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Re: Overflow bugs in m_get &c.
mouse%Rodents-Montreal.ORG@localhost (Mouse) writes:
>> We've had a class of bugs that works like this:
>> [...network drivers assuming MCLBYTES can hold any packet...]
>This gets especially bad with jumbograms, I wokuld imagine. Or are
>jumbogram-capable drivers smarter about this because they got bit
>already by getting sloppy?
Drivers that support jumbograms are well aware of this. You can't
just pump out a big frame and expect it to work :)
For input, the drivers allocate private DMA buffers and attach them
to mbufs as external storage. Or for small packets, they just copy
the data to a regular mbuf.
For output, you usually have a chain of mbufs and these are either
used for a scatter/gather DMA engine or copied to linear DMA buffers.
Jumbograms also rarely make sense. Modern systems have a couple of
offloading engines that are more flexible and efficient. Not that we
actually support these.
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