Index: linux-4.1.52/net/ipv4/netfilter/nf_nat_ipsec.c
===================================================================
--- linux-4.1.52.orig/net/ipv4/netfilter/nf_nat_ipsec.c	2018-01-22 14:21:12.665630788 +0800
+++ linux-4.1.52/net/ipv4/netfilter/nf_nat_ipsec.c	2018-01-24 13:53:14.032768520 +0800
@@ -46,8 +46,10 @@
    struct iphdr *iph = ip_hdr(skb);
    struct udphdr *udph = (void *)iph + iph->ihl * 4;
 
+#if 0 //PeterSu
    /* make sure source port is 500 */
    udph->source = htons(IPSEC_PORT);
+#endif
    udph->check = 0;
    
    return NF_ACCEPT;