[Bloat] shaper team forming up

[Jonathan Morton]

On 14 Mar, 2011, at 9:26 pm, Dave Täht wrote:

> Over the weekend, Dan Siemons uncovered a possible bad interaction
> between ECN and the default pfifo_fast qdisc in Linux.
> 
> http://www.coverfire.com/archives/2011/03/13/pfifo_fast-and-ecn/

This seems to be more complicated that it appears.  It looks as though Linux has re-used the LSB of the old TOS field for some "link local" flag which is used by routing.

It's not immediately obvious whether pfifo_fast is using this new interpretation though.  If it isn't, the fix should be to remove the RTO_ONLINK bit from the mask it's using on the tos field.  The other half of the mask correctly excludes the ECN bits from the field.

 - Jonathan