[tor-relays] FreeBSD's global IP ID (was: Platform diversity in Tor network)

[Philipp Winter <phw@xxxxxxxxx>]

On Wed, Nov 05, 2014 at 04:04:41AM -0500, grarpamp wrote:
>  173 FreeBSD

FreeBSD still seems to use globally incrementing IP IDs by default.
That's an issue as it leaks fine-grained information about how many
packets a relay's networking stack processes.  (However, nobody
investigated the exact impact on Tor relays so far, which makes this a
FUD-heavy topic.) It looks like approximately 50 out of the 131 FreeBSD
relays I tested (38%) use global IP IDs.

There's a sysctl variable called "net.inet.ip.random_id" which makes a
FreeBSD's IP ID behaviour random.  FreeBSD relay operators should set
this to "1".

Note that this issue was already discussed earlier this year in a thread
called "Lots of tor relays send out sequential IP IDs; please fix
that!".

Cheers,
Philipp
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