[Qemu-devel] Re: [PATCH] tun: orphan an skb on tx

[Herbert Xu]

On Tue, Apr 13, 2010 at 08:31:03PM +0200, Eric Dumazet wrote:
>
> Herbert Acked your patch, so I guess its OK, but I think it can be
> dangerous.

The tun socket accounting was never designed to stop it from
flooding another tun interface.  It's there to stop it from
transmitting above a destination interface TX bandwidth and
cause unnecessary packet drops.  It also limits the total amount
of kernel memory that can be pinned down by a single tun interface.

In this case, all we're doing is shifting the accounting from the
"hardware" queue to the qdisc queue.

So your ability to flood a tun interface is essentially unchanged.

BTW we do the same thing in a number of hardware drivers, as well
as virtio-net.

Cheers,
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