nbr_find_ip
nbr = nbr_find_ip(iface, p.nexthop.s_addr);
struct nbr *nbr_find_ip(struct iface *, u_int32_t);
if ((nbr_find_ip(iface, ip_hdr.ip_src.s_addr) == NULL) &&
if ((nbr = nbr_find_ip(iface, ip_hdr.ip_src.s_addr))
nbr = nbr_find_ip(iface, src.sin_addr.s_addr);
struct nbr *nbr_find_ip(struct iface *, u_int32_t);