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Thu, 29 Oct 2026 19:33:00 -0700 (PDT) Received: from localhost.localdomain ([58.247.233.220]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8a9eef95f2dsm152216b3a.10.2026.10.29.19.32.54 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Thu, 29 Oct 2026 19:32:59 -0700 (PDT) From: Rongzheng Wang To: netdev@vger.kernel.org Cc: Maciej Fijalkowski , Magnus Karlsson , Jason Xing , Stanislav Fomichev , Jesper Dangaard Brouer , stable@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Rongzheng Wang Subject: [PATCH net v4 0/2] xsk: fix multi-buffer TX software checksum Date: Fri, 30 Oct 2026 10:32:46 +0800 Message-Id: <20261030023248.78802-1-testwrzwrz@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This is v4 of the AF_XDP multi-buffer TX software checksum fix. I found this while testing multi-buffer TX with XDP_UMEM_TX_SW_CSUM: a two-descriptor packet had a bad wire checksum, while a single descriptor was correct. There was no production or syzbot report. Patch 1 moves the software checksum calculation from xsk_skb_metadata() to the point where the last descriptor has been added to the skb. The old code calculated the checksum after the first descriptor, so multi-buffer packets only included the first fragment in the checksum. Patch 2 sends the packet using every descriptor count from 1 through MAX_SKB_FRAGS + 1, and runs the existing metadata and checksum verification for each case. The last case is the copy-mode frame limit documented in af_xdp.rst. Patch 1 is unchanged since v3. The updated selftest passes in a local QEMU run. v4: - exercise every descriptor count up to MAX_SKB_FRAGS + 1 (Maciej) - keep the last descriptor within the packet length (Maciej) - fix the local variable declaration order (Maciej) v3: https://lore.kernel.org/all/20261028025026.11401-1-testwrzwrz@gmail.com/ v2: https://lore.kernel.org/all/20261024141157.59301-1-testwrzwrz@gmail.com/ v1: https://lore.kernel.org/all/20261024091256.17918-1-testwrzwrz@gmail.com/ Rongzheng Wang (2): xsk: defer software checksum until the skb is complete selftests/bpf: cover AF_XDP multi-buffer TX software checksum net/xdp/xsk.c | 23 ++- .../selftests/bpf/prog_tests/xdp_metadata.c | 147 +++++++++++------- 2 files changed, 107 insertions(+), 63 deletions(-) -- 2.39.5 (Apple Git-154)