From 6bd455b7e3995cad7f770a78b00d938a5bbf0032 Mon Sep 17 00:00:00 2001
From: Kevin Hester <kevinh@geeksville.com>
Date: Mon, 21 Dec 2020 15:43:20 +0800
Subject: [PATCH] tun test case

---
 tests/tuntest.py | 67 +++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 64 insertions(+), 3 deletions(-)

diff --git a/tests/tuntest.py b/tests/tuntest.py
index dffc14d..a4245e3 100644
--- a/tests/tuntest.py
+++ b/tests/tuntest.py
@@ -1,6 +1,67 @@
 # delete me eventually
+# pip install python-pytuntap
+# sudo ip tuntap del mode tun tun0
+
+from tuntap import TunTap,Packet
+import logging
+from _thread import start_new_thread
+
+"""A list of chatty UDP services we should never accidentally
+forward to our slow network"""
+udpBlacklist = {
+    1900, # SSDP
+    5353, # multicast DNS
+}
+
+def hexstr(barray):
+    return ":".join('{:02x}'.format(x) for x in barray)
+
+def readnet_u16(p, offset):
+    """Read big endian u16 (network byte order)"""
+    return p[offset] * 256 + p[offset + 1]
+
+def readtest(tap):
+    while not tap.quitting:
+        p = tap.read()
+        if not p:
+            continue
+        packet = Packet(data=p)
+        if not packet.get_version()==4: # only consider IPV4 for now
+            continue
+
+        protocol = p[8 + 1]
+        srcaddr = p[12:16]
+        destaddr = p[16:20]
+        subheader = 20
+        ignore = False # Assume we will be forwarding the packet
+        if protocol == 0x02: # IGMP
+            ignore = True
+            logging.debug("Ignoring IGMP packet")
+        elif protocol == 0x11: # UDP
+            srcport = readnet_u16(p, subheader)
+            destport = readnet_u16(p, subheader + 2)
+            logging.debug(f"udp srcport={srcport}, destport={destport}")
+            if destport in udpBlacklist:
+                ignore = True
+                logging.debug(f"ignoring blacklisted UDP port {destport}")
+        else:
+            logging.warn(f"unexpected protocol 0x{protocol:02x}, srcadddr {hexstr(srcaddr)}")
+
+        if not ignore:
+            logging.debug(f"Forwarding packet bytes={hexstr(p)}")
+
+        # reply to pings
+        #pingback = p[:12]+p[16:20]+p[12:16]+p[20:]
+        #tap.write(pingback)
+
+logging.basicConfig(level=logging.DEBUG)
+
+tun = TunTap(nic_type="Tun") # nic_name="tun0"
+# tun.create()
+tun.config(ip="10.115.1.2",mask="255.255.0.0")
+
+start_new_thread(readtest,(tun,))
+input("press return key to quit!")
+tun.close()
 
-from tuntap import TunTap
 
-tun = TunTap(nic_type="Tun",nic_name="tun0")
-tun.config(ip="10.115.1.2",mask="255.255.0.0")
\ No newline at end of file