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SubjectRe: [PATCH] implement in-kernel keys & keyring management


On Sun, 8 Aug 2004, James Morris wrote:
>
> I'm not disagreeing with the above, but what about performance? Part of
> the reason I suggested Netlink is that it's likely to be more efficient
> to send messages over a socket than to exec a program for each key
> request from the kernel.

Yes. However, I don't see that the kernel really would ask for new keys
very often. Any normal operation is that you have the key already.

> It's difficult to know if performance will actually be an issue without
> understanding the potential workload more. What if many thousands of
> clients are connected to a fileserver? Would calling /sbin/request-key
> for each key request be likely to cause performance problems?

The fileserver generally is the one that _asks_ for keys, not the other
way around.

So the "I don't have a key" case is more of an issue where somebody tries
to mount an encrypted filesystem, and the filesystem says "you don't have
a key".

It's not a thing like "you tried to open a file" that happens thousands of
times a second - that one would get an EACCES if you don't have a key.

It would be more like "the mount binary needs a key to mount this volume,
so let's request that key first".

David, have you actually coded up something that uses the user callback,
maybe you can describe a realistic schenario...

But at least to me, the /sbin/request-key thing is more like loading a
module. You might do it to mount a filesystem or read an encrypted volume,
but you wouldn't do it in the "normal" workload. It's a major event.

Linus
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