[tor-relays] BWAUTH weightings too volatile. . ."twitchy"

teor teor2345 at gmail.com
Sat Jun 6 18:12:18 UTC 2015

> Date: Sat, 06 Jun 2015 02:43:09 -0400
> From: starlight.2015q2 at binnacle.cx
>> One reason this vexes is that I
> would like to see how well the relay
> runs with Address Sanitizer active.
> ASAN provides obvious benefits
> w/r/t security, but entails a
> performance trade-off.  With the
> BWauths throwing darts, eyes closed,
> when choosing weighting, it's
> impossible to gauge the performance
> impact of various adjustments.
Good timing!

Tor on x86_64 is currently Address Sanitizer and Undefined Behavior Sanitizer clean. I've just submitted a branch with instructions for building, running, and testing Tor with ASAN and UBSAN.

The following known issues exist:

Two of the tests deliberately invoke undefined / illegal behavior, the instructions provide a blacklist file and an environmental variable to exempt them from ASAN/UBSAN.

Architectures without (x86?) 64-bit assembler use donna C code that left-shifts 1 bits into and past the sign bit of signed integers.
Until https://trac.torproject.org/projects/tor/ticket/13538
is resolved, this particular file can be exempted from UBSAN.

Please let me know how you go - the 0.2.6.x series should also be relatively ASAN and UBSAN clean, as Tor has been tested with them since late 2014.


teor2345 at gmail dot com
pgp 0xABFED1AC

teor at blah dot im
OTR D5BE4EC2 255D7585 F3874930 DB130265 7C9EBBC7

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