ip_srcroute
if ((opts = ip_srcroute(m)) == NULL &&
*mp = sbcreatecontrol(ip_srcroute(m), sizeof(struct in_addr),
struct mbuf *ip_srcroute(struct mbuf *);
ipopts = (m) ? ip_srcroute(m) : NULL;
inp->inp_options = (m) ? ip_srcroute(m) : NULL;