PF_RT_RETURN_ICMP
snl_add_msg_attr_u16(nw, PF_RT_RETURN_ICMP, r->return_icmp);
{ .type = PF_RT_RETURN_ICMP, .off = _OUT(r.return_icmp), .cb = snl_attr_get_uint16 },
{ .type = PF_RT_RETURN_ICMP, .off = _OUT(return_icmp), .cb = nlattr_get_uint16 },
nlattr_add_u16(nw, PF_RT_RETURN_ICMP, rule->return_icmp);