[Pkg-utopia-maintainers] Bug#418023: Interfaces managed by NetworkManager have MTU 576

[Sjoerd Simons]

On Fri, Apr 06, 2007 at 12:38:34PM +0200, Michel Dänzer wrote:
> I noticed that all interfaces managed by NetworkManager seem to
> have an MTU of 576 bytes (the minimum). This seems to have a negative
> effect on download speed, or certainly not a positive one. As
> nm_system_get_mtu() in src/backends/NetworkManagerDebian.c returns 0,
> NetworkManager doesn't seem to set the MTU explicitly though, so I'm not
> sure where the default is coming from. I verified that hacking the above
> function to return 1500 results in interfaces managed by NetworkManager
> having an MTU of 1500, with a line like
> 
> Apr  6 12:18:52 thor NetworkManager: <information>^ISetting MTU of
> interface 'sungem' to 1500 in syslog.

  I've personally never seen this behaviour. I've also got a powerbook with a
  sungem network card and network-manager keeps it nicely at mtu 1500. 
  
  When nm_system_get_mtu() returns 0, NM should just leave the mtu at the
  default value.. Looking at the code, if the configured mtu == 0, the set_mtu
  function just exits. So that all seems fine.

  So it seems we have ourselves a little mystery here :) I noticed your running
  kernel 2.6.21-rc5, could you try debian's 2.6.20-1 kernel to see if that
  changes the behaviour ? I know that that works fine on my powerpc with a
  sungem, so it allows us to easily see if the .21-rc kernel is doing strange
  things.

  Sjoerd
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