Re: [PATCH v6 bpf-next 03/11] tcp: Keep TCP_CLOSE sockets in the reuseport group.

From:   Martin KaFai Lau <redacted>
Date:   Wed, 19 May 2021 23:26:48 -0700

On Mon, May 17, 2021 at 09:22:50AM +0900, Kuniyuki Iwashima wrote:

quoted

+static int reuseport_resurrect(struct sock *sk, struct sock_reuseport *old_reuse,
+			       struct sock_reuseport *reuse, bool bind_inany)
+{
+	if (old_reuse == reuse) {
+		/* If sk was in the same reuseport group, just pop sk out of
+		 * the closed section and push sk into the listening section.
+		 */
+		__reuseport_detach_closed_sock(sk, old_reuse);
+		__reuseport_add_sock(sk, old_reuse);
+		return 0;
+	}
+
+	if (!reuse) {
+		/* In bind()/listen() path, we cannot carry over the eBPF prog
+		 * for the shutdown()ed socket. In setsockopt() path, we should
+		 * not change the eBPF prog of listening sockets by attaching a
+		 * prog to the shutdown()ed socket. Thus, we will allocate a new
+		 * reuseport group and detach sk from the old group.
+		 */

For the reuseport_attach_prog() path, I think it needs to consider
the reuse->num_closed_socks != 0 case also and that should belong
to the resurrect case.  For example, when
sk_unhashed(sk) but sk->sk_reuseport == 0.

In the path, reuseport_resurrect() is called from reuseport_alloc() only
if reuse->num_closed_socks != 0.

But, should this be

	if (sk->sk_state == TCP_CLOSE && reuse->num_closed_socks)

because we need not allocate a new group when we attach a bpf prog to
listeners?

+			/* sk was shutdown()ed before */
+			int err = reuseport_resurrect(sk, reuse, NULL, bind_inany);
+
+			spin_unlock_bh(&reuseport_lock);
+			return err;
+		}
+
 		/* Only set reuse->bind_inany if the bind_inany is true.
 		 * Otherwise, it will overwrite the reuse->bind_inany
 		 * which was set by the bind/hash path.