Multicast
RFC 8815 deprecated interdomain PIM-ASM (any-source multicast) so PIM-SSM (source-specific multicast) is the way to go!
Setup
For it to work, you’ll need to do the following:
- Ask your peering to enable IPv4/IPv6 multicast AFI on your peering
- Set up IPv4/IPv6 PIM for the (s,g) joins to pass through
- Be prepared to setup IGMPv3 and MLDv2 from your listeners
You’re done! You should receive the multicast routes from peers advertising them.
Configuration
frr configuration
Enable PIM:
router pim
no autorp discovery
exit
router pim6
exit
For IPv4, you can also add the send-v6-secondary directive, which allows you to omit an IPv4 address (as with “extended next hop”) on the interface. (Does this work? I haven’t tried it yet.)
Import kernel multicast table into frr:
ip import-table [TABLE NUMBER] mrib
ipv6 import-table [TABLE NUMBER] mrib
This method is suitable when frr is used only as a multicast routing daemon and another daemon, such as bird, is used for BGP. In this case, bird can export the unicast routes intended for multicast to a special kernel routing table, and frr can import them. If frr also handles BGP, it can store the corresponding unicast routes directly in mrib.
Enable PIM on a interface:
interface [INTERFACE NAME]
ip pim
ip pim use-source [SOURCE IPv4 ADDRESS]
ipv6 pim
ipv6 pim use-source [SOURCE IPv6 ADDRESS]
exit
Specifying a source address is optional, but can be used if frr would otherwise select the wrong address.
Enable multicast for a client:
interface client21
ip igmp
ip igmp max-groups 32
ip igmp require-router-alert
ip igmp version 3
ip pim
ip pim passive
ipv6 mld
ipv6 mld max-groups 32
ipv6 mld require-router-alert
ipv6 mld version 2
ipv6 pim
ipv6 pim passive
exit
The number of maximum groups is optional and can be set freely. For security reasons, this number should not be set unreasonably high. Specifying an explicit IGMP or MLD version is also optional.
IGMP and MLD messages must follow a specific format. require-router-alert filters out invalid messages.
Even if an interface is only intended to handle IGMP/MLD, PIM must be enabled on it. If you still do not want to use PIM, a firewall rule is recommended.
nftables configuration
Allow PIM:
iifname "[INTERFACE NAME]" ip6 saddr [SOURCE ADDRESS] ip6 daddr ff02::d meta protocol ip6 meta l4proto pim counter accept;
iifname "[INTERFACE NAME]" ip saddr [SOURCE ADDRESS] ip daddr 224.0.0.13 meta protocol ip meta l4proto pim counter accept;
Allow MLDv2:
set icmp6_mld {
type icmpv6_type . icmpv6_code;
flags interval;
elements = {
mld-listener-query . 0,
mld2-listener-report . 0
};
}
iifname [CLIENT INTERFACE NAME] icmpv6 type . icmpv6 code @icmp6_mld ip6 hoplimit 1 exthdr hbh exists ip6 saddr fe80::/10 counter accept;
Allow IGMPv3:
iifname [CLIENT INTERFACE NAME] ip protocol igmp igmp type { membership-query, membership-report-v3 } ip ttl 1 counter accept;
Participants
Current participants:
- NOP-MNT
- MIRSAL-MNT
- C4TG1RL5-MNT
- KIOUBIT-MNT
- PREVARINITE-MNT
- MARK22K-MNT
Feel free to ask for a peering and set it up!
Current streams
NOP music stream
cs broadcasts a 48 kHz, 24-bit music stream. An SDP file is required to receive it:
v=0
o=- 0 0 IN IP4 172.23.199.110
s=-
i=NOP 48 kHz 24-bit music stream
[email protected]
c=IN IP4 232.2.3.2
m=audio 1234 RTP/AVP 96
a=rtpmap:96 L24/48000/2
a=recvonly
a=type:broadcast
a=source-filter: incl IN IP4 232.2.3.2 172.23.199.110
v=0
o=- 0 0 IN IP6 fd40:cc1e:c0de::fffe
s=-
i=NOP 48 kHz 24-bit music stream
[email protected]
c=IN IP6 ff3e::8232:232
m=audio 1234 RTP/AVP 96
a=rtpmap:96 L24/48000/2
a=recvonly
a=type:broadcast
a=source-filter: incl IN IP6 ff3e::8232:232 fd40:cc1e:c0de::fffe
also there is low bandwidth sap/sdp announcements of the format (samplerate could be 44.1khz, 48khz, 96khz 192khz or 384khz, bitdepts also change from 16bit, 24bit or 32bit, MSB) to 172.23.199.110,232.2.3.1:9875 that needs altering in terms of addresses embedded within, however vlc can pick it up
The stream can then be streamed with ffplay -protocol_whitelist file,fd,udp,rtp -fflags +genpts /path/to/sdp_file or mplayer or vlc.
the actual RFC 8866-sdp could be extracted from RFC 2974-sap… when its not aes67 (rtp+sap+sdp) then it may be scream
mping
mping is a program that sends a ping message to a multicast group every second (and responds to incoming pings, if any). There are two implementations:
- The original implementation by troglobit, which supports both sending and receiving.
- A reimplementation, which supports only sending.
Streams:
mcjoin -j -i [INTERFACE] [fd00:8e13:ce5d::9bee],[ff3e::8000:42]:4321mping-sender