kernel/drivers/net/ethernet/mscc/ocelot_vcap.c, branch linux-6.18.y

net: mscc: ocelot: treat 802.1ad tagged traffic as 802.1Q-untagged

2024-08-16T08:59:32Z

I was revisiting the topic of 802.1ad treatment in the Ocelot switch [0] and realized that not only is its basic VLAN classification pipeline improper for offloading vlan_protocol 802.1ad bridges, but also improper for offloading regular 802.1Q bridges already. Namely, 802.1ad-tagged traffic should be treated as VLAN-untagged by bridged ports, but this switch treats it as if it was 802.1Q-tagged with the same VID as in the 802.1ad header. This is markedly different to what the Linux bridge expects; see the "other_tpid()" function in tools/testing/selftests/net/forwarding/bridge_vlan_aware.sh. An idea came to me that the VCAP IS1 TCAM is more powerful than I'm giving it credit for, and that it actually overwrites the classified VID before the VLAN Table lookup takes place. In other words, it can be used even to save a packet from being dropped on ingress due to VLAN membership. Add a sophisticated TCAM rule hardcoded into the driver to force the switch to behave like a Linux bridge with vlan_filtering 1 vlan_protocol 802.1Q. Regarding the lifetime of the filter: eventually the bridge will disappear, and vlan_filtering on the port will be restored to 0 for standalone mode. Then the filter will be deleted. [0]: https://lore.kernel.org/netdev/20201009122947.nvhye4hvcha3tljh@skbuf/ Fixes: 7142529f1688 ("net: mscc: ocelot: add VLAN filtering") Signed-off-by: Vladimir Oltean Signed-off-by: David S. Miller

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2022-05-12T23:15:30Z

No conflicts. Build issue in drivers/net/ethernet/sfc/ptp.c 54fccfdd7c66 ("sfc: efx_default_channel_type APIs can be static") 49e6123c65da ("net: sfc: fix memory leak due to ptp channel") https://lore.kernel.org/all/20220510130556.52598fe2@canb.auug.org.au/ Signed-off-by: Jakub Kicinski

net: mscc: ocelot: avoid corrupting hardware counters when moving VCAP filters

2022-05-06T02:15:17Z

Given the following order of operations: (1) we add filter A using tc-flower (2) we send a packet that matches it (3) we read the filter's statistics to find a hit count of 1 (4) we add a second filter B with a higher preference than A, and A moves one position to the right to make room in the TCAM for it (5) we send another packet, and this matches the second filter B (6) we read the filter statistics again. When this happens, the hit count of filter A is 2 and of filter B is 1, despite a single packet having matched each filter. Furthermore, in an alternate history, reading the filter stats a second time between steps (3) and (4) makes the hit count of filter A remain at 1 after step (6), as expected. The reason why this happens has to do with the filter->stats.pkts field, which is written to hardware through the call path below: vcap_entry_set / | \ / | \ / | \ / | \ es0_entry_set is1_entry_set is2_entry_set \ | / \ | / \ | / vcap_data_set(data.counter, ...) The primary role of filter->stats.pkts is to transport the filter hit counters from the last readout all the way from vcap_entry_get() -> ocelot_vcap_filter_stats_update() -> ocelot_cls_flower_stats(). The reason why vcap_entry_set() writes it to hardware is so that the counters (saturating and having a limited bit width) are cleared after each user space readout. The writing of filter->stats.pkts to hardware during the TCAM entry movement procedure is an unintentional consequence of the code design, because the hit count isn't up to date at this point. So at step (4), when filter A is moved by ocelot_vcap_filter_add() to make room for filter B, the hardware hit count is 0 (no packet matched on it in the meantime), but filter->stats.pkts is 1, because the last readout saw the earlier packet. The movement procedure programs the old hit count back to hardware, so this creates the impression to user space that more packets have been matched than they really were. The bug can be seen when running the gact_drop_and_ok_test() from the tc_actions.sh selftest. Fix the issue by reading back the hit count to tmp->stats.pkts before migrating the VCAP filter. Sure, this is a best-effort technique, since the packets that hit the rule between vcap_entry_get() and vcap_entry_set() won't be counted, but at least it allows the counters to be reliably used for selftests where the traffic is under control. The vcap_entry_get() name is a bit unintuitive, but it only reads back the counter portion of the TCAM entry, not the entire entry. The index from which we retrieve the counter is also a bit unintuitive (i - 1 during add, i + 1 during del), but this is the way in which TCAM entry movement works. The "entry index" isn't a stored integer for a TCAM filter, instead it is dynamically computed by ocelot_vcap_block_get_filter_index() based on the entry's position in the &block->rules list. That position (as well as block->count) is automatically updated by ocelot_vcap_filter_add_to_block() on add, and by ocelot_vcap_block_remove_filter() on del. So "i" is the new filter index, and "i - 1" or "i + 1" respectively are the old addresses of that TCAM entry (we only support installing/deleting one filter at a time). Fixes: b596229448dd ("net: mscc: ocelot: Add support for tcam") Signed-off-by: Vladimir Oltean Signed-off-by: Jakub Kicinski

net: mscc: ocelot: fix VCAP IS2 filters matching on both lookups

2022-05-06T02:15:16Z

The VCAP IS2 TCAM is looked up twice per packet, and each filter can be configured to only match during the first, second lookup, or both, or none. The blamed commit wrote the code for making VCAP IS2 filters match only on the given lookup. But right below that code, there was another line that explicitly made the lookup a "don't care", and this is overwriting the lookup we've selected. So the code had no effect. Some of the more noticeable effects of having filters match on both lookups: - in "tc -s filter show dev swp0 ingress", we see each packet matching a VCAP IS2 filter counted twice. This throws off scripts such as tools/testing/selftests/net/forwarding/tc_actions.sh and makes them fail. - a "tc-drop" action offloaded to VCAP IS2 needs a policer as well, because once the CPU port becomes a member of the destination port mask of a packet, nothing removes it, not even a PERMIT/DENY mask mode with a port mask of 0. But VCAP IS2 rules with the POLICE_ENA bit in the action vector can only appear in the first lookup. What happens when a filter matches both lookups is that the action vector is combined, and this makes the POLICE_ENA bit ineffective, since the last lookup in which it has appeared is the second one. In other words, "tc-drop" actions do not drop packets for the CPU port, dropped packets are still seen by software unless there was an FDB entry that directed those packets to some other place different from the CPU. The last bit used to work, because in the initial commit b596229448dd ("net: mscc: ocelot: Add support for tcam"), we were writing the FIRST field of the VCAP IS2 half key with a 1, not with a "don't care". The change to "don't care" was made inadvertently by me in commit c1c3993edb7c ("net: mscc: ocelot: generalize existing code for VCAP"), which I just realized, and which needs a separate fix from this one, for "stable" kernels that lack the commit blamed below. Fixes: 226e9cd82a96 ("net: mscc: ocelot: only install TCAM entries into a specific lookup and PAG") Signed-off-by: Vladimir Oltean Signed-off-by: Jakub Kicinski

net: mscc: ocelot: fix last VCAP IS1/IS2 filter persisting in hardware when deleted

2022-05-06T02:15:15Z

ocelot_vcap_filter_del() works by moving the next filters over the current one, and then deleting the last filter by calling vcap_entry_set() with a del_filter which was specially created by memsetting its memory to zeroes. vcap_entry_set() then programs this to the TCAM and action RAM via the cache registers. The problem is that vcap_entry_set() is a dispatch function which looks at del_filter->block_id. But since del_filter is zeroized memory, the block_id is 0, or otherwise said, VCAP_ES0. So practically, what we do is delete the entry at the same TCAM index from VCAP ES0 instead of IS1 or IS2. The code was not always like this. vcap_entry_set() used to simply be is2_entry_set(), and then, the logic used to work. Restore the functionality by populating the block_id of the del_filter based on the VCAP block of the filter that we're deleting. This makes vcap_entry_set() know what to do. Fixes: 1397a2eb52e2 ("net: mscc: ocelot: create TCAM skeleton from tc filter chains") Signed-off-by: Vladimir Oltean Signed-off-by: Jakub Kicinski

net: mscc: ocelot: don't use magic numbers for OCELOT_POLICER_DISCARD

2022-05-05T03:42:15Z

OCELOT_POLICER_DISCARD helps "kill dropped packets dead" since a PERMIT/DENY mask mode with a port mask of 0 isn't enough to stop the CPU port from receiving packets removed from the forwarding path. The hardcoded initialization done for it in ocelot_vcap_init() is confusing. All we need from it is to have a rate and a burst size of 0. Reuse qos_policer_conf_set() for that purpose. Signed-off-by: Vladimir Oltean Signed-off-by: Jakub Kicinski

net: mscc: ocelot: drop port argument from qos_policer_conf_set

2022-05-05T03:42:15Z

The "port" argument is used for nothing else except printing on the error path. Print errors on behalf of the policer index, which is less confusing anyway. Signed-off-by: Vladimir Oltean Signed-off-by: Jakub Kicinski

net: mscc: ocelot: use list_for_each_entry in ocelot_vcap_filter_add_to_block

2022-05-05T03:42:15Z

Unify the code paths for adding to an empty list and to a list with elements by keeping a "pos" list_head element that indicates where to insert. Initialize "pos" with the list head itself in case list_for_each_entry() doesn't iterate over any element. Note that list_for_each_safe() isn't needed because no element is removed from the list while iterating. Signed-off-by: Vladimir Oltean Signed-off-by: Jakub Kicinski

net: mscc: ocelot: add to tail of empty list in ocelot_vcap_filter_add_to_block

2022-05-05T03:42:14Z

This makes no functional difference but helps in minimizing the delta for a future change. Signed-off-by: Vladimir Oltean Signed-off-by: Jakub Kicinski

net: mscc: ocelot: use list_add_tail in ocelot_vcap_filter_add_to_block()

2022-05-05T03:42:14Z

list_add(..., pos->prev) and list_add_tail(..., pos) are equivalent, use the later form to unify with the case where the list is empty later. Signed-off-by: Vladimir Oltean Signed-off-by: Jakub Kicinski