Linux上keepalive为什么不起作用2
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发布时间：2023-10-21 13:48
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热心网友
时间：2024-12-04 14:04
/proc/sys/net/ipv4/tcp_keepalive_intvl 当探测没有确认时，重新发送探测的频度。缺省是75秒。
/proc/sys/net/ipv4/tcp_keepalive_probes 在认定连接失效之前，发送多少个TCP的keepalive探测包。缺省值是9。这个值乘以tcp_keepalive_intvl之后决定了，一个连接发送了keepalive之后可以有多少时间没有回应。
tcp_keepalive_time（开启keepalive的闲置时长）tcp_keepalive_intvl（keepalive探测包的发送间隔） 和tcp_keepalive_probes （如果对方不予应答，探测包的发送次数）
There are two ways to configure keepalive parameters inside the kernel via userspace commands:
procfs interface
sysctl interface
We mainly discuss how this is accomplished on the procfs interface because it's the most used, recommended and the easiest to understand. The sysctl interface, particularly regarding the sysctl(2) syscall and not the sysctl(8) tool, is only here for the purpose of background knowledge.
The procfs interface
This interface requires both sysctl and procfs to be built into the kernel, and procfs mounted somewhere in the filesystem (usually on/proc, as in the examples below). You can read the values for the actual parameters by "catting" files in /proc/sys/net/ipv4/directory:
# cat /proc/sys/net/ipv4/tcp_keepalive_time 7200
# cat /proc/sys/net/ipv4/tcp_keepalive_intvl 75
# cat /proc/sys/net/ipv4/tcp_keepalive_probes 9
The first two parameters are expressed in seconds, and the last is the pure number. This means that the keepalive routines wait for two hours (7200 secs) before sending the first keepalive probe, and then resend it every 75 seconds. If no ACK response is received for nine consecutive times, the connection is marked as broken.
Modifying this value is straightforward: you need to write new values into the files. Suppose you decide to configure the host so that keepalive starts after ten minutes of channel inactivity, and then send probes in intervals of one minute. Because of the high instability of our network trunk and the low value of the interval, suppose you also want to increase the number of probes to 20.
Here's how we would change the settings:
# echo 600 > /proc/sys/net/ipv4/tcp_keepalive_time
# echo 60 > /proc/sys/net/ipv4/tcp_keepalive_intvl
# echo 20 > /proc/sys/net/ipv4/tcp_keepalive_probes
To be sure that all succeeds, recheck the files and confirm these new values are showing in place of the old ones.
这样，上面的三个参数配置完毕。
