weinshec / scapy-gptp

scapy layer definition and tools for GPTP (IEEE 802.1as)

scapy-gptp - scapy layer definition and tools for GPTP (IEEE 802.1as)

This python module contains the layer definition for PTPv2 (GPTP) which includes custom definitions for Timestamp and ClockIdentity fields. It further provide some handy utils when analyzing PTPv2 traces.

Usage

The PTPv2 layer is automatically bound to the Ethernet layer based on its type field (0x88F7). Just import the PTPv2 layer definition to make scapy aware of this bond and for example read a pcap file to dissect

from gptp.layers import PTPv2
from scapy.utils import rdpcap

pcap = rdpcap("traces.pcap")

for p in pcap:
    if p.haslayer('PTPv2'):
        p.show()

which yields something like

###[ Ethernet ]###
  dst       = 01:83:b0:02:21:fe
  src       = 7a:1b:31:80:11:06
  type      = 0x88f7
###[ PTPv2 ]###
     transportSpecific= 1
     messageType= Sync
     reserved0 = 0x0
     versionPTP= 2
     messageLength= 44
     domainNumber= 0
     reserved1 = 0x0
     flags     = TIMESCALE+TWO_STEP
     correctionField= 0
     reserved2 = 0x0
     sourcePortIdentity= 7a:1b:31:80:11:06/1
     sequenceId= 2081
     control   = 0x0
     logMessageInterval= -3
     reserved3 = None
###[ Padding ]###
        load      = '\x00\x00\x00\x00\x00\x00'

A handy addition when analyzing PTP traces is the MatchedList from utils module. You can add PTP packets to it and it will automatically find matching (Sync, FollowUp) message pairs as well as (PdelayReq, PdelayResp, PdelayRespFollowUp) message triplets, providing them as lists for easy processing and analysis.

from gptp.utils import MatchedList

pcap = rdpcap("traces.pcap")
matched_list = MatchedList([p for p in pcap if p.haslayer('PTPv2')])

(sync, fup) = matched_list.sync[0]
assert sync.sequenceId == fup.sequenceId
print(fup.preciseOriginTimestamp)  # prints 1602135835.0758622