Messages in this thread | | | From | Amit Klein <> | Date | Wed, 16 Jun 2021 16:19:54 +0300 | Subject | Re: [PATCH 5.4 175/244] inet: use bigger hash table for IP ID generation |
| |
On Wed, Jun 16, 2021 at 1:19 PM David Laight <David.Laight@aculab.com> wrote:
> > Can someone explain why this is a good idea for a 'normal' system? >
This patch mitigates some techniques that leak internal state due to table hash collisions.
> Why should my desktop system 'waste' 2MB of memory on a massive > hash table that I don't need.
In the patch's defense, it only consumes 2MB when the physical RAM is >= 16GB.
> It might be needed by systems than handle massive numbers > of concurrent connections - but that isn't 'most systems'. > > Surely it would be better to detect when the number of entries > is comparable to the table size and then resize the table.
Security-wise, this approach is not effective. The table size was increased to reduce the likelihood of hash collisions. These start happening when you have ~N^(1/2) elements (for table size N), so you'll need to resize pretty quickly anyway.
| |