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CAN

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CAN – Controller Area Network

SocketCAN

The SocketCAN is an implementation of CAN protocols (Controller Area Network) for Linux. 

CAN is a network transport protocol widely used in, automotive, and industrial embedded devices.

SocketCAN uses the Berkeley socket API to provide CAN device drivers and expose CAN devices as network interfaces. 

The SocketCAN API has been designed very closer as for socket API used for TCP/IP protocols.

SocketCAN drivers expose the CAN interface as a standard networking device, visible in /sys/class/net, and usable via the Berkeley Sockets Layer via the PF_CAN protocol family. SocketCAN is documented in Documentation/networking/can.txt

SocketCAN provides the following types of CAN interfaces:

  1. Native interfaces. These are CAN interfaces associated with real hardware (such as a USB-to-CAN adapter). They are named as can0, can1, …

  2. Virtual interfaces. These are CAN interfaces that are not associated with any real hardware. They are named as vcan0, vcan1, …

  3. SLCAN based interfaces. SLCAN interfaces provide a serial interface. They are named as slcan0, slcan1, … Socket wrapper for serial-to-CAN interfaces, supporting the slcan protocol. A /dev/tty device is turned into a CAN socket device.

  4. Virtual CAN tunnel interface: tunnel interface to forward traffic to a container. It is named as vxcan1, vxcan2, …

Get statistics: ip -details -statistics link show canX or in file /proc/net/can/stats

Virtual CAN Interface

Create a virtual CAN network interface with the name vcan0

sudo ip link add dev vcan0 type vcan
sudo ip link set up vcan0

To check the virtual can interface is created

ip link show vcan0
# result command:
4: vcan0: <NOARP,UP,LOWER_UP> mtu 72 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/can

CAN Tools

The can-utils package provides a set of commands that can be used either on real or virtual CAN bus.  

Monitor received data

The candump is a command to print received data by a CAN interface. It is used in a dedicated terminal window.

# monitor window
candump vcan0

cansniffer displays frames that are currently on the bus, but filters out frames with data that is not changing. This is very useful for reverse engineering CAN bus systems. A CAN bus sniffer software is a specialized program designed to intercept and decode communication on a CAN bus.

# monitor window
cansniffer vcan0

Send Can frame

To send a CAN frame with identifier 0x1A (26 dec) and 8 bytes of data

cansend vcan0 01A#1122334455667788

The received data by can0 interface appears in the monitor terminal (candump).

# monitor window
vcan0  01A   [8]  11 22 33 44 55 66 77 88

Send bulk random data

To send large amount of data in a random way

cangen vcan0 -v

Record dump file

To record all received data in a file using timestamp

# monitor window
candump -l vcan0
Disabled standard output while logging.
Enabling Logfile 'candump-2024-08-15_124705.log'

Print dumped log data 

log2asc -I candump-2024-08-15_123738.log vcan
# output:
date Thu Aug 15 12:37:38 2024
base hex  timestamps absolute
no internal events logged
   0.000000 1  75D            Rx   d 0
   0.200313 1  70             Rx   d 2 AB 1C
   0.400709 1  A8             Rx   d 1 B6
   0.601096 1  7BF            Rx   d 1 39
   0.801489 1  5CB            Rx   d 0
   1.001887 1  CE             Rx   d 8 51 80 7E 5E 49 A7 4E 72
   1.202286 1  1C1            Rx   d 8 30 72 6D 04 D5 EF 56 6E
   1.402672 1  19F            Rx   d 1 F5
   1.603068 1  791            Rx   d 5 08 C7 13 63 01
   1.803453 1  127            Rx   d 4 CA 60 DD 75
   2.003735 1  555            Rx   d 0
   2.204012 1  6A1            Rx   d 6 27 73 B8 69 6D 44
   2.404304 1  436            Rx   d 8 F1 F6 A6 77 05 FD B7 3E
   2.604603 1  48C            Rx   d 3 4E A4 06
   2.804910 1  8E             Rx   d 8 23 1E 7D 5E 2D EA 81 2C
   3.005228 1  6CF            Rx   d 8 29 33 DD 68 60 3E 68 75
   3.205552 1  36E            Rx   d 2 62 3E

Replay scenario

The can data log file can be sent again to reproduce the same scenario.

canplayer -I candump-2024-08-15_123738.log

To send the data scenario to another CAN interface than the origin CAN interface.

canplayer vcan0=can1 -v -I candump-2024-08-15_123738.log