From 386994d7e2f32a386a06ebe0825abee8557ad88d Mon Sep 17 00:00:00 2001
From: uhi22 <uhi@hnng.de>
Date: Mon, 24 Oct 2022 23:21:17 +0200
Subject: [PATCH] added TCP sniffer for EXI

---
 pyPlcIpv6.py | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/pyPlcIpv6.py b/pyPlcIpv6.py
index 9a50b2e..7c161e0 100644
--- a/pyPlcIpv6.py
+++ b/pyPlcIpv6.py
@@ -131,7 +131,7 @@ class ipv6handler():
                 showAsHex(self.udpPayload, "V2GTP ")
                 self.evccPort = self.sourceport
                 v2gptPayloadType = self.udpPayload[2] * 256 + self.udpPayload[3]
-                # 0x8001 EXI encoded V2G message
+                # 0x8001 EXI encoded V2G message (Will NOT come with UDP. Will come with TCP.)
                 # 0x9000 SDP request message (SECC Discovery)
                 # 0x9001 SDP response message (SECC response to the EVCC)
                 if (v2gptPayloadType == 0x9000):
@@ -165,8 +165,34 @@ class ipv6handler():
     def enterListenMode(self):
         self.iAmEvse = 0 # not emulating a charging station
         self.iAmPev = 0 # not emulating a vehicle
+        
+    def evaluateV2GTP(self):
+        # We sniffed a V2GTP frame via TCP. This should contain an EXI encoded payload.
+        v2gptPayloadType = self.v2gframe[2] * 256 + self.v2gframe[3]
+        # 0x8001 EXI encoded V2G message
+        if (v2gptPayloadType == 0x8001):
+            self.ExiPacket = self.v2gframe[8:] # the exi payload, without the 8 bytes V2GTP header
+            print("EXI from " + str(self.tcpsourceport) + " to " + str(self.tcpdestinationport))
+            showAsHex(self.ExiPacket)
+            # Todo: further process the EXI packet. E.g. write it into file for offline analysis.
+            # And send it to decoder.
 
+    def evaluateTcpPacket(self):
+        # We received a TCP packet. We do NOT want to make real TCP here (the OS will do it much better). We
+        # just want to listen to the conversation of two others, and extract what we hear.
+        self.tcpsourceport = self.myreceivebuffer[54] * 256 + self.myreceivebuffer[55]
+        self.tcpdestinationport = self.myreceivebuffer[56] * 256 + self.myreceivebuffer[57]
+        if ((self.tcpsourceport == 15118) or (self.tcpdestinationport == 15118)):
+            if (len(self.myreceivebuffer)>=74+9): # 74 is the TCP without any data. A V2GTP has 8 bytes header, plus at least 1 payload byte.
+                startOfV2gtp = 74 # the index of the first V2GTP byte in the ethernet buffer
+                if ((self.myreceivebuffer[startOfV2gtp] == 0x01) and (self.myreceivebuffer[startOfV2gtp+1] == 0xFE)):
+                    # version and inverted version of the V2GTP are fine -> it is a V2G TP frame.
+                    self.v2gframe = self.myreceivebuffer[startOfV2gtp:]
+                    self.evaluateV2GTP()
+        
+        
     def evaluateReceivedPacket(self, pkt):
+        # The evaluation function for received ipv6 packages.
         if (len(pkt)>60):
             self.myreceivebuffer = pkt
             self.nextheader = self.myreceivebuffer[20]
@@ -184,6 +210,8 @@ class ipv6handler():
                         #print("index " + str(i) + " " + hex(self.myreceivebuffer[62+i]))
                         self.udpPayload[i] = self.myreceivebuffer[62+i]
                     self.evaluateUdpPayload()
+            if (self.nextheader == 0x06): # it is an TCP frame
+                self.evaluateTcpPacket()
                         
     def __init__(self, transmitCallback):
         self.enterEvseMode()