[469] in linux-net channel archive
Boing.. 8)
daemon@ATHENA.MIT.EDU (Alan Cox)
Tue Jun 13 07:13:42 1995
From: iialan@iifeak.swan.ac.uk (Alan Cox)
To: linux-net@vger.rutgers.edu
Date: Tue, 13 Jun 1995 10:07:32 +0100 (BST)
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Pete the domainless writes..
> Some of the features I'm planning on putting in are:
>
> - Committed Information Rate: at any time, traffic from specified
> addresses will be guaranteed bandwidth up to the CIR
> - Bursting: any connection can at any time use up any additional
> available bandwidth, as long as it doesn't infringe on someone else's CIR
> usage (the burst ceiling can be set arbitrarily)
> - All parameters configurable on an IP-address or IP-group level, for
> in-bound and/or out-bound traffic
> - Accounting to track all CIR/bursting usage by address
> - Time-sensitive parameters (for instance, CIR could be effective during
> business hours only for some customers, or CIR could be adjusted to
> different levels to allow for special events, etc)
You definitely ought to look at the internet RSVP drafts (RSVP is a
resource reservation protocol). It doesn't really do what you want but
it has similar ideas.
> (packet_size/rate). This seems to work better, but I'm worried about the
> repercussions of having busy-wait code in ip.c. I don't know if it'd be
> permissable to busy-wait with yield() (is there such a kernel call?), or
> maybe have some kind of call-back, where I calculate the required time to
> send, then have the IP process sleep until that time had elapsed (I don't
> know how I'd do this, unfortunately).
You'll screw performance totally. What I think you would need to do is a bit
different something in ip_forward() like
ctrlblock=find_block_for(iph->saddr);
if(ctrlblock) /* Throttled */
{
if(ctrlblock->used+skb->len>ctrlblock->limit)
{
kfree_skb(skb, FREE_READ);
return;
}
if(ctrlblock->used+skb->len>ctrlblock->thresh)
{
skb_queue_tail(&ctrlblock->queue,skb);
schedule_timer(ctrlblock);
return;
}
ctrlblock->used+=skb->len;
}
/* Drop through */
>
ie if the queue is full, drop frames, if its semi full queue them and schedule
a timer (which is what the imaginary schedule_timer function does) else if
it fits send it. Its effectively your busy wait done properly with an
additional check so the queue cannot grow forever
> Am I approaching this right? Is the ip.c code the right place to do this,
> or should I look into a network device driver implementation? I think
> that a device-driver implementation might be easier, but only if it could
> be a device on top of the actual network device driver, so that every
> device driver wouldn't have to be modified. Can Linux even do this? Isn't
> that how the IP-tunnel driver works in 1.3.0?
Its currently a little messy to do (needs to copy the buffer) but works. I'm
working on the messyness bit slowly.
Alan
