From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 7A1BC3A4F35 for ; Wed, 20 May 2026 08:08:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779264535; cv=none; b=f63u4jciWvF5w8/cW8nQYyVCiz2ueSz4jngWtBjfjdWxkGkIENoPXFAa8PB+zVP6x8riZNf1Tr+TCIKYexIN+NAEKPG8vioWJJ4JxnLJLKBRUJOIlD0MjaZLq5g609UNkZw1aAT+SOrjKGHA9480z3Uz+E03WTxQX8MGwrWh55Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779264535; c=relaxed/simple; bh=BRXJwfMfnV1zMnJtM7GywPXGIHyYEcE6F4GmrqYaR2Y=; h=From:To:Cc:Subject:Message-ID:In-Reply-To:References:MIME-Version: Content-Type:Date; b=IpsnWMrT27oLbyC55tdAgNJDetHMaofzYxDRZ2jzGoldfXrzKmyq0Jq/DOT7BkIOww9M1DR5M5Ih6R39DymZNen67BgWN2NqnoxUM9wakp5OEPXlas4Wd2Xj28N0zpFPQL8PI9wEA1JklRM735yjar2V8ZSqWJXxPbvFMSAosow= 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=SU3r7/Pp; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=F7Ms0UGX; arc=none smtp.client-ip=170.10.129.124 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="SU3r7/Pp"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="F7Ms0UGX" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1779264533; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1cPESQ7LAH4zMILZd/axqS8ovydxXDBYxaaBJksIM40=; b=SU3r7/Pp4Kq14u/s1dyPEeB/3IfbcT5GBQRgELTw3RfDhmOHKamgcftwOc4dZ8dnYzDNyq hyBDIHcVLkpE2qEBVtP9K4UplYfiH3CtmxWDsC3NwwVcvtrdRPDm7OTqGmNSLqgJaTmfcq DXWeoDEpnkxwxfKXC7inIQ9+yYvJmnQ= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-317-cuomzbFUMjioA0Ji7BDU6w-1; Wed, 20 May 2026 04:08:52 -0400 X-MC-Unique: cuomzbFUMjioA0Ji7BDU6w-1 X-Mimecast-MFC-AGG-ID: cuomzbFUMjioA0Ji7BDU6w_1779264531 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-48fd396daedso28487375e9.0 for ; Wed, 20 May 2026 01:08:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1779264531; x=1779869331; darn=vger.kernel.org; h=date:content-transfer-encoding:mime-version:organization:references :in-reply-to:message-id:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=1cPESQ7LAH4zMILZd/axqS8ovydxXDBYxaaBJksIM40=; b=F7Ms0UGXd1NRVAXhXsX1Ppoky26tWJIavAUFUYwddybbXZBqgjmukKPyl2Mesj2aAl W269pjTRypFQo59Nf1peEKueGjnj0jTyiDFyGqu6+LwX17ubG9GNAfoV6eXhTOH1N2N3 O1Ar5u2MABDeNzU4N05mr965UlzffYXt2lJnq7Ll0FBkQ1HeiozV4JWajkJBAJjKR2CT 3FyUZIjOn3YJwjQJmKWZQPt63s2LxxpJpRpMLlfemsIxMNJZJcWfeX1Sake2lZqp4wAf rPR3C61mK8IIxXNu2og/AYLaRj/8/gQtaB3MydqbqHn2wmZCIdqh4eBlB593XCmLEMr+ 3glQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779264531; x=1779869331; h=date:content-transfer-encoding:mime-version:organization:references :in-reply-to:message-id:subject:cc:to:from:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=1cPESQ7LAH4zMILZd/axqS8ovydxXDBYxaaBJksIM40=; b=UtVxooilyJ0L8opa08u5GBKjjf2C6WPQ0tlginbNpVDjXQkS9K+2RfMistluoJYKb3 q4bgEdiwCNB0+CP4j6RtZSooHkNyLvyEv3as9PDC5jWGg9sDyJOtRcyf1jmulukzbwyw e3HrVYvEtXir4/tPaJzdHttvdn5pHr+uD6MC5k8uQqkFfYYtI6+aWXPwOoFhZzHAsa99 zceCaIEb0CTwlI2BRrnG0PtPLKhq5sa57Ykq6tz4ItngSHoRig3MKNvfN3vdfUQ///b+ +VLTtG5LKPwqKdHWhCM/xlLAsLKWfL3i3oe48Am817Iz7SH32vSMKdLkG7VuKfwmphPI AokQ== X-Forwarded-Encrypted: i=1; AFNElJ+MYTKu69WL+4PqT7eHaUve86TFnVl0ruLC/N38zqAK4K4MuO5LGygdQNQxOxalWOAJKuYUdYLXpltUsvqHZi8=@vger.kernel.org X-Gm-Message-State: AOJu0Yx2SM8rBbqpa/WBBQ6DcWVlt9ixPxIm0H5NfGo7UAacsxbu9dJQ 2a/DOacuiL0LTtG/WbhA/U5RqEMxaPRct+P1l32UiEYgE6k0FPB74MywN/GTXD3SdDSwbqjInPG VMLAccymLrN6j+foBgkuE3g0ZlEk3uDn3dV6I4IQlLbMewPmHG5YBPsOED/NWkpqadzAcDQ== X-Gm-Gg: Acq92OHWPGjeuAWoCfa0x5p9fc4XNqGG1FTHD5zJJD2avKSwmt6o+4viiHTV/A1UAbC A34N+4Iqe0ORHyD7xBXniJ5rjmB+Szg5RMnnomTdHZ4jqhqCpX7jk/MhRDnAiL1cMp5Ba2lpFup 0sUjKo4zp7rkQdAQx+yNFoYXDRaJ8wzSagOPCold9BZAYY6FmdFkF/udMLVPbSu8eJ3bdMNiqrG QgVeXHkT+PO33HPPmZA3gJaD/AFJ7B+z5Nv+AACAsmPjgbOue4aczG4ea33aFm+5FEtkU8l/0aR C3QY2Ey1xmUOhlwoT28uoRVgdo5/tCKdAVhwF3MIeo0VqLknRklp9fSBGF1E710GhE8lDSiHGZF yZNv7uGzK45ubduddND5aa4qokbnFUwNV X-Received: by 2002:a05:600c:1389:b0:48f:fe2a:107c with SMTP id 5b1f17b1804b1-49001285b87mr227310215e9.6.1779264530719; Wed, 20 May 2026 01:08:50 -0700 (PDT) X-Received: by 2002:a05:600c:1389:b0:48f:fe2a:107c with SMTP id 5b1f17b1804b1-49001285b87mr227309635e9.6.1779264530196; Wed, 20 May 2026 01:08:50 -0700 (PDT) Received: from maya.myfinge.rs (ifcgrfdd.trafficplex.cloud. [2a10:fc81:a806:d6a9::1]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48fe4c833fcsm379368225e9.2.2026.05.20.01.08.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 May 2026 01:08:49 -0700 (PDT) From: Stefano Brivio To: Jakub Kicinski Cc: "David S. Miller" , Eric Dumazet , Paolo Abeni , Pavel Emelyanov , Laurent Vivier , David Gibson , Jon Maloy , Dmitry Safonov , Andrei Vagin , netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Neal Cardwell , Kuniyuki Iwashima , Simon Horman , Shuah Khan Subject: Re: [PATCH net v2 0/2] Fix race condition between TCP_REPAIR dump and data receive Message-ID: <20260520100843.3646f1f6@elisabeth> In-Reply-To: <20260519190352.45c8478e@kernel.org> References: <20260518183424.3144867-1-sbrivio@redhat.com> <20260519190352.45c8478e@kernel.org> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.49; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Date: Wed, 20 May 2026 10:08:48 +0200 (CEST) On Tue, 19 May 2026 19:03:52 -0700 Jakub Kicinski wrote: > On Mon, 18 May 2026 20:34:22 +0200 Stefano Brivio wrote: > > Stefano Brivio (2): > > tcp: Don't accept data when socket is in repair mode > > Not sure Eric is on board with this patch in the first place. > Sound like it's not the intended use case for REPAIR so IMO > it's up to TCP maintainers whether we want to support this. > And it's definitely not a Fix. Jakub, thanks for looking into this. As I was pointing out on the v1 thread, I think it's a race condition regardless of the usage, because after you switch a socket to repair mode you can do separate operations on the socket and the outcome will be inconsistent between them. It depends on external conditions and looks quite fragile. For example, you could dump a given length of the receive queue, just to read it a moment later, but now the length is wrong. Note that now, on the v1 thread, also Andrei, one of the authors of TCP_REPAIR and the matching feature in CRIU, agreed that my "fix" makes things safer: https://lore.kernel.org/all/CAEWA0a4d-PpWpVexYGP5SLRuzj8hs1W1_Ww6qA4BBrkzSs4umQ@mail.gmail.com/ But I won't certainly insist on handling it as a fix and I'm now taking care of the new feedback coming from Eric of course. > > selftests: Add data path tests for TCP_REPAIR mode > > Please don't add a new target, fold it under net. > Targets are a PITA to deal with in kselftests. Sorry, I had no idea, I'll change that. -- Stefano