内核keepalive是否自动触发？还是我必须从代​​码中触发它们？

Question

内核提供诸如“ tcp_keepalive_time”，“ tcp_keepalive_intvl”，“ tcp_keepalive_probes”之类的设置...这些探针是否可以自动工作？还是我必须在代码中做一些事情才能真正激活它？

Answer 1

您需要在套接字上启用这些值。例如在C：

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/tcp.h>

void set_tcp_keepalive (int fd)
{
    int val;

    val = 1;
    if (setsockopt (fd, SOL_SOCKET, SO_KEEPALIVE, &val, sizeof (val)) == -1) {
        perror ("setsockopt(SO_KEEPALIVE)");
    }

    val = 60;
    if (setsockopt (fd, IPPROTO_TCP, TCP_KEEPIDLE, &val, sizeof (val)) == -1) {
        perror ("setsockopt(TCP_KEEPIDLE)");
    }

    val = 30;
    if (setsockopt (fd, IPPROTO_TCP, TCP_KEEPINTVL, &val, sizeof (val)) == -1) {
        perror ("setsockopt(TCP_KEEPINTVL)");
    }

    val = 2;
    if (setsockopt (fd, IPPROTO_TCP, TCP_KEEPCNT, &val, sizeof (val)) == -1) {
        perror ("setsockopt(TCP_KEEPCNT)");
    }
}