Supporting datapath hash allows user to set up rules that provide load balancing of traffic across multiple vports and for ECMP path selection while keeping the number of rule at minimum.
Instead of matching on exact flow spec, which requires a rule per flow, user can define rules based on hashing on the packet headers and distribute the flows to different buckets. The number of rules in this case will be constant and equal to the number of buckets. The datapath hash functionality is achieved in two steps - performing the hash action and then matching on the result, as part of the packet's classification. To compute the hash value, the api offers 2 methods: 1. Linux implementation of an asymmetric hash algorithm which is performed on the L4 headers of the packet. This method is usable via an extention to act_skbedit and allows user to provide a basis value to be included in the computation. 2. User provided bpf program that implements a hash computation algorithm. This option is usable via a new type of tc action - action_hash. Through both methods, the hash value is calculated and stored in the skb->hash field so it can be matched later as a key in the cls flower classifier. where the hash function can be standard asymetric hashing that Linux offers or alternatively user can provide a bpf program that performs hash calculation on a packet. Usage is as follows: For hash calculation: $ tc filter add dev ens1f0_0 ingress \ prio 1 chain 0 proto ip \ flower ip_proto tcp \ action hash object-file <file> section <hash_section>\ action goto chain 2 Or: $ tc filter add dev ens1f0_0 ingress \ prio 1 chain 0 proto ip \ flower ip_proto udp \ action skbedit hash asym_l4 basis <basis> \ action goto chain 2 Matching on hash result: $ tc filter add dev ens1f0_0 ingress \ prio 1 chain 2 proto ip \ flower hash 0x0/0xf \ action mirred egress redirect dev ens1f0_1 $ tc filter add dev ens1f0_0 ingress \ prio 1 chain 2 proto ip \ flower hash 0x1/0xf \ action mirred egress redirect dev ens1f0_2 v2 -> v3: *Split hash algorithm option into 2 different actions. Asym_l4 available via act_skbedit and bpf via new act_hash. Ariel Levkovich (4): net/sched: Add skb->hash field editing via act_skbedit net/sched: Introduce action hash net/flow_dissector: add packet hash dissection net/sched: cls_flower: Add hash info to flow classification include/linux/skbuff.h | 4 + include/net/act_api.h | 2 + include/net/flow_dissector.h | 9 + include/net/tc_act/tc_hash.h | 20 ++ include/net/tc_act/tc_skbedit.h | 2 + include/uapi/linux/pkt_cls.h | 4 + include/uapi/linux/tc_act/tc_hash.h | 25 ++ include/uapi/linux/tc_act/tc_skbedit.h | 7 + net/core/flow_dissector.c | 17 ++ net/sched/Kconfig | 11 + net/sched/Makefile | 1 + net/sched/act_hash.c | 348 +++++++++++++++++++++++++ net/sched/act_skbedit.c | 38 +++ net/sched/cls_api.c | 1 + net/sched/cls_flower.c | 16 ++ 15 files changed, 505 insertions(+) create mode 100644 include/net/tc_act/tc_hash.h create mode 100644 include/uapi/linux/tc_act/tc_hash.h create mode 100644 net/sched/act_hash.c -- 2.25.2