hsr: Implement more robust duplicate discard for HSR

The HSR duplicate discard algorithm had even more basic problems than the
described for PRP in the previous patch. It relied only on the last
received sequence number to decide if a new frame should be forwarded to
any port. This does not work correctly in any case where frames are
received out of order. The linked bug report claims that this can even
happen with perfectly fine links due to the order in which incoming frames
are processed (which can be unexpected on multi-core systems). The issue
also occasionally shows up in the HSR selftests. The main reason is that
the sequence number that was last forwarded to the master port may have
skipped a number which will in turn never be delivered to the host.

As the problem (we accidentally skip over a sequence number that has not
been received but will be received in the future) is similar to PRP, we can
apply a similar solution. The duplicate discard algorithm based on the
"sparse bitmap" works well for HSR if it is extended to track one bitmap
for each port (A, B, master, interlink). To do this, change the sequence
number blocks to contain a flexible array member as the last member that
can keep chunks for as many bitmaps as we need. This design makes it easy
to reuse the same algorithm in a potential PRP RedBox implementation.

The duplicate discard algorithm functions are modified to deal with
sequence number blocks of different sizes and to correctly use the array of
bitmap chunks. There is a notable speciality for HSR: the port type has a
special port type NONE with value 0. This leads to the number of port types
being 5 instead of actually 4. To save memory, remove the NONE port from
the bitmap (by subtracting 1) when setting up the block buffer and when
accessing the bitmap chunks in the array.

Removing the old algorithm allows us to get rid of a few fields that are
not needed any more: time_out and seq_out for each port. We can also remove
some functions that were only necessary for the previous duplicate discard
algorithm.

The removal of seq_out is possible despite its previous usage in
hsr_register_frame_in: it was used to prevent updates to time_in when
"invalid" sequence numbers were received. With the new duplicate discard
algorithm, time_in has no relevance for the expiry of sequence numbers
anymore. They will expire based on the timestamps in the sequence number
blocks after at most 400ms. There is no need that a node "re-registers" to
"resume communication": after 400ms, all sequence numbers are accepted
again. Also, according to the IEC 62439-3:2021, all nodes are supposed to
send no traffic for 500ms after boot to lead exactly to this expiry of seen
sequence numbers. time_in is still used for pruning nodes from the node
table after no traffic has been received for 60sec. Pruning is only needed
if the node is really gone and has not been sending any traffic for that
period.

seq_out was also used to report the last incoming sequence number from a
node through netlink. I am not sure how useful this value is to userspace
at all, but added getting it from the sequence number blocks. This number
can be outdated after node merging until a new block has been added.

Update the KUnit test for the PRP duplicate discard so that the node
allocation matches and expectations on the removed fields are removed.

Reported-by: Yoann Congal <yoann.congal@smile.fr>
Closes: https://lore.kernel.org/netdev/7d221a07-8358-4c0b-a09c-3b029c052245@smile.fr/
Signed-off-by: Felix Maurer <fmaurer@redhat.com>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/36dc3bc5bdb7e68b70bb5ef86f53ca95a3f35418.1770299429.git.fmaurer@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

0 files changed, 0 insertions, 0 deletions