net, bpf: Introduces a new ebpf delay connect flag

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I7LE1H

---------------------------------------------------

The bpf_defer_connect bit is added for inet_sock to indicate
whether the current socket is changed to the bpf program to
delay link establishment.
Signed-off-by: Nzhang-mingyi66 <zhangmingyi5@huawei.com>

include/net/inet_sock.h

@@ -238,10 +238,11 @@ struct inet_sock {
 				nodefrag:1;
 	__u8			bind_address_no_port:1,
 				recverr_rfc4884:1,
-				defer_connect:1; /* Indicates that fastopen_connect is set
+				defer_connect:1, /* Indicates that fastopen_connect is set
 						  * and cookie exists so we defer connect
 						  * until first data frame is written
 						  */
+				bpf_defer_connect:1;
 	__u8			rcv_tos;
 	__u8			convert_csum;
 	int			uc_index;

net/ipv4/tcp.c

@@ -582,7 +582,8 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
 
 		if (urg_data & TCP_URG_VALID)
 			mask |= EPOLLPRI;
-	} else if (state == TCP_SYN_SENT && inet_sk(sk)->defer_connect) {
+	} else if (state == TCP_SYN_SENT &&
+			(inet_sk(sk)->defer_connect || inet_sk(sk)->bpf_defer_connect)) {
 		/* Active TCP fastopen socket with defer_connect
 		 * Return EPOLLOUT so application can call write()
 		 * in order for kernel to generate SYN+data