TCP mode support probe and interval parameters configuration.

[angelyouyou]

Currently, only the keepalive function is enabled or disabled, but the probe and interval parameters are not supported.
In many Internet scenarios, the default interval of keepalive in the Linux kernel is too large, which will cause firewalls and other devices to disconnect.

#define TCP_KEEPALIVE_PROBES 9 /* Max of 9 keepalive probes /
#define TCP_KEEPALIVE_INTVL (75HZ)