163 lines
3.6 KiB
C
163 lines
3.6 KiB
C
/*++
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Copyright (C) 1999 Microsoft Corporation
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Module Name:
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isdhcp.c
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Abstract:
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test program to see if a DHCP server is around or not.
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Environment:
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Win2K+
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--*/
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#include <nt.h>
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#include <ntrtl.h>
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#include <nturtl.h>
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#include <windows.h>
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#include <dhcpcapi.h>
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#include <iprtrmib.h>
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#include <iphlpapi.h>
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#include <stdio.h>
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#include <winsock2.h>
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BOOL
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IsDhcpServerAround(
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VOID
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)
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/*++
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Routine Description:
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This routine attempts to check if a dhcp
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server is around by trying to get a dhcp lease.
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If that fails, then it assume that no dhcp server
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is around.
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Return Values:
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TRUE -- DHCP server is around
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FALSE -- DHCP server not around
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In case of internal failures, it will return FALSE
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--*/
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{
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PMIB_IPADDRTABLE IpTable;
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DWORD Size, Error, i;
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DHCP_CLIENT_UID DhcpClientUID = {
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"ISDHCP", 6
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};
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DHCP_OPTION_LIST DummyOptList;
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LPDHCP_LEASE_INFO LeaseInfo;
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LPDHCP_OPTION_INFO DummyOptionInfo;
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BOOL fFound;
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Size = 0; IpTable = NULL;
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do {
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if( IpTable ) {
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LocalFree(IpTable);
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IpTable = NULL;
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}
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if( Size ) {
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IpTable = LocalAlloc( LPTR, Size );
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if( NULL == IpTable ) {
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Error = GetLastError();
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break;
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}
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}
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Error = GetIpAddrTable( IpTable, &Size, FALSE );
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} while( ERROR_INSUFFICIENT_BUFFER == Error );
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if( NO_ERROR != Error ) {
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#ifdef DBG
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DbgPrint("ISDHCP: GetIpAddrTable: 0x%lx\n", Error);
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#endif
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return FALSE;
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}
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//
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// Now walk through the ip addr table trying to obtain
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// a lease off of it
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//
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#ifdef DBG
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DbgPrint("ISDHCP: IpTable has 0x%lx entries\n", IpTable->dwNumEntries );
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#endif
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fFound = FALSE;
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for( i = 0; i < IpTable->dwNumEntries ; i ++ ) {
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DWORD Addr = IpTable->table[i].dwAddr;
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#ifdef DBG
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DbgPrint("ISDHCP: Verifying for IP address: 0x%lx\n", Addr );
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#endif
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if( Addr == INADDR_ANY ||
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Addr == INADDR_LOOPBACK ||
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Addr == 0x0100007f
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) {
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//
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// oops. not a usable address
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//
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continue;
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}
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LeaseInfo = NULL;
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Error = DhcpLeaseIpAddress(
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RtlUlongByteSwap(Addr), &DhcpClientUID, 0, &DummyOptList,
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&LeaseInfo, &DummyOptionInfo
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);
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if( NO_ERROR != Error ) {
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//
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// lease request failed.
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//
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#ifdef DBG
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DbgPrint("ISDHCP: lease request failed 0x%lx\n", Error);
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#endif
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if( ERROR_ACCESS_DENIED == Error ) {
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//
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// We only get access denied if the dhcp server
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// is around to NAK it. So we have found a dhcp
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// server
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//
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fFound = TRUE;
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break;
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}
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continue;
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}
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if( LeaseInfo->DhcpServerAddress != INADDR_ANY &&
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LeaseInfo->DhcpServerAddress != INADDR_NONE ) {
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//
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// Valid address, so dhcp is there.
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//
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#ifdef DBG
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DbgPrint("ISDHCP: DHCP server found: 0x%lx\n", LeaseInfo->DhcpServerAddress);
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#endif
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DhcpReleaseIpAddressLease(
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RtlUlongByteSwap(Addr), LeaseInfo
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);
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fFound = TRUE;
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break;
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}
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}
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LocalFree( IpTable);
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return fFound;
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}
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