On 01/11/2017 07:19 PM, Andy Lutomirski wrote:
On Wed, Jan 11, 2017 at 1:09 AM, Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
[...]
Ok. Sleeping over this a bit, how about a general rename into
"prog_tag" for fdinfo and TCA_BPF_TAG resp. TCA_ACT_BPF_TAG for
the netlink attributes, fwiw, it might reduce any assumptions on
this being made? If this would be preferable, I could cook that
patch against -net for renaming it?
That would be fine with me.
I think there are two reasonable approaches to computing the actual tag.
1. Use a standard, modern cryptographic hash. SHA-256, SHA-512,
Blake2b, whatever. SHA-1 is a bad choice in part because it's partly
broken and in part because the implementation in lib/ is a real mess
to use (as you noticed while writing the code).
2. Use whatever algorithm you like but make the tag so short that it's
obviously not collision-free. 48 or 64 bits is probably reasonable.
The intermediate versions are just asking for trouble.
Yeah agree, I've just sent a patch to rework this a bit and it got
also reasonably small for net. Cleanups, if needed, can be done in
net-next once that's pulled into it.
Thanks,
Daniel
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