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Message-ID: References: <20261005154533.4147685-1-kuniyu@google.com> <20261005154533.4147685-3-kuniyu@google.com> 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-Disposition: inline In-Reply-To: <20261005154533.4147685-3-kuniyu@google.com> On 10/05, Kuniyuki Iwashima wrote: > The legacy SOCK_OPS guards some hooks with a per-socket flag, > tp->bpf_sock_ops_cb_flags. > > In contrast, bpf_tcp_ops was initially designed without per-socket > flags so that users can simply define only the callbacks they need. > > However, it turned out that even attaching a bpf_tcp_ops with a NULL > callback incurs measurable overhead in the fast path. [0] > > We could reuse tp->bpf_sock_ops_cb_flags, but it is u8 and has only > 1 bit left for a new opt-in callback, while not all of the 7 existing > opt-in hooks are in the fast path and really need a flag guard. > > Moreover, tp->bpf_sock_ops_cb_flags has two bpf helper functions to > update it, both of which require sock_owned_by_me(sk): > > * bpf_sock_ops_cb_flags_set() > * bpf_setsockopt(TCP_BPF_SOCK_OPS_CB_FLAGS) Can we return -EINVAL from these when used with sock_ops? If we keep one flag we can presumably put both tcp_call_bpf_Xarg and bpf_tcp_ops_call under the same if conditional?