igmp_client.h

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// Copyright 2025 The Aerospace Corporation.
// This file is a part of SatCat5, licensed under CERN-OHL-W v2 or later.
 
#pragma once
 
#include <satcat5/ip_core.h>
#include <satcat5/list.h>
#include <satcat5/net_protocol.h>
#include <satcat5/polling.h>
 
// Enable support for IPv4 multicast and IGMP?
// For memory-constrained projects that do not need to receive multicast
// packets, dropping IGMP support can reduce code size by about 3 kB.
// For GCC/G++: compiler flag "-DSATCAT5_IGMP_ENABLE=0" to disable.
#ifndef SATCAT5_IGMP_ENABLE
#define SATCAT5_IGMP_ENABLE 1
#endif
 
namespace satcat5 {
    namespace igmp {
        // Destination addresses for IGMP broadcasts:
        constexpr satcat5::ip::Addr
            DST_ALL_SYSTEMS(224, 0, 0, 1),      
            DST_ALL_ROUTERS(224, 0, 0, 2),      
            DST_IGMPV3_REPORT(224, 0, 0, 22);   
 
        constexpr unsigned
            MIN_LEN_SHORTS  = 4,
            MIN_LEN_BYTES   = 2 * MIN_LEN_SHORTS,
            MAX_LEN_SHORTS  = 730,
            MAX_LEN_BYTES   = 2 * MAX_LEN_SHORTS,
            MAX_V3_RECORDS  = (MAX_LEN_SHORTS - 4) / 4;
 
        // Protocol constants:
        constexpr u16
            MASK_TYPE           = 0xFF00,   
            MASK_MAXLEN         = 0x00FF,   
            TYPE_QUERY          = 0x1100,   
            TYPE_REPORT_V1      = 0x1200,   
            TYPE_REPORT_V2      = 0x1600,   
            TYPE_LEAVE_V2       = 0x1700,   
            TYPE_REPORT_V3      = 0x2200,   
            RECORD_MODE_INCL    = 0x0100,   
            RECORD_MODE_EXCL    = 0x0200,   
            RECORD_CHANGE_INCL  = 0x0300,   
            RECORD_CHANGE_EXCL  = 0x0400,   
            RECORD_ALLOW_NEW    = 0x0500,   
            RECORD_BLOCK_OLD    = 0x0600;   
 
        bool igmp_send(
            satcat5::ip::Dispatch* iface,
            const satcat5::ip::Addr& dst,
            const unsigned wcount, u16* data);
 
        u32 decode_maxdly(u16 hdr, bool v3);
 
        class Client final
            #if SATCAT5_IGMP_ENABLE
            : protected satcat5::net::Protocol
            , protected satcat5::poll::Timer
            #endif
        {
        public:
            explicit Client(satcat5::ip::Dispatch* iface);
            ~Client();
 
            void join(satcat5::igmp::Address& obj, const satcat5::ip::Addr& addr);
 
            void leave(satcat5::igmp::Address& obj);
 
        protected:
            #if SATCAT5_IGMP_ENABLE
            void frame_rcvd(satcat5::io::LimitedRead& src) override;
            void timer_event() override;
            satcat5::igmp::Address* find_match(const satcat5::ip::Addr& group) const;
            void send_leave(const satcat5::ip::Addr& group);
            void send_report(const satcat5::ip::Addr& group);
            void set_timer(u32& timer, u32 max_msec);
 
            satcat5::ip::Dispatch* const m_iface;
            satcat5::util::List<satcat5::igmp::Address> m_groups;
            u32 m_reply_timer;
            u8 m_version;
            #endif
        };
 
        struct Address {
        public:
            constexpr Address()
                #if SATCAT5_IGMP_ENABLE
                : m_igmp_group(0), m_igmp_timer(0), m_next(nullptr)
                #endif
                {}  // Empty stub if IGMP is disabled.
 
            inline void join(satcat5::igmp::Client* igmp, const satcat5::ip::Addr& addr)
                { igmp->join(*this, addr); }
 
            inline void leave(satcat5::igmp::Client* igmp)
                { igmp->leave(*this); }
 
        protected:
            #if SATCAT5_IGMP_ENABLE
            // Required state for the IGMP protocol.
            friend satcat5::igmp::Client;
            satcat5::ip::Addr m_igmp_group;
            u32 m_igmp_timer;
 
            // Linked list to the next IgmpAddress object.
            friend satcat5::util::ListCore;
            satcat5::igmp::Address* m_next;
            #endif
        };
    }
}