SocketPanda python library (#2073)

* SocketPanda python library

* fix spelling

* can0 should be the default

* CAN-FD support

python/socketpanda.py

@@ -0,0 +1,94 @@
+import socket
+import struct
+
+# /**
+#  * struct canfd_frame - CAN flexible data rate frame structure
+#  * @can_id: CAN ID of the frame and CAN_*_FLAG flags, see canid_t definition
+#  * @len:    frame payload length in byte (0 .. CANFD_MAX_DLEN)
+#  * @flags:  additional flags for CAN FD
+#  * @__res0: reserved / padding
+#  * @__res1: reserved / padding
+#  * @data:   CAN FD frame payload (up to CANFD_MAX_DLEN byte)
+#  */
+# struct canfd_frame {
+# 	canid_t can_id;  /* 32 bit CAN_ID + EFF/RTR/ERR flags */
+# 	__u8    len;     /* frame payload length in byte */
+# 	__u8    flags;   /* additional flags for CAN FD */
+# 	__u8    __res0;  /* reserved / padding */
+# 	__u8    __res1;  /* reserved / padding */
+# 	__u8    data[CANFD_MAX_DLEN] __attribute__((aligned(8)));
+# };
+CAN_HEADER_FMT = "=IBB2x"
+CAN_HEADER_LEN = struct.calcsize(CAN_HEADER_FMT)
+CAN_MAX_DLEN = 8
+CANFD_MAX_DLEN = 64
+
+CANFD_BRS = 0x01 # bit rate switch (second bitrate for payload data)
+CANFD_FDF = 0x04 # mark CAN FD for dual use of struct canfd_frame
+
+# socket.SO_RXQ_OVFL is missing
+# https://github.com/torvalds/linux/blob/47ac09b91befbb6a235ab620c32af719f8208399/include/uapi/asm-generic/socket.h#L61
+SO_RXQ_OVFL = 40
+
+def create_socketcan(interface:str, recv_buffer_size:int, fd:bool) -> socket.socket:
+  # settings mostly from https://github.com/linux-can/can-utils/blob/master/candump.c
+  socketcan = socket.socket(socket.AF_CAN, socket.SOCK_RAW, socket.CAN_RAW)
+  if fd:
+    socketcan.setsockopt(socket.SOL_CAN_RAW, socket.CAN_RAW_FD_FRAMES, 1)
+  socketcan.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, recv_buffer_size)
+  # TODO: why is it always 2x the requested size?
+  assert socketcan.getsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF) == recv_buffer_size * 2
+  # TODO: how to dectect and alert on buffer overflow?
+  socketcan.setsockopt(socket.SOL_SOCKET, SO_RXQ_OVFL, 1)
+  socketcan.bind((interface,))
+  return socketcan
+
+# Panda class substitute for socketcan device (to support using the uds/iso-tp/xcp/ccp library)
+class SocketPanda():
+  def __init__(self, interface:str="can0", bus:int=0, fd:bool=False, recv_buffer_size:int=212992) -> None:
+    self.interface = interface
+    self.bus = bus
+    self.fd = fd
+    self.flags = CANFD_BRS | CANFD_FDF if fd else 0
+    self.data_len = CANFD_MAX_DLEN if fd else CAN_MAX_DLEN
+    self.recv_buffer_size = recv_buffer_size
+    self.socket = create_socketcan(interface, recv_buffer_size, fd)
+
+  def __del__(self):
+    self.socket.close()
+
+  def get_serial(self) -> tuple[int, int]:
+    return (0, 0) # TODO: implemented in panda socketcan driver
+
+  def get_version(self) -> int:
+    return 0 # TODO: implemented in panda socketcan driver
+
+  def can_clear(self, bus:int) -> None:
+    # TODO: implemented in panda socketcan driver
+    self.socket.close()
+    self.socket = create_socketcan(self.interface, self.recv_buffer_size, self.fd)
+
+  def set_safety_mode(self, mode:int, param=0) -> None:
+    pass # TODO: implemented in panda socketcan driver
+
+  def has_obd(self) -> bool:
+    return False # TODO: implemented in panda socketcan driver
+
+  def can_send(self, addr, dat, bus=0, timeout=0) -> None:
+    msg_len = len(dat)
+    msg_dat = dat.ljust(self.data_len, b'\x00')
+    can_frame = struct.pack(CAN_HEADER_FMT, addr, msg_len, self.flags) + msg_dat
+    self.socket.sendto(can_frame, (self.interface,))
+
+  def can_recv(self) -> list[tuple[int, bytes, int]]:
+    msgs = list()
+    while True:
+      try:
+        dat, _ = self.socket.recvfrom(self.recv_buffer_size, socket.MSG_DONTWAIT)
+        assert len(dat) == CAN_HEADER_LEN + self.data_len, f"ERROR: received {len(dat)} bytes"
+        can_id, msg_len, _ = struct.unpack(CAN_HEADER_FMT, dat[:CAN_HEADER_LEN])
+        msg_dat = dat[CAN_HEADER_LEN:CAN_HEADER_LEN+msg_len]
+        msgs.append((can_id, msg_dat, self.bus))
+      except BlockingIOError:
+        break # buffered data exhausted
+    return msgs