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Received: from sslproxy02.your-server.de ([78.47.166.47]) by www62.your-server.de with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.96.2) (envelope-from ) id 1vg1iq-0002ns-2O; Wed, 14 Jan 2026 15:19:44 +0100 Received: from localhost ([127.0.0.1]) by sslproxy02.your-server.de with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1vg1ip-000D2A-2T; Wed, 14 Jan 2026 15:19:43 +0100 Message-ID: <56ff9000-34e9-45ae-843e-78baab79e208@iogearbox.net> Date: Wed, 14 Jan 2026 15:19:42 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] bpftool: Add 'prepend' option for tcx attach to insert at chain start To: gyutae.opensource@navercorp.com, Quentin Monnet , bpf@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Alexei Starovoitov , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Gyutae Bae , Siwan Kim , Daniel Xu , Jiayuan Chen , Tao Chen , Kumar Kartikeya Dwivedi References: <43c23468-530b-45f3-af22-f03484e5148c@kernel.org> <20260112034516.22723-1-gyutae.opensource@navercorp.com> Content-Language: en-US From: Daniel Borkmann Autocrypt: addr=daniel@iogearbox.net; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Clear (ClamAV 1.4.3/27880/Wed Jan 14 08:26:22 2026) On 1/12/26 4:45 AM, gyutae.opensource@navercorp.com wrote: > From: Gyutae Bae > > Add support for the 'prepend' option when attaching tcx_ingress and > tcx_egress programs. This option allows inserting a BPF program at > the beginning of the TCX chain instead of appending it at the end. > > The implementation uses BPF_F_BEFORE flag which automatically inserts > the program at the beginning of the chain when no relative reference > is specified. > > This change includes: > - Modify do_attach_tcx() to support prepend insertion using BPF_F_BEFORE > - Update documentation to describe the new 'prepend' option > - Add bash completion support for the 'prepend' option on tcx attach types > - Add example usage in the documentation > - Add validation to reject 'overwrite' for non-XDP attach types > > The 'prepend' option is only valid for tcx_ingress and tcx_egress attach > types. For XDP attach types, the existing 'overwrite' option remains > available. > > Example usage: > # bpftool net attach tcx_ingress name tc_prog dev lo prepend > > This feature is useful when the order of program execution in the TCX > chain matters and users need to ensure certain programs run first. Acked-by: Daniel Borkmann