具有 NAT64 网络的 IPv6 套接字

Question

我正在尝试使用 BSD 套接字为 UE3 实现 IPv6 套接字连接。我已经成功地从 UE4 移植了使用所有 sockaddr_in6 和其他相对于 IPv6 结构和变量的代码。

连接到常规网络或 4G 时连接工作正常，但通过 Mac 共享功能连接到 NAT64 网络（Apple 批准要求）时，Connect() 始终返回 ENETUNREACH。我已经用 iPad4 和 iPhone6S 对其进行了许多代码修改（删除 setIPv6Only 函数，查看 AF_UNSPEC 等），但其中任何一个都没有运气。

调试一些数据发现getaddrinfo() 正在从 DNS 返回 IPv4，即使我已经在我的 DNS 表中设置了 AAAA 配置，指向允许 IPv6 的 Amazon AWS 服务器（我最后添加了这个最近的一部分，因为我之前认为服务器端也应该需要 IPv6）

这里是 DNS 查询：

FScopeLock ScopeLock(&HostByNameSynch);
addrinfo* AddrInfo = NULL;

// We are only interested in IPv6 addresses.
addrinfo HintAddrInfo;
appMemzero(&HintAddrInfo, sizeof(HintAddrInfo));

/* We only care about IPV6 results */
HintAddrInfo.ai_family = AF_INET6;//AF_UNSPEC;
HintAddrInfo.ai_socktype = SOCK_STREAM;
HintAddrInfo.ai_flags = AI_DEFAULT;

INT ErrorCode = SE_HOST_NOT_FOUND;
ErrorCode = getaddrinfo(HostName, NULL, &HintAddrInfo, &AddrInfo);
//ESocketErrors SocketError = TranslateGAIErrorCode(ErrorCode);
if (ErrorCode == SE_NO_ERROR)
{
    for (; AddrInfo != nullptr; AddrInfo = AddrInfo->ai_next)
    {
        if (AddrInfo->ai_family == AF_INET6)
        {
            /*sockaddr_in6* IPv6SockAddr = reinterpret_cast<sockaddr_in6*>(AddrInfo->ai_addr);
            if (IPv6SockAddr != nullptr)
            {
                static_cast<FInternetAddrBSDIPv6&>(OutAddr).SetIp(IPv6SockAddr->sin6_addr);
                return SE_NO_ERROR;
            }*/

            struct sockaddr_in6 input_socket6;
            memset (&input_socket6, 0, sizeof(struct sockaddr_in6));
            memcpy (&input_socket6, AddrInfo->ai_addr, AddrInfo->ai_addrlen);

            Addr.SetIp(input_socket6.sin6_addr);
            ErrorCode = 0;  // good to go.
            break;
        }
    }
}

freeaddrinfo(AddrInfo);

return ErrorCode;

这里是连接部分：

UBOOL FSocketBSD::Connect(const FInternetAddrBSDIPv6& Addr)
{
INT Err = 0;

Err = connect(Socket, (sockaddr*)(FInternetAddrBSDIPv6&)Addr, sizeof(sockaddr_in6));//connect(Socket,Addr,sizeof(struct sockaddr_in));

debugf(TEXT("TCP Connect to with V6 %s"), *Addr.ToString(TRUE) );

if (Err == 0)
{
    return TRUE;
}
else 
{
    debugf(TEXT("TCP ERROR Connect with result: %s"), GSocketSubsystem->GetSocketError(Err) );
}

Err = GSocketSubsystem->GetLastErrorCode();
INT Return = FALSE;
switch (Err)
{
    case 0:
    case EAGAIN:
    case EINPROGRESS:
    case EINTR:
        Return = TRUE;
        break;
}
return Return;
}

这里是套接字的创建：

SOCKET Socket = INVALID_SOCKET;
FSocketBSD* NewSocket = NULL;

// Creates a stream (TCP) socket
Socket = socket(AF_INET6, SOCK_STREAM, IPPROTO_TCP);
NewSocket = (Socket != INVALID_SOCKET) ? new FSocketBSD(Socket,SOCKTYPE_Streaming,SocketDescription) : NULL;

if (!NewSocket)
{
    debugf(NAME_Init, TEXT("Failed to create IPv6 socket %s [%s]"), *SocketDescription);
}
else 
{
    NewSocket->SetIPv6Only(false);

    // disable the SIGPIPE exception 
    int bAllow = 1;
    setsockopt(Socket, SOL_SOCKET, SO_NOSIGPIPE, &bAllow, sizeof(bAllow)); 
}

return NewSocket;


UBOOL FSocketBSD::SetIPv6Only(UBOOL bIPv6Only)
{
    INT v6only = bIPv6Only ? 1 : 0;
    UBOOL bOk = setsockopt(Socket,IPPROTO_IPV6,IPV6_V6ONLY,(char*) &v6only,sizeof( v6only )) == 0;

    if(bOk == false)
    {
        //check(SocketSubsystem);
        debugf(NAME_Init, TEXT("Failed to set sock opt for socket (%s)"), GSocketSubsystem->GetSocketError());
    }

    return bOk;
}

这是一些调试信息：

[0009.49] Log: TCP SetIp TCHAR u101si.info
[0009.49] Log: TCP GetHostByNameFromCache with FInternetAddrBSDIPv6
[0009.49] Log: TCP GetHostByName starting async task
[0009.49] Log: TCP Performing DNS lookup for u101si.info
[0009.66] Log: TCP SetIp in6_addr
[0009.66] Log: TCP AddHostNameToCache with FInternetAddrBSDIPv6
[0009.66] Log: TCP Tick DNS lookup
[0009.66] Log: TCP AInternetLink Resolve success
[0009.66] ScriptLog: [TcpLinkClient] resolved to 54.169.208.63:4646
[0009.66] Log: Host addr is WIFI: 169.254.23.45
[0009.66] Log: TCP BindPort with NewSocket at 0.0.0.0
[0009.66] Log: TCP SetIp FInternetIpAddr for 0.0.0.0
[0009.66] Log: TCP SetIp in_addr
[0009.66] Log: TCP Using IPv4 address: 0.0.0.0  on an ipv6 socket
[0009.66] Log: TCP Bind for 0.0.0.0:0 result: 1
[0009.66] ScriptLog: [TcpLinkClient] Bound to port: 60885
[0009.66] Log: TCP Open with 54.169.208.63
[0009.66] Log: TCP SetIp with INT value: 917098559
[0009.66] Log: TCP SetIp in_addr
[0009.66] Log: TCP Using IPv4 address: 54.169.208.63  on an ipv6 socket
[0009.66] Log: TCP Connect to with V6 [::ffff:54.169.208.63]:4646
[0009.66] Log: TCP ERROR Connect with result: SE_ENETUNREACH

我从未使用过 IPv6 协议或低级套接字连接，所以我在这里迷路了。这是由客户端问题引起的吗？ DNS查找问题？服务器不接受 IPv6 客户端？

提前致谢！

Answer 1

在设备中经过多次测试后，我成功了。

问题在于 DNS 的缓存，它返回过时的 IP 并来自对 getaddrinfo() 的调用。添加端口参数时，它触发了 DNS 中的正确注册：A 代表 IPv4，AAAA 代表 IPv6。

这是适用于 IPv4 和 IPv6 的调用：

FInternetAddrBSDIPv6& Addr;
struct addrinfo *res, *res0;

// We are only interested in IPv6 addresses.
addrinfo HintAddrInfo;
appMemzero(&HintAddrInfo, sizeof(HintAddrInfo));

HintAddrInfo.ai_family = AF_UNSPEC;
HintAddrInfo.ai_socktype = SOCK_STREAM;
//HintAddrInfo.ai_protocol = IPPROTO_TCP;
HintAddrInfo.ai_flags = AI_DEFAULT;

INT ErrorCode = SE_HOST_NOT_FOUND;
ErrorCode = getaddrinfo(HostName, "1212", &HintAddrInfo, &res0);

if (ErrorCode == SE_NO_ERROR)
{
    for (res = res0; res; res = res->ai_next) 
    {
        debugf(TEXT("TCP GetHostByName with DNS successful"));

        if (res->ai_addr != 0)
        {
            if( res->ai_family == AF_INET6 )
            {
                struct sockaddr_in6 input_socket6;
                memset (&input_socket6, 0, sizeof(struct sockaddr_in6));
                memcpy (&input_socket6, res->ai_addr, res->ai_addrlen);

                Addr.SetIp(input_socket6.sin6_addr);
                ErrorCode = 0;  // good to go.
                break;
            }
            else if( res->ai_family == AF_INET )
            {
                const in_addr &IP = ((sockaddr_in *) res->ai_addr)->sin_addr;
                Addr.SetIp(IP);
                ErrorCode = 0;  // good to go.
                break;
            }
        }

    }
}

freeaddrinfo(res0);

return ErrorCode;