sdk/fidl/fuchsia.net.tcp/tcp.fidl

// Copyright 2025 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

/// TCP types used across multiple FIDL endpoints.
@available(added=NEXT)
library fuchsia.net.tcp;

/// TCP congestion control state machine state.
type CongestionControlState = strict enum {
    /// No indication of duplicate ACKs or loss. Everything is fine.
    OPEN = 0;
    /// Received SACK blocks duplicate ACKs, assumed to be due to packet loss
    /// or reordering.
    DISORDER = 1;
    /// Sending rate reduced due to congestion signal. This is either an ECN or
    /// local queue overrun.
    CONGESTION_WINDOW_REDUCED = 2;
    /// Sender has entered either fast recovery (after seeing enough duplicate
    /// ACKs) or SACK-based recovery
    RECOVERY = 3;
    /// Sender hit RTO and entered slow start. Exits when all retransmitted
    /// packets have been ACKed.
    LOSS = 4;
};

/// TCP state machine state.
type State = strict enum {
    ESTABLISHED = 1;
    SYN_SENT = 2;
    SYN_RECV = 3;
    FIN_WAIT1 = 4;
    FIN_WAIT2 = 5;
    TIME_WAIT = 6;
    CLOSE = 7;
    CLOSE_WAIT = 8;
    LAST_ACK = 9;
    LISTEN = 10;
    CLOSING = 11;
};

/// TCP protocol state.
type Info = table {
    /// The current state of the TCP state machine.
    1: state State;
    /// The current state of the TCP congention avoidance state machine.
    2: ca_state CongestionControlState;
    // 3: tcpi_retransmits uint8;
    // 4: tcpi_probes uint8;
    // 5: tcpi_backoff uint8;
    // 6: tcpi_options uint8;
    // 7: ... // tcpi_snd_wscale : 4,
    // 8: ... // tcpi_rcv_wscale : 4;
    // 9: ... // tcpi_delivery_rate_app_limited : 1,
    // 10: ... // tcpi_fastopen_client_fail : 2;
    /// The current RTO value in microseconds.
    11: rto_usec uint32;
    // 12: tcpi_ato uint32;
    // 13: tcpi_snd_mss uint32;
    // 14: tcpi_rcv_mss uint32;
    // 15: tcpi_unacked uint32;
    // 16: tcpi_sacked uint32;
    // 17: tcpi_lost uint32;
    // 18: tcpi_retrans uint32;
    // 19: tcpi_fackets uint32;
    /// Time since data was last sent on the connection in milliseconds.
    20: tcpi_last_data_sent_msec uint32;
    // 21: tcpi_last_ack_sent uint32;
    // 22: tcpi_last_data_recv uint32;
    /// Time since the most recent ACK was received in milliseconds.
    23: tcpi_last_ack_recv_msec uint32;
    // 24: tcpi_pmtu uint32;
    // 25: tcpi_rcv_ssthresh uint32;
    /// The estimated smoothed roundtrip time in microseconds.
    26: rtt_usec uint32;
    /// The smoothed mean deviation of the roundtrip time in microseconds.
    27: rtt_var_usec uint32;
    /// The sending slow start threshold in segments.
    28: snd_ssthresh uint32;
    /// The current sending congestion window in segments.
    29: snd_cwnd uint32;
    // 30: tcpi_advmss uint32;
    // 31: tcpi_reordering uint32;
    // 32: tcpi_rcv_rtt uint32;
    // 33: tcpi_rcv_space uint32;
    /// The total number of retransmission events.
    34: tcpi_total_retrans uint32;
    // 35: tcpi_pacing_rate uint64;
    // 36: tcpi_max_pacing_rate uint64;
    // 37: tcpi_bytes_acked uint64;
    // 38: tcpi_bytes_received uint64;
    /// The total number of segments transmitted.
    39: tcpi_segs_out uint64;
    /// The total number of segments received.
    40: tcpi_segs_in uint64;
    // 41: tcpi_notsent_bytes uint32;
    // 42: tcpi_min_rtt uint32;
    // 43: tcpi_data_segs_in uint32;
    // 44: tcpi_data_segs_out uint32;
    // 45: tcpi_delivery_rate uint64;
    // 46: tcpi_busy_time uint64;
    // 47: tcpi_rwnd_limited uint64;
    // 48: tcpi_sndbuf_limited uint64;
    // 49: tcpi_delivered uint32;
    // 50: tcpi_delivered_ce uint32;
    // 51: tcpi_bytes_sent uint64;
    // 52: tcpi_bytes_retrans uint64;
    // 53: tcpi_dsack_dups uint32;
    /// Whether the connection thinks it has ever seen reordering.
    // TODO(https://fxbug.dev/434682660): This is different from Linux, where
    // this field is the number of reordering events seen.
    54: reorder_seen bool;
    // 55: tcpi_rcv_ooopack uint32;
    // 56: tcpi_snd_wnd uint32;
};