Re: 2.2.13 ISDN funnies

Alan Cox (alan@lxorguk.ukuu.org.uk)
Thu, 28 Oct 1999 13:24:35 +0100 (BST)


> e.g. a eth0 and a syncppp interface.
> A packet comes from the ethernet, the ethernet devices allocates the skb for
> it (I think with no additional headroom, because it don't know about the
> destination of this packet) then it is send to the network stack, which
> send it to the syncppp device.
> Which function allocates skb with the right headroom ?

Firstly there is a magic 16 byte slop allocated to handle this, secondly the
IP code catches the odd packets it fails to cover and reallocs them to fit
the required driver headroom

> > I really doubt that the problem is caused inside the linux network layers.
> > Otherwise, the same bug would trigger skb_uflow panics with any
> > net_device driver.
>
> I heared similar problems with ppp over ethernet and normal ppp.

There was a sign bug months ago with this that bit Alpha users for one. That
was fixed. Other than that we haven't seen anything. So right now I believe
the bug is in the isdn layers or whatever they call.

It could be a compressor bug, that is the obvious candidate. Do people see it
with all the compression disabled ?

Alan

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