Re: [Tails-dev] Debian 9: Build fails consistently, name re…

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Autore: Arnaud
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To: The Tails public development discussion list
Oggetto: Re: [Tails-dev] Debian 9: Build fails consistently, name resolution fails sooner or later
Hi all,

thanks for your support !

I updated to Tails 3.0-beta2, destroyed the VM, started again, failed
again !

My build config is very 'vanilla', I didn't touch anything. So it means
that the build happens within the VM, with apt-cacher-ng enabled. The VM
has the default settings: 512M of RAM, and enough storage (I didn't find
where that one is defined btw).

However, after a lot of investigation (mostly in the wrong direction),
I'm pretty sure to know what's wrong. It's not Tails, it's not the VM,
it's not my config. It seems to be the network here in Vietnam.

So yep, I'm living in Vietnam. Overall, the network is not that bad
here, however they have a problem with the underwater cable AAG (Asia
America Gateway). Basically, from time to time the AAG stops working,
and the AAG is the main cable that connects Vietnam to the rest of the
world. What happens then is a bit unclear to me, to say the least.

Well, from a user point of view, what happens is very clear. The web
becomes a bit unreliable. Sometimes, websites are very slow to load, or
become completely unavailable for a few minutes. Amazingly, google
searches are still fast (more on that later). I've seen `apt-get update`
on my machine starting very fast, then slowing down and down, then
stalled. So I opened my `sources.list`, got rid of the
`httpredir.debian.org` url, replaced by `debian.xtdv.net` (the only
Vietnamese Debian mirror that I know) to ensure my traffic remains in
Vietnam, and now it works like a charm.

From a technical point of view, what happens is quite unclear. I played
a bit with `nmap --traceroute --script traceroute-geolocation`, and this
is a great tool ! I can see that requests to
time-based.snapshots.deb.tails.boum.org go a long way through Europe.
Requests to www.vagrantup.com go through Japan, which seems a bit more
direct. Amazingly, requests to google go directly from Vietnam to the
States. Which explains why they are still fast when everything else is
slow, and which makes me wonder if google has private undersea cables.

Anyway, I'm no expert, and I'm not sure how to interpret these results.
I have no idea how it will look like when I run the same traceroute
tomorrow. So let's get back to Tails.

The build process involves downloading a lot of data. Most of it from
Tails server, and I think the problem here is just that the connectivity
in Vietnam right now is way too bad to handle that. Somehow it always
fails sooner or later, it timeouts or something.

From my understanding, I can change the Debian mirror used for
provisioning the VM. But when it comes to build the Tails iso, I have no
choice but to download the packages from the Tails mirror, right ? Same
goes for TorBrowser ?

Right now I'm working on tweaking the build system, and adding retries
here and there, so that the build keeps going and doesn't give up so
easily. I think that `apt-cacher-ng` should help me to mitigate the
problem, but up to now I destroyed the VM too often to take advantage of
it ;)

I'll keep trying and let you know how it goes.

Cheers !

----

If you were interested in all this conversation (a bit off-topic), you
might find the following links interesting:

http://www.submarinecablemap.com

https://www.citypassguide.com/en/travel/ho-chi-minh-city/daily/news/neverending-story-vietnam-and-the-undersea-internet-cable-ruptures