Now that we have a means to perform a UDP socket lookup without taking a reference, it is feasible to have flow dissector crack open UDP encapsulated packets. Generally, we would expect that the UDP source port or the flow label in IPv6 would contain enough entropy about the encapsulated flow. However, there will be cases, such as a static UDP tunnel with fixed ports, where dissecting the encapsulated packet is valuable.
The model is here is similar to that implemented for UDP GRO. A tunnel implementation (e.g. GUE) may set a flow_dissect function in the udp_sk. In __skb_flow_dissect a case has been added for UDP to check if there is a socket with flow_dissect set. If there is the function is called. The (per tunnel implementation) function can parse the encapsulation headers and return the next protocol for __skb_flow_dissect to process and it's position in nhoff. Since performing a UDP lookup on every packet might be expensive I added a static key check to bypass the lookup if there are no sockets with flow_dissect set. I should mention that doing the lookup wasn't particularly a big hit anyway. Fou/gue was modified to perform tunnel dissection. This is enabled on each listener socket via a netlink configuration option. Tested: Running 200 streams with TCP_RR. GRE/GUE variable source port (baseline) RSS distributes packets, RFS is effective 1211702 tps 147/241/442 50/90/99% latencies 87.95 CPU utilization GRE/GUE fixed source port All packets to one CPU, RFS is ineffective 173680 tps 1170/1377/1853 50/90/99% latencies 7.42 CPU utilization GRE/GUE fixed source port with deep hash enabled All packets to one CPU, but now RFS is effective 730359 tps 263/325/464 50/90/99% latencies 38.25% CPU utilization (Interrupting CPU is maxed out) Tom Herbert (5): udp: Add socket lookup functions with noref udp: UDP flow dissector udp: Add UDP flow dissection functions to IPv4 and IPv6 udp: UDP tunnel flow dissection infrastructure fou: Support flow dissection include/linux/netdevice.h | 5 +++ include/linux/udp.h | 7 +++++ include/net/flow_dissector.h | 8 +++++ include/net/udp.h | 12 ++++++++ include/net/udp_tunnel.h | 5 +++ include/uapi/linux/fou.h | 1 + net/core/flow_dissector.c | 73 ++++++++++++++++++++++++++++++++++++++++++-- net/ipv4/fou.c | 68 ++++++++++++++++++++++++++++++++++++++++- net/ipv4/udp.c | 11 +++++++ net/ipv4/udp_offload.c | 39 +++++++++++++++++++++++ net/ipv4/udp_tunnel.c | 5 +++ net/ipv6/udp.c | 10 ++++++ net/ipv6/udp_offload.c | 38 +++++++++++++++++++++++ 13 files changed, 279 insertions(+), 3 deletions(-) -- 2.9.3
