Internet Group Management Protocol (IGMPv3)

RFC 3678 Summary - IGMPv3 API

RFC 3678 describes the API functions for handling IGMPv3 from userspace. It defines two API variants – the basic API already exists for IGMPv2 and was extended for IGMPv3 – the advanced API was newly created:

Basic API (delta based)
- Any-Source Multicast API = exclude mode
- Source-Specific Multicast API = include mode
Advanced API (full-state)

Further more, there are two implementations – once only for IPv4 and a second for both, IPv4 and IPv6:

IPv4 API
Protocol independent API (supports IPv4 and IPv6)

IPv4 specific

Basic API (delta based) – Any-Source Multicast API (exclude mode)

IP_ADD_MEMBERSHIP (struct ip_mreq)
IP_BLOCK_SOURCE (struct ip_mreq_source)
IP_UNBLOCK_SOURCE (struct ip_mreq_source)
IP_DROP_MEMBERSHIP (struct ip_mreq)

Basic API (delta based) – Source-Specific Multicast API (include mode)

IP_ADD_SOURCE_MEMBERSHIP (struct ip_mreq_source)
IP_DROP_SOURCE_MEMBERSHIP (struct ip_mreq_source)
IP_DROP_MEMBERSHIP (struct ip_mreq)

Advanced API (full-state)

setipv4sourcefilter(...)
getipv4sourcefilter(...)

Protocol Independent

Any-Source Multicast API (exclude mode)

MCAST_JOIN_GROUP (struct group_req)
MCAST_BLOCK_SOURCE (struct group_source_req)
MCAST_UNBLOCK_SOURCE (struct group_source_req)
MCAST_LEAVE_GROUP(struct group_req)

struct group_req
{
	/* Interface index. */
	uint32_t gr_interface;
	/* Group address. */
	struct sockaddr_storage gr_group;
};

struct group_source_req
{
	/* Interface index. */
	uint32_t gsr_interface;
	/* Group address. */
	struct sockaddr_storage gsr_group;
	/* Source address. */
	struct sockaddr_storage gsr_source;
};

Source-Specific Multicast API (include mode)

MCAST_JOIN_SOURCE_GROUP(struct group_source_req)
MCAST_LEAVE_SOURCE_GROUP(struct group_source_req)
MCAST_LEAVE_GROUP (struct group_req)

Advanced API (full-state)

setsourcefilter
getsourcefilter

Source: RFC 3678 (Socket Interface Extensions for Multicast Source Filters)

RFC 3376 Summary – IGMPv3

Message Formats

Type Number (hex)	Message Name
0x11	Membership Query
0x22	Version 3 Membership Report
for interoperation with previous versions of IGMP
0x12	Version 1 Membership Report [RFC-1112]
0x16	Version 2 Membership Report [RFC-2236]
0x17	Version 2 Leave Group [RFC-2236]

Unrecognized message types MUST be silently ignored.

Membership Queries

There are three variants of the Query message:

A "General Query" is sent by a multicast router to learn the complete multicast reception state of the neighboring interfaces (that is, the interfaces attached to the network on which the Query is transmitted). In a General Query, both the Group Address field and the Number of Sources (N) field are zero.
A "Group-Specific Query" is sent by a multicast router to learn the reception state, with respect to a *single* multicast address, of the neighboring interfaces. In a Group-Specific Query, the Group Address field contains the multicast address of interest, and the Number of Sources (N) field contains zero.
A "Group-and-Source-Specific Query" is sent by a multicast router to learn if any neighboring interface desires reception of packets sent to a specified multicast address, from any of a specified list of sources. In a Group-and-Source-Specific Query, the Group Address field contains the multicast address of interest, and the Source Address [i] fields contain the source address(es) of interest.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Type = 0x11  | Max Resp Code |           Checksum            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Group Address                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Resv  |S| QRV |     QQIC      |     Number of Sources (N)     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Source Address [1]                      |
      +-                                                             -+
      |                       Source Address [2]                      |
      +-                              .                              -+
      .                               .                               .
      .                               .                               .
      +-                                                             -+
      |                       Source Address [N]                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The Group Address field is set to zero when sending a General Query, and set to the IP multicast address be- ing queried when sending a Group-Specific Query or Group-and-Source-Specific Query.

Membership Reports

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Type = 0x22  |    Reserved   |           Checksum            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Reserved            |  Number of Group Records (M)  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                        Group Record [1]                       .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                        Group Record [2]                       .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               .                               |
      .                               .                               .
      |                               .                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                        Group Record [M]                       .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Record Type  |  Aux Data Len |     Number of Sources (N)     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Multicast Address                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Source Address [1]                      |
      +-                                                             -+
      |                       Source Address [2]                      |
      +-                                                             -+
      .                               .                               .
      .                               .                               .
      .                               .                               .
      +-                                                             -+
      |                       Source Address [N]                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                         Auxiliary Data                        .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Group Record Types:

The “Current-State Record” is sent in response to a Query.
1 = MODE_IS_INCLUDE
2 = MODE_IS_EXCLUDE
The “Filter-Mode-Change Record” is sent when a local invocation of IPMulticastListen causes a change of the filter mode (e.g. from INCLUDE to EXCLUDE)
3 = CHANGE_TO_INCLUDE_MODE
4 = CHANGE_TO_EXCLUDE_MODE
The “Source-List-Change Record” is sent when a local invocation of IPMulticastListen causes a change of the source list (and the filter mode is not changed).
5 = ALLOW_NEW_SOURCES
6 = BLOCK_OLD_SOURCES

Version 3 Reports are sent with an IP destination address of 224.0.0.22, to which all IGMPv3-capable multi- cast routers listen. A system that is operating in version 1 or version 2 compatibility modes sends version 1 or version 2 Reports to the multicast group specified in the Group Address field of the Report.

Source: RFC 3376 (Internet Group Management Protocol, Version 3)