没有连接到网络（AF_ROUTE）时没有这样的过程（3）

Question

当我连接到网络时，我可以struct rt_msghdr*向内核发送并接收相应的路由。但是，当我断开网络连接并尝试发送相同的路由消息标头时，套接字失败，并send()显示errno = ESRCH (3) No such process.

通用代码：（在 MacOS 上测试）

int sd = create_socket(AF_ROUTE, IPPROTO_RAW, AF_UNSPEC);

memset(&buffer[0], 0, buffer.size());
struct rt_msghdr* rmh = (struct rt_msghdr*)(&buffer[0]);
rmh->rtm_msglen       = sizeof(struct rt_msghdr) + sizeof(struct sockaddr_in);
rmh->rtm_version      = RTM_VERSION;
rmh->rtm_type         = RTM_GET;
rmh->rtm_addrs        = RTA_DST;
rmh->rtm_pid          = getpid();
rmh->rtm_seq          = 1;
struct sockaddr_in* sa_in = (struct sockaddr_in*)(rmh + 1);
sa_in->sin_len            = sizeof(struct sockaddr_in);
sa_in->sin_family         = AF_INET;

int status;
if ((status = send(sd, rmh, rmh->rtm_msglen, 0) < 0) {
    // process errno
    // * issue happens here when not connected to a network
}

// receive kernel response(s)
// process responses

close(sd);

我确认进程 ID (pid) 在标头中设置正确。netstat -nr未连接到网络时返回默认路由不会出现问题。我无法理解为什么此代码依赖于网络连接。