Hi everyone,

During a few tests with madwifi-hal-testing and madwifi-free branches, I've
noticed strange packet loss at the sender.

I'm using iperf to send small (100 bytes long) UDP packets to a unicast
destination (in ad-hoc mode, without any protection) and ask purposefully for
a sending rate of 54 Mbps, just to see how fast the card is able to transmit
in that very environment.

Sometimes these packets get lost before they even have a chance to get sent by
the hardware.  Iperf happily shows it is sending at the requested 54 Mbps,
which is clearly impossible given the mode, the hardware, and given what
iperf at the server side is reporting (more or less 5 Mbps).  There are many
gaps in the iperf sequence numbers, but not in the MAC sequence numbers, as
reported by the monitor trace from a third machine.  In other words, there may
very well be a big gap of iperf sequence numbers in two packets in two
successive MAC frames (according to the MAC sequence numbers).

The strangest thing is that if I enable tx debugging (athdebug +xmit), the
problem disappears at least in a great part and the sender iperf correctly
reports around 5 Mbps, most of the time.

I'm actually becoming familiar with the code, so I looked at ath_hardstart and
ath_tx_start, but can't really figure out what the ATH_DEBUG_XMIT setting
could really change regarding the above problem.

Any idea?

-- 
If you're not living on the edge, you're taking up too much space.

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