igmp_client.h File Reference

Detailed Description

Client-side implementation of the Internet Group Management Protocol (IGMP)

Any IPv4 packet sent to 224.0.0.0/8 (i.e., 224.*.*.*) is a "multicast" packet. Routers should send multicast packets to interested recipients, including routers with downstream recipients, but avoid sending them to uninterested hosts. IGMP is the protocol that routers to determine which next-hop interface(s) have members subscribed to a given multicast address (i.e., a "group"), so it can forward only to those port(s).

This file implements the "host" (i.e., client/endpoint) side of IGMP:

• ip::IgmpAddress represents a client subscription to a multicast group.
• ip::IgmpClient is the host endpoint that responds to IGMP queries.

As required by IETF, the client defaults to IGMPv3, but is fully backwards compatible with IGMPv1 and IGMPv2, and will downgrade as needed to support networks with legacy routers. However, SatCat5 does not currently support the source-address filtering features of IGMPv3, always responding as if the end-user has requested an exclude-none policy.

IGMPv1 is defined by IETF RFC-1112. IGMPv2 is defined by IETF RFC-2236. IGMPv3 is defined by IETF RFC-9776.

Definition in file igmp_client.h.

#include <satcat5/ip_core.h>
#include <satcat5/list.h>
#include <satcat5/net_protocol.h>
#include <satcat5/polling.h>

Include dependency graph for igmp_client.h:

This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Classes
class	satcat5::igmp::Client
	Host/Client for the Internet Group Management Protocol (IGMP). More...
struct	satcat5::igmp::Address
	Client state for an IGMP multicast subscription. More...

Macros
#define	SATCAT5_IGMP_ENABLE   1

Functions
constexpr satcat5::ip::Addr	satcat5::igmp::DST_ALL_SYSTEMS (224, 0, 0, 1)
constexpr satcat5::ip::Addr	satcat5::igmp::DST_ALL_ROUTERS (224, 0, 0, 2)
	< All endpoints on subnet.
constexpr satcat5::ip::Addr	satcat5::igmp::DST_IGMPV3_REPORT (224, 0, 0, 22)
	< All routers on subnet. More...
bool	satcat5::igmp::igmp_send (satcat5::ip::Dispatch *iface, const satcat5::ip::Addr &dst, const unsigned wcount, u16 *data)
	Given IGMP message contents, write Eth/IP headers and send packet. More...
u32	satcat5::igmp::decode_maxdly (u16 hdr, bool v3)
	Given the first word of the IGMP query header, decode max delay. More...

Variables
constexpr u16	satcat5::igmp::MASK_TYPE = 0xFF00
	Bit-mask "type" from first header word.
constexpr u16	satcat5::igmp::MASK_MAXLEN = 0x00FF
	Bit-mask "length" from first header word.
constexpr u16	satcat5::igmp::TYPE_QUERY = 0x1100
	IGMP query (all versions)
constexpr u16	satcat5::igmp::TYPE_REPORT_V1 = 0x1200
	Reply to IGMPv1 query.
constexpr u16	satcat5::igmp::TYPE_REPORT_V2 = 0x1600
	Reply to IGMPv2 query.
constexpr u16	satcat5::igmp::TYPE_LEAVE_V2 = 0x1700
	Leaving group (v2 / v3)
constexpr u16	satcat5::igmp::TYPE_REPORT_V3 = 0x2200
	Reply to IGMPv3 query.
constexpr u16	satcat5::igmp::RECORD_MODE_INCL = 0x0100
	Record type: Include mode.
constexpr u16	satcat5::igmp::RECORD_MODE_EXCL = 0x0200
	Record type: Exclude mode.
constexpr u16	satcat5::igmp::RECORD_CHANGE_INCL = 0x0300
	Record type: Change to INCL mode.
constexpr u16	satcat5::igmp::RECORD_CHANGE_EXCL = 0x0400
	Record type: Change to EXCL mode.
constexpr u16	satcat5::igmp::RECORD_ALLOW_NEW = 0x0500
	Record type: Append to allow list.
constexpr u16	satcat5::igmp::RECORD_BLOCK_OLD = 0x0600
	Record type: Append to block list.
constexpr unsigned	satcat5::igmp::MIN_LEN_SHORTS = 4
	Set upper and lower bounds for the length of an IGMP message.
constexpr unsigned	satcat5::igmp::MIN_LEN_BYTES = 2 * MIN_LEN_SHORTS
	Set upper and lower bounds for the length of an IGMP message.
constexpr unsigned	satcat5::igmp::MAX_LEN_SHORTS = 730
	Set upper and lower bounds for the length of an IGMP message.
constexpr unsigned	satcat5::igmp::MAX_LEN_BYTES = 2 * MAX_LEN_SHORTS
	Set upper and lower bounds for the length of an IGMP message.
constexpr unsigned	satcat5::igmp::MAX_V3_RECORDS = (MAX_LEN_SHORTS - 4) / 4
	Set upper and lower bounds for the length of an IGMP message.

Function Documentation

decode_maxdly()

u32 satcat5::igmp::decode_maxdly	(	u16	hdr,
		bool	v3
	)

Given the first word of the IGMP query header, decode max delay.

The overall message length allows the IGMP version to be inferred.

Returns

Maximum delay in milliseconds.

Definition at line 60 of file igmp_client.cc.

DST_IGMPV3_REPORT()

constexpr satcat5::ip::Addr satcat5::igmp::DST_IGMPV3_REPORT	(	224	,
		0	,
		0	,
		22
	)

< All routers on subnet.

Group for IGMPv3 reports.

igmp_send()

bool satcat5::igmp::igmp_send	(	satcat5::ip::Dispatch *	iface,
		const satcat5::ip::Addr &	dst,
		const unsigned	wcount,
		u16 *	data
	)

Given IGMP message contents, write Eth/IP headers and send packet.

This helper function is used by igmp::Client and igmp::Server.

Definition at line 26 of file igmp_client.cc.