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When I used the DhcpGetClientInfoV6 function in dhcpsapi.h, it returned code 2. After searching, I found the content, but I couldn't understand it.

$ .\Err_6.4.5.exe 2 # for hex 0x2 / decimal 2 BTH_ERROR_NO_CONNECTION bthdef.h DEVICE_QUEUE_NOT_BUSY bugcodes.h CDERR_INITIALIZATION cderr.h CR_OUT_OF_MEMORY cfgmgr32.h DHCP_DROP_NOMEM dhcpssdk.h MD_ERROR_SUB400_INVALID_DEPTH iiscnfg.h MD_ERROR_SUB401_LOGON_CONFIG iiscnfg.h MD_ERROR_SUB403_READ_ACCESS_DENIED iiscnfg.h MD_ERROR_SUB404_DENIED_BY_POLICY iiscnfg.h MD_ERROR_SUB423_NO_CONFLICTING_LOCK iiscnfg.h MD_ERROR_SUB502_PREMATURE_EXIT iiscnfg.h MD_ERROR_SUB503_APP_CONCURRENT iiscnfg.h IME_RS_NOIME ime.h # IME is not installed RSVP_Err_POLICY lpmapi.h RSVP_Erv_Bandwidth lpmapi.h # /* Insufficient bandwidth */ RSVP_Erv_No_Serv lpmapi.h # /* Unknown Service */ RSVP_Erv_API lpmapi.h # /* API logic error */ POLICY_ERRV_UNSUPPORTED_CREDENTIAL_TYPE lpmapi.h POLICY_ERRV_GLOBAL_GRP_FLOW_COUNT lpmapi.h MSIDBERROR_REQUIRED msiquery.h # non-nullable column no null values allowed NMERR_INVALID_HFILTER netmon.h SMART_INVALID_FLAG ntdddisk.h # Invalid command flag DS_NAME_ERROR_NOT_FOUND ntdsapi.h STATUS_WAIT_2 ntstatus.h ODBC_ERROR_INVALID_BUFF_LEN odbcinst.h MSDRI_S_MMI_PENDING pbdaerrors.h MFE_NOT_FORWARDING routprot.h # not fwding for an unspecified reason SCESTATUS_RECORD_NOT_FOUND scesvc.h SE_ERR_FNF shellapi.h # file not found SNMP_ERRORSTATUS_NOSUCHNAME snmp.h SNMP_GENERICTRAP_LINKDOWN snmp.h ICERR_NEWPALETTE vfw.h WDSMCCLIENT_CATEGORY wdsmcerr.h # WDS Multicast Client WINBIO_FP_TOO_LOW winbio_err.h # Position your finger higher on the fingerprint reader. CMC_STATUS_FAILED wincrypt.h CMC_FAIL_BAD_REQUEST wincrypt.h DRM_S_MORE_DATA windowsplayready.h ERROR_FILE_NOT_FOUND winerror.h # The system cannot find the file specified. ERROR_LABEL_QUESTIONABLE winioctl.h # Label could be invalid due to unit attention condition. LDAP_PROTOCOL_ERROR winldap.h SNMP_ERROR_NOSUCHNAME winsnmp.h # as an HRESULT: Severity: SUCCESS (0), FACILITY_NONE (0x0), Code 0x2 # for hex 0x2 / decimal 2 WINBIO_FP_TOO_LOW winbio_err.h # Position your finger higher on the fingerprint reader. # as an HRESULT: Severity: SUCCESS (0), FACILITY_NULL (0x0), Code 0x2 ERROR_FILE_NOT_FOUND winerror.h # The system cannot find the file specified. # 43 matches found for "2"

The possible code is ERROR_FILE_NOT_FOUND in winerror.h. However, after I changed the corresponding code in winerror.h and recompiled, the return code was still 2. I can't determine where the problem occurred. Please help.

This my code:

std::string LookupIPv6(const std::string& ip) { struct in6_addr addr; if (inet_pton(AF_INET6, ip.c_str(), &addr) != 1) { throw std::invalid_argument("Invalid IPv6 address"); } DHCP_SEARCH_INFO_V6 query; ZeroMemory(&query, sizeof(query)); query.SearchType = Dhcpv6ClientIpAddress; memcpy(&query.SearchInfo.ClientIpAddress, &addr, sizeof(addr)); LPDHCP_CLIENT_INFO_V6 result = nullptr; DWORD ret = DhcpGetClientInfoV6(nullptr, &query, &result); if (ret != ERROR_SUCCESS || !result) { FreeClientInfoMemoryV6(result); throw std::runtime_error("Failed to get DHCP client info, error code: " + std::to_string(ret)); } char mac[64]; BYTE* macData = result->ClientDUID.Data; snprintf(mac, sizeof(mac), "%02x:%02x:%02x:%02x:%02x:%02x", macData[0], macData[1], macData[2], macData[3], macData[4], macData[5]); FreeClientInfoMemoryV6(result); return std::string(mac); }
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  • 1
    editing a header won't change the behaviour of a compiled library, the documentation gives a list of return codes Commented Dec 5, 2024 at 8:11
  • 1
    The library was compiled before you changed the header file so changing the header file will not change the behaviour of the library. In fact you don't even know if the library uses that header file. Never change header files that do not belong to you, that's a sure recipe for confusion. Commented Dec 5, 2024 at 8:16
  • @AlanBirtles To be fair to the OP 2 is not one of the documented possible error codes. Commented Dec 5, 2024 at 8:18
  • 1
    My guess is that the problem is that you are passing nullptr as the first parameter to DhcpGetClientInfoV6. That parameter is supposed to be the ip address or hostname of your DCHP server. As far as I can tell from the documentation passing nullptr for that parameter is not permitted. Commented Dec 5, 2024 at 8:21
  • @john But When I use DhcpGetClientInfoV4 use nullptr it works fine😭 Commented Dec 5, 2024 at 9:02

1 Answer 1

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Invalid IPv6 Format Provided

I found the issue: the IPv6 address I was using for the query was incorrect. After fixing it, the following code worked as expected:

int main() { DHCP_CLIENT_INFO_V6 clientInfo = { 0 }; DHCP_IPV6_ADDRESS clientAddress = { 0 }; // Correct IPv6 address: 2022::74c0:f5e6:feca:3fb3 clientAddress.HighOrderBits = 0x2022000000000000; clientAddress.LowOrderBits = 0x74c0f5e6feca3fb3; clientInfo.ClientIpAddress = clientAddress; DHCP_SEARCH_INFO_V6 query{}; query.SearchType = Dhcpv6ClientIpAddress; query.SearchInfo.ClientIpAddress = clientAddress; LPDHCP_CLIENT_INFO_V6 result{ 0 }; DWORD ret = DhcpGetClientInfoV6(L"WIN-QI9RF26NQVN", &query, &result); if (ret == ERROR_SUCCESS) { // // Process the result... // } else { std::cout << std::to_string(ret) << std::endl; } }

To make the implementation more robust, I wrote a helper function to convert IN6_ADDR to DHCP_IPV6_ADDRESS:

// Converts IN6_ADDR to DHCP_IPV6_ADDRESS static void convertToDHCPIPv6(const IN6_ADDR* in6Addr, DHCP_IPV6_ADDRESS* dhcpAddr) { if (!in6Addr || !dhcpAddr) return; dhcpAddr->HighOrderBits = 0; dhcpAddr->LowOrderBits = 0; for (size_t i = 0; i < 4; i++) { dhcpAddr->HighOrderBits = (dhcpAddr->HighOrderBits << 16) | ntohs(in6Addr->u.Word[i]); } for (size_t i = 4; i < 8; i++) { dhcpAddr->LowOrderBits = (dhcpAddr->LowOrderBits << 16) | ntohs(in6Addr->u.Word[i]); } }

Here’s the complete, improved implementation:

static std::string LookupIPv6(const std::string& ip) { IN6_ADDR addr{}; if (inet_pton(AF_INET6, ip.c_str(), &addr) != 1) { throw std::invalid_argument("Invalid IPv6 address"); } DHCP_IPV6_ADDRESS clientIp; convertToDHCPIPv6(&addr, &clientIp); DHCP_SEARCH_INFO_V6 query{}; query.SearchType = Dhcpv6ClientIpAddress; query.SearchInfo.ClientIpAddress = clientIp; LPDHCP_CLIENT_INFO_V6 result{ 0 }; DWORD ret = DhcpGetClientInfoV6(DHCPSERVER, &query, &result); if (ret != ERROR_SUCCESS || !result) { std::string msg; switch (ret) { case ERROR_DHCP_JET_ERROR: case ERROR_DHCP_INVALID_DHCP_CLIENT: msg = "DHCP client not found."; break; default: msg = "Failed to get DHCP client info, error code : " + std::to_string(ret); break; } FreeClientInfoMemoryV6(result); throw std::runtime_error(msg); } char mac[128]{}; BYTE* macData = result->ClientDUID.Data; size_t macLength = result->ClientDUID.DataLength; size_t len = macLength < sizeof(mac) / 3 ? macLength : sizeof(mac) / 3; char* macPtr = mac; for (size_t i = 0; i < len; i++) { int printed = (i == len - 1) ? snprintf(macPtr, sizeof(mac) - (macPtr - mac), "%02x", macData[i]) : snprintf(macPtr, sizeof(mac) - (macPtr - mac), "%02x:", macData[i]); macPtr += printed; } FreeClientInfoMemoryV6(result); return std::string(mac); }

Issue: Status Code Returns 2

Although this code now works correctly, I am still unsure why the status code returns 2. If anyone can provide insights into this specific error code, it would be much appreciated.

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