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([2001:ee0:4f0e:fb30:933:3ee4:f75:4ee9]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-73dbfae97dasm10558954b3a.162.2025.04.23.07.58.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 23 Apr 2025 07:58:23 -0700 (PDT) Message-ID: <6ed8452b-f370-4443-94ce-f7d65cd51a9e@gmail.com> Date: Wed, 23 Apr 2025 21:58:16 +0700 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] xsk: respect the offsets when copying frags To: Stanislav Fomichev Cc: netdev@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , John Fastabend , Eric Dumazet , Paolo Abeni , Simon Horman , Maciej Fijalkowski , Alexander Lobakin , bpf@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250423101047.31402-1-minhquangbui99@gmail.com> Content-Language: en-US From: Bui Quang Minh In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/23/25 21:41, Stanislav Fomichev wrote: > On 04/23, Bui Quang Minh wrote: >> Add the missing offsets when copying frags in xdp_copy_frags_from_zc(). > Can you please share more about how you've hit this problem? > I don't see the caller of this function (xdp_build_skb_from_zc) > being used at all. > > Alexander, do you have plans to use it? Or should we remove it for now? Hi, I've been playing around to add support for zerocopy XDP socket with multi buffer mergeable buffer in virtio-net (this TODO: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/tree/drivers/net/virtio_net.c#n1312). In that case, I'll have a XDP buff with frags. When we have XDP_PASS return, I need to convert the XDP buff with frags to skb with frags, so I think the helper is quite helpful. I used it and got packet dropped due to checksum error. Debugging the problem, I've found out this issue which makes the skb's frag data incorrect. Thanks, Quang Minh.