dpdk.org (Postfix) with ESMTP id 2980640151 for ; Fri, 28 Aug 2026 19:38:57 +0200 (CEST) Received: by inbox.dpdk.org (Postfix, from userid 33) id 1D6DD4CFA5; Fri, 28 Aug 2026 19:38:57 +0200 (CEST) From: bugzilla@dpdk.org To: dev@dpdk.org Subject: [DPDK/ethdev Bug 2015] memif: ring semantics differ from VPP Date: Fri, 28 Aug 2026 17:38:57 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: DPDK X-Bugzilla-Component: ethdev X-Bugzilla-Version: 26.11 X-Bugzilla-Keywords: X-Bugzilla-Severity: minor X-Bugzilla-Who: stephen@networkplumber.org X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Resolution: X-Bugzilla-Priority: Normal X-Bugzilla-Assigned-To: dev@dpdk.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status bug_severity priority component assigned_to reporter target_milestone Message-ID: Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 X-Bugzilla-URL: https://bugs.dpdk.org/ Auto-Submitted: auto-generated X-Auto-Response-Suppress: All MIME-Version: 1.0 X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org https://bugs.dpdk.org/show_bug.cgi?id=3D2015 Bug ID: 2015 Summary: memif: ring semantics differ from VPP Product: DPDK Version: 26.11 Hardware: All OS: All Status: UNCONFIRMED Severity: minor Priority: Normal Component: ethdev Assignee: dev@dpdk.org Reporter: stephen@networkplumber.org Target Milestone: --- Found when doing AI assisted analysis and comparison of DPDK memif with VPP. The two memif implementations disagree by one about what the hello limit fields mean. DPDK sends h->max_region =3D ETH_MEMIF_MAX_REGION_NUM - 1, treating the field as an inclusive maximum index, and checks received indices with >=3D against ETH_MEMIF_MAX_REGION_NUM. VPP sends h->max_region =3D MEMIF_MAX_REGION (256) and checks received indices with > rather than >=3D, so it accepts index 256 and therefore 257 regions. The same > form is used for its ring index checks. Nothing is memory-unsafe on either side today, because both clamp what they actually use, and VPP's regions are vectors. But the accepted range and the advertised range do not agree, and the two stacks do not agree with each other. There is no memif specification outside VPP's tree, so this is the kind of thing that only gets settled by writing it down. It should be pinned in whatever wire contract comes out of the current memif hardening work, and DPDK's side adjusted to match once the meaning is agreed. Raised here so it is on the record and does not get fixed unilaterally in one stack in a way that breaks the other. --=20 You are receiving this mail because: You are the assignee for the bug.=