套接字创建失败，但socket（）和bind（）方法不返回-1

Question

我致力于基于网络安全的ios应用。我正在尝试创建一个本地套接字用于线程之间的通信。我在ios app中使用C语言这样做。

问题是当我创建和绑定套接字时，它不会给出任何错误。但是，当我尝试通过此套接字发送一些数据时，它失败了。 socket的create和bind代码如下：

int open_and_bind_socket(int *sockfd, const char *sname)
{
  //sname is socket name with full path
    size_t len = strlen (sname);

    size_t bytes = sizeof (struct sockaddr_un) + len + 1 - sizeof (((struct sockaddr_un *)0)->sun_path);

    struct sockaddr_un *unaddr = (struct sockaddr_un *)malloc (bytes);

     size_t size;

    if((*sockfd = socket (AF_LOCAL, SOCK_DGRAM, 0)) < 0)
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Failed to open socket");
        return ~0;
    }

    unaddr->sun_family = AF_UNIX;
    unaddr->sun_len = bytes;
    memcpy(unaddr->sun_path, sname,len+1);

    size = (offsetof (struct sockaddr_un, sun_path)
                + strlen (unaddr->sun_path));

    if( bind(*sockfd,(struct sockaddr*)unaddr,size ) < 0)
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Failed to bind the socket");
        AGENT_DEBUG(LOG_ERR, "Recvfrom MSG_PEEK Failure: %s, Socket Fd = %d\n",
                    strerror(errno), sockfd);
        return ~0;
    }

    if(0 != chmod(sname, 0666))
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Unable to chmod Socket");
        return ~0;
    }
     //unlink(sname);
    return 0;
}

在socket上发送数据的代码如下：

int data_send(int sockfd, tsIpcMsg *pMsgData)
{
    memset(x,'\0', sizeof(x));
    strcpy(x, buffer);
    strcat(x,"/AGENTSOCKET");
    size_t len = strlen (x);

    size_t bytes = sizeof (struct sockaddr_un) + len + 1 - sizeof (((struct sockaddr_un *)0)->sun_path);

    struct sockaddr_un *saun = (struct sockaddr_un *)malloc (bytes);

    memset(saun, 0, sizeof(*saun));
    saun->sun_family = AF_UNIX;    
    saun->sun_len=bytes;
    memcpy(saun->sun_path, x,len+1);
    memset(x,'\0', sizeof(x));

    if(-1 == (sendto(sockfd,(void*)pMsgData, sizeof(tsIpcMsg)+pMsgData->dataLen , 0, (struct sockaddr *)saun, sizeof(*saun))))
   {
        AGENT_DEBUG(LOG_ERR, "%s", "Failed to send message from thread to main");
        return ~0;
    }
    return 0;
}

当我记录sendto（）函数返回的errno时，它会给出值＆＃39; 2＆＃39;这意味着＆＃34;不存在这样的文件或目录：路径名中的组件不存在或者是悬挂的符号链接，或者路径名是空的。＆＃34;

所以，我认为socket没有被正确创建，这就是sendto（）方法失败的原因，而socket和bind方法没有给出任何错误。

我在ios模拟器（iPhone 7 plus）上运行此应用程序。套接字的路径如下： ＆＃34; /用户/管理员/库/开发商/ CoreSimulator /设备/ FC85979F-A627-4361-B4BD-DD794AB009C9 /数据/容器/数据/应用/ C45B9A05-F482-4011-8EA0-947A8C489367 /文件/应用/ AGENTSOCKET＆ ＃34;，其中AGENTSOCKET是套接字的名称。

我正在创建目录结构，直到app文件夹，然后在以下列方式创建套接字时将套接字名称附加到它：

mkdir(path,0777);//path is till app directory
strcat(path, "/AGENTSOCKET");

任何人都可以帮我解决这个问题。

感谢。

Answer 1

sun_path字段限制为92-108个字符（取决于平台），包括空终止符。您为x显示的data_send()字符串是185个字符，没有空终止符。因此，如果它被截断，则可能会导致您遇到的ENOENT错误。

话虽如此，您正在错误地计算sockaddr_un的大小，并将错误的地址大小传递给bind()和sendto()。此外，open_and_bind_socket()和data_send()正在泄露内存。

尝试更像这样的东西：

int open_and_bind_socket(int *sockfd, const char *sname)
{
    *sockfd = -1;

    //sname is socket name with full path
    size_t len = strlen (sname);

    size_t size = offsetof (struct sockaddr_un, sun_path) + len + 1;

    struct sockaddr_un *unaddr = (struct sockaddr_un *) malloc (size);
    if (!unaddr)
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Failed to allocate memory\n");
        return ~0;
    }

    memset(unaddr, 0, size);
    unaddr->sun_family = AF_UNIX;
    memcpy(unaddr->sun_path, sname, len);
    unaddr->sun_len = SUN_LEN(unaddr);

    int sock = socket (AF_LOCAL, SOCK_DGRAM, 0);
    if (sock < 0)
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Failed to create socket: %s\n", strerror(errno));
        free(unaddr);
        return ~0;
    }

    if (bind(sock, (struct sockaddr*)unaddr, unaddr->sun_len) < 0)
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Failed to bind the socket: %s\n", strerror(errno));
        close(sock);
        free(unaddr);
        return ~0;
    }

    if (0 != chmod(sname, 0666))
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Unable to chmod socket: %s\n", strerror(errno));
        close(sock);
        free(unaddr);
        return ~0;
    }

    free(unaddr);

    //unlink(sname);

    *sockfd = sock;

    return 0;
}

int data_send(int sockfd, tsIpcMsg *pMsgData)
{
    // this is a buffer overflow waiting to happen!
    memset(x, '\0', sizeof(x));
    strcpy(x, buffer);
    strcat(x, "/AGENTSOCKET");

    size_t len = strlen (x);

    size_t size = offsetof (struct sockaddr_un, sun_path) + len + 1;

    struct sockaddr_un *saun = (struct sockaddr_un *) malloc (size);
    if (!saun)
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Failed to allocate memory\n");
        return ~0;
    }

    memset(saun, 0, size);
    saun->sun_family = AF_UNIX;    
    memcpy(saun->sun_path, x, len);
    saun->sun_len = SUN_LEN(saun);

    if (sendto(sockfd, (void*)pMsgData, sizeof(tsIpcMsg) + pMsgData->dataLen, 0, (struct sockaddr *)saun, saun->sun_len) < 0)
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Failed to send message from thread to main: %s\n", strerror(errno));
        free(saun);
        return ~0;
    }

    free(saun);
    return 0;
}

或者，您根本不需要动态分配sockaddr_un：

int open_and_bind_socket(int *sockfd, const char *sname)
{
    *sockfd = -1;

    struct sockaddr_un unaddr;

    memset(&unaddr, 0, sizeof(unaddr));
    unaddr.sun_family = AF_UNIX;
    strncpy(unaddr.sun_path, sname, sizeof(unaddr.sun_path)-1);
    unaddr.sun_len = SUN_LEN(&unaddr);

    int sock = socket (AF_LOCAL, SOCK_DGRAM, 0);
    if (sock < 0)
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Failed to create socket: %s\n", strerror(errno));
        return ~0;
    }

    if (bind(sock, (struct sockaddr*) &unaddr, unaddr.sun_len) < 0)
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Failed to bind the socket: %s\n", strerror(errno));
        close(sock);
        return ~0;
    }

    if (0 != chmod(sname, 0666))
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Unable to chmod socket: %s\n", strerror(errno));
        close(sock);
        return ~0;
    }

    //unlink(sname);

    *sockfd = sock;

    return 0;
}

int data_send(int sockfd, tsIpcMsg *pMsgData)
{
    // this is a buffer overflow waiting to happen!
    memset(x, '\0', sizeof(x));
    strcpy(x, buffer);
    strcat(x, "/AGENTSOCKET");

    struct sockaddr_un saun;

    memset(&saun, 0, sizeof(saun));
    saun.sun_family = AF_UNIX;    
    strncpy(saun.sun_path, x, sizeof(saun.sun_path)-1);
    // alternatively this is safer:
    // snprintf(saun.sun_path, sizeof(saun.sun_path), "%s/AGENTSOCKET", buffer); 
    saun.sun_len = SUN_LEN(&saun);

    if (sendto(sockfd, (void*)pMsgData, sizeof(*pMsgData) + pMsgData->dataLen, 0, (struct sockaddr *) &saun, saun.sun_len) < 0)
    {
        AGENT_DEBUG(LOG_ERR, "%s", "Failed to send message from thread to main: %s\n", strerror(errno));
        return ~0;
    }

    return 0;
}