[tor-dev] Connections failed to default obfs4 bridges

Rob Jansen rob.g.jansen at nrl.navy.mil
Wed Mar 28 18:14:10 UTC 2018

> On Mar 28, 2018, at 12:23 PM, David Fifield <david at bamsoftware.com> wrote:
> On Wed, Mar 28, 2018 at 10:57:13AM -0400, Rob Jansen wrote:
>> In a recent connectivity test to the default obfs4 bridges [0], we found that we are unable to connect to 10 or so of them (from open networks, i.e., no local filtering).
>> Is this a feature, like some of them only respond to users in certain parts of the world? Or is this a bug, like the default list of bridges refers to old bridges that are no longer available? Or am I misunderstanding functionality here?
> Do you mean 10 distinct IP addresses, or 10 ports on a few IP addresses?
> Not all the IP addresses in the list are distinct.

Turns out this was 10 ports on the same IP address. And we did the measurements back in December, so they are already a bit dated.

> Even while Lynn Tsai, Qi Zhong, and I were closely monitoring default
> bridge reachability, a lot of the default bridges were often offline,
> because of reboots, iptables problems, etc. See for example the "Orbot
> bridges" strip of Figure 5.2 here; the gray and red areas that precede
> blocking are where the bridge was simply offline:
> https://www.bamsoftware.com/papers/thesis/fifield-thesis.pdf#page=43
> We have a lot of past measurements of default bridges. The rows with
> site="eecs-login" are from the U.S.
> https://www.bamsoftware.com/proxy-probe/ (download the repo, not
> probe.csv.gz, which isn't as recent)

Ahh, this is great, thanks for sending!

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