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[35.245.46.111]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-6740ebe7a62sm5007306d50.1.2026.09.28.09.36.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Sep 2026 09:36:00 -0700 (PDT) Date: Mon, 28 Sep 2026 12:36:00 -0400 From: Willem de Bruijn To: Eric Dumazet , "Michael S . Tsirkin" Cc: Simon Horman , Willem de Bruijn , netdev@vger.kernel.org, edumazet@kernel.org, "David S . Miller" , Jakub Kicinski , Paolo Abeni Message-ID: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit In-Reply-To: <20260928144254.3361044-3-edumazet@kernel.org> References: <20260928144254.3361044-1-edumazet@kernel.org> <20260928144254.3361044-3-edumazet@kernel.org> Subject: Re: [PATCH v2 net 2/2] selftests: net: tun: add test for VLAN-tagged GSO without NEEDS_CSUM Eric Dumazet wrote: > Add a selftest in tun.c verifying that a VLAN-tagged (802.1Q) TCPv4 GSO > packet without VIRTIO_NET_HDR_F_NEEDS_CSUM (both flags = 0 and > flags = VIRTIO_NET_HDR_F_DATA_VALID) is accepted when written to a TAP > device (/dev/net/tun with IFF_TAP | IFF_NO_PI | IFF_VNET_HDR). Thanks. We must not regress users. Even those that do dubious things.. What is the use case for TSO without checksum offload? Do we know of real users? It would not work whenever segmentation is actually needed. So maybe for on-host VM-to-VM communication? But that won't segment with properly configured checksum offload either.