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Re: ipv6 apt issue



On Tue, Mar 28, 2017 at 1:50 PM, Sven Joachim <svenjoac@gmx.de> wrote:
On 2017-03-28 13:24 -0500, Matt Zagrabelny wrote:

> I'm hitting an IPv6 snafu.
>
> I've got a dual stack host and when doing various apt-y things I attempt to
> connect to:
>
> # apt update
> 0% [Connecting to ftp-chi.osuosl.org (2600:3402:200:227::2)
>
> but it hangs and doesn't seem to complete its connection.

Apparently ftp-chi.osuosl.org works for me, can you reach other IPv6
sites?

Well...

% ping ftp-chi.osuosl.org
PING ftp-chi.osuosl.org(ftp-chi.osuosl.org (2600:3402:200:227::2)) 56 data bytes
^C
--- ftp-chi.osuosl.org ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 3052ms

Not there.


% ping google.com
PING google.com(ja-in-x8b.1e100.net (2607:f8b0:4001:c0c::8b)) 56 data bytes
64 bytes from ja-in-x8b.1e100.net (2607:f8b0:4001:c0c::8b): icmp_seq=1 ttl=41 time=24.4 ms
64 bytes from ja-in-x8b.1e100.net (2607:f8b0:4001:c0c::8b): icmp_seq=2 ttl=41 time=24.0 ms
^C
--- google.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 24.097/24.259/24.421/0.162 ms

Yep.

% ping ftp.us.debian.org
PING ftp.us.debian.org(debian.gtisc.gatech.edu (2610:148:1f10:3::89)) 56 data bytes
64 bytes from debian.gtisc.gatech.edu (2610:148:1f10:3::89): icmp_seq=1 ttl=51 time=30.8 ms
64 bytes from debian.gtisc.gatech.edu (2610:148:1f10:3::89): icmp_seq=2 ttl=51 time=31.0 ms
^C
--- ftp.us.debian.org ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 30.844/30.926/31.009/0.194 ms
 
Yep.

 
> If I look at my sources lists:
>
> % grep http /etc/apt/sources.list.d/*.list | sed -e 's/.*http:\/\///' | uniq
> ftp.us.debian.org/debian/ experimental main
> ftp.us.debian.org/debian/ jessie main contrib non-free
> ftp.us.debian.org/debian/ sid main contrib non-free
> ftp.us.debian.org/debian/ stretch main contrib non-free
>
> I don't have an /etc/apt/sources.list file. To my observation, my host
> should only be connecting ftp.us.debian.org.

That's correct, but there are many machines behind ftp.us.debian.org.

DNS queries return all the possible entries (even for round robin.) The resolver chooses one.
 

> Which has the following v6 addresses:
>
> % dig ftp.us.debian.org aaaa +short
> 2610:148:1f10:3::89
> 2620:0:861:1:208:80:154:15
>
> So, where does the above ftp-chi.osuosl.org (2600:3402:200:227::2) coming
> from?

>From DNS round robin, see https://en.wikipedia.org/wiki/Round_robin_DNS.


The entries in the RR were returned in the above dig command. Those are the only two AAAA records for ftp.us.debian.org. 2600:3402:200:227::2 was not part of the round robin entries.

Here is 10,000 queries for the AAAA records of ftp.us.debian.org:

% for f in `seq 1 10000`; do
dig ftp.us.debian.org aaaa +short
done | sort | uniq
2610:148:1f10:3::89
2620:0:861:1:208:80:154:15

I (always) get the same two addresses.

Looking at the v4 systems for ftp.us.debian.org:

% dig ftp.us.debian.org +short | sort
128.30.2.26
128.61.240.89
208.80.154.15
64.50.233.100
64.50.236.52

% for host in `dig ftp.us.debian.org a +short | sort`; do
echo "$host => $(dig -x $host +short)"
done
128.30.2.26 => mirror-0.csail.mit.edu.
128.61.240.89 => debian.gtisc.gatech.edu.
208.80.154.15 => sodium.wikimedia.org.
64.50.233.100 => ftp-nyc.osuosl.org.
64.50.236.52 => ftp-chi.osuosl.org.

and the v6 systems for ftp.us.debian.org:

% for host in `dig ftp.us.debian.org aaaa +short | sort`; do
echo "$host => $(dig -x $host +short)"
done
2610:148:1f10:3::89 => debian.gtisc.gatech.edu.
2620:0:861:1:208:80:154:15 => sodium.wikimedia.org.

Curiously, when running various apt commands my system does seem to want to connect to:

% dig aaaa ftp-nyc.osuosl.org. +short
2600:3404:200:237::2

% dig aaaa ftp-chi.osuosl.org. +short
2600:3402:200:227::2

Even though those systems are not listed in the round robin set for the AAAA records of ftp.us.debian.org.

I'm puzzled.

-m
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