如何检查 ioctl 是否已执行？

问题描述

我正在配置接口的 IP 地址，并在我的应用程序中使用 ioctl() 调用进行设置和运行。我的应用程序在带有 raspbian 的 raspBerry pi 上运行。

我发现 ioctl() 需要一些时间才能生效，因为在配置后 bind() 调用套接字失败并显示 Cannot assign requested address。只有在我的应用程序执行之前接口关闭时，调用才会失败。在第一次运行失败后再次执行时，我的应用程序按预期工作。

最后我发现 sleep() 后面的短 ioctl() 可以防止错误发生。除了简短的 ioctl() 之外，我如何确定 sleep() 调用已完成？

这是我编写的用于配置接口的代码：

int setIpInterface(char *ipAddress,char *ipNetmask,int ipPrefixlen){

    int foundIF = 0;
    char line[255];
    FILE *file = fopen("/proc/net/dev","r");

    // Read each line in the file to check if the interface name is present
    while(fgets(line,sizeof(line),file) != NULL){

        if(strstr(line,INTERFACE) != NULL) {
            foundIF = 1;
            break;
        }

    }

    // Close the file
    fclose(file);
    file =  NULL;

    // Error handling
    if(foundIF == 0) {
        printf("Error Could not find interface name: %s\n",INTERFACE);
        return ERR_IF_NOT_FOUND;
    }

    // Get the socket file descriptor for ioctl
    int socketFD = socket(IPVERSION,SOCK_DGRAM,IPPROTO_IP);

    // Error handling
    if(socketFD == -1){
        perror("Error getting socket file descriptor Failed");
        return ERR_SOCKET_Failed;
    }

    // Set the interace name in the ifr
    struct ifreq ifr;
    snprintf(ifr.ifr_name,sizeof(ifr.ifr_name),"%s",INTERFACE);

    // Check which IP version should be used
    if(IPVERSION == AF_INET){

        // Fill in the address values
        struct sockaddr_in *addr = (struct sockaddr_in*)&ifr.ifr_addr;
        addr->sin_family = AF_INET;
        inet_pton(AF_INET,ipAddress,&addr->sin_addr);

        // Set the interface address
        if(ioctl(socketFD,SIOCSIFADDR,&ifr) < 0){
            printf("Error Could not set interface address: %s\n",strerror(errno));
            close(socketFD);
            return ERR_IOCTL_ADDRESS;
        }

        //  Fill in the netmask values
        addr = (struct sockaddr_in*)&ifr.ifr_addr;
        inet_pton(AF_INET,ipNetmask,&addr->sin_addr);

        // Set the interface IP netmask
        if(ioctl(socketFD,SIOCSIFNETMASK,&ifr) < 0){
            printf("Error Could not set interface netmask: %s\n",strerror(errno));
            close(socketFD);
            return ERR_IOCTL_MASK;
        }

    }else{

        // Get the ifrindex of the interface name
        if(ioctl(socketFD,SIOGIFINDEX,&ifr) < 0){
            printf("Error Could not get the interface index: %s\n",strerror(errno));
            close(socketFD);
            return ERR_IOCTL_INDEX;
        }

        // Fill in the name,prefixlen and address
        struct in6_ifreq ifr6;
        ifr6.ifr6_ifindex = ifr.ifr_ifindex;
        ifr6.ifr6_prefixlen = ipPrefixlen;
        inet_pton(AF_INET6,&ifr6.ifr6_addr);

        // Set the interface address and prefixlen
        if(ioctl(socketFD,&ifr6) < 0){

            // Check if the error occured because the interface
            // was already configured with that IPv6 address
            if(errno != EEXIST){
                printf("Error Could not set interface address: %s\n",strerror(errno));
                close(socketFD);
                return ERR_IOCTL_ADDRESS;
            }

        }

    }

    // Get the interface flags
    if(ioctl(socketFD,SIocgIFFLAGS,&ifr) < 0) {
        printf("Error Could not get interface flags: %s\n",strerror(errno));
        close(socketFD);
        return ERR_IOCTL_FLAGS;
    }

    // Set the interface up and running
    ifr.ifr_flags  |= (IFF_UP | IFF_RUNNING);
    if(ioctl(socketFD,SIOCSIFFLAGS,&ifr) < 0){
        printf("Error Could not set interface flags: %s\n",strerror(errno));
        close(socketFD);
        return ERR_IOCTL_IFUP;
    }

    // Close the  socket
    close(socketFD);
    return 0;
}

解决方法

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