从套接字读取的SocketCAN仅返回11cobid

问题描述

我正在尝试从socketCAN中读取，并且味精始终会过滤11位标识符。 设置29位标识符的rpoper标志应该可以解决此问题，但是我找不到任何人可以提供帮助的地方...

    struct can_frame message;
    struct sockaddr_can addr;
    struct ifreq ifr;
    int   fd = -1;                  // file descriptor (it´s a socket)

    if((fd = socket(PF_CAN,SOCK_RAW,CAN_RAW)) < 0)
    {
        LE_INFO("cannot open socket");
        return;
    }
    strcpy(ifr.ifr_name,"can0");
    ioctl(fd,SIocgIFINDEX,&ifr);
    addr.can_family = AF_CAN;
    addr.can_ifindex = ifr.ifr_ifindex;
    if(bind(fd,(struct sockaddr *)&addr,sizeof(addr)) < 0)
    {
        printf("cannot bind socket\n");
        return;
    }

    uint8_t nbytes;

    message.can_id |= CAN_EFF_FLAG;

    while(1)
    {
        nbytes = read(fd,&message,sizeof(struct can_frame));

        if (nbytes < 0) {
                perror("can raw socket read");
                return;
        }

        /* paranoid check ... */
        if (nbytes < sizeof(struct can_frame)) {
                fprintf(stderr,"read: incomplete CAN frame\n");
                return;
        }

        printf("READ COB_ID:%x\n",message.can_id | CAN_EFF_FLAG);
        
    }
    return;

我正在发送一个idx x901的CAN帧，这是打印出来的内容：

读取COB_ID：80000101

读取COB_ID：80000101

读取COB_ID：80000101

我已经以许多不同的方式对这一问题进行了故障排除，似乎C代码正在按预期方式工作，但是我怀疑问题出在哪一个mcp251x的内核模块没有正确接收扩展标志？或者可能需要在运行内核模块之前进行一些初始化？

在此先感谢任何可以提供帮助的人。

解决方法

您对 CAN 标志和过滤的理解不正确。看看linux can.h的摘录：

from typing import List


class A:
    def __init__(self):
        self.var1 = 1
        self.var2 = 2

class B:
    def __init__(self):
        self.my_list: List[A] = []

    def add(self,a_object: A):
        self.my_list.append(a_object)

    def show(self):
        for a_object in self.my_list:
            print(a_object.var1,a_object.var2)

这是一个适用于 SFF 和 EFF 消息的示例：

/* special address description flags for the CAN_ID */
#define CAN_EFF_FLAG 0x80000000U /* EFF/SFF is set in the MSB */
#define CAN_RTR_FLAG 0x40000000U /* remote transmission request */
#define CAN_ERR_FLAG 0x20000000U /* error message frame */

/* valid bits in CAN ID for frame formats */
#define CAN_SFF_MASK 0x000007FFU /* standard frame format (SFF) */
#define CAN_EFF_MASK 0x1FFFFFFFU /* extended frame format (EFF) */
#define CAN_ERR_MASK 0x1FFFFFFFU /* omit EFF,RTR,ERR flags */

现在发送这些消息：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/socket.h>

#include <linux/can.h>
#include <linux/can/raw.h>

int main(int argc,char **argv)
{
    struct can_frame message;
    struct sockaddr_can addr;
    struct ifreq ifr;
    int   fd = -1;                  // file descriptor (it´s a socket)

    if((fd = socket(PF_CAN,SOCK_RAW,CAN_RAW)) < 0)
    {
        printf("cannot open socket");
        return -9;
    }
    strcpy(ifr.ifr_name,"vcan0");
    ioctl(fd,SIOCGIFINDEX,&ifr);
    addr.can_family = AF_CAN;
    addr.can_ifindex = ifr.ifr_ifindex;
    if(bind(fd,(struct sockaddr *)&addr,sizeof(addr)) < 0)
    {
        printf("cannot bind socket\n");
        return -1;
    }

    u_int8_t nbytes;

    message.can_id |= CAN_EFF_FLAG | CAN_RTR_FLAG | CAN_EFF_MASK;

    while(1)
    {
        nbytes = read(fd,&message,sizeof(struct can_frame));

        if (nbytes < 0) {
                perror("can raw socket read");
                return -2;
        }

        /* paranoid check ... */
        if (nbytes < sizeof(struct can_frame)) {
                fprintf(stderr,"read: incomplete CAN frame\n");
                return -3;
        }

        printf("READ COB_ID: %x\n",message.can_id & CAN_EFF_MASK);

    }

    return 0;
}

给出正确的输出：

cansend vcan0 00000123#FFFFFFFFFFFFFFFF
cansend vcan0 12345678#FFFFFFFFFFFFFFFF