Understanding and using socket RTT

[Vikash Kumar]

Hi,

I am writing an application in kernel which needs to make decisions based
on RTT of the socket open with another host. So, I was looking at TCP code
to find out how can I get that information from it. Whatever little I have
understood from the code, it looks like tcp_sock->srtt (smoothed round trip
time) is the one I can more or less trust to be the current rtt of the
socket and that this value is in jiffies.

However I got confused due to the comment on its declaration.

u32     srtt;           /* smoothed round trip time << 3        */

Questions I have
1) Does this mean that the value stored in this variable is already left
shifted by 3 or it should be left shifted by 3 before using it ?
Or the value is simply the computed rtt in jiffies and it has no relation
with the left shift operation ?

2) Is the SRTT correct value to look at for rtt or should another metric /
value be used for this?


Regards,
Vikash Kumar
http://VikashKumar.com/
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