From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 76F1938D69B for ; Tue, 24 Mar 2026 16:19:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774369141; cv=none; b=Aazngk6Rzi+aYKXNZIHoUAMPjEdtalnRRQnmadfPauuzGF21mgl4AFuA4djp44u7ujWu8gvD8x9ckTb/IljnqtRZ0/bbqTqI7EFUkWzA4wQshtywgbsxwVBz/kvB2Wj7VWnbEfSlMk6pxKz7GhL+fwD53DrdUlnRhCncwgx/Wls= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774369141; c=relaxed/simple; bh=j2vmMAgZBEIHOIcyw/exgvoqxhaoAAncNtLEhyVK7V8=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=Z1naIY26aTR95VLyIfddJ+EUQjZGl5115z+NmPO8U3O9K0ch+FafTeiclzI5gGXpopqm3NsIM6mmDiO4o5njCVsjsLM96FE5QHdBWyiWAt2fTR2Ut17D2Q2EYeVeJ0Srp87echpBg6bgz/ysFSVRTRm+80tuvtzUk33ApqelgJQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=UvWNF0wg; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=rUmU6YOm; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UvWNF0wg"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="rUmU6YOm" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1774369139; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=0pLGEONAHfojUOfaOSp5cChM4XB6HpkP9CDLtETY2Zg=; b=UvWNF0wgSnxfP19DhIuC8JjD76fiIkslCDX4/NMpmxQjVX4QBESwrbJJDbBDYIjiZM21/w HtU27K8qMP0CfUO4RM7dbJrJaBEvfkSSEvjugzhh2QF09LhIyK8Aw8gQGls1GFxookIIMX HlEicRAq+l6D/vQK/CpMRxgdEeGD4ew= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-26-TN82wwAjPlCqCQkKMvu1TQ-1; Tue, 24 Mar 2026 12:18:58 -0400 X-MC-Unique: TN82wwAjPlCqCQkKMvu1TQ-1 X-Mimecast-MFC-AGG-ID: TN82wwAjPlCqCQkKMvu1TQ_1774369137 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-43b3d3d2d22so4693443f8f.0 for ; Tue, 24 Mar 2026 09:18:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1774369137; x=1774973937; darn=vger.kernel.org; h=mime-version:message-id:date:references:in-reply-to:subject:cc:to :from:from:to:cc:subject:date:message-id:reply-to; bh=0pLGEONAHfojUOfaOSp5cChM4XB6HpkP9CDLtETY2Zg=; b=rUmU6YOm3ZCZMZ7EHRgBKorXwzUWJWZyvVQK2SXrCg0xIYrY28uBtwIT4j0wrCZOIq /GRGXn/UnVt5NfO3Mls1U1Ekx/w0M6seRDG+T4BTaurcKpQlnit7qfYnVBmmmmiJ6RDx MFq8Rh+CQUgHb/CBoM0XKX1WtJo/4MZjkruQBBwW65VjtlhrhwOyaFhbmpF91R7iY3oW SKcdCmb1T4EuAjfw0iq/pDCufgTmGFYA0Hx9fSo3VWjTx53FjxVCmuw3J/lwqQSp47kj RtLHSvMECkQfCmVy8+D6FFworxn8+EsTstLaureeD9XjKhLU+/Ij1ugvz1QzeJyRAscF h+IA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774369137; x=1774973937; h=mime-version:message-id:date:references:in-reply-to:subject:cc:to :from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=0pLGEONAHfojUOfaOSp5cChM4XB6HpkP9CDLtETY2Zg=; b=djgU5EjkpNd6pmZO/1zXdqt+SYDFcukQTkoWWpIy0CCEyby7/fDULT/IumZ8vNHlCR ZMtpIVArUayVgSdPgu96wlXEOh8BXRf4GjobAN6aijrwQLQpP98xVETKhRbtv4oS+mKR a6ZCOL5873b3DjIexl4GkU7Au6E97xLfPCX3b+mTsAT8VXJX/BFQ3HfRItKZ+9Qb2qYC ef7snUDEcZWUGaw+SA9Z3QtneEqbRqsxKyCsPaF5QxRGJLazKsy1yOIxmmF/00gg4YqA QY5/z0TytVtaeabxVeYT+1+3yA/c/3Z1OOH9iK6alCKZFYwHehK7/zA3+xtCmdpaP3jc JoHg== X-Forwarded-Encrypted: i=1; AJvYcCWWQ28vRppS5Cc/g4DMc+00VOc3Gn3NiXxO+WDBY+RD2WPqHPvTXMyX+o9FHG6H5rBK3FUeDgE0c3Le/TPma8Q=@vger.kernel.org X-Gm-Message-State: AOJu0Yzh7AVNhtGzi/PmkvTIDYTie2cdlX7nDQwSeVIQkBFQe61JCKSv 26vPnYXS8QMBlkNgU+e1aTS/KrhPZawHtELDvIyfrJmUyd3trRcEaJbpcySeo9VD0WZQXO1pYMd uz7wvS6jRcyLoALykTCQ1wUmbvV5zyRUvz6ZnDWicsHAkoRIVdRpxxsZS25pFebFwXRP12g== X-Gm-Gg: ATEYQzyeCVH2fl7SGAFxOzfLFHh1fhW4bzpGJD6DsMbRR4u6dxxonou5z1E/PMEA1Oa 58MrlRo6Idv6JMJPyFw/kFVgeHAvHaq9bVHzJj3oiZ4a8ILpqhJvEDrMhDuPb8XrWDSbfP6e7JC N0h4c75EAh9e92gDftfU3n+tahEYQHYyZN2X2FpA77HGqRulgpZO3tNMByY8fLjQaErvx0WtuCd AQRWjFJKsv+BCwsSVzJpON2QOceamZA+cDgLk+1meZRSiE2+oVGpjgZouSbe1AuMLmMBpYzT9sW z3CFIa92JlvX4Mmq4jGZpRlVKMqtuLf9PzXCiGoQ9A/3gla65w3SLCe4Y6uCMA8DsdNSlylD0ye mzUb7hwZchNwVGAMRT67keNJ/duOx4/Jnn0HwfHRnQmvoohJU X-Received: by 2002:a05:6000:2509:b0:43b:4920:56bb with SMTP id ffacd0b85a97d-43b88a0cfc1mr107786f8f.52.1774369136492; Tue, 24 Mar 2026 09:18:56 -0700 (PDT) X-Received: by 2002:a05:6000:2509:b0:43b:4920:56bb with SMTP id ffacd0b85a97d-43b88a0cfc1mr107724f8f.52.1774369135946; Tue, 24 Mar 2026 09:18:55 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk (alrua-x1.borgediget.toke.dk. [2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43b64717e97sm41173985f8f.35.2026.03.24.09.18.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Mar 2026 09:18:55 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 24AE35A470F; Tue, 24 Mar 2026 17:18:54 +0100 (CET) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Leon Hwang , bpf@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , "David S . Miller" , Jakub Kicinski , Jesper Dangaard Brouer , Leon Hwang , Lorenzo Bianconi , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, netdev@vger.kernel.org, kernel-patches-bot@fb.com Subject: Re: [PATCH bpf-next 1/3] bpf: Disallow freplace on XDP with mismatched xdp_has_frags values In-Reply-To: <20260324150444.68166-2-leon.hwang@linux.dev> References: <20260324150444.68166-1-leon.hwang@linux.dev> <20260324150444.68166-2-leon.hwang@linux.dev> X-Clacks-Overhead: GNU Terry Pratchett Date: Tue, 24 Mar 2026 17:18:54 +0100 Message-ID: <87ecl9mc9d.fsf@toke.dk> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Leon Hwang writes: > xdp_has_frags was introduced by the commit > c2f2cdbeffda ("bpf: introduce BPF_F_XDP_HAS_FRAGS flag in prog_flags loading the ebpf program"). > > The commit f45d5b6ce2e8 ("bpf: generalise tail call map compatibility check") > was to ensure backwards compatibility against tail calls. However, it > missed that XDP progs can be extended by freplace progs, which could break > the backwards compatibility, e.g. xdp_has_frags=true freplace progs are > allowed to attach to xdp_has_frags=false XDP progs. > > To avoid breaking the backwards compatibility via freplace, disallow > freplace on XDP programs with different xdp_has_frags values. The problem you describe is not actually a problem, though? A frags-aware program can run on a non-frags interface just fine. You're messing with long-standing behaviour (since 5.18!) to solve a non-existent problem. In a way that completely breaks the frags handling in libxdp[0]: Running tests from ./test-libxdp.sh [test_link_so] PASS [test_link_a] PASS [test_old_dispatcher] PASS [test_xdp_devbound] PASS [test_xdp_frags] FAIL Kernel supports XDP programs with frags check_load_frags: FAILED check_load_nofrags_success: PASSED check_load_nofrags_fail: PASSED check_load_frags_multi: FAILED check_load_mix_big: FAILED check_load_mix_small: FAILED Test test_xdp_frags exited with return code: 1 Please don't do that. -Toke [0] Run 'make test' here: https://github.com/xdp-project/xdp-tools