Ticket #6299 (closed defect: fixed)
presence service should disable salut in the presence of school servers on mesh
|Reported by:||robot101||Owned by:||Collabora|
|Keywords:||release?||Cc:||jg, dwmw2, mbletsas, dcbw, cjb, mstone, wad, dgilmore, Collabora|
|Deployments affected:||Blocked By:|
Currently the algorithm in presence service starts Salut automatically when avahi is available, and then when we get an IPv4 address from Network Manager, we start trying to connect with gabble in parallel, and disable salut if we succeed at connecting with gabble.
Salut makes mDNS queries to discover presence records when it;s running. Combined with flood-fill multicast, this has the result that the network is hugely clogged with mDNS resolution traffic, and actively prohibits other users from DHCPing, registering, or connecting to the XMPP server, causing them to in turn stay on mDNS, exacerbating the problem further still.
However, given that DHCP on the XOs is modified to unicast to a well known "anycast" MAC address on the school server, we can look for this MAC address to determine that a school server is present, and we should then shut down salut to stop *any* mDNS activity.
dwmw2 can confirm a way to determine that this MAC address is reachable, but it seems to be something along the lines of try and send traffic to it somehow, then inspect the mesh routing table to see if it appeared in there
The algorithm would then look more like:
stop salut if we're on mesh, and the school server is reachable by anycast:
try to connect with gabble sleep
connect with salut while 1:
try to connect with gabble if we succeed:
We should run this algorithm every time we arrive on a new network, and when we resume from sleep.
We need to decide three timeouts:
1) start of day: how long do we look for the school server anycast MAC before we decide we're OK to enable salut? 2) kids wander off/server dies: how long after we're disconnected from the school server before we decide its OK to enable to salut? 3) kids wander back/server resurrected: how often do we look for the school server anycast address when we're using salut, to decide we should switch salut off and wait for gabble to work instead?