import org.pcap4j.packet.TcpPacket.TcpOption; //导入依赖的package包/类
static Packet createSyncAck(
		MacAddress srcAddress_mac,
		MacAddress dstAddrress_mac,
		Inet4Address srcAddress,short srcPort,
		Inet4Address dstAddress,short dstPort,
		int ack_sequence,int sequence,short ident){

	TcpPacket.Builder builder_tcp=new TcpPacket.Builder();
	//builder_tcp.payloadBuilder(new UnknownPacket.Builder().rawData(new byte[0]));
	builder_tcp.correctChecksumAtBuild(true);
	builder_tcp.correctLengthAtBuild(true);
	builder_tcp.paddingAtBuild(true);
	builder_tcp.ack(true);
	builder_tcp.acknowledgmentNumber(ack_sequence);
	//builder_tcp.checksum(tcpHeader.getChecksum());
	//builder_tcp.dataOffset((byte) 8);
	builder_tcp.dstAddr(dstAddress);
	builder_tcp.dstPort(new TcpPort(dstPort,""));
	//builder_tcp.fin(tcpHeader.getFin());


	ArrayList<TcpOption> tcp_options=new ArrayList<TcpOption>();
	
	TcpNoOperationOption nop=TcpNoOperationOption.getInstance();

	TcpMaximumSegmentSizeOption seg_option=new TcpMaximumSegmentSizeOption.Builder().maxSegSize(mtu).correctLengthAtBuild(true).build();
	tcp_options.add(seg_option);
	
	tcp_options.add(nop);
	tcp_options.add(nop);

	TcpSackPermittedOption sack_permit_option=TcpSackPermittedOption.getInstance();
	tcp_options.add(sack_permit_option);
	
	tcp_options.add(nop);

	TcpWindowScaleOption win_option=new TcpWindowScaleOption.Builder().shiftCount(shiftCount).correctLengthAtBuild(true).build();
	tcp_options.add(win_option);

	builder_tcp.options(tcp_options);

	//builder_tcp.padding(tcpHeader.getPadding());
	builder_tcp.psh(false);
	builder_tcp.reserved((byte) 0);
	builder_tcp.rst(false);
	builder_tcp.sequenceNumber(sequence);
	builder_tcp.srcAddr(srcAddress);
	builder_tcp.srcPort(new TcpPort(srcPort,""));
	builder_tcp.syn(true);
	builder_tcp.urg(false);
	//builder_tcp.urgentPointer(tcpHeader.getUrgentPointer());
	builder_tcp.window( window);

	IpV4Packet.Builder builder_ipv4=new IpV4Packet.Builder();
	builder_ipv4.correctChecksumAtBuild(true);
	builder_ipv4.correctLengthAtBuild(true);
	builder_ipv4.paddingAtBuild(true);
	builder_ipv4.dstAddr(dstAddress);
	builder_ipv4.dontFragmentFlag(true);
	builder_ipv4.fragmentOffset((short)0);
	//builder_ipv4.headerChecksum(ipV4Header.getHeaderChecksum());
//	short identification= Math.abs(random.nextInt(Short.MAX_VALUE));
	builder_ipv4.identification(ident);
	builder_ipv4.ihl((byte) 5);
	//builder_ipv4.moreFragmentFlag(ipV4Header.getMoreFragmentFlag());
	//builder_ipv4.options(ipV4Header.getOptions());
	//builder_ipv4.padding(ipV4Header.getPadding());

	builder_ipv4.protocol(IpNumber.TCP);
	//		builder_ipv4.reservedFlag(ipV4Header.getReservedFlag());
	builder_ipv4.srcAddr(srcAddress);
	builder_ipv4.tos(IpV4Rfc1349Tos.newInstance((byte) 0));
	//builder_ipv4.totalLength( 52);
	builder_ipv4.ttl(ttl);
	builder_ipv4.version(IpVersion.IPV4);
	builder_ipv4.payloadBuilder(builder_tcp);
	//
	Packet p = buildIpV4(srcAddress_mac,dstAddrress_mac,builder_ipv4);
	return p;

}
 

import org.pcap4j.packet.TcpPacket.TcpOption; //导入依赖的package包/类
/**
 * Build packet
 */
public void buildPacket() {

    int calculatedLength = getPacketLength() - 14;

    String payloadString = payload.getPayloadType().getPadPayloadString(payload.getPayloadPattern(), calculatedLength * 2);

    UnknownPacket.Builder unknownb = null;
    if (calculatedLength != 0) {
        unknownb = new UnknownPacket.Builder();
        unknownb.rawData(payload.getPayloadPad(payloadString, calculatedLength));
    }
    ArrayList<TcpOption> options = new ArrayList<TcpOption>();

    options.add(TcpEndOfOptionList.getInstance());

    tcpBuilder = new TcpPacket.Builder();
    tcpBuilder.dstPort(dstPort)
            .srcPort(srcPort)
            .sequenceNumber(sequenceNumber)
            .acknowledgmentNumber(acknowledgmentNumber)
            .dataOffset(dataOffset)
            .reserved(reserved)
            .urg(urg)
            .ack(ack)
            .psh(psh)
            .rst(rst)
            .syn(syn)
            .fin(fin)
            .window(window)
            .checksum(checksum)
            .urgentPointer(urgentPointer)
            .options(options)
            .padding(new byte[]{(byte) 0xaa})
            .correctChecksumAtBuild(false)
            .correctLengthAtBuild(false)
            .paddingAtBuild(false);

    if (calculatedLength != 0) {
        tcpBuilder.payloadBuilder(unknownb);
    }
    this.packet = tcpBuilder.build();
}