Stephen C. Steel wrote:
> The attached patch fixes some problems in the function
> getIPHelperDNSEntries() found in the file
> sipXportlib\src\os\Wnt\getWindowsDNSServers.cpp. This function attempts to
> obtain the list of DNS servers from Windows using the iphlpapi.dll function
> available under most versions of Windows. However, under Windows XP, this
> function was ALWAYS failing. This failure was masked because
> getWindowsDNSServers() calls getDNSEntriesFromRegistry() if
> getIPHelperDNSEntries() doesn't find anything - getDNSEntriesFromRegistry()
> is intended to deal with Windows NT4 systems that don't support
> iphlpapi.dll. Under Windows XP, getDNSEntriesFromRegistry() does succeed if
> the DNS server list was obtained by DHCP, but it fails if the DNS servers
> are statically configured, as they are stored in a different registry
> location than they were under NT4 (under an adapter specific key).
>
> The changes I made were as follows:
> ===================================
>
> 1. The function pointer GetNetworkParams was being set to NULL just before
> calling loadIPHelperAPI(). Not only isn't this necessary (as it is
> statically initialized to NULL), if the call to loadIPHelperAPI() that
> occurs here is not the first time loadIPHelperAPI() is called (and it
> frequently isn't), then the address of the iphlpapi.dll function is lost as
> loadIPHelperAPI() only sets the function pointers the FIRST time it is
> called).
>
> 2. I changed getIPHelperDNSEntries() to return early for the cases where it
> fails (wrong windows version or unable to load iphlpapi.dll).
>
> 3. The code for Windows 2000 and XP, called GetInterfaceInfo() to get a list
> of adapter names and the corresponding index, and looked for and adapter
> with a name matching the return value from getContractAdapterName().
> However, the test used to determine this was backwards:
>
> if (contactAdapterName.contains(szAdapterName))
>
> Since contactAdapterName (obtained from getContactAdapterName()) returns a
> name of the form "{GUID}", while szAdapterName (obtained from the list
> returned from GetInterfaceInfo()) is of the form "\DEVICE\TCPIP_{GUID}".
> Thus, this test never succeeded. Instead of using getContactAdapterName() to
> find the adapter by name, I've changed the code to walk the list of adapters
> looking for one with the correct IP address (which is how
> getContactAdapterName() gets the name in the first place) and then just use
> its index directly to call GetPerAdapterInfo().
>
>
>
> I've only been able to test the code path used by Windows XP (but same code
> should also be used by Windows 2000 and Windows Vista). The code path used
> by Windows 98/Me systems (using the GetNetworkParams() function in
> iphlpapi.dll) hasn't changed, and I haven't changed
> getDNSEntriesFromRegistry() which is used for NT4.
>
> Stephen C. Steel
The DNS code has more bugs than this. For example it uses ethN style
adapter names, but if you add a new adapter, or enable a previosly
disabled one, adapters can be renumbered, thus sipxtapi might not work
properly at all.
Jaro
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