[Bugs] #2148 UNSP: disconnection of network not noticed

[Sugar Labs Bugs]

#2148: disconnection of network not noticed
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    Reporter:  quozl                      |          Owner:  fran                       
        Type:  defect                     |         Status:  accepted                   
    Priority:  Unspecified by Maintainer  |      Milestone:  Unspecified by Release Team
   Component:  Irc                        |        Version:  Unspecified                
    Severity:  Minor                      |       Keywords:                             
Status_field:  Assigned                   |   Distribution:  Unspecified                
   Seeta_dev:                             |  
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Changes (by quozl):

  * status_field:  Needinfo => Assigned


Comment:

 G'day Fran.

 I remember the event clearly, and I had gathered technical information at
 the time.  The Sugar Neighbourhood View showed that the wireless network
 connection was still operational.  The IRC activity did not show
 disconnected or timed out, and never did, although it was left for at
 least half an hour.  ''tcpdump'' on the root console of the laptop showed
 TCP packets for port 6667 were leaving the laptop, but none were
 returning.  All other connections made by the laptop, such as by Browse,
 were working fine.

 The root cause of the event was momentary loss of power to last mile
 equipment, such as an ADSL router, or in my case an HSDPA wireless
 broadband service.  This caused the public IP address to be changed.  This
 caused the existing IRC TCP session on port 6667 to go silent; in that no
 packets were returned to the laptop, not even TCP RST, or ICMP.  This
 configuration and event is not unusual.

 Under these circumstances there is no way for the client to detect a
 problem except by detecting a lack of data from the server.

 Other IRC clients cover this possibility by enforcing a local timeout on
 the connection.  If no data is received, the connection is timed out at
 the local host.  Other activities that use TCP connections, such as
 Browse, have similar logic.

 The situation can be simulated by installing a local ircd, connecting to
 it with the IRC activity, and then sending a SIGSTOP signal to the ircd.
 The connection will behave the same way as I observed, with the addition
 of TCP ACK packets.

 The NetworkManager state on the laptop had not changed, and so any
 solution relating to NetworkManager state is inappropriate and
 unjustified.  It might well be a good idea to do something with state
 notification, but not for solving this problem.

 Hope that helps!

-- 
Ticket URL: <http://bugs.sugarlabs.org/ticket/2148#comment:6>
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