[Feature][ZXW-65]merged P49 base code

Change-Id: I3e09c0c3d47483bc645f02310380ecb7fc6f4041
diff --git a/ap/os/linux/linux-3.4.x/include/net/tcp.h b/ap/os/linux/linux-3.4.x/include/net/tcp.h
index b5d2d14..a118f21 100755
--- a/ap/os/linux/linux-3.4.x/include/net/tcp.h
+++ b/ap/os/linux/linux-3.4.x/include/net/tcp.h
@@ -1300,6 +1300,8 @@
 {
 	if (sk->sk_send_head == skb_unlinked)
 		sk->sk_send_head = NULL;
+	if (tcp_sk(sk)->highest_sack == skb_unlinked) //CVE-2016-6828
+		tcp_sk(sk)->highest_sack = NULL;
 }
 
 static inline void tcp_init_send_head(struct sock *sk)