Fedora 20 XO-4 ad-hoc partitioning, failure of IBSS coalesce

James Cameron quozl at laptop.org
Fri Sep 26 20:13:24 EDT 2014

On Tue, Sep 23, 2014 at 12:24:12PM +1000, Niraj Nakrani wrote:
> - Group of 3 laptop all auto connected to adhoc channel 1, but looks
> like they all have created a separate individual network. Also
> observed Joining of all into same ad-hoc network in channel 1, 6 and
> 11 are not working. In the neighborhood view I cant see the other
> laptop even though all are auto connected to same adhoc channel.

When this is happening, wireshark shows ad-hoc beacons have;

- same BSS ID,
- two different sequence number ranges,
- two different timestamp ranges,
- two different HT capabilities and HT information fields,

The wireless firmware should coalesce separate networks if they are
compatible.  The different HT capabilities and information fields are
preventing this.

Since we haven't changed kernel, this is either Network Manager or

On Fedora 18, the card is commanded to scan for the SSID before it is
commanded to join the IBSS, and the BSS ID of an existing network may
be used in the join.

On Fedora 20, the card is only commanded to join an IBSS by SSID,
there is no command to scan immediately prior, so the join command
does not have the existing BSS ID.  This contributes to the
partitioning; assuming also a bug in kernel or firmware that fails to
set HT capabilities and information fields reliably.

Has anyone reproduced this on Sugar 0.102 with Fedora 18?

James Cameron

More information about the Devel mailing list