[lxc-users] Intermittent connection issues

[Antonio Tapiador del Dujo]

I am experiencing connection issues inside a LXC that are driving me mad.
They are intermitent. They appear during some time, and they suddenly
disappear.
Scenario

A lxc inside a host. Both are running Debian GNU/Linux 8.3 In the lxc there
is an installation of Piwik (open source PHP software for stats, with
apache, mysql) and an ssh server. The lxc apache is reachable through an
nginx proxy in the host

The lxc config:

lxc.tty = 6
lxc.pts = 1024
lxc.rootfs = /var/lib/lxc/hammond/rootfs
lxc.cgroup.devices.deny = a
# /dev/null and zero
lxc.cgroup.devices.allow = c 1:3 rwm
lxc.cgroup.devices.allow = c 1:5 rwm
# consoles
lxc.cgroup.devices.allow = c 5:1 rwm
lxc.cgroup.devices.allow = c 5:0 rwm
lxc.cgroup.devices.allow = c 4:0 rwm
lxc.cgroup.devices.allow = c 4:1 rwm
# /dev/{,u}random
lxc.cgroup.devices.allow = c 1:9 rwm
lxc.cgroup.devices.allow = c 1:8 rwm
lxc.cgroup.devices.allow = c 136:* rwm
lxc.cgroup.devices.allow = c 5:2 rwm
# rtc
lxc.cgroup.devices.allow = c 254:0 rwm

# mounts point
lxc.mount.entry=proc /var/lib/lxc/hammond/rootfs/proc proc
nodev,noexec,nosuid 0 0
lxc.mount.entry=devpts /var/lib/lxc/hammond/rootfs/dev/pts devpts defaults 0 0
lxc.mount.entry=sysfs /var/lib/lxc/hammond/rootfs/sys sysfs defaults  0 0

# networking
lxc.utsname = hammond
lxc.network.type = veth
#lxc.network.macvlan.mode = private
lxc.network.flags = up
lxc.network.link = br-hammond
lxc.network.ipv4 = 192.168.100.2/24
lxc.network.ipv4.gateway = 192.168.100.1
lxc.network.hwaddr = 00:1E:10:C1:6B:C9

lxc.start.auto = 1

# http://serverfault.com/questions/658052/systemd-journal-in-debian-jessie-lxc-container-eats-100-cpu
lxc.autodev = 1
lxc.kmsg = 0

Issues:1. Cannot connect to local database

Suddenly, Piwik reports:

SQLSTATE[HY000] [2003] Can't connect to MySQL server on '127.0.0.1' (111)

The database is running, of course.

   - If I telnet from inside the lxc (127.0.0.1:3306), I can connect to the
   database
   - If I telnet the apache from inside the lxc (127.0.0.1:80), Piwik works
   fine. It connects to the database, renders the page as usual and doesn't
   report any error.
   - If I telnet the apache from the host (192.168.100.2:80), Piwik reports
   the database error.

2. SSH freezes

I am tunneling the ssh connection to the lxc using ProxyCommand

ProxyCommand ssh -q host nc -q0 192.168.100.2 22

After the ssh negotiation phase, the connection freezes. If I type keys,
they don't show up in the console. Finally, the connection timeouts with

packet_write_wait: Connection to UNKNOWN: Broken pipe

I have sniffed the packets with tcpdump and ssh key exchanges goes fine.
Then, the traffic stops after 0.5 seconds

I think this is a bug in last Debian kernel updates. It used to work fine,
but I am experiencing these problems since a few weeks ago. As I mention,
they are intermittent. Suddenly, everything goes fine.

Suggestions on how to investigate further are welcomed
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.linuxcontainers.org/pipermail/lxc-users/attachments/20160126/a4d326ea/attachment.html>