Fixing "Slipping in the window" before 4.11-release

[Lars Erik Gullerud]

On Thu, 6 Jan 2005, Mike Silbersack wrote:

> Don convinced me of the same thing, using similar reasoning.
>
> I think that you're right that "there could be times when ignoring SYNs might 
> be fine."  I think that we track how long a connection has been idle; my plan 
> is to only respond to SYNs if the connection has been idle for more than 30 
> seconds or more.  That should ensure that we handle the client crashing case 
> properly (even if the client reboots instantly, it'll keep retransmitting 
> SYNs for more than 30 sceonds), but also ensure that we do not let a forged 
> SYN flood prod us into sending unnecessary ACKs. I'll try to get this coded 
> up this weekend.

OK, time to chime in here - if you read Don's comments, the particular 
example he chose to use was BGP, where one end crashes and tries to bring 
up a new session. BGP stability in particular was also one of the main 
reasons this particular draft received so much attention recently. Now, 
I'm a network engineer, not a developer. And if there is one thing I 
would hate if a BGP process were to crash, it is for the reestablishment 
of this connection to be delayed for up to 30 seconds because the other 
end thinks it is a good idea to ignore these SYNs. So please - don't.

Why not stick to the procedures outlined in the draft as they are? The 
acronym "KISS" also comes to mind here, I don't really see that sending a 
few extra ACKs in this situation is a particularly relevant problem, I 
have problems seeing how this would realistically be used as a vector for 
a DoS or other nastiness.

/leg