fl4_icmp_type
fl4->fl4_icmp_type = type;
icmp_type = fl4->fl4_icmp_type;
fl4.fl4_icmp_type = user_icmph.type;
fl4->fl4_icmp_type = rfv->hdr.icmph.type;
fl4.fl4_icmp_type = 0;
fl4->fl4_icmp_type = flkeys->icmp.type;
(fl4->fl4_icmp_type == ICMP_DEST_UNREACH ||
fl4->fl4_icmp_type == ICMP_TIME_EXCEEDED))