在 C++ 中将 IPv6 转换为 IPv4 格式？

Question

我正在维护一个在 IPv4 格式上运行良好的旧系统，我发现当请求者来自 IPv6 时侦听器没有触发。我有以下代码行

    SOCKADDR_IN SocketAddr;
    INT nBufferSize=sizeof(SocketAddr);
    hConnectSocket=WSAAccept(m_hListenSocket,(SOCKADDR *)&SocketAddr,&nBufferSize,NULL,NULL);

     
    if (hConnectSocket==INVALID_SOCKET) return false;

我也用谷歌搜索过，我知道我应该将 SOCKADDR_IN6 用于 IPv6。是否可以将 SOCKADDR_IN6 转换为 SOCKADDR_IN 格式，以便应用程序的其余部分正常工作？

谢谢。

Answer 1

您无法将所有 IPv6 地址都转换为 IPv4 - IPv6 地址比 IPv4 地址多。解决此问题的最佳方法是更新/升级您的应用程序，以便它了解和存储 IPv6 地址。这个thread 可能有用。

Answer 2

我前段时间实施了一个可以使用 IPV4 和 IPV6 地址的解决方案。我什至确实封装了来自外部世界的属性。

程序的其余部分应该只知道套接字。如果您的代码接受 IPV6 或 IPV4 格式的地址并不重要/接受之后）。

重要的一点是您需要指定ai_family 和AF_UNSPEC。然后它将处理两个地址族。而对于accept函数，你可以传递一个足够大的参数来容纳两种地址类型。

我不确定，但也许这对你有帮助。

请看下面我几年前用 C++98 开发的代码 sn-p。

// The following structures are used in order to be independent from the internet address families
// e.g. IPV4 or IPV6.  The basic original functions have been designed for IPV4 only. 
// But now we are in the age of IPV6. And we need to have means to deal with both address types
// So we have one Data type, that can hold both IPV4 and IPV6 (because it has the length of the 
// larger IPV6 address). The pointer of this structure can be casted to the original data type
// that the functions always expected.
// The first field in the structures denotes the IP Address Family

// This is the big storage that can hold either a IPV4 or a IPV6 address
typedef struct sockaddr_storage SocketAddressStorage;

// This Type can hold the length of the IP Address container
typedef socklen_t SocketAddressStorageLength;


// This type is the Socket Address that OS function expect. We will cast the pointer of the big
// data type to this one
typedef struct sockaddr SocketAddress;

// The next 2 are specific address containers for either IPV4 or IPV6. 
// One of them will be a part of the big "struct sockaddr_storage"
typedef struct sockaddr_in SocketAddressInternetIPV4;
typedef struct sockaddr_in6 SocketAddressInternetIPV6;


// We use the big structure that can hold an IPV4 and IPV6 address
// because we do not know, who is contacting this node
SocketAddressStorage addressOfCommunicationPartner;
// Get the length of the above define data structure
SocketAddressStorageLength socketAddressStorageLength = sizeof(addressOfCommunicationPartner);


// Accept the connection request from a client
// handle is the filedescriptor bound to this node and listening for connection requests
// The function will return a new file descriptor for the connected socket. This is a specific socket
// for the just established connection. The handle will continue to listen for more connection requests
// So this is a factory. We are listening for connection requests and if we get one, we create a new
// file descriptor for the specific communication purposes
// The information of the foreign node will be put in the "addressOfCommunicationPartner"

// Accept the connection request from a client
//lint -e{740,929,1924}
const Handle connectionHandle = accept(handle, reinterpret_cast<SocketAddress *>(&addressOfCommunicationPartner), &socketAddressStorageLength);
// Check, if connection could be established and we have a valid file descriptor
if (connectionHandle > null<Handle>())
{
    // Now we want to get the IP address of the partner. Can be IPv4 or IPv6
    // The following old style C String can hold both IPv4 and IPv6 address strings
    mchar ipAddressCString[INET6_ADDRSTRLEN+1];
    
    // This is a pointer into the address structure of the communication partner
    // It points either to sin_addr for IPv4 or sin6_addr for IPv6
    const void *ipAddressPEitherV4orV6;

    // This will contain the IP Version as a string
    std::string ipVersion;
    
    // Now check, what family, what type of IP adress we have
    //lint -e{911,1960}
    if (AF_INET == addressOfCommunicationPartner.ss_family)
    {
        // So, it is IPv4. Remember that
        ipVersion = "IPv4";

        // Get a pointer to the appropriate element of the struct, which contains IP address info. And this depending on the IP Family/Type
        //lint --e{740,925,929}     Yes indeed, an unusual pointer cast
        ipAddressPEitherV4orV6 = static_cast<const void *>(  &((reinterpret_cast<const SocketAddressInternetIPV4 *const>(&addressOfCommunicationPartner))->sin_addr)  );
    }
    else
    {
        // It is IPv6. Remember that
        ipVersion = "IPv6";                     

        // Get a pointer to the appropriate element of the struct, which contains IP address info. And this depending on the IP Family/Type
        //lint --e{740,925,929}  Yes indeed, an unusual pointer cast
        ipAddressPEitherV4orV6 = static_cast<const void *>(  &((reinterpret_cast<const SocketAddressInternetIPV6 *const>(&addressOfCommunicationPartner))->sin6_addr)  );
    }
    
    // Convert native IP address format to readable C-String
    //lint -e{917,1960}
    if (null<mchar *>() == inet_ntop(addressOfCommunicationPartner.ss_family, ipAddressPEitherV4orV6, ipAddressCString, sizeof(ipAddressCString)))
    {
        // If this did not work then we will not show any IP Address. We can live with that
        ipAddressCString[0] = '\x0';
    }
    
    
    // Debug Output
    {
        static long i=1;
        ui << "Connection accepted " << i << " " << ipVersion << " " << ipAddressCString << " " << machineNetworkAddressInfo.portNumberString << std::endl;
        i++;
    }
    
    
    
    // So. The connection request was established. We gathered all information
    
    // Create a new TCP connection
    TcpConnectionBase *tcpConnectionBase =tcpConnectionFactory->createInstance(machineNetworkAddressInfo.portNumberString, connectionHandle);
    // And put a pointer to it in our internal list of Tcp Connection
    tcpConnection.push_back(tcpConnectionBase);

你可以找到其余的here