I have a small app that temporary adds several (3-4) IP addresses using AddIPAddress function from IP Helper. After some seconds (2-3), it deletes these addresses using DeleteIPAddress function.
The function DeleteIPAddress works and returns no error, but sometimes (once every 3 or 4 rounds of adding and deleting) it triggers a disconnection event on the interface (exactly like disconnecting and connecting the cable).
I want to avoid these disconnections as they cut any communication being done in the same interface, but I cannot see anything in the documentation regarding this behavior.
This is how I add each IP address:
auto dwRetVal = AddIPAddress(iaIPAddress, iaIPMask, _idx, &NTEContext, &NTEInstance);
if (dwRetVal == ERROR)
{
std::cout << "Error on AddIPAddress" << std::endl;
}
And this is how I delete them:
auto dwRetVal = DeleteIPAddress(ipContext);
if (dwRetVal != NO_ERROR)
{
std::cout << "Error on DeleteIPAddress" << std::endl;
}
Am I missing something?
You are not checking the return value from AddIPAddress correctly, you should test != ERROR_SUCCESS.
If AddIPAddress fails you should not call delete.
Related
Our program has a piece of code that calculates the list of computers on our local network. It uses the Windows Networking API (WNetOpenEnum/WNetEnumResource) to unwind the network. For many years, the resulting list was identical to the one that can be seen in Windows Explorer under the "Network" entry. However, recently we have noticed that the same code returns an empty list. During debugging I found that WNetOpenEnum returns error 1231 (ERROR_NETWORK_UNREACHABLE) when it is called for the "Microsoft Windows Network" under the root node.
I have to mention, though I'm pretty sure it has nothing to do with the matter, that the network unwinding is done multithreaded, to avoid possible delays in the main GUI thread. Each time a node of type RESOURCEUSAGE_CONTAINER is encountered, a new worker thread is launched. The thread function calls the following procedure:
DWORD WINAPI EnumNetwork(NETRESOURCE_M* lpNR)
{
const int BUF_SIZE = 16384; // 16K is a good size.
HANDLE hEnum;
DWORD Result;
// Call the WNetOpenEnum function to begin the enumeration.
Result = ::WNetOpenEnum(RESOURCE_GLOBALNET, // all network
RESOURCETYPE_ANY, // all resource types
0, // enumerate all
(LPNETRESOURCE)lpNR,// parent resource
&hEnum); // enumeration handle
if (Result != NO_ERROR) // -> for "Microsoft Windows Network" Result = 1231
return Result;
std::vector<std::wstring> SrvList;
// Allocate buffer for enumeration.
LPNETRESOURCE lpEnumNR = (LPNETRESOURCE)new char[BUF_SIZE];
if (lpEnumNR == 0)
Result = ERROR_OUTOFMEMORY;
else
{
while (1)
{
::ZeroMemory(lpEnumNR, BUF_SIZE); // Initialize the buffer.
DWORD NumEntries = -1; // Enumerate all entries.
DWORD BufSize = BUF_SIZE;
// Call WNetEnumResource to continue the enumeration.
Result = ::WNetEnumResource(hEnum, // enumeration handle
&NumEntries,// number of entries to enumerate
lpEnumNR, // array of resources to return
&BufSize); // buffer size
if (Result == NO_ERROR)
{
// If the call succeeds, loop through the array.
for (unsigned i = 0; i < NumEntries; ++i)
{
if (lpEnumNR[i].dwDisplayType == RESOURCEDISPLAYTYPE_SERVER)
{
// Collect servers.
LPCWSTR SrvName = lpEnumNR[i].lpRemoteName;
if (PathHelpers::IsFullPath(SrvName))
SrvList.push_back(SrvName);
}
else if ((lpEnumNR[i].dwUsage & RESOURCEUSAGE_CONTAINER) &&
lpEnumNR[i].lpRemoteName != 0)
{
TCHAR PathBuf[1024] = {0};
if (lpNR && lpNR->Path)
{
_tcscpy(PathBuf, lpNR->Path);
::PathAddBackslash(PathBuf);
}
_tcscat(PathBuf, lpEnumNR[i].lpRemoteName);
if (RegisterServer(PathBuf))
{
// Start new thread for recursive enumeration.
NETRESOURCE_M* lpChildNR = DeepCopyNR(&lpEnumNR[i], PathBuf);
ExploreNetwork(lpChildNR); // -> this starts a worker thread
}
else
{
GetLogger().LogMessage(
_T("Cycles found while unwinding network: %s"), PathBuf);
}
}
}
}
else
{
if (Result == ERROR_NO_MORE_ITEMS)
Result = NO_ERROR;
break;
}
} // end while
delete [] (char*)lpEnumNR;
} // end if
::WNetCloseEnum(hEnum);
if (!SrvList.empty())
NotifyServerAdded(SrvList);
return Result;
}
where NETRESOURCE_M is the structure
struct NETRESOURCE_M
{
NETRESOURCE NR;
LPTSTR Path;
};
Trying to figure out what could have caused such a sudden change in behavior, I found in Google that a few years ago Microsoft disabled the SMB1 protocol, which could affect Network Discovery. However, I can't believe they could have damaged their own API without saying a word in the documentation.
EDIT: At the same time, Windows Explorer has a bunch of computers under its "Network" node. In the network settings, the network type is "Domain", and the network discovery is ON. Services "Function Discovery Provider Host" and "Function Discovery Resources Publication" are running. Windows OS build is 19042.685.
Edit 2: The Sysinternals' "ShareEnum" tool also fails with the error: "No domains or workgroups where found on your network". Because of this, and also because some time ago our company moved all of its computers to a different network, I got the feeling that the problem is in the network configuration. Such as though the network is declared as "Domain", the computers were not enrolled to this domain. I do not understand much in that, but something like this.
I've got a block of code that throws an Access Violation when executed. It is the async_connect handler for boost::asio.
//------------------------------------------------------------------------------
void MyClient::OnConnect(const boost::system::error_code & errorCode, boost::asio::ip::tcp::resolver::iterator endpoint)
{
if (errorCode || endpoint == boost::asio::ip::tcp::resolver::iterator())
{
// Error - An error occured while attempting to connect
// Most likely these error codes correspond to https://msdn.microsoft.com/en-us/library/windows/desktop/ms740668(v=vs.85).aspx
std::ostringstream msg;
msg << "An error occured while attempting to connect to " << endpoint->host_name()
<< ". Error code: " << errorCode
<< ". Error Message: " << ErrorCodeToString(errorCode);
LogError(msg.str().c_str(), __FUNCSIG__, __FILE__, __LINE__);
return;
}
// We connected to an endpoint
m_connectionState |= CONNECTED;
In the debugger it looks like the problem is inside endpoint->host_name(), because it tried to get values_[0] while values_ are null.
This is a common Connection Refused scenario. I thought the handler got the endpoint so that it knew who it was trying to connect to! Is there some manner of check I can do on the iterator before I try to call a method on it?
It seems to pass and still throw access violation on
if( endpoint != boost::asio::ip::tcp::resolver::iterator() )
{
std::string blah = endpoint->host_name();
}
Probably you've figured this out by now, but I'll post a few lines in case someone else happens upon it.
This problem looks similar to one I had.
This will not work, and will give similar results to what you're describing.
void establish_connection() {
tcp::resolver resolver(get_asio_io_service()); // this is a problem
tcp::resolver::query q{server_name, "https"};
resolver.async_resolve(q,
[&](asio::error_code ec,
tcp::resolver::iterator it) {
this->handle_resolve(ec, it);
});
}
where establish_connection() is a method in the object that deals with communication to the server.
The resolver object disappears after the establish_connection() exits. You have to find a way to make it stick around. The various demos on the web have it as an attribute of the client object.
Please share your experience with this problem.
Originally posted here, but found off topic: https://serverfault.com/questions/617459/faster-processing-of-sendarp-function
I've been working on a network scanner for Windows. I have successfully written the code, but the problem is it takes too much time to scan the hosts that aren't up. When I tried scanning a subnet (1 to 255), it took more than half hour. I couldn't find a function to control the time limit or a way to control the time-out of SendARP function.
DestIp = inet_addr(strn.c_str()); //Setting Destination IPv4 dotted-decimal address into a proper address for the IN_ADDR structure.
SrcIp = inet_addr(SrcIpString);
memset(&MacAddr, 0xff, sizeof(MacAddr)); //Initializing MAC Address to ff-ff-ff-ff-ff-ff
dwRetVal = SendARP(DestIp, SrcIp, &MacAddr, &PhysAddrLen); //Sending ARP request to the destined IP Address
if (dwRetVal == NO_ERROR) {
bPhysAddr = (BYTE *)& MacAddr;
if (PhysAddrLen) {
std::cout << strn<<std::endl;
for (int i = 0; i < (int)PhysAddrLen; i++) {
if (i == ((int)PhysAddrLen - 1))
printf("%.2X\n", (int)bPhysAddr[i]);
else
printf("%.2X-", (int)bPhysAddr[i]);
}
}
}
You're using a convenience function from the "IP Helper" library. That's not performance-oriented.
The ServerFault comments actually hit the mail on the head: use threads. With <thread> that's nowadays quite simple. Just do 255 std::async calls to your function. Of course, make sure that all the MacAddr and PhysAddrLen references aren't invalidated.
I'm using libcurl with C++. I have made a thread-safe class for downloading webpages. Each call to static download method creates "easy" handle, performs the job and frees the handle. When I use it from the single thread - everything's fine. But when I spawn several threads to download several pages in parallel I sometimes (not fro every download, but quite often) get error saying "timeout". I have a reasonably high timeout configured (5 sec connection timeout and 25 sec global timeout).
Any ideas as to what might be the cause and how to fix it?
P. S. It happens on both Windows and Linux.
Here's the code of the method in question:
void CHttpDownloaderLibcurl::downloaderThread( const CUrl& url, CThreadSafeQueue<CHtmlPage>& q)
{
CHtmlPage page (url);
CURL* handle = curl_easy_init();
if (!handle)
{
assert(handle);
return;
}
int curlErr = setCurlOptions(handle, url, (void*)onCurlDownloadCallback, (void*)&page.byteArray());
if (CURLE_OK != curlErr)
{
assert("Error setting options" == (char*)curlErr);
return;
}
curlErr = curl_easy_perform(handle);
page._info = getInfo(handle);
curl_easy_cleanup(handle);
if (CURLE_OK != curlErr)
{
if (curlErr == CURLE_OPERATION_TIMEDOUT)
{
CLogger() << "Curl timeout!";
}
else
CLogger() << url.urlString() << ": Error performing download = " << curlErr;
return;
}
q.push(page);
}
I think you are my last hope. I have got here a Bluetooth device (it is a sensor to be more precisely) which I want to connect to and read data from. The device offers SPP (Serial Port Profile). To avoid the problem of reliable mapping from Bluetooth addresses and virtual serial ports (COM Ports), I am going to use sockets.
Unfortunately the application always crashes before returning from WinAPI function connect(...) with: 0xC0000005: Access violation reading location 0x00000004, so I get no error code.
BUT, and that is weird, when I right-click on the Bluetooth System Tray Icon to to show available devices, my device shows up being authenticated and connected. This list was empty before, of course.
My OS is Windows 7 64 Bit, the IDE is Visual Studio 2010, Microsoft Bluetooth Stack. Code to find and connect to my only device:
#include <iostream>
#include <string>
#include <algorithm>
#include <cassert>
#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <BluetoothAPIs.h>
#include <Winsock2.h>
#include <Ws2bth.h>
BOOL auth_callback_ex(LPVOID pvParam, PBLUETOOTH_AUTHENTICATION_CALLBACK_PARAMS authParams)
{
BLUETOOTH_AUTHENTICATE_RESPONSE response;
response.bthAddressRemote = authParams->deviceInfo.Address;
response.authMethod = authParams->authenticationMethod; // == BLUETOOTH_AUTHENTICATION_METHOD_LEGACY
UCHAR pin[] = "1234";
std::copy(pin, pin+sizeof(pin), response.pinInfo.pin);
response.pinInfo.pinLength = sizeof(pin)-1; //excluding '\0'
response.negativeResponse = false;
HRESULT err = BluetoothSendAuthenticationResponseEx(NULL, &response);
if (err)
{
std::cout << "BluetoothSendAuthenticationResponseEx error = " << err << std::endl;
}
return true;
}
int main()
{
BLUETOOTH_DEVICE_SEARCH_PARAMS btSearchParams;
btSearchParams.dwSize = sizeof(BLUETOOTH_DEVICE_SEARCH_PARAMS);
btSearchParams.cTimeoutMultiplier = 5; //5*1.28s search timeout
btSearchParams.fIssueInquiry = true; //new inquiry
//return all known and unknown devices
btSearchParams.fReturnAuthenticated = true;
btSearchParams.fReturnConnected = true;
btSearchParams.fReturnRemembered = true;
btSearchParams.fReturnUnknown = true;
btSearchParams.hRadio = NULL; //search on all local radios
BLUETOOTH_DEVICE_INFO btDeviceInfo;
ZeroMemory(&btDeviceInfo, sizeof(BLUETOOTH_DEVICE_INFO)); //"initialize"
btDeviceInfo.dwSize = sizeof(BLUETOOTH_DEVICE_INFO);
HBLUETOOTH_DEVICE_FIND btDeviceFindHandle = NULL;
btDeviceFindHandle = BluetoothFindFirstDevice(&btSearchParams, &btDeviceInfo);
if(btDeviceFindHandle)
{
HBLUETOOTH_AUTHENTICATION_REGISTRATION authCallbackHandle = NULL;
DWORD err = BluetoothRegisterForAuthenticationEx(&btDeviceInfo, &authCallbackHandle, &auth_callback_ex, NULL);
if (err != ERROR_SUCCESS)
{
DWORD err = GetLastError();
std::cout << "BluetoothRegisterForAuthentication Error" << err << std::endl;
}
/////////////// Socket
WSADATA wsaData;
err = WSAStartup(MAKEWORD(2,2), &wsaData);
if (err)
{
std::cout << "WSAStartup error = " << err << std::endl;
}
// create BT socket
SOCKET s = socket (AF_BTH, SOCK_STREAM, BTHPROTO_RFCOMM);
assert(s != INVALID_SOCKET); //WSAGetLastError //throw // runtime check release?
SOCKADDR_BTH btSockAddr;
btSockAddr.addressFamily = AF_BTH;
btSockAddr.btAddr = btDeviceInfo.Address.ullLong;
btSockAddr.serviceClassId = RFCOMM_PROTOCOL_UUID; //SerialPortServiceClass_UUID (no difference)
btSockAddr.port = BT_PORT_ANY;
err = connect(s, reinterpret_cast<SOCKADDR*>(&btSockAddr), sizeof(SOCKADDR_BTH));
/* <--- never got so far --> */
if (err)
{
DWORD wsaErr = WSAGetLastError();
std::cout << "connect error = " << wsaErr << std::endl;
}
else
{
//err = shutdown(s, SD_BOTH);
err = closesocket(s);
if (err)
{
std::cout << "closesocket error = " << err << std::endl;
}
}
WSACleanup();
///////////////Socket
BOOL ok = BluetoothUnregisterAuthentication(authCallbackHandle);
if (!ok)
{
DWORD err = GetLastError();
std::cout << "BluetoothUnregisterAuthentication Error" << err << std::endl;
}
ok = BluetoothFindDeviceClose(btDeviceFindHandle);
if (!ok)
{
DWORD err = GetLastError();
std::cout << "BluetoothDeviceClose Error" << err << std::endl;
}
}
else
{
DWORD err = GetLastError();
std::cout << "BluetoothFindFirstDevice Error" << err << std::endl;
}
std::cin.get();
}
I have made some few more observations:
The authentication callback and the BluetoothSendAuthenticationResponseEx function are working fine, there is no error given back.
If I do not install the authentication callback (BluetoothRegisterForAuthenticationEx) and therefore have to manually enter the PIN (the UI shows up automatically while trying to connect), connect function returns properly and everything works fine, too. I even got data (the recv part is omitted in this snippet).
If I search and pair completely manually (Bluetooth Tray Icon -> Add Device), everything is fine, too. A service and a virtual serial port is installed. Data come via putty.
So somewhere between calling the authentication callback and end of the connect function something is going wrong. Maybe when trying to get a certain structure data via a pointer, which should not be NULL, plus offset.
Or am I doing something wrong? Is there something missing?
Thanks...
The problem is that your function is using the wrong calling convention. According to MSDN, you need to use the CALLBACK macro, as in:
BOOL CALLBACK auth_callback_ex(LPVOID pvParam, PBLUETOOTH_AUTHENTICATION_CALLBACK_PARAMS authParams)
Having the wrong calling convention will result in a stack mismatch on return, which could cause an access violation inside the MS Bluetooth code when it can't find its local variables.
Or it could result in the parameters to your function being all jumbled. If authParams and pvParam are swapped, because the cdecl calling convention expects args pushed from right to left and stdcall pushes them left to right, you'd get NULL in authParams, and then authParams->deviceInfo.Address will try to read address 0x04.
The compiler should have caught this. Compile with maximum warnings turned on (/W4). You'll have to ignore the warnings about unknown pragma, this is a bug in the header which I'm reporting to Microsoft (misspelled #pragma deprecated).
Unfortunately there's a second bug in the header, much more serious, of not specifying the calling convention explicitly, with the result that it will only work correctly on x86 (32-bit code) if /Gz is used. Yuck!
Followup: In the SDK headers shipped with VS2013, both issues are fixed.
You have a null-pointer access somewhere. "Access violation reading location 0x00000004" indicates that, as it is only 4 bytes away from zero.
I have a couple of thoughts to share with you, but be advised that these are hunches. I haven't compiled and debugged your code, although I commend you for posting a complete sample.
I think the crash may be within your authentication callback function, due to a '''NULL''' pointer dereference.
These lines:
response.bthAddressRemote = authParams->deviceInfo.Address;
response.authMethod = authParams->authenticationMethod; // == BLUETOOTH_AUTHENTICATION_METHOD_LEGACY
will cause the message you describe, if you are running on 32-bit Windows, and '''authParams''' may be '''NULL''' -- in that case, '''deviceInfo''' contributes a zero offset (it is at the beginning of the '''BLUETOOTH_AUTHENTICATION_CALLBACK_PARAMS'''), and '''.Address''' does contribute an offset of 4 ('''NULL + 4 == 0x00000004'''), because it follows a '''DWORD''' and nothing else within the '''BLUETOOTH_DEVICE_INFO''' layout.
Is it possible that '''authParams''' is NULL when your callback is called?
As another poster has already mentioned, this could be due to incorrect calling convention (lack of '''CALLBACK''' macro) -- causing otherwise correct parameters to mis-align with the positions the compiled code is reading.
The second thought was:
BLUETOOTH_DEVICE_INFO btDeviceInfo;
ZeroMemory(&btDeviceInfo, sizeof(BLUETOOTH_DEVICE_INFO)); //"initialize"
btDeviceInfo.dwSize = sizeof(BLUETOOTH_DEVICE_INFO);
Can be represented by:
BLUETOOTH_DEVICE_INFO btDeviceInfo = {sizeof(BLUETOOTH_DEVICE_INFO)};
According to the standard, this will zero the other fields of '''btDeviceInfo'''.
Or write managed code and use my Bluetooth library 32feet.NET Super simple. http://32feet.codeplex.com/
Will it crash then -- if so there's something wrong on your PC...