93 lines
3.1 KiB
C++
93 lines
3.1 KiB
C++
#ifndef SPONGE_LIBSPONGE_TCP_SENDER_HH
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#define SPONGE_LIBSPONGE_TCP_SENDER_HH
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#include "byte_stream.hh"
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#include "tcp_config.hh"
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#include "tcp_segment.hh"
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#include "wrapping_integers.hh"
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#include <functional>
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#include <queue>
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//! \brief The "sender" part of a TCP implementation.
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//! Accepts a ByteStream, divides it up into segments and sends the
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//! segments, keeps track of which segments are still in-flight,
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//! maintains the Retransmission Timer, and retransmits in-flight
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//! segments if the retransmission timer expires.
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class TCPSender {
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private:
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//! our initial sequence number, the number for our SYN.
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WrappingInt32 _isn;
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//! outbound queue of segments that the TCPSender wants sent
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std::queue<TCPSegment> _segments_out{};
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//! retransmission timer for the connection
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unsigned int _initial_retransmission_timeout;
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//! outgoing stream of bytes that have not yet been sent
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ByteStream _stream;
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//! the (absolute) sequence number for the next byte to be sent
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uint64_t _next_seqno{0};
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public:
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//! Initialize a TCPSender
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TCPSender(const size_t capacity = TCPConfig::DEFAULT_CAPACITY,
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const uint16_t retx_timeout = TCPConfig::TIMEOUT_DFLT,
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const std::optional<WrappingInt32> fixed_isn = {});
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//! \name "Input" interface for the writer
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//!@{
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ByteStream &stream_in() { return _stream; }
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const ByteStream &stream_in() const { return _stream; }
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//!@}
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//! \name Methods that can cause the TCPSender to send a segment
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//!@{
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//! \brief A new acknowledgment was received
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void ack_received(const WrappingInt32 ackno, const uint16_t window_size);
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//! \brief Generate an empty-payload segment (useful for creating empty ACK segments)
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void send_empty_segment();
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//! \brief create and send segments to fill as much of the window as possible
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void fill_window();
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//! \brief Notifies the TCPSender of the passage of time
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void tick(const size_t ms_since_last_tick);
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//!@}
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//! \name Accessors
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//!@{
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//! \brief How many sequence numbers are occupied by segments sent but not yet acknowledged?
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//! \note count is in "sequence space," i.e. SYN and FIN each count for one byte
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//! (see TCPSegment::length_in_sequence_space())
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size_t bytes_in_flight() const;
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//! \brief Number of consecutive retransmissions that have occurred in a row
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unsigned int consecutive_retransmissions() const;
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//! \brief TCPSegments that the TCPSender has enqueued for transmission.
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//! \note These must be dequeued and sent by the TCPConnection,
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//! which will need to fill in the fields that are set by the TCPReceiver
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//! (ackno and window size) before sending.
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std::queue<TCPSegment> &segments_out() { return _segments_out; }
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//!@}
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//! \name What is the next sequence number? (used for testing)
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//!@{
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//! \brief absolute seqno for the next byte to be sent
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uint64_t next_seqno_absolute() const { return _next_seqno; }
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//! \brief relative seqno for the next byte to be sent
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WrappingInt32 next_seqno() const { return wrap(_next_seqno, _isn); }
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//!@}
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};
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#endif // SPONGE_LIBSPONGE_TCP_SENDER_HH
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