组播发送的流程
组播都是udp报文发送，发送用的地方在选路
ns3有组播的例子，加默认路由，静态组播路由，这几个例子我没看懂。FIXME
这几个例子与我想要的区别是，我要针对quagga加增内容，改造，而不能像ns3的组播路由那样自由发挥FIXME
现状：采用dce直接路由组播的结果是：
assert failed. cond="oif", msg="Try to send on link-local multicast address, and no interface index is given!", file=../model/ipv4-dce-routing.cc, line=409
terminate called without an active exception
需要变更成组播顺利发送
另一个想法：如果直接使用linux栈（日本人做的那个ns-next-sim协议栈），可能是一切工作正常的。那个栈的劣势是和ns3其他部分有些脱离。FIXME
回来处理那个assert
Breakpoint 4, ns3::Ipv4DceRouting::LookupStatic (this=0x6c1d40, dest=..., oif=...) at ../model/ipv4-dce-routing.cc:409
409 NS_ASSERT_MSG (oif, "Try to send on link-local multicast address, and no interface index is given!");
(gdb) bt
#0 ns3::Ipv4DceRouting::LookupStatic (this=0x6c1d40, dest=..., oif=...) at ../model/ipv4-dce-routing.cc:409
#1 0x00007ffff7ac912b in ns3::Ipv4DceRouting::RouteOutput (this=0x6c1d40, p=..., header=..., oif=..., sockerr=@0x7fffffffcfec: 32767) at ../model/ipv4-dce-routing.cc:664
#2 0x00007ffff6d1170a in ns3::UdpSocketImpl::DoSendTo (this=0x7fffdc006200, p=..., dest=..., port=646) at ../src/internet/model/udp-socket-impl.cc:621
#3 0x00007ffff6d140ca in ns3::UdpSocketImpl::SendTo (this=0x7fffdc006200, p=..., flags=64, address=...) at ../src/internet/model/udp-socket-impl.cc:807
#4 0x00007ffff7a44df4 in ns3::UnixDatagramSocketFd::MainSendTo (this=0x7fffdc007ed0, r=0x7ffff0a29e6c, p=..., f=64, ad=...) at ../model/unix-datagram-socket-fd.cc:510
#5 0x00007ffff7a45787 in ns3::EventImpl* ns3::MakeEvent<void (ns3::UnixDatagramSocketFd::*)(int*, ns3::Ptr<ns3::Packet>, unsigned int, ns3::Address), ns3::UnixDatagramSocketFd*, int*, ns3::Ptr<ns3::Packet>, int, ns3::Address>(void (ns3::UnixDatagramSocketFd::*)(int*, ns3::Ptr<ns3::Packet>, unsigned int, ns3::Address), ns3::UnixDatagramSocketFd*, int*, ns3::Ptr<ns3::Packet>, int, ns3::Address)::EventMemberImpl4::Notify() (this=0x7fffdc024bf0) at /home/z/new/dce/build/include/ns3.23/ns3/make-event.h:452
#6 0x00007ffff733b5e7 in ns3::EventImpl::Invoke (this=0x7fffdc024bf0) at ../src/core/model/event-impl.cc:51
#7 0x00007ffff7a8a5ba in ns3::TaskManager::Schedule (this=0x67dc00) at ../model/task-manager.cc:441
#8 0x00007ffff7a8c5ad in ns3::EventImpl* ns3::MakeEvent<void (ns3::TaskManager::*)(), ns3::TaskManager*>(void (ns3::TaskManager::*)(), ns3::TaskManager*)::EventMemberImpl0::Notify() (this=0x64f120) at /home/z/new/dce/build/include/ns3.23/ns3/make-event.h:323
#9 0x00007ffff733b5e7 in ns3::EventImpl::Invoke (this=0x64f120) at ../src/core/model/event-impl.cc:51
#10 0x00007ffff73402ac in ns3::DefaultSimulatorImpl::ProcessOneEvent (this=0x6b1870) at ../src/core/model/default-simulator-impl.cc:147
#11 0x00007ffff7340638 in ns3::DefaultSimulatorImpl::Run (this=0x6b1870) at ../src/core/model/default-simulator-impl.cc:200
#12 0x00007ffff733c378 in ns3::Simulator::Run () at ../src/core/model/simulator.cc:204
#13 0x000000000040cd90 in main (argc=1, argv=0x7fffffffdc08) at ../myscripts/ns-3-dce-quagga/example/dce-quagga-mpls.cc:219
(gdb)
发送是由ldp hello触发的，
查看
#2 0x00007ffff6d1170a in ns3::UdpSocketImpl::DoSendTo (this=0x7fffdc006200, p=..., dest=..., port=646) at ../src/internet/model/udp-socket-impl.cc:621
发现m_boundnetdevice是0，表示并没有发生过bind操作。
查这篇文章，看到client和server都是有bind的。
http://www.cnblogs.com/hnrainll/archive/2011/11/07/2238671.html
查quagga，发现hello有绑定的
mpls_socket_bind
mpls_socket_udp_sendto
如此找bind，linux kernel的处理代码是inet_bind，对于组播来说，这个绑定也许真没用FIXME
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