The IInetLogInformation::GetClientHostName method obtains the IP address of the client.
virtual LPSTR STDMETHODCALLTYPE GetClientHostName( IN PCHAR pszClientHostName, IN PDWORD pcbSize );
Logging modules should query for this method if a server instance has set the MD_EXTLOG_CLIENT_IP flag of the MD_LOGEXT_FIELD_MASK metabase identifier.
LogExtFileClientIp, MD_LOGEXT_FIELD_MASK