[LARTC] Weird rate in HTB

[Andy Furniss]

Daniel Harold L. wrote:
> Dear all,
> 
> First, sorry for my bad English ..
> 
> To night one of my client is the victim of UDP attack from internet. It's tons 
> of UDP packets from internet with destination to port 80. But when I look at 
> class of that victim client, the actual class rate is over than configured 
> rate class.  
> 
> Below is my screen capture. You can see at class 1:913 which have actual rate 
> 105136bit while configured with ceil at 96000bit. Also it's parent class 
> (1:91) which have actual rate 107680bit while configured with ceil at 
> 96000bit.
> 
> Is this normal? Or I have miss something in my script. Sometimes ago I found 
> this situation but I forgot to capture the screen and the traffic is UDP too 
> (maybe from torrent-like client)

Yes it is normal!

The rate tables that tc use normally have an 8 byte steps, so it is 
possible for up to a 56bit/s error per packet and you have 300 pps.

There was a small patch submitted for tc to make the error fall on the 
underrate rather than overrate side, but I think it got lost in the 
middle of the long ATM overhead patch thread on netdev.

Andy.