From 02055a4f1dc7a390d3448bd964828bbce2678753 Mon Sep 17 00:00:00 2001
From: Elliot Nunn <elliotnunn@me.com>
Date: Tue, 13 Oct 2020 19:45:21 +0800
Subject: [PATCH] Packet dumper, based on NetBoot.py

---
 LocalTalkMonitor.py | 99 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100755 LocalTalkMonitor.py

diff --git a/LocalTalkMonitor.py b/LocalTalkMonitor.py
new file mode 100755
index 0000000..37a1479
--- /dev/null
+++ b/LocalTalkMonitor.py
@@ -0,0 +1,99 @@
+#!/usr/bin/env python3
+
+# Multicast client
+# Adapted from: http://chaos.weblogs.us/archives/164
+
+import socket
+import os
+from os import path
+import struct
+
+
+
+ANY = "0.0.0.0"
+MCAST_ADDR = "239.192.76.84"
+MCAST_PORT = 1954
+
+# Create a UDP socket
+sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP) # IPPROTO_UDP could just be 0
+
+# Allow multiple sockets to use the same PORT number
+sock.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR,1)
+sock.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEPORT,1)
+
+# Bind to the port that we know will receive multicast data
+sock.bind((ANY,MCAST_PORT))
+
+# Tell the kernel that we want to add ourselves to a multicast group
+# The address for the multicast group is the third param
+status = sock.setsockopt(socket.IPPROTO_IP,
+socket.IP_ADD_MEMBERSHIP,
+socket.inet_aton(MCAST_ADDR) + socket.inet_aton(ANY))
+
+
+
+while 1:
+    data, addr = sock.recvfrom(1024)
+
+    if len(data) < 4: continue
+    data = data[4:] # Trim down to LLAP packet (not "frame")
+
+    if len(data) < 3: continue
+    llap_dest_node = data[0]
+    llap_src_node = data[1]
+    llap_proto_type = data[2]
+    data = data[3:] # Trim down to LLAP payload
+
+    if llap_proto_type == 1:
+        # ddp, short
+        if len(data) < 5: continue
+        ddp_len, ddp_dest_socket, ddp_src_socket, ddp_proto_type = struct.unpack_from('>HBBB', data)
+        data = data[5:ddp_len]
+    elif llap_proto_type == 2:
+        # ddp, long (what should we do with this extra information?)
+        if len(data) < 13: continue
+        ddp_len, ddp_cksum, ddp_dest_net, ddp_src_net, ddp_dest_node, ddp_src_node, ddp_dest_socket, ddp_src_socket = struct.unpack_from('>4H5B', data)
+        ddp_hop_count = (ddp_len >> 10) & 0xF
+        ddp_len &= 0x3FF
+        data = data[13:ddp_len]
+    else:
+        # llap control packet -- can probably ignore!
+        continue
+
+    print(f'datagram {llap_src_node}:{ddp_src_socket}->{llap_dest_node}:{ddp_dest_socket}')
+
+    if ddp_proto_type == 2: # NBP
+        if len(data) < 2: continue
+        nbp_func = data[0] >> 4
+        nbp_tuple_cnt = data[0] & 0xF
+        nbp_id = data[1]
+        data = data[2:]
+
+        nbp_tuples = []
+        while data and len(nbp_tuples) < nbp_tuple_cnt:
+            if len(data) < 5: break
+            this_tuple = list(struct.unpack_from('>HBBB', data))
+            data = data[5:]
+            for i in range(3):
+                # This should be coded more defensively, perhaps using exceptions
+                this_tuple.append(data[1:1+data[0]].decode('mac_roman'))
+                data = data[1+data[0]:]
+            nbp_tuples.append(tuple(this_tuple))
+
+        print('    NBP func', nbp_func, 'id', nbp_id)
+        for t in nbp_tuples:
+            print(f'    net:node:sock={t[0]}:{t[1]}:{t[2]} enum={t[3]} object:type@zone={t[4]}:{t[5]}@{t[6]}')
+
+    elif ddp_proto_type == 10: # ATBOOT
+        if len(data) < 2: continue
+        boot_type, boot_vers = struct.unpack_from('>BB', data)
+        data = data[2:]
+
+        if boot_type == 1:
+            print('    ATBOOT "syn"')
+        if boot_type == 2:
+            print('    ATBOOT "ack"')
+        elif boot_type == 3:
+            print('    ATBOOT image request')
+        elif boot_type == 4:
+            print('    ATBOOT image reply')