From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=205.220.168.131 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794507920; b=yNVVPN2Oby/dTbOfGipdX1hA9irjrKqEYS64gGu23eSgETdWoNp4gHb5lJZ8VWC7b80j sQUZQPWPgFD92HjDZCrrx87bl+Sztb44cDjawP0yua4GwQahLl1knqOITmXsTOf6gU/PF 1ZzjldynS9kmB3IcCAmrtZE491k/siEtgjRVGRsymlbzHixSPLUN8IZ0JTRz49S41cEjF fmMsMvrUTl62/qVytOwZ4E1T0a720rAeiaSo6+Uj/9qRDa1Ni7ysGN3j5ovRXRRKcwXfC tRopvKfHUpfeM09TjSSXi50zMXE1tchNqH/baPXssSd7HjNQZpESBbcK7zFGoL7dR3g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794507920; h=DMARC-Filter:Received:DKIM-Signature:Received:Received: DKIM-Signature:X-Google-DKIM-Signature:X-Forwarded-Encrypted: X-Gm-Message-State:X-Gm-Gg:X-Received:X-Received:Received:From:To:Cc: References:In-Reply-To:Subject:Date:Message-ID:MIME-Version: Content-Type:Content-Transfer-Encoding:X-Mailer:Thread-Index: Content-Language:X-Proofpoint-ORIG-GUID:X-Proofpoint-Spam-Info: X-Proofpoint-GUID:X-Proofpoint-Spam-Details-Enc:X-Authority-Analysis: X-Proofpoint-Virus-Version:X-Proofpoint-Spam-Details; bh=mVvldvpyxAhIq+ppmRm7JhIT/5XgL424hW+SaFUm69I=; b=ou4eTVAQpQ3PFqs5k4jmPelWS1WYWg65bLD/3p0uXhsP76m+RapOsVsMCN6NbXn6VROa u4I6uuavDXWzUey1+11syfDcRdIKzCZfIPuLB+BMgyAPgR3f1jHEaw+CoZeHo6HUQXgL8 aGeM+dTn4NoKKX8Hst44j157W13nOOWP6dEqJNGEjHDXEQCcw3CkchWPlQJtHvdnW4eG9 Eh10CrZesRMzJk4D0gZliuCAefhZvW3oxTaxq9oeb3IAPTh33huUS53Zj9Jod3b5pEtRV +JAsFlkN+/ffTklVvDdkeLj5/v47XS1J7V80/G2+vjA3VUE2JAI2kqJonEHVr35Xiig== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=oss.qualcomm.com; spf=pass smtp.mailfrom=oss.qualcomm.com; dkim=pass header.d=qualcomm.com header.i=@qualcomm.com header.a=rsa-sha256 header.s=qcppdkim1 header.b=XJ0kl1r4; dkim=pass header.d=oss.qualcomm.com header.i=@oss.qualcomm.com header.a=rsa-sha256 header.s=google header.b=BnxGa1wt; arc=none smtp.remote-ip=205.220.168.131 Received: from mx0a-0031df01.pphosted.com (mx0a-0031df01.pphosted.com [205.220.168.131]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 55C66606A323 for ; Thu, 12 Nov 2026 18:25:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 55C66606A323 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=oss.qualcomm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=oss.qualcomm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=qualcomm.com header.i=@qualcomm.com header.a=rsa-sha256 header.s=qcppdkim1 header.b=XJ0kl1r4; dkim=pass (2048-bit key) header.d=oss.qualcomm.com header.i=@oss.qualcomm.com header.a=rsa-sha256 header.s=google header.b=BnxGa1wt Received: from pps.filterd (m0279865.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 6ACFZVeZ1736540 for ; Thu, 12 Nov 2026 18:25:19 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=qualcomm.com; h= cc:content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=qcppdkim1; bh= mVvldvpyxAhIq+ppmRm7JhIT/5XgL424hW+SaFUm69I=; b=XJ0kl1r4PmpOxrHL SxXklADFwad1BhX9bdWXs5UdELiENRzSfpxO8XWD37sH/LuLfyKKgUbg3jciLRSD BgaN9g5GTYq3DLvS0kA9SFeruSRvsOjqw+gBJk/4wsMPL6EzGo2RxgSrff6q6vkr qVy1YPYOPEUTmeXg8oCqsOH9M/9UIXUQ/XCQO8oRIIEHLOVyPVh1Rjnrzd89Mfcc 7/FMf14NXnkHf3unZsXRqFNHBKQZBUS8lhs0Ik3h1yn68R2mXQkjmmD6dFYrvJzS VNqpXd86ga17ihZtQEVpaC1XAeqNMj73cpFwOftHhH7vqUcRmQIU/ckRdhr/O+vo ch+gNQ== Received: from mail-dl1-f72.google.com (mail-dl1-f72.google.com [74.125.82.72]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 4hw7nc2trq-1 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NOT) for ; Thu, 12 Nov 2026 18:25:19 +0000 (GMT) Received: by mail-dl1-f72.google.com with SMTP id a92af1059eb24-1b3a348a6dbso11475c88.1 for ; Thu, 12 Nov 2026 10:25:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oss.qualcomm.com; s=google; t=1794507919; x=1795112719; darn=vger.kernel.org; h=content-language:thread-index:content-transfer-encoding :content-type:mime-version:message-id:date:subject:in-reply-to :references:cc:to:from:from:to:cc:subject:date:message-id:reply-to :content-type; bh=mVvldvpyxAhIq+ppmRm7JhIT/5XgL424hW+SaFUm69I=; b=BnxGa1wtpCEa0essbLR0R/MxXeR49k9FVUypTpMGDWBLwGr/JlQlj8eUYCw4Zc+HwV NmACMj8+lbm2h9FXcCyxJQoW3ikoW62or34zPzrEk9CmMWaB7j9aTskSqS55w77LisJ+ 0v9ezu1RN+hP1PHT4B+rzejtNBUXo4Y0g0vb7Widd9rg2HGNO/8vKBY7N70XOm/gXE+l eBA1Q+mxcUT+2Q3C+6Vrz30L4hfnmW+unn/t+NawPipsaU2WLBLYkJS8tEGlqDjdKZXl YgbRrooxzYd+B83oZcStKM394JvgdcHYFwhZajeJPTTHdyrGqIMyKEfJeBDF08y/Rp/6 t1AA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1794507919; x=1795112719; h=content-language:thread-index:content-transfer-encoding :content-type:mime-version:message-id:date:subject:in-reply-to :references:cc:to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to:content-type; bh=mVvldvpyxAhIq+ppmRm7JhIT/5XgL424hW+SaFUm69I=; b=oFTon5l3BKbCj6uupETWibCgbgq+leahDBUUKKAwvMAZI0X2IFlOKTjYi+BTQBd1SG IYortZ91UttkO2rkJ0CktV8vskBAYspZwtuMuoWD3lVQ9m4mTmBpd5UYsGZM1TELnf37 HlYM2IRdhwnbYUqwOMgMYG9bk+X2Suuak/YbX74gArvgzykDJyiQj1nsJxMFl5Ljzh09 6aF//gVIxt8JbgG/62orjZmqlwN3egVwwybGy7C7Zsm9DZU5aTlw+4yraCvdkOrRN6Wr 9YB8uGrdIKEFj3MKx75WMvIHCF8RnNTIxhwyCPWKKb7Mz4C6nYer/HHOTBCfYjZv1QL2 LAxQ== X-Forwarded-Encrypted: i=1; AL+hErG6RBKcuWsrosI9l67KAbmWXfKSq/L5W1C+0YhqajJLKFx9UwcAJ1goc21SRq17CS/rbtLlVotvBkd4ses=@vger.kernel.org X-Gm-Message-State: APuU4Z/VxOWZgfZg4GPL35livsrFfQ4bAmS5O7jHXts+sXslaw0WQIWr XlqJ+Fv8BNdHD2NY1HqffOqDT7lFXqR40ErF5VlQo/Pv3V7YB/PlygTul6FHrldx3i4boShFKME npq668G5Q1DxvKrvdOVVwqptppfAmMmpzC//hoci1OVIWlQDCsA8UTZq7gf5SSfvcxZ8= X-Gm-Gg: AYBFou2vxwBwGKDeQp+Y81RjoHOG6KkhcRUXVgnl/LHzfFI7ko6+e7cGqtQt+vtVaa+ jHC45Y3QySUkSp+1nGR5MisCLn1bFxpleVzQYK/DPzhdCx1/12Lk1Y7CwCD7soaiOOukyUufTux Hb+eEYcKBBywBTyaQDSIbEJIrCWlb29+gO3TZIsxEzYvSk93l5tN4vLOcGnWtsoe25Yg486VyYX pkshLC8lqPe49MBbNXb3LTsuE4Db4Rolh0YMlPUJBDJsr/CZjBXo3WzAeF2ckFbWD+y0hOqARsG yjX8ah4q+LYfJ4caRlZWlipNpXsA+LrFp1Wr6o62rtcGqvJndBmWhB+FDhoo5eRiAJEvQwmNv7s 4X6sgXWWae9UL17lHPhtCUdCrCT90AA23Nx9uZfvQkY17ZuJatY51V00yGe3C08IydL5lqTTaOT TxVFB/WvLc2UUP3mXQsXAeWibrYv/rE1dcfkmqyrD3Kw== X-Received: by 2002:a05:7022:b045:20b0:190:d0d9:3110 with SMTP id a92af1059eb24-1b50319306fmr310201c88.45.1794507918803; Thu, 12 Nov 2026 10:25:18 -0800 (PST) X-Received: by 2002:a05:7022:b045:20b0:190:d0d9:3110 with SMTP id a92af1059eb24-1b50319306fmr310171c88.45.1794507918224; Thu, 12 Nov 2026 10:25:18 -0800 (PST) Received: from QCOMk1gASIiYhG (Global_NAT1.qualcomm.com. [129.46.96.20]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1b503191a43sm614392c88.10.2026.11.12.10.25.16 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 12 Nov 2026 10:25:17 -0800 (PST) From: To: "'Jakub Kicinski'" Cc: , , , , , , References: <20261108075727.2031331-1-subash.a.kasiviswanathan@oss.qualcomm.com> <20261112083311.641a2216@kernel.org> In-Reply-To: <20261112083311.641a2216@kernel.org> Subject: RE: [PATCH net v4] net: qualcomm: rmnet: Update MTU handling during format changes Date: Thu, 12 Nov 2026 11:25:16 -0700 Message-ID: <000001dd72d3$2b06ba30$81142e90$@oss.qualcomm.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 16.0 Thread-Index: AQFkeIhnkKVssrYvBGDElDQ/wtA9kAHp7JEquA1kPmA= Content-Language: en-us X-Proofpoint-ORIG-GUID: jvgD_dMtbzjTOv25FVpr0nD0tl_CQlYB X-Proofpoint-Spam-Info: AW1haW4tMjYxMTEyMDA3MyBTYWx0ZWRfXxpEweNrNCn8M pmQ0Lsi7j5eCn7u8eda7TVBDQS15UM1N1lntW7AqIATI5J6w7llyEzPXZDzCyBYd11y8a5pCu03 QcnjzNacmtL6BBJaRHOuLCsKnGNmINw= X-Proofpoint-GUID: jvgD_dMtbzjTOv25FVpr0nD0tl_CQlYB X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTEyMDA3MyBTYWx0ZWRfX7ofVqO/3Mrd+ 5jleBvjZ/looKvosArOXMTSVaamcQ0XTjqKNdnN3VmwkSQLjqliKd9DrFqjp20dBVU2vL8RL6Yr XPx3Irk079Q32LvD2YguoIJPnbUGJeNFmtBKyEnR591wmt5mmyDIi1E9B7E3FC1uGl5BXJx1/LA k8aF1eZ2X9oByevPyDZSDWN2i69ILAlRNN9Un6Hlk1tn5IF70FutkSMCSt9UZfRMH6QH9UZMaDU U76vAzCDMDEAKqosqOXRSAcNWnXceNA7Ib6HUxdMo0sIkU7qQE1uaKEayu+eNse0GrXDl1ONVpp 5Rk8OwjGaTfqgl0160U864u4ubkst1mMpdhHDZeGp+yHKLMaCFd3x0q2bq/uSyfBXNgFeDIX9GP y8R0EFv8EJzuvbUJ7+cOs214/h3qDtTwFe+G+5UJTZXljF1khh6NbktYN3xrogQa0s1IsmiMKJO ZCyZbb2NyypJ84XSlbw== X-Authority-Analysis: v=2.4 cv=A8b5rKWG c=1 sm=1 tr=0 ts=6af6048f cx=c_pps a=bS7HVuBVfinNPG3f6cIo3Q==:117 a=ouPCqIW2jiPt+lZRy3xVPw==:17 a=kj9zAlcOel0A:10 a=zJRp6_cAMcgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=Um2Pa8k9VHT-vaBCBUpS:22 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=J1Y8HTJGAAAA:8 a=20KFwNOVAAAA:8 a=mXP6K7Sk1cvqIwA962kA:9 a=CjuIK1q_8ugA:10 a=vBUdepa8ALXHeOFLBtFW:22 a=y1Q9-5lHfBjTkpIzbSAN:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-12_02,2026-11-11_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 malwarescore=0 spamscore=0 clxscore=1015 impostorscore=0 priorityscore=1501 lowpriorityscore=0 bulkscore=0 suspectscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2611040001 definitions=main-2611120073 > -----Original Message----- > From: Jakub Kicinski > Sent: Thursday, November 12, 2026 9:33 AM > To: Subash Abhinov Kasiviswanathan > > Cc: sean.tranchetti@oss.qualcomm.com; andrew+netdev@lunn.ch; > davem@davemloft.net; edumazet@kernel.org; pabeni@redhat.com; > netdev@vger.kernel.org; linux-kernel@vger.kernel.org > Subject: Re: [PATCH net v4] net: qualcomm: rmnet: Update MTU handling > during format changes > > On Sat, 7 Nov 2026 23:57:27 -0800 Subash Abhinov Kasiviswanathan wrote: > > rmnet derives the MTU of its devices from the real device MTU minus > > the headroom needed by the egress data format. Several problems exist > > in how this is handled when the data format is set or changed: > > > > - The headroom only accounts for the V4 egress checksum header and > > ignores the V5 one, so devices using V5 checksum offload get an MTU > > that is too large for the real device. > > - rmnet_newlink() sizes the first device from the port's data format > > before the requested IFLA_RMNET_FLAGS have been applied, so the MTU > > does not match the format that ends up being used. > > - A real device MTU smaller than the headroom underflows the unsigned > > subtraction, and a real device with a jumbo MTU makes the creation of > > the first device fail while resizing an existing one clamps it. > > - Existing endpoints are shrunk by writing dev->mtu directly. No MTU > > notifiers run and userspace gets no link notification. The helper > > also returns -1, and changelink flattens every failure into -EINVAL. > > - rmnet_changelink() publishes the new data format before resizing the > > endpoints and reverts it on failure, so the datapath can observe a > > format whose headers do not fit the MTUs. A failed resize can also > > leave some endpoints shrunk, and a mux_id change requested in the > > same call is kept even though the call returned an error. > > > > Fix these by calculating the headroom from the requested data format, > > These should probably be 5 separate fixes in a patch series? Sure, I'll split the patch and send it as a series.