diff --git a/platform/src/acceptor_kni_v3.cpp b/platform/src/acceptor_kni_v3.cpp
index 512cc71..5a81848 100644
--- a/platform/src/acceptor_kni_v3.cpp
+++ b/platform/src/acceptor_kni_v3.cpp
@@ -284,6 +284,11 @@ struct tcp_option_window_scale{
 	uint8_t shift_count;
 };
 
+struct tcp_option_sack{
+	uint8_t kind;
+	uint8_t length;
+};
+
 static int fake_tcp_handshake(struct tfe_proxy *proxy, struct tcp_restore_info *restore_info)
 {
     char buffer[1500] = {0};
@@ -338,6 +343,32 @@ static int fake_tcp_handshake(struct tfe_proxy *proxy, struct tcp_restore_info *
 		tcp_option_length_s += sizeof(struct tcp_option_window_scale);
 	}
 
+	/*
+	 * SACK option: Kind: 4, Length: 2
+	 * +---------+---------+
+	 * | Kind=4  |Length=2 |
+	 * +---------+---------+
+	 *      1         1
+	 */
+	if (client->sack_perm && server->sack_perm)
+	{
+		// padding
+		memset(tcp_option_buffer_c + tcp_option_length_c, 1, 2);
+		tcp_option_length_c += 2;
+		memset(tcp_option_buffer_s + tcp_option_length_s, 1, 2);
+		tcp_option_length_s += 2;
+
+		struct tcp_option_sack *option_c = (struct tcp_option_sack *)(tcp_option_buffer_c + tcp_option_length_c);
+		option_c->kind = 4;
+		option_c->length = 2;
+		tcp_option_length_c += sizeof(struct tcp_option_sack);
+
+		struct tcp_option_sack *option_s = (struct tcp_option_sack *)(tcp_option_buffer_s + tcp_option_length_s);
+		option_s->kind = 4;
+		option_s->length = 2;
+		tcp_option_length_s += sizeof(struct tcp_option_sack);
+	}
+
 	if (client->addr.ss_family == AF_INET6)
 	{
 		struct sockaddr_in6 *sk_client = (struct sockaddr_in6 *)&client->addr;
@@ -372,7 +403,7 @@ static int fake_tcp_handshake(struct tfe_proxy *proxy, struct tcp_restore_info *
        		buffer, // buffer
        	 	&raw_socket_c->mac_addr, &raw_socket_s->mac_addr, 0, ETH_P_IPV6, // Ether
         	&sk_client->sin6_addr, &sk_server->sin6_addr, 55,  // IPv6
-			port_client, port_server, c_seq, s_seq, TCP_SYN_FLAG, client->window, // TCP Header
+			port_client, port_server, c_seq, s_seq, TCP_ACK_FLAG, client->window, // TCP Header
 			NULL, 0, // TCP Options
 			NULL, 0); // Payload
 		raw_socket_send(raw_socket_c, buffer, length);