CODEWITHSUNDEEP
pythonscapy
Astron
Astron

Reputation: 1221

Increment PCAP timestamp values

Scapy has the capability to modify timestamps on a per packet basis therefore am wondering what might be the best way to modify the the timestamps on a number of packets in a PCAP by specifying a start value. I am able to modify the packets but have yet to successfully increment the microseconds value.

For example would like to modify packets timestamps in a PCAP which contains:

1360806997.231777 IP 192.168.1.100.50496 > 192.168.1.200.http: S 4211078664:4211078664(0) win 14600 <mss 1460,sackOK,timestamp 199086437 0,nop,wscale 3>
1360806997.231808 IP 192.168.1.200.http > 192.168.1.100.50496: S 256066681:256066681(0) ack 4211078665 win 14480 <mss 1460,sackOK,timestamp 199086195 199086437,nop,wscale 3>
1360806997.232034 IP 192.168.1.100.50496 > 192.168.1.200.http: . ack 1 win 1825 <nop,nop,timestamp 199086437 199086195>
1360806997.232043 IP 192.168.1.100.50496 > 192.168.1.200.http: P 1:19(18) ack 1 win 1825 <nop,nop,timestamp 199086437 199086195>
1360806997.232063 IP 192.168.1.200.http > 192.168.1.100.50496: . ack 19 win 1810 <nop,nop,timestamp 199086195 199086437>

to the following:

1234567890.000000 IP 192.168.1.100.50496 > 192.168.1.200.http: S 4211078664:4211078664(0) win 14600 <mss 1460,sackOK,timestamp 199086437 0,nop,wscale 3>
1234567890.000001 IP 192.168.1.200.http > 192.168.1.100.50496: S 256066681:256066681(0) ack 4211078665 win 14480 <mss 1460,sackOK,timestamp 199086195 199086437,nop,wscale 3>
1234567890.000002 IP 192.168.1.100.50496 > 192.168.1.200.http: . ack 1 win 1825 <nop,nop,timestamp 199086437 199086195>
1234567890.000003 IP 192.168.1.100.50496 > 192.168.1.200.http: P 1:19(18) ack 1 win 1825 <nop,nop,timestamp 199086437 199086195>
1234567890.000004 IP 192.168.1.200.http > 192.168.1.100.50496: . ack 19 win 1810 <nop,nop,timestamp 199086195 199086437>

Upvotes: 2

Views: 1448

Answers (2)

Arturo Gomez Molina
Arturo Gomez Molina

Reputation: 21

I have tried to find all around internet without finding the solution but if you want to maintain the delta between packets you can use the following code which is a modification of the previous one.

def process_packets():
   pkts = rdpcap('file.pcap')
   cooked=[]
   timestamp = 1234567890.000000
   i = 0
   for p in pkts:
      i += 1
      if i == 1:
         delta = p.time
         p.time = timestamp
      else:
         delta = p.time - delta
         timestamp += delta
         p.time = timestamp
      pmod=p
      cooked.append(pmod)
   wrpcap("dump.pcap", cooked)

Upvotes: 2

Astron
Astron

Reputation: 1221

This seems to work:

def process_packets():
    pkts = rdpcap(infile)
    cooked=[]
    timestamp = 1234567890.000000
    for p in pkts:
        p.time = timestamp
        timestamp += 0.000001
        pmod=p
        cooked.append(pmod)
    wrpcap("dump.pcap", cooked)

Code will write new time value for each packet to a new PCAP with the specified second and increment the microsecond value. If there's a more graceful method, please let me know.

Upvotes: 2

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