Re: [PATCH net-next 5/5] mptcp: implement delegated actions

@@ -428,6 +429,7 @@ static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 static struct tcp_request_sock_ops subflow_request_sock_ipv6_ops;
 static struct inet_connection_sock_af_ops subflow_v6_specific;
 static struct inet_connection_sock_af_ops subflow_v6m_specific;
+static struct proto tcpv6_prot_override;
 
 static int subflow_v6_conn_request(struct sock *sk, struct sk_buff *skb)
 {

@@ -509,6 +511,14 @@ static void subflow_ulp_fallback(struct sock *sk,
 	icsk->icsk_ulp_ops = NULL;
 	rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
 	tcp_sk(sk)->is_mptcp = 0;
+
+	/* undo override */
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (sk->sk_prot == &tcpv6_prot_override)
+		sk->sk_prot = &tcpv6_prot;
+	else
+#endif
+		sk->sk_prot = &tcp_prot;