commaai/openpilot · error

Failed to create CAN socket

Error message

Failed to create CAN socket

What it means

Emitted by SocketCanStream::connect() in tools/cabana/streams/socketcanstream.cc when socket(PF_CAN, SOCK_RAW, CAN_RAW) returns a negative fd. Creating a raw CAN socket requires kernel SocketCAN support and (for raw sockets) appropriate privilege; failure at this first step means the process cannot talk to any CAN interface at all.

Source

Thrown at openpilot/tools/cabana/streams/socketcanstream.cc:48

SocketCanStream::~SocketCanStream() {
  stop();
  if (sock_fd >= 0) {
    ::close(sock_fd);
    sock_fd = -1;
  }
}

bool SocketCanStream::available() {
  int fd = socket(PF_CAN, SOCK_RAW, CAN_RAW);
  if (fd < 0) return false;
  ::close(fd);
  return true;
}

bool SocketCanStream::connect() {
  sock_fd = socket(PF_CAN, SOCK_RAW, CAN_RAW);
  if (sock_fd < 0) {
    fprintf(stderr, "Failed to create CAN socket\n");
    return false;
  }

  // Enable CAN-FD
  int fd_enable = 1;
  setsockopt(sock_fd, SOL_CAN_RAW, CAN_RAW_FD_FRAMES, &fd_enable, sizeof(fd_enable));

  struct ifreq ifr = {};
  strncpy(ifr.ifr_name, config.device.c_str(), IFNAMSIZ - 1);
  if (ioctl(sock_fd, SIOCGIFINDEX, &ifr) < 0) {
    fprintf(stderr, "Failed to get interface index for %s\n", config.device.c_str());
    ::close(sock_fd);
    sock_fd = -1;
    return false;
  }

  struct sockaddr_can addr = {};
  addr.can_family = AF_CAN;

View on GitHub (pinned to 516ec1e682)

Solutions

1. Verify SocketCAN: `sudo modprobe can can_raw` then re-run; check /proc/net/can exists.
2. Run with privileges for the raw socket: root, or grant CAP_NET_RAW to the cabana binary (`setcap cap_net_raw+ep $(which cabana)`).
3. Confirm the platform: SocketCAN needs a real Linux kernel — on WSL use WSL2 with usbip, on macOS use a different stream type.
4. Check that available() is honored in the stream picker so the option is hidden on unsupported hosts.

Example fix

# before
# stderr: Failed to create CAN socket
lsmod | grep can_raw   # nothing

# after
sudo modprobe can can_raw
sudo setcap cap_net_raw+ep $(which cabana)
cabana   # socket(PF_CAN, SOCK_RAW, CAN_RAW) now returns a valid fd

// Honor the library's own availability probe before offering/starting the stream:
if (!SocketCanStream::available()) {
  // socket(PF_CAN, SOCK_RAW, CAN_RAW) would fail here: hide/disable the option
  return;
}
// Or probe directly:
int fd = socket(PF_CAN, SOCK_RAW, CAN_RAW);
bool socketcanSupported = fd >= 0;
if (fd >= 0) ::close(fd);

When it happens

Trigger: Starting a SocketCAN stream (connect()) on a machine where the kernel lacks the can/can_raw modules (socket() fails with EAFNOSUPPORT/EPROTONOSUPPORT), or the process lacks privileges for SOCK_RAW (EACCES — raw sockets need CAP_NET_RAW or root). Note SocketCanStream::available() uses the same call, so this usually implies available() was bypassed or raced.

Common situations: Running cabana on a non-Linux platform or a minimal kernel without CONFIG_CAN; container/WSL1 environments without CAN support; unprivileged user without CAP_NET_RAW (no udev/CAP granting); can_raw module not loaded (`modprobe can_raw` never run and not auto-loaded).

Related errors

• Failed to bind CAN socket
• Failed to get interface index for %s
• too few samples found in route
• signal %s out of bounds.start_bit: %d size: %d
• error: --socketcan is only supported on Linux

AI-assisted analysis of commaai/openpilot@516ec1e682 (2026-08-15). Data as JSON: /api/errors/d6cda68fe1d178c4. Report an issue: GitHub.