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This new set type allows for intervals in concatenated fields, which are expressed in the usual way, that is, simple byte concatenation with padding to 32 bits for single fields, and given as ranges by specifying start and end elements containing, each, the full concatenation of start and end values for the single fields. Ranges are expanded to composing netmasks, for each field: these are inserted as rules in per-field lookup tables. Bits to be classified are divided in 4-bit groups, and for each group, the lookup table contains 4^2 buckets, representing all the possible values of a bit group. This approach was inspired by the Grouper algorithm: http://www.cse.usf.edu/~ligatti/projects/grouper/ Matching is performed by a sequence of AND operations between bucket values, with buckets selected according to the value of packet bits, for each group. The result of this sequence tells us which rules matched for a given field. In order to concatenate several ranged fields, per-field rules are mapped using mapping arrays, one per field, that specify which rules should be considered while matching the next field. The mapping array for the last field contains a reference to the element originally inserted. The notes in nft_set_pipapo.c cover the algorithm in deeper detail. A pure hash-based approach is of no use here, as ranges need to be classified. An implementation based on "proxying" the existing red-black tree set type, creating a tree for each field, was considered, but deemed impractical due to the fact that elements would need to be shared between trees, at least as long as we want to keep UAPI changes to a minimum. A stand-alone implementation of this algorithm is available at: https://pipapo.lameexcu.se together with notes about possible future optimisations (in pipapo.c). This algorithm was designed with data locality in mind, and can be highly optimised for SIMD instruction sets, as the bulk of the matching work is done with repetitive, simple bitwise operations. At this point, without further optimisations, nft_concat_range.sh reports, for one AMD Epyc 7351 thread (2.9GHz, 512 KiB L1D$, 8 MiB L2$): TEST: performance net,port [ OK ] baseline (drop from netdev hook): 10190076pps baseline hash (non-ranged entries): 6179564pps baseline rbtree (match on first field only): 2950341pps set with 1000 full, ranged entries: 2304165pps port,net [ OK ] baseline (drop from netdev hook): 10143615pps baseline hash (non-ranged entries): 6135776pps baseline rbtree (match on first field only): 4311934pps set with 100 full, ranged entries: 4131471pps net6,port [ OK ] baseline (drop from netdev hook): 9730404pps baseline hash (non-ranged entries): 4809557pps baseline rbtree (match on first field only): 1501699pps set with 1000 full, ranged entries: 1092557pps port,proto [ OK ] baseline (drop from netdev hook): 10812426pps baseline hash (non-ranged entries): 6929353pps baseline rbtree (match on first field only): 3027105pps set with 30000 full, ranged entries: 284147pps net6,port,mac [ OK ] baseline (drop from netdev hook): 9660114pps baseline hash (non-ranged entries): 3778877pps baseline rbtree (match on first field only): 3179379pps set with 10 full, ranged entries: 2082880pps net6,port,mac,proto [ OK ] baseline (drop from netdev hook): 9718324pps baseline hash (non-ranged entries): 3799021pps baseline rbtree (match on first field only): 1506689pps set with 1000 full, ranged entries: 783810pps net,mac [ OK ] baseline (drop from netdev hook): 10190029pps baseline hash (non-ranged entries): 5172218pps baseline rbtree (match on first field only): 2946863pps set with 1000 full, ranged entries: 1279122pps v4: - fix build for 32-bit architectures: 64-bit division needs div_u64() (kbuild test robot <lkp@intel.com>) v3: - rework interface for field length specification, NFT_SET_SUBKEY disappears and information is stored in description - remove scratch area to store closing element of ranges, as elements now come with an actual attribute to specify the upper range limit (Pablo Neira Ayuso) - also remove pointer to 'start' element from mapping table, closing key is now accessible via extension data - use bytes right away instead of bits for field lengths, this way we can also double the inner loop of the lookup function to take care of upper and lower bits in a single iteration (minor performance improvement) - make it clearer that set operations are actually atomic API-wise, but we can't e.g. implement flush() as one-shot action - fix type for 'dup' in nft_pipapo_insert(), check for duplicates only in the next generation, and in general take care of differentiating generation mask cases depending on the operation (Pablo Neira Ayuso) - report C implementation matching rate in commit message, so that AVX2 implementation can be compared (Pablo Neira Ayuso) v2: - protect access to scratch maps in nft_pipapo_lookup() with local_bh_disable/enable() (Florian Westphal) - drop rcu_read_lock/unlock() from nft_pipapo_lookup(), it's already implied (Florian Westphal) - explain why partial allocation failures don't need handling in pipapo_realloc_scratch(), rename 'm' to clone and update related kerneldoc to make it clear we're not operating on the live copy (Florian Westphal) - add expicit check for priv->start_elem in nft_pipapo_insert() to avoid ending up in nft_pipapo_walk() with a NULL start element, and also zero it out in every operation that might make it invalid, so that insertion doesn't proceed with an invalid element (Florian Westphal) Signed-off-by: Stefano Brivio <sbrivio@redhat.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> |
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