/*
* Copyright 2010 NCHOVY
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.krakenapps.pcap.decoder.icmp;
import java.nio.ByteBuffer;
import org.krakenapps.pcap.util.Buffer;
import org.krakenapps.pcap.util.Checksum;
/**
* Calculates ICMP checksum.
*
* @author xeraph
*
*/
public class IcmpChecksum {
private IcmpChecksum() {
}
public static int sum(IcmpPacket p) {
Buffer data = p.getData();
int dataLen = 0;
if (data != null)
dataLen = data.readableBytes();
ByteBuffer bb = ByteBuffer.allocate(8 + dataLen);
bb.put((byte) p.getType());
bb.put((byte) p.getCode());
bb.putShort((short) p.getChecksum());
bb.putShort((short) p.getId());
bb.putShort((short) p.getSeq());
while (!data.isEOB())
bb.put(data.get());
data.rewind();
bb.flip();
short[] words = new short[bb.limit() / 2];
for (int i = 0; i < words.length; i++)
words[i] = bb.getShort();
return Checksum.sum(words);
}
}