Ejabberd Configuration

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The OLPC Jabber server at jabber.laptop.org is running ejabberd 1.1.3 with a few extra modules and patches. We're aiming to reduce the odd configuration and patches in favour of a self-contained server component which can be connected up (using XEP-0114) to any unmodified Jabber server to carry out OLPC's activity and buddy indexing/searching (see XMPP Extensions). We're not there yet, so in the mean time if you want to run your own server...

Patches

XOs use an extension called PEP (XEP-0163: Personal Eventing via PubSub) to publish information about OLPC-specific buddy properties (key, colour, etc) and the activities people are taking part in. At the present time, ejabberd's PEP support comes from an external project, which enhances the existing mod_pubsub. It is stored in ejabberd-modules SVN repository.

There is a backport of the work to 1.1.2 in pep/branches/1.1.2. The build system for this seemed pretty weird, it seems to involve lightly modified copies of files copied from the ejabberd source tree, so I turned it into a patch against the ejabberd source itself.

We also have a patch to the shared roster support so that already-connected clients are notified about new accounts which are registered after you connect (this happens a lot in development environments). There's also a patch which you may apply to add some extra features to the ejabberdctl command (see Tips below).

You should apply all of these patches:

• pep.diff
• shared_roster_push.diff
• ejabberdctl-extra.diff

For those running Debian, there are also packages available here.

Configuration

Enable Modules

As well as normal ejabberd configuration (setting your hostname and configuring an admin user), you must enable the following modules in the configuration file:

• mod_caps
• mod_muc
• mod_pubsub
• mod_ctlextra

Note that PEP fails in very cryptic ways if mod_caps is not enabled.

MUC

The default MUC configuration is to assume that conference.yourserver is a valid hostname. This isn't actually important for the XOs, but it must exist from the perspective of the server. You could put it into /etc/hosts for example.

Disable S2S

Currently the XOs don't do a very good job with authorisation because they assume that only other XOs eg from the same school will be connected to the server, and "all see all" is an acceptable policy. For Internet-connected servers, it's best to disable "s2s" (server to server) connections to avoid people from outside connecting in and breaking this assumption. Change:

 {5269, ejabberd_s2s_in,  [{shaper, s2s_shaper},
                           {max_stanza_size, 131072}]},

To:

% {5269, ejabberd_s2s_in,  [{shaper, s2s_shaper},
%                           {max_stanza_size, 131072}]},

As a trivial optimisation, you can also edit the configuration of mod_disco to stop clients calling out to users.jabber.org, which will always fail because s2s is disabled. Change:

  {mod_disco,      [{extra_domains, ["users.jabber.org"]}]},

To:

  {mod_disco,      []},

Raising The Limits

Until a few constants are tweaks (see #5018), the XOs send larger than normal stanzas through the server, which triggers a maximum stanza size limit and can make the jabber server disconnect you eg when inserting an image into a shared document. To fix this, we raise the maximum stanza limit. Change:

{max_stanza_size, 65536},

To:

{max_stanza_size, 524288}

In both the port 5222 and port 5223 ejabberd_c2s listen stanzas.

You can also aid interactivity by allowing the clients to send data at a faster rate by changing:

{access, c2s_shaper, [{none, admin},
                      {normal, all}]}.

To:

{access, c2s_shaper, [{none, admin},
                      {fast, all}]}.

Setting Up Shared Roster

You must perform this step by logging in to ejabberd's web admin interface, or your XOs will never see any buddies.

Log in as your ejabberd's administrative user on the web admin interface at http://yourserver:5280/admin/ and select Virtual Hosts, then your server hostname, then Shared Roster. Add a group called Everybody with the following settings:

• Name: Everybody
• Members: @all@
• Displayed Groups: Everybody

See here for more information.

Tips

Every time you flash an XO, it will generate a new key and hence register a new account on the server. This can lead to quite a lot of accounts floating around on the server, so you get more and more irrelevant users which will never be used again. If you applied the mod_ctlextra patch, you may use ejabberdctl delete-older-users 30 to delete users who havn't logged in for a month, for example. Note that this will probably also delete your admin account because you're unlikely to ever log into it using a Jabber client, but you can re-add it with ejabberdctl register yourserver admin password.