Difference between revisions of "User:Llib"

Revision as of 19:18, 17 December 2011

0.25pre [8bf5157] allows users to connect to their backend servers via IPv6

IPv6 use isn't mandatory.

Configure IPv6

Interfaces typically have multiple IPv6 addresses. For help picking the right one, see #Which IPv6 address should be used?.

If IPv6 is known to be working, just complete the following. Otherwise, see #Prerequsites.

Stop all frontends and backends.

Using mythtv-setup go to the General page, enter the address of choice in the Local Backend IP address: and in the Master Backend IP address: fields.

The fields should look like this.

Local Backend IP address:  fe01:a:b:1::123
Master Backend IP address: fe01:a:b:1::123

Note the address isn't enclosed in [brackets] nor is there a trailing percent sign and Scope ID (%eth0.)

Use mythtv-setup to configure any slave backends with their own IPv6 addresses.

Restart the backend(s). Frontends will connect to them via IPv6 as they're restarted.

Which IPv6 address should be used?

Most likely, a Unique Local Address (ULA.) Use a ULA if all access to the backend will be within a LAN.

Details on constructing ULAs can be found in RFC 4193. An easier read is this Wiki.

Hosts must have a Global (e.g. 2001:db8::1) address configured only if it is necessary for a frontend/slave located outside of the Master Backend's LAN to access it.

Site Local (fec0::/10) addresses were deprecated in 2004.

Host (::1) and Link Local (fe80::/64) addresses are not routable and shouldn't be used.

To list currently assigned IPv6 addresses, type ifconfig ethX | grep inet6

inet6 addr: fe80::222:22ff:fe22:2222/64 Scope:Link
inet6 addr: fe01:a:b:1::123/64 Scope:Site
inet6 addr: 2001:db8::123/64 Scope:Global

In the above, the middle address is probably the best choice. It is also probably one that must be assigned manually.

Use the configuration tool provided with the host's distribution to add it.

An entry in /etc/hosts (DHCP, router etc.) is desirable. The following is an example for one host:

192.168.1.123              masterbe.local    masterbe
fe80::222:22ff:fe22:2222   masterbe-ll.local masterbe.ll
fe01:a:b:1::123            masterbe.local    masterbe
2001:db8::123              masterbe.local    masterbe

#Configure IPv6

Prerequsites

Verify that IPv6 is active on each MythTV host.

If ssh, for example, is known to work, a simple test (run from the Master Backend) is:

for HOST in <list all frontend and slave backends here>
do  ssh -6 $HOST ls -l /bin/ls
done

If the test works for all frontends and slave backends, the system is ready for conversion.

If the above fails, see the following section.

#Configure IPv6

What if there's a problem

• Make sure IPv6 hasn't been disabled either system wide or for the interface MythTV will be using:

sysctl -a | grep ipv6. Watch for values set to 1:

net.ipv6.conf.all.disable_ipv6 = 0
net.ipv6.conf.default.disable_ipv6 = 0
net.ipv6.conf.lo.disable_ipv6 = 0
net.ipv6.conf.eth0.disable_ipv6 = 0

• There is currently an issue if:

net.ipv6.bindv6only = 1

This can shutdown MythTV completely, before it is converted to use IPv6 addresses, as IPv4 addresses won't be able to connect to the backend #9820, #9840 and #10165. A fix is being tested off-ticket/off-list.

Any of the above can be controlled by changing files in /etc/sysctl.d in some distributions.

If there are no files with the value(s) that need to be changed, create a file like 60-bindv6only.conf for example, and put net.ipv6.bindv6only = 0 in it.

• Be sure any firewalls have been adjusted to accept the IPv6 addresses being used.

• MySQL connections are currently selected by the information in config.xml and mysql.txt files. Unless a version of MySQL that supports IPv6 is being used, no changes are required.

If there are entries in /etc/hosts (etc.), for both IPv4 and IPv6 addresses that have the same hostname (which is perfectly legal,) make sure the host's preferences pick IPv4 first. /etc/gai.conf may exist and control this.

#Configure IPv6

Tools and sample output

These examples are all from a host with mythbackend running and using IPv6. MySQL is running and using IPv4. Obviously, they can be run on frontends and slave backends.

To make sure mythbackend and mysqld are listening for connections:

sudo netstat -pant | egrep '3306|6543'

When the backend is running, but no frontends are connected, expect:

tcp   0 0  0.0.0.0:3306      0.0.0.0:*     LISTEN      1436/mysqld     
tcp6  0       0 :::6543           :::*     LISTEN      2123/mythbackend

With a frontend connected, expect:

tcp   0 0 0.0.0.0:3306            0.0.0.0:*            LISTEN      1436/mysqld     
tcp   0 0 192.168.1.123:3306      192.168.1.200:33878  ESTABLISHED 1436/mysqld     
...
tcp6  0 0 :::6543                 :::*                 LISTEN      2123/mythbackend
tcp6  0 0 fe01:a:b:1::123:6543 fe01:a:b:1::456:35220   ESTABLISHED 2123/mythbackend
tcp6  0 0 fe01:a:b:1::123:6543 fe01:a:b:1::456:35219   ESTABLISHED 2123/mythbackend

If installed, nmap may help diagnose the reason that a connection fails. For example, a firewall could be blocking access.

nmap -P0 -p 3306,6543 -6 --reason someHostName

The expected response is:

PORT     STATE SERVICE REASON
3306/tcp closed mysql   conn-refused
6543/tcp open   mythtv  syn-ack

Port 3306 fails in this test, as expected, because the MySQL version doesn't support IPv6 (remove the -6 flag above and this will work.)

As always, both mythbackend and mythfrontend can be started with additional logging enabled:

<code>mythbackend --verbose general,network --nodblog --quiet \
    --logpath=/var/log/mythtv --loglevel=debug</code>

A currently running backend's logging can be changed with:

mythbackend --setverbose network --quiet --nodblog

#Configure IPv6

All addresses in this Wiki are fake. No animals were harmed in their creation.