.

tmcast.py

@@ -4,10 +4,11 @@
 from __future__ import print_function
 
 
-import sys, struct, time
+import sys, time
 from socket import socket, AF_INET, SOCK_DGRAM, IPPROTO_UDP, SOL_SOCKET, \
     SO_REUSEADDR, IPPROTO_IP, IP_ADD_MEMBERSHIP, IP_MULTICAST_TTL, IP_MULTICAST_LOOP,   \
     inet_aton, INADDR_ANY
+from struct import pack
 
 from golang import b, u
 from golang import sync, context
@@ -23,7 +24,7 @@ def mjoin_tx(group, port, ttl=2):
     sk = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)
 
     # set ttl and default destination address (for tx)
-    sk.setsockopt(IPPROTO_IP, IP_MULTICAST_TTL, ttl)
+    sk.setsockopt(IPPROTO_IP, IP_MULTICAST_TTL, pack('b', ttl))
     sk.connect((group, port))
 
     # so that what we send is received locally as well
@@ -36,10 +37,10 @@ def mjoin_rx(group, port):
     sk = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)
 
     sk.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
-    sk.bind(('', port))
+    sk.bind((group, port))
 
     # join the group (for rx)
-    mreq = struct.pack("4sl", inet_aton(group), INADDR_ANY)
+    mreq = pack("4sl", inet_aton(group), INADDR_ANY)
     sk.setsockopt(IPPROTO_IP, IP_ADD_MEMBERSHIP, mreq)
 
     return sk

topo-B-A-C.sh

+#!/bin/bash
+# topo B-A-C creates the following network topology:
+#
+#
+#    netns=B          netns=A         netns=C
+#
+#       B  --- br0 ---  A  --- br1 ---  C
+#        b1           a1 a2           c1
+#
+# should be run under unshare -mrun .
+# use nsenter --net={A,B,C} to enter into network namespace of A/B/C.
+
+touch A B C
+
+ip link add br0 type bridge     # vlan_filtering 1 mcast_snooping 0
+ip link add type a1 veth peer b1
+ip link set b1 master br0
+ip link set a1 up
+ip link set b1 up
+ip link set br0 up