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Thu, 10 Sep 2026 02:00:38 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 226799B972F; Thu, 10 Sep 2026 11:00:37 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Ihor Solodrai , Andrii Nakryiko , Eduard Zingerman , Alexei Starovoitov , Daniel Borkmann , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis Cc: Andrii Nakryiko , bpf@vger.kernel.org Subject: Re: [PATCH bpf-next 1/4] libbpf: Add bpf_program__add_flags() and bpf_program__clear_flags() In-Reply-To: <261c5e00-31d8-4090-aab4-a633924d336c@linux.dev> References: <20260903092416.223294-1-toke@redhat.com> <261c5e00-31d8-4090-aab4-a633924d336c@linux.dev> X-Clacks-Overhead: GNU Terry Pratchett Date: Thu, 10 Sep 2026 11:00:37 +0200 Message-ID: <87jyoteb0q.fsf@toke.dk> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Ihor Solodrai writes: > On 9/3/26 2:24 AM, Toke H=C3=B8iland-J=C3=B8rgensen wrote: >> When changing BPF program flags, applications often need to just add or >> remove a single flag. The bpf_program__set_flags() function clobbers any >> existing flags value, making this awkward to do non-destructively. > > I think the whole "non-destructively" language in the series is misleadin= g. > > bpf_program__add_flags(prog, BPF_F_XDP_DEV_BOUND_ONLY); > > does exactly the same thing as=20 > > bpf_program__set_flags(prog, bpf_program__flags(prog) | BPF_F_XDP_DEV= _BOUND_ONLY); > > That is: overwriting the prog->prog_flags value. Where is the > non-destructiveness? bpf_program__add_flags(prog, BPF_F_XDP_DEV_BOUND_ONLY) doesn't overwrite any existing flag values, but bpf_program__set_flags(prog, BPF_F_XDP_DEV_BOUND_ONLY) does. In your example you handle this in the caller, but you have to take pains to do that (which, judging from the fixups I had to do earlier, was not something everyone did :)). However, > Let's call this for what it is: a convenience API. I don't mind changing the description - will respin with this change. Thanks for reviewing! -Toke