/**
* Constructor. Establishes a TCP socket connection with the DHCP client daemon on port 5818.
*
* @throws IOException if unable to establish the connection with the DHCP client daemon.
*/
private Poller(long timeout) throws IOException {
DhcpdConfigFactory dcf = DhcpdConfigFactory.getInstance();
try {
LOG.debug(
"Poller.ctor: opening socket connection with DHCP client daemon on port {}",
dcf.getPort());
m_connection = new Socket(InetAddressUtils.addr("127.0.0.1"), dcf.getPort());
LOG.debug("Poller.ctor: setting socket timeout to {}", timeout);
m_connection.setSoTimeout((int) timeout);
// Establish input/output object streams
m_ins = new ObjectInputStream(m_connection.getInputStream());
m_outs = new ObjectOutputStream(m_connection.getOutputStream());
m_outs.reset();
m_outs.flush();
} catch (IOException ex) {
LOG.error("IO Exception during socket connection establishment with DHCP client daemon.", ex);
if (m_connection != null) {
try {
m_ins.close();
m_outs.close();
m_connection.close();
} catch (Throwable t) {
}
}
throw ex;
} catch (Throwable t) {
LOG.error(
"Unexpected exception during socket connection establishment with DHCP client daemon.",
t);
if (m_connection != null) {
try {
m_ins.close();
m_outs.close();
m_connection.close();
} catch (Throwable tx) {
}
}
throw new UndeclaredThrowableException(t);
}
}
/**
* This method actually tests the remote host to determine if it is running a functional DHCP
* server.
*
* <p>Formats a DHCP query and encodes it in a client request message which is sent to the DHCP
* daemon over the established TCP socket connection. If a matching DHCP response packet is not
* received from the DHCP daemon within the specified timeout the client request message will be
* re-sent up to the specified number of retries.
*
* <p>If a response is received from the DHCP daemon it is validated to ensure that:
*
* <ul>
* <li>The DHCP response packet was sent from the remote host to which the original request
* packet was directed.
* <li>The XID of the DHCP response packet matches the XID of the original DHCP request packet.
* </ul>
*
* <p>If the response validates 'true' is returned. Otherwise the request is resent until max
* retry count is exceeded.
*
* <p>Before returning, a client disconnect message (remote host field set to zero) is sent to the
* DHCP daemon.
*
* @return response time in milliseconds if the specified host responded with a valid DHCP offer
* datagram within the context of the specified timeout and retry values or negative one (-1)
* otherwise.
*/
static long isServer(InetAddress host, long timeout, int retries) throws IOException {
boolean isDhcpServer = false;
// List of DHCP queries to try. The default when extended
// mode = false must be listed first. (DISCOVER)
byte[] typeList = {
(byte) DHCPMessage.DISCOVER, (byte) DHCPMessage.INFORM, (byte) DHCPMessage.REQUEST
};
String[] typeName = {"DISCOVER", "INFORM", "REQUEST"};
DhcpdConfigFactory dcf = DhcpdConfigFactory.getInstance();
if (!paramsChecked) {
String s_extendedMode = dcf.getExtendedMode();
if (s_extendedMode == null) {
extendedMode = false;
} else {
extendedMode = Boolean.parseBoolean(s_extendedMode);
}
LOG.debug("isServer: DHCP extended mode is {}", extendedMode);
String hwAddressStr = dcf.getMacAddress();
LOG.debug("isServer: DHCP query hardware/MAC address is {}", hwAddressStr);
setHwAddress(hwAddressStr);
String myIpStr = dcf.getMyIpAddress();
LOG.debug("isServer: DHCP relay agent address is {}", myIpStr);
if (myIpStr == null || myIpStr.equals("") || myIpStr.equalsIgnoreCase("broadcast")) {
// do nothing
} else {
try {
InetAddressUtils.toIpAddrBytes(myIpStr);
s_myIpAddress = setIpAddress(myIpStr);
relayMode = true;
} catch (IllegalArgumentException e) {
LOG.warn("isServer: DHCP relay agent address is invalid: {}", myIpStr);
}
}
if (extendedMode == true) {
String requestStr = dcf.getRequestIpAddress();
LOG.debug("isServer: REQUEST query target is {}", requestStr);
if (requestStr == null
|| requestStr.equals("")
|| requestStr.equalsIgnoreCase("targetSubnet")) {
// do nothing
} else if (requestStr.equalsIgnoreCase("targetHost")) {
targetOffset = false;
} else {
try {
InetAddressUtils.toIpAddrBytes(requestStr);
s_requestIpAddress = setIpAddress(requestStr);
reqTargetIp = false;
targetOffset = false;
} catch (IllegalArgumentException e) {
LOG.warn("isServer: REQUEST query target is invalid: {}", requestStr);
}
}
LOG.debug(
"REQUEST query options are: reqTargetIp = {}, targetOffset = {}",
reqTargetIp,
targetOffset);
}
paramsChecked = true;
}
int j = 1;
if (extendedMode == true) {
j = typeList.length;
}
if (timeout < 500) {
timeout = 500;
}
Poller p = new Poller(timeout);
long responseTime = -1;
try {
pollit:
for (int i = 0; i < j; i++) {
Message ping = getPollingRequest(host, (byte) typeList[i]);
int rt = retries;
while (rt >= 0 && !isDhcpServer) {
LOG.debug(
"isServer: sending DHCP {} query to host {} with Xid: {}",
typeName[i],
InetAddressUtils.str(host),
ping.getMessage().getXid());
long start = System.currentTimeMillis();
p.m_outs.writeObject(ping);
long end;
do {
Message resp = null;
try {
resp = (Message) p.m_ins.readObject();
} catch (InterruptedIOException ex) {
resp = null;
}
if (resp != null) {
responseTime = System.currentTimeMillis() - start;
// DEBUG only
LOG.debug(
"isServer: got a DHCP response from host {} with Xid: {}",
InetAddressUtils.str(resp.getAddress()),
resp.getMessage().getXid());
if (host.equals(resp.getAddress())
&& ping.getMessage().getXid() == resp.getMessage().getXid()) {
// Inspect response message to see if it is a valid DHCP response
byte[] type = resp.getMessage().getOption(MESSAGE_TYPE);
if (type[0] == DHCPMessage.OFFER) {
LOG.debug("isServer: got a DHCP OFFER response, validating...");
} else if (type[0] == DHCPMessage.ACK) {
LOG.debug("isServer: got a DHCP ACK response, validating...");
} else if (type[0] == DHCPMessage.NAK) {
LOG.debug("isServer: got a DHCP NAK response, validating...");
}
// accept offer or ACK or NAK
if (type[0] == DHCPMessage.OFFER
|| (extendedMode == true
&& (type[0] == DHCPMessage.ACK || type[0] == DHCPMessage.NAK))) {
LOG.debug(
"isServer: got a valid DHCP response. responseTime= {}ms", responseTime);
isDhcpServer = true;
break pollit;
}
}
}
end = System.currentTimeMillis();
} while ((end - start) < timeout);
if (!isDhcpServer) {
LOG.debug("Timed out waiting for DHCP response, remaining retries: {}", rt);
}
--rt;
}
}
LOG.debug("Sending disconnect request");
p.m_outs.writeObject(getDisconnectRequest());
LOG.debug("wait half a sec before closing connection");
Thread.sleep(500);
p.close();
} catch (IOException ex) {
LOG.error("IO Exception caught.", ex);
p.close();
throw ex;
} catch (Throwable t) {
LOG.error("Unexpected Exception caught.", t);
p.close();
throw new UndeclaredThrowableException(t);
}
// Return response time if the remote box IS a DHCP
// server or -1 if the remote box is NOT a DHCP server.
if (isDhcpServer) {
return responseTime;
} else {
return -1;
}
}
