Re: [Airo-linux-gen80211] Retransmission stats

[Douglas S. J. De C. <de...@cs...>]

you are right that the firmware handles retransmissions.  However, part 
of the information returned to the driver after the card is finished 
sending tha packet includes retry information.I have hacked drivers to 
get appropriate information from the aironet cards -- when the card 
finishes sending a packet, the driver can ask the card for information 
such as # of retransmits, etc.

but I remember being skeptical about the results, as they didn't make 
sense according to my experiments.

Probably the best thing is to have a 3rd computer sniffing...

I have attached a source file from a version of the driver I was using, 
see line 2215.  That's where the driver handles the TXC (transmission 
complete) interrupt, and reads a few statistics from the card, notable 
long & short retries.  I think long retries are resending the whole 
packets, and short retries are resending RTS.  I found that even with 
RTS/CTS disabled the cards would have short retries.

This file uses some other includes that are specific to my project 
(http://pdos.lcs.mit.edu/grid, http://pdos.lcs.mit.edu/roofnet), but it 
gives you an idea of how to get the data.

hope it helps.

d