71 lines
2.4 KiB
C++
71 lines
2.4 KiB
C++
#ifndef SPONGE_LIBSPONGE_TCP_RECEIVER_HH
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#define SPONGE_LIBSPONGE_TCP_RECEIVER_HH
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#include "byte_stream.hh"
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#include "stream_reassembler.hh"
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#include "tcp_segment.hh"
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#include "wrapping_integers.hh"
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#include <optional>
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//! \brief The "receiver" part of a TCP implementation.
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//! Receives and reassembles segments into a ByteStream, and computes
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//! the acknowledgment number and window size to advertise back to the
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//! remote TCPSender.
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class TCPReceiver {
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//! Our data structure for re-assembling bytes.
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StreamReassembler _reassembler;
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//! The maximum number of bytes we'll store.
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size_t _capacity;
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WrappingInt32 _isn{0};
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WrappingInt32 _ackno{0};
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uint64_t _abs_ackno{0};
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bool _syn{};
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public:
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//! \brief Construct a TCP receiver
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//!
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//! \param capacity the maximum number of bytes that the receiver will
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//! store in its buffers at any give time.
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TCPReceiver(const size_t capacity) : _reassembler(capacity), _capacity(capacity) {}
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//! \name Accessors to provide feedback to the remote TCPSender
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//!@{
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//! \brief The ackno that should be sent to the peer
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//! \returns empty if no SYN has been received
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//!
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//! This is the beginning of the receiver's window, or in other words, the sequence number
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//! of the first byte in the stream that the receiver hasn't received.
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std::optional<WrappingInt32> ackno() const;
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//! \brief The window size that should be sent to the peer
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//!
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//! Operationally: the capacity minus the number of bytes that the
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//! TCPReceiver is holding in its byte stream (those that have been
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//! reassembled, but not consumed).
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//!
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//! Formally: the difference between (a) the sequence number of
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//! the first byte that falls after the window (and will not be
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//! accepted by the receiver) and (b) the sequence number of the
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//! beginning of the window (the ackno).
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size_t window_size() const;
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//!@}
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//! \brief number of bytes stored but not yet reassembled
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size_t unassembled_bytes() const { return _reassembler.unassembled_bytes(); }
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//! \brief handle an inbound segment
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void segment_received(const TCPSegment &seg);
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//! \name "Output" interface for the reader
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//!@{
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ByteStream &stream_out() { return _reassembler.stream_out(); }
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const ByteStream &stream_out() const { return _reassembler.stream_out(); }
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//!@}
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};
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#endif // SPONGE_LIBSPONGE_TCP_RECEIVER_HH
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