[Cake] Peeling question

[Jonathan Morton]

I'm not *absolutely* sure that the following is correct - I'm extrapolating
a little.

Except to say that GSO and GRO have zero impact on packet format or size on
the wire (unlike jumbo frames).  It's entirely reasonable for packets sent
with GSO to be received without GRO and vice versa.  Of that I am certain.

Interfaces that don't support GSO, or where it is turned off, will
automatically receive only individual packets.  You can examine this
capability using ethtool, which works fine on wifi interfaces as well as
genuine Ethernet.

I haven't tried ethtool on PPP-anything, but I wouldn't expect to see
support for offloads there.  If for some reason it is there, by all means
turn it off.

Probably the easiest way to observe GSO in action it to run Codel or
fq_codel on the relevant interfaces, without shaping, and put a heavy but
simple TCP load, such as nttcp, through it.  Watch the maxpacket stat in tc
-s qdisc.  Some hardware is more aggressive than others.

- Jonathan Morton
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