RE: [PATCH v01] net/af_packet: add rollover and defrag options

[Gur Stavi <gur.stavi@huawei.com>]

> On Tue, 29 Oct 2024 15:48:05 +0200
> Gur Stavi <gur.stavi@huawei.com> wrote:
> 
> > net_af_packet PMD multi "queue" support relies on Linux FANOUT
> capability.
> > Linux FANOUT is a SW based load balancer that is similar to HW RSS
> which is
> > more common for DPDK PMDs. Instead of multiple HW descriptor queues, AF
> PACKET
> > uses multiple sockets.
> > HW RSS will typically drop a packet if its selected RX queue is empty.
> However,
> > Linux FANOUT, as a SW load balancer, can be configured to avoid this
> packet
> > drop by rolling over to the next socket.
> > This rollover functionality was ALWAYS enabled in net_af_packet. It is
> > surrounded by ifdef, but only to allow compilation on ancient Linux
> versions
> > that did not have it.
> >
> > Since DPDK applications are usually designed for HW based PMDs, this
> rollover
> > functionality, which the developers are likely unaware of, could be
> confusing.
> >
> > Another option that is part of Linux FANOUT is DEFRAG that instructs
> Linux to
> > compose complete IP packet out of fragments before delivering it to the
> PACKET
> > socket. Again, this behavior typically does not exist for HW based PMDs
> and may
> > confuse users.
> >
> > This patch adds 2 options to control these features:
> > rollover=[0|1],defrag=[0|1]
> > For backward compatibility both features are enabled by default even
> though most
> > users will probably want both of them disabled.
> >
> > Signed-off-by: Gur Stavi <gur.stavi@huawei.com>
> > ---
> 
> Makes sense to expose kernel options. But have all combinations been
> tested?

I tested the command line parsing of the new options.
I tested that the PMD is initialized successfully with all combinations.
I did not test if Linux actually behaves according to the man page. I did
not test traffic at all.