Counter of the duplicated packets from a pcap file

[salwa17]

I want to count the duplicated packets from a pcap file. Duplicated packets are the packets whose the sequence number were already seen previously For that I extract firstly the list of the sequence number with this function:

  def seq_list(s):
    v = []
    a = [p['TCP'].seq if p.haslayer(TCP) else None
              for p in s]
    return a

Then I check if the current sequence number has already seen previously : (I'm not sure about this function)

   def is_dupl(s):
       v = seq_list(s)	
       a = []
       for p in s: 
          if p.haslayer(TCP):
              for i in range(0, len(v)):
                  a += v[0:i+1:1]
                  if p[TCP].seq in a:
                      return True 
          return False	

After that I made a function to get the list of the duplicated packet: (I'm not sure about this function)

    def find_dupl(s):
        tcpSeq = [p[TCP].seq if p.haslayer(TCP) and is_dupl(p) else None
                  for p in s]
        counter = Counter(tcpSeq)
        #del counter[None]
        print("---------------------length of counter dictionary : --", counter.items())
        return [[s[index] for index, seq in enumerate(tcpSeq)
            if seq == key]
            for (key, value) in counter.items()
            if value > 1]

And finally my counter:

    def duplication_pkt_count(s, s_ip, c_ip):
        sCount = 0
        cCount = 0
        duplication = find_dupl(s)

        for dup in duplication:
            for p in dup[1:]:
                if p.haslayer(IP):
                    if (p[IP].src == s_ip):
                        sCount += 1
                    if (p[IP].src == c_ip):
                        cCount += 1
        return (sCount, cCount)

And then I called the function duplication_pkt_count in my main.py code
The result is wrong. The number of the duplicated packets is wrong.

Please any help ?