taglinefilesource code
RTF_DYNAMIC497net/ipv4/icmp.cip_rt_add((RTF_DYNAMIC | RTF_MODIFIED | RTF_GATEWAY),
RTF_DYNAMIC531net/ipv4/route.cif (flags & RTF_DYNAMIC) 
RTF_DYNAMIC1116net/ipv4/route.crt->rt_flags = RTF_DYNAMIC | RTF_MODIFIED | RTF_HOST | RTF_GATEWAY | RTF_UP;