Performance evaluation of Linux CAN-related system calls Michal Sojka , Pavel P´ ıˇ sa, Zdenˇ ek Hanz´ alek Czech Technical University in Prague, Faculty of Electrical Engineering Email: { sojkam1,pisa,hanzalek } @fel.cvut.cz SESAMO Security and Safety Modelling Workshop on Factory Communication Systems (WFCS) May 7, 2014 – Toulouse, France M. Sojka, et al. Linux CAN-related system calls WFCS2014 1 / 15
Introduction Motivation Security of on-board networks M. Sojka, et al. Linux CAN-related system calls WFCS2014 2 / 15
Introduction Motivation Security of on-board networks S D I Intrusion detection system M. Sojka, et al. Linux CAN-related system calls WFCS2014 2 / 15
Introduction Motivation Security of on-board networks S D I Intrusion detection system Needs to be "tuned" to avoid false positives M. Sojka, et al. Linux CAN-related system calls WFCS2014 2 / 15
Introduction Motivation Security of on-board networks S D I Intrusion detection system Needs to be "tuned" to avoid false positives Data from outdoor experiments M. Sojka, et al. Linux CAN-related system calls WFCS2014 2 / 15
Introduction Motivation Security of on-board networks S D I Intrusion detection system Needs to be "tuned" to avoid false positives Data from outdoor experiments Logging M. Sojka, et al. Linux CAN-related system calls WFCS2014 2 / 15
Introduction Motivation Security of on-board networks S D I Intrusion detection system Needs to be "tuned" to avoid false positives Data from outdoor experiments Logging M. Sojka, et al. Linux CAN-related system calls WFCS2014 2 / 15
Introduction Requirements ◮ All CAN traffic from a car has to be logged in real-time. ◮ Up to 20 CAN buses needs to be logged simultaneously. ◮ Logs are analyzed off-line. M. Sojka, et al. Linux CAN-related system calls WFCS2014 3 / 15
Introduction Outline CAN support in Linux Virtual CAN interface method Gateway-based method Low-latency sockets Conclusion M. Sojka, et al. Linux CAN-related system calls WFCS2014 4 / 15
CAN support in Linux Linux networking subsystem Application (user space) RX/TX path overheads: Socket layer (can/raw.c) ◮ Interrupt ◮ Socket, protocol, Protocol layer (af_can.c) Qdisc Kernel ◮ System call Queuing Device driver discipline Poll ◮ We are interested in the interface between ISR applications and the kernel. CAN controller (HW) M. Sojka, et al. Linux CAN-related system calls WFCS2014 5 / 15
CAN support in Linux Linux networking subsystem Application (user space) RX/TX path overheads: Socket layer (can/raw.c) ◮ Interrupt ◮ Socket, protocol, Protocol layer (af_can.c) Qdisc Kernel ◮ System call Queuing Device driver discipline Poll ◮ We are interested in the interface between ISR applications and the kernel. CAN controller (HW) M. Sojka, et al. Linux CAN-related system calls WFCS2014 5 / 15
CAN support in Linux Linux networking API Sockets: ◮ Raw CAN sockets – most common ◮ Memory mapped socket (PF PACKET) ◮ Non-blocking I/O (O NONBLOCK) ◮ New “Low-latency” sockets (Linux 3.11 – 9/2013) Operations on sockets: ◮ read/write (send/recv) ◮ sendmmsg/recvmmsg M. Sojka, et al. Linux CAN-related system calls WFCS2014 6 / 15
CAN support in Linux Memory-mapped sockets PF PACKET Application (user space) Reception ◮ no system call Protocol & socket layer (af_packet.c) ◮ wait: poll() Kernel Queuing Device driver Transmission discipline Poll ◮ Notify the kernel ISR about ready messages. CAN controller (HW) M. Sojka, et al. Linux CAN-related system calls WFCS2014 7 / 15
Virtual CAN interface method Single/multiple messages per system call ◮ Comparison of recv() and recvmmsg() system calls ◮ Use of virtual CAN interface (vcan) Application TX socket RX socket read/recv write/send RX queue Kernel af_can.c, raw.c vcan Experiment 1. Send X messages – kernel queues them in an RX queue 2. Receive X messages from the RX queue M. Sojka, et al. Linux CAN-related system calls WFCS2014 8 / 15
Virtual CAN interface method With or without mmsg – results Embedded system (MPC5200B) PC 16 40 450 3000 read read 14 35 400 recvmmsg 2500 recvmmsg 350 12 30 write write 300 2000 Time [ms] 10 sendmmsg 25 Time [ms] sendmmsg 250 8 20 1500 200 6 15 150 1000 4 10 100 500 2 5 50 0 0 0 0 0 5 10 15 20 25 30 35 40 45 50 0 5 10 15 20 25 30 35 40 45 50 Frames [×1000] Frames [×1000] ◮ recvmmsg 7% faster ◮ recvmmsg 19% faster ◮ sendmmsg 12% faster ◮ sendmmsg 35% faster M. Sojka, et al. Linux CAN-related system calls WFCS2014 9 / 15
Gateway-based method Embedded system used for experiments ◮ PowerPC ◮ Freescale MPC5200B ◮ 400 Mhz ◮ 128 MB RAM ◮ on-chip CAN controller ◮ Linux 3.12.3 M. Sojka, et al. Linux CAN-related system calls WFCS2014 10 / 15
ff Gateway-based method Gateway-based experiments msg 1 CAN bus 0 CAN gateway (Linux) msg 1' CAN bus 1 GW latency Duration time T otal latency RX timestamp 1 RX timestamp 2 M. Sojka, et al. Linux CAN-related system calls WFCS2014 11 / 15
ff Gateway-based method Gateway-based experiments msg 1 CAN bus 0 CAN gateway (Linux) msg 1' CAN bus 1 GW latency Duration time T otal latency RX timestamp 1 RX timestamp 2 M. Sojka, et al. Linux CAN-related system calls WFCS2014 11 / 15
ff Gateway-based method Gateway-based experiments msg 1 CAN bus 0 CAN gateway (Linux) msg 1' CAN bus 1 GW latency Duration time T otal latency RX timestamp 1 RX timestamp 2 M. Sojka, et al. Linux CAN-related system calls WFCS2014 11 / 15
ff Gateway-based method Gateway-based experiments msg 1 CAN bus 0 CAN gateway (Linux) msg 1' CAN bus 1 GW latency Duration time T otal latency RX timestamp 1 RX timestamp 2 M. Sojka, et al. Linux CAN-related system calls WFCS2014 11 / 15
ff Gateway-based method Gateway-based experiments msg 1 CAN bus 0 CAN gateway (Linux) msg 1' CAN bus 1 GW latency Duration time T otal latency RX timestamp 1 RX timestamp 2 M. Sojka, et al. Linux CAN-related system calls WFCS2014 11 / 15
Gateway-based method Gateway-based experiments Di ff erent implemntations msg 1 CAN bus 0 CAN gateway (Linux) msg 1' CAN bus 1 GW latency Duration time T otal latency RX timestamp 1 RX timestamp 2 M. Sojka, et al. Linux CAN-related system calls WFCS2014 11 / 15
Gateway-based method Results – one message at a time 250 ◮ Blocking system GW latency [µs] 200 calls 150 ◮ Non-blocking/busy 100 waiting ◮ Linux kernel & 50 RTEMS (no Linux) 0 read-write mmap-write mmap-mmap mmsg-mmsg M. Sojka, et al. Linux CAN-related system calls WFCS2014 12 / 15
Gateway-based method Results – one message at a time 250 ◮ Blocking system GW latency [µs] 200 calls 150 ◮ Non-blocking/busy 100 waiting ◮ Linux kernel & 50 RTEMS (no Linux) 0 mmapbusy-mmap mmapbusy-write readnb-write readbusy-write readbusynoirq-write readnb-mmap read-write mmap-write mmap-mmap mmsg-mmsg M. Sojka, et al. Linux CAN-related system calls WFCS2014 12 / 15
Gateway-based method Results – one message at a time 250 ◮ Blocking system GW latency [µs] 200 calls 150 ◮ Non-blocking/busy 100 waiting ◮ Linux kernel & 50 RTEMS (no Linux) 0 rtems kernel mmapbusy-mmap mmapbusy-write readnb-write readbusy-write readbusynoirq-write readnb-mmap read-write mmap-write mmap-mmap mmsg-mmsg M. Sojka, et al. Linux CAN-related system calls WFCS2014 12 / 15
Gateway-based method Results – periodic messages 70 µ s 70 µ s Bitrate: 1 Mbps, Payload: 2 bytes period Median of 3200 frames read-write 20000 10000 GW latency [µs] ± packet loss 5000 2000 1000 500 200 100 50 8-byte frame length 20 120 125 130 135 140 145 150 155 160 Frame period [µs] M. Sojka, et al. Linux CAN-related system calls WFCS2014 13 / 15
Gateway-based method Results – periodic messages 70 µ s 70 µ s Bitrate: 1 Mbps, Payload: 2 bytes period Median of 3200 frames read-write 20000 mmap-write 10000 GW latency [µs] ± packet loss 5000 2000 1000 500 200 100 50 8-byte frame length 20 120 125 130 135 140 145 150 155 160 Frame period [µs] M. Sojka, et al. Linux CAN-related system calls WFCS2014 13 / 15
Gateway-based method Results – periodic messages 70 µ s 70 µ s Bitrate: 1 Mbps, Payload: 2 bytes period Median of 3200 frames read-write 20000 mmap-write mmsg-mmsg 10000 mmap-mmap GW latency [µs] ± packet loss 5000 2000 1000 500 200 100 50 8-byte frame length 20 120 125 130 135 140 145 150 155 160 Frame period [µs] M. Sojka, et al. Linux CAN-related system calls WFCS2014 13 / 15
Gateway-based method Results – periodic messages 70 µ s 70 µ s Bitrate: 1 Mbps, Payload: 2 bytes period Median of 3200 frames read-write 20000 mmap-write mmsg-mmsg 10000 mmap-mmap GW latency [µs] ± packet loss kernel 5000 2000 1000 500 200 100 50 8-byte frame length 20 120 125 130 135 140 145 150 155 160 Frame period [µs] M. Sojka, et al. Linux CAN-related system calls WFCS2014 13 / 15
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