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Miller" , "Eric Dumazet" , "Jakub Kicinski" , "Paolo Abeni" , "Simon Horman" , "Neal Cardwell" , "Kuniyuki Iwashima" , "David Ahern" , "Alexei Starovoitov" , "Daniel Borkmann" , "Andrii Nakryiko" , "Martin KaFai Lau" , "Eduard Zingerman" , "Song Liu" , "Yonghong Song" , "KP Singh" , "Stanislav Fomichev" , "Hao Luo" , "Jiri Olsa" , "Shuah Khan" , "Michal Luczaj" , "Stefano Garzarella" , "Cong Wang" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH bpf-next v1 1/3] bpf, sockmap: Fix incorrect copied_seq calculation In-Reply-To: <5a66955891ef8db94b7288bbb296efcc0ac357cf@linux.dev> (Jiayuan Chen's message of "Thu, 20 Nov 2025 02:49:43 +0000") References: <20251117110736.293040-1-jiayuan.chen@linux.dev> <20251117110736.293040-2-jiayuan.chen@linux.dev> <87zf8h6bpd.fsf@cloudflare.com> <5a66955891ef8db94b7288bbb296efcc0ac357cf@linux.dev> Date: Thu, 20 Nov 2025 13:58:23 +0100 Message-ID: <87tsyo6ets.fsf@cloudflare.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Thu, Nov 20, 2025 at 02:49 AM GMT, Jiayuan Chen wrote: > November 20, 2025 at 03:53, "Jakub Sitnicki" wrote: > > [...] >> > +/* The BPF program sets BPF_F_INGRESS on sk_msg to indicate data needs to be >> > + * redirected to the ingress queue of a specified socket. Since BPF_F_INGRESS is >> > + * defined in UAPI so that we can't extend this enum for our internal flags. We >> > + * define some internal flags here while inheriting BPF_F_INGRESS. >> > + */ >> > +enum { >> > + SK_MSG_F_INGRESS = BPF_F_INGRESS, /* (1ULL << 0) */ >> > + /* internal flag */ >> > + SK_MSG_F_INGRESS_SELF = (1ULL << 1) >> > +}; >> > + >> > >> I'm wondering if we need additional state to track this. >> Can we track sk_msg's construted from skb's that were not redirected by >> setting `sk_msg.sk = sk` to indicate that the source socket is us in >> sk_psock_skb_ingress_self()? > > Functionally, that would work. However, in that case, we would have to hold > a reference to sk until the sk_msg is read, which would delay the release of > sk. One concern is that if there is a bug in the read-side application, sk > might never be released. We don't need to grab a reference to sk if we're talking about setting it only in sk_psock_skb_ingress_self(). psock already holds a ref for psock->sk, and we purge psock->ingress_msg queue when destroying the psock before releasing the sock ref in sk_psock_destroy(). While there's nothing wrong with an internal flaag, I'm trying to see if we make things somewhat consistent so as a result sk_msg state is easier to reason about. My thinking here is that we already set sk_msg.sk to source socket in sk_psock_msg_verdict() on sendmsg() path, so we know that this is the purpose of that field. We could mimic this on recvmsg() path.