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McastSocket
McastSocket — Click element; a multicast UDP socket transport (user-level)
McastSocket(MCASTIP, MCASTPORT [, SOURCEIP] [, SOURCEPORT] [, KEYWORDS])
Ports: at most 1 input, at most 1 output
Transports packets over multicast UDP. Packets do not flow through McastSocket elements (i.e., McastSocket is an "x/y" element). Instead, input packets are sent via multicast to any number of remote hosts or processes, and packets from the remote hosts or processes are emitted on the output.
If "SOURCEIP" (and optionally "SOURCEPORT") is specified, the address is used as the source of outgoing packets, and the multicast traffic is only sent and received on the interface designated by SOURCEIP.
If "SOURCEIP" is not specified, the system routing table determines the source address and interface for sending and receiving the multicast traffic.
Note that since the McastSocket listens on the same multicast address as it sends to, it will by default receive copies of its own packets. If a source IP is specified, McastSocket will automatically drop these looping packets. If a source IP is not specified, disabling the LOOP option can be an alternative, if no other subscribing processes run on the same host as the Click process.
McastSocket inputs are agnostic, i.e., they may be either "pull" or "push". If pushed, packets will block on the underlying socket; otherwise, the socket will pull packets as it can accept them. For best performance, place a Notifier element (such as NotifierQueue) upstream of a "pull" McastSocket.
Keyword arguments are:
- LOOP — Boolean. Whether processes on the local machine (including this one!) should receive copies of the outgoing traffic (IP_MULTICAST_LOOP). The default is true.
- SNAPLEN — Unsigned integer. Maximum length of packets that can be received. Default is 2048 bytes.
- SNDBUF — Unsigned integer. Sets the maximum size in bytes of the underlying socket send buffer. The default value is set by the wmem_default sysctl and the maximum allowed value is set by the wmem_max sysctl.
- RCVBUF — Unsigned integer. Sets the maximum size in bytes of the underlying socket receive buffer. The default value is set by the rmem_default sysctl and the maximum allowed value is set by the rmem_max sysctl.
- TIMESTAMP — Boolean. If set, sets the timestamp field on received packets to the current time. Default is true.
- HEADROOM — Integer. Per-packet headroom. Defaults to 28.
Start the following Click router:
link :: McastSocket(239.0.0.0, 1234);
arpR :: ARPResponder(10.0.0.1/32 02:02:02:02:02:02) -> link;
arpQ :: ARPQuerier(10.0.0.1, 02:02:02:02:02:02) -> link;
ip :: Strip(14)
-> CheckIPHeader()
-> IPClassifier(icmp and dst host 10.0.0.1)
-> CheckICMPHeader()
-> ICMPPingResponder()
-> arpQ;
// Note DROP_OWN to prevent multicast loop from messing things up.
link
-> HostEtherFilter(02:02:02:02:02:02, DROP_OWN true, DROP_OTHER true)
-> Classifier(
12/0806 20/0001, // ARP query
12/0806 20/0002, // ARP reply
12/0800, // IP
) => arpR, [1]arpQ, ip;
Then grab any Linux live CD image and start a QEMU virtual machine with the following options:
qemu -net nic -net socket,mcast=239.0.0.0:1234 -cdrom livecd.iso
After adding an IP address, you will be able to ping 10.0.0.1 from the virtual machine. The use of multicast transparently bridges any number of Click and QEMU processes on any number of hosts on a LAN.
Generated by click-elem2man from ../elements/userlevel/mcastsocket.hh:11 on 2018/10/03.