[Enhancement] 设置合理的keep alive idle及interval，避免额外的电量消耗

[cubarco]

用surfboard连接vmess服务端，用tcpdump抓包可以看到客户端发起的keep alive的心跳：

15:39:12.949262 eth3  In  IP x.x.x.x.32954 > 192.168.1.158.xxxx: Flags [.], ack 2041, win 282, options [nop,nop,TS val 830384092 ecr 318136215], length 0
15:39:12.949386 eth3  Out IP 192.168.1.158.xxxx > x.x.x.x.32954: Flags [.], ack 2506, win 578, options [nop,nop,TS val 318151319 ecr 830293576], length 0

15:39:28.055572 eth3  In  IP x.x.x.x.32954 > 192.168.1.158.xxxx: Flags [.], ack 2041, win 282, options [nop,nop,TS val 830399196 ecr 318151319], length 0
15:39:28.055734 eth3  Out IP 192.168.1.158.xxxx > x.x.x.x.32954: Flags [.], ack 2506, win 578, options [nop,nop,TS val 318166425 ecr 830293576], length 0

golang默认将keep alive的心跳间隔设置在15s，而在xray-core已经给streamsettings增加了两个字段tcpKeepAliveIdle和tcpKeepAliveInterval，用于手动设置keep alive的心跳参数。

surfboard作为移动端应用，建议参考clash for android的做法禁用keepalive，或者配置xray参数，给tcpKeepAliveIdle和tcpKeepAliveInterval设置较长的时间间隔。

XTLS/Xray-core#1166
v2ray/v2ray-core#2564

[getsurfboard]

感谢反馈，将在下个版本跟进

[getsurfboard]

会考虑改成，默认禁用，在override中可以修改成开启

[getsurfboard]

Will be released in 2.18.4

[cubarco]

@getsurfboard
升级2.18.4之后还是有keep-alive心跳。
调试了一下，发现xray有个bug，单独设置"tcpKeepAliveInterval": -1并不会生效，可以改成"tcpKeepAliveIdle": -1来workaround

详见：XTLS/Xray-core#1328

[getsurfboard]

感谢反馈

[getsurfboard]

Will be released in 2.18.5