#3593 NORM Trial-3: Mesh channel randomization breaks NM 'mesh-start' tweakable

[Jim Gettys]

Note that this problem has exactly the symptoms seen by Carla, and that
I've seen over last weekend, and Dan has seen. 

I think we should accept this patch.
                                 - Jim


On Wed, 2007-09-19 at 07:58 -0400, Kim Quirk wrote:
> Dan,
> Please move this out to FRS and we can continue some testing and
> discussion as to whether the default should be channel 1. 
> 
> If two laptops under a tree come up about the same time I think it is
> conceivable (maybe it will be the normal case) that they each start a
> mesh on different channels and never see each other. That would be
> bad. As long as we can pick the mesh channel, we can get around this
> for Trial-3. 
> 
> For FRS, we want this scenario to come up working without intervention
> 100% of the time.
> 
> Kim
> 
> 
> On 9/19/07, Dan Williams <dcbw at redhat.com> wrote:
>         On Wed, 2007-09-19 at 06:18 -0400, Walter Bender wrote: 
>         > I would recommend not making the patch; I think I found it
>         confusing
>         > only because I didn't know that random impacted link-local.
>         But do we
>         > still default to channel 1 if no school server is found? 
>         
>         No, I'm not confident that we do.
>         
>         Dan
>         
>         
>         > -walter
>         >
>         > On 9/18/07, Zarro Boogs per Child <bugtracker at laptop.org>
>         wrote:
>         > > #3593: Mesh channel randomization breaks NM 'mesh-start'
>         tweakable 
>         > >
>         -----------------------------+----------------------------------------------
>         > >  Reporter:  dcbw             |       Owner:  jg
>         > >      Type:  defect           |      Status:  new
>         > >  Priority:  normal           |   Milestone:  Trial-3 
>         > > Component:  network manager  |     Version:
>         > >  Keywords:                   |    Verified:  0
>         > >
>         -----------------------------+----------------------------------------------
>         > >  Since we switched back to randomized mesh channels two
>         weeks ago at the 
>         > >  request of the server team, this inadvertently broke
>         expectations about
>         > >  how the /etc/NetworkManager/mesh-start file affects
>         things when using
>         > >  local-only.  In this case, if you do local-only through
>         mesh-start, you 
>         > >  are not guaranteed to come up on channel 1 because the
>         start channel is
>         > >  random.
>         > >
>         > >  Please determine if this is trial-3 material or
>         not.  Obviously, the
>         > >  factors against fixing this for trial-3 are that: 
>         > >
>         > >  1) our target users for trial 3 aren't expected to have
>         to do this
>         > >  2) you can always switch directly to mesh-1 from the UI
>         > >  3) we are in code freeze
>         > >
>         > >  However, the fix is low-risk and does not affect normal
>         codepaths.
>         > >
>         > >  ```
>         > >  Index: src/nm-device-802-11-mesh-olpc.c
>         >
>         >  =================================================================== 
>         > >  --- src/nm-device-802-11-mesh-olpc.c    (revision 2824)
>         > >  +++ src/nm-device-802-11-mesh-olpc.c    (working copy)
>         > >  @@ -459,7 +459,10 @@
>         > >                  self->priv->use_mesh_beacons = TRUE; 
>         > >          }
>         > >
>         > >  -       self->priv->channel = get_random_channel ();
>         > >  +       if (self->priv->default_first_step ==
>         MESH_S4_P2P_MESH)
>         > >  +               self->priv->channel = 1; 
>         > >  +       else
>         > >  +               self->priv->channel = get_random_channel
>         ();
>         > >
>         > >          self->priv->activation_started_ids =
>         g_hash_table_new
>         > >  (g_direct_hash, 
>         > >  g_direct_equal);
>         > >  @@ -1718,7 +1721,10 @@
>         > >                  nm_device_set_active_link (NM_DEVICE
>         (self), FALSE);
>         > >                  if (reinit_state) {
>         > >                          self->priv->step =
>         self->priv->default_first_step; 
>         > >  -                       self->priv->channel =
>         get_random_channel ();
>         > >  +                       if
>         (self->priv->default_first_step ==
>         > >  MESH_S4_P2P_MESH)
>         > >  +                               self->priv->channel = 1; 
>         > >  +                       else
>         > >  +                               self->priv->channel =
>         get_random_channel
>         > >  ();
>         > >                          self->priv->chans_tried = 0; 
>         > >                          self->priv->channel_locked =
>         FALSE;
>         > >                  }
>         > >  @@ -1754,7 +1760,10 @@
>         > >                          self->priv->channel =
>         > >  nm_act_request_get_mesh_channel (req); 
>         > >                          self->priv->channel_locked =
>         TRUE;
>         > >                  } else {
>         > >  -                       self->priv->channel =
>         get_random_channel ();
>         > >  +                       if
>         (self->priv->default_first_step == 
>         > >  MESH_S4_P2P_MESH)
>         > >  +                               self->priv->channel = 1;
>         > >  +                       else
>         > >  +                               self->priv->channel =
>         get_random_channel 
>         > >  ();
>         > >                  }
>         > >          }
>         > >  ```
>         > >
>         > > --
>         > > Ticket URL: <https://dev.laptop.org/ticket/3593>
>         > > One Laptop Per Child <https://dev.laptop.org>
>         > > OLPC bug tracking system
>         > >
>         >
>         >
>         
>         _______________________________________________ 
>         Devel mailing list
>         Devel at lists.laptop.org
>         http://lists.laptop.org/listinfo/devel
> 
> _______________________________________________
> Devel mailing list
> Devel at lists.laptop.org
> http://lists.laptop.org/listinfo/devel
-- 
Jim Gettys
One Laptop Per Child