SocketCAN 仅从套接字读取 returns 11cobid

Question

我正在尝试从 socketCAN 中读取，并且始终针对 11 位标识符过滤消息。这应该是一个可以通过为 29 位标识符设置 rperper 标志来解决的问题，但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 (itÂ´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;

我正在发送一个带有 idx x901 的 CAN 帧，这是打印的内容：

阅读COB_ID:80000101

我已经用很多不同的方法解决了这个问题，看起来 C 代码可以正常工作，但我怀疑问题出在 mcp251x 的内核模块上，它没有正确接收扩展标志？或者它可能是我需要在运行内核模块之前做一些初始化？？？

提前感谢任何可以提供帮助的人。

Answer 1

您对 CAN 标志和过滤的理解不正确。看看摘自 linux can.h:

/* 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 */

这是一个适用于 SFF 和 EFF 消息的示例：

#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 (itÂ´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;
}

现在发送这些消息：

cansend vcan0 00000123#FFFFFFFFFFFFFFFF
cansend vcan0 12345678#FFFFFFFFFFFFFFFF

给出正确的输出：

READ COB_ID: 123
READ COB_ID: 12345678

SocketCAN 仅从套接字读取 returns 11cobid

SocketCAN read from socket only returns 11cobid

c

linux

can-bus

socketcan

legato