h2/proto/
settings.rs

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1use crate::codec::UserError;
2use crate::error::Reason;
3use crate::proto::*;
4use std::task::{Context, Poll};
5
6#[derive(Debug)]
7pub(crate) struct Settings {
8    /// Our local SETTINGS sync state with the remote.
9    local: Local,
10    /// Received SETTINGS frame pending processing. The ACK must be written to
11    /// the socket first then the settings applied **before** receiving any
12    /// further frames.
13    remote: Option<frame::Settings>,
14    /// Whether the connection has received the initial SETTINGS frame from the
15    /// remote peer.
16    has_received_remote_initial_settings: bool,
17}
18
19#[derive(Debug)]
20enum Local {
21    /// We want to send these SETTINGS to the remote when the socket is ready.
22    ToSend(frame::Settings),
23    /// We have sent these SETTINGS and are waiting for the remote to ACK
24    /// before we apply them.
25    WaitingAck(frame::Settings),
26    /// Our local settings are in sync with the remote.
27    Synced,
28}
29
30impl Settings {
31    pub(crate) fn new(local: frame::Settings) -> Self {
32        Settings {
33            // We assume the initial local SETTINGS were flushed during
34            // the handshake process.
35            local: Local::WaitingAck(local),
36            remote: None,
37            has_received_remote_initial_settings: false,
38        }
39    }
40
41    pub(crate) fn recv_settings<T, B, C, P>(
42        &mut self,
43        frame: frame::Settings,
44        codec: &mut Codec<T, B>,
45        streams: &mut Streams<C, P>,
46    ) -> Result<(), Error>
47    where
48        T: AsyncWrite + Unpin,
49        B: Buf,
50        C: Buf,
51        P: Peer,
52    {
53        if frame.is_ack() {
54            match &self.local {
55                Local::WaitingAck(local) => {
56                    tracing::debug!("received settings ACK; applying {:?}", local);
57
58                    if let Some(max) = local.max_frame_size() {
59                        codec.set_max_recv_frame_size(max as usize);
60                    }
61
62                    if let Some(max) = local.max_header_list_size() {
63                        codec.set_max_recv_header_list_size(max as usize);
64                    }
65
66                    if let Some(val) = local.header_table_size() {
67                        codec.set_recv_header_table_size(val as usize);
68                    }
69
70                    streams.apply_local_settings(local)?;
71                    self.local = Local::Synced;
72                    Ok(())
73                }
74                Local::ToSend(..) | Local::Synced => {
75                    // We haven't sent any SETTINGS frames to be ACKed, so
76                    // this is very bizarre! Remote is either buggy or malicious.
77                    proto_err!(conn: "received unexpected settings ack");
78                    Err(Error::library_go_away(Reason::PROTOCOL_ERROR))
79                }
80            }
81        } else {
82            // We always ACK before reading more frames, so `remote` should
83            // always be none!
84            assert!(self.remote.is_none());
85            self.remote = Some(frame);
86            Ok(())
87        }
88    }
89
90    pub(crate) fn send_settings(&mut self, frame: frame::Settings) -> Result<(), UserError> {
91        assert!(!frame.is_ack());
92        match &self.local {
93            Local::ToSend(..) | Local::WaitingAck(..) => Err(UserError::SendSettingsWhilePending),
94            Local::Synced => {
95                tracing::trace!("queue to send local settings: {:?}", frame);
96                self.local = Local::ToSend(frame);
97                Ok(())
98            }
99        }
100    }
101
102    /// Sets `true` to `self.has_received_remote_initial_settings`.
103    /// Returns `true` if this method is called for the first time.
104    /// (i.e. it is the initial SETTINGS frame from the remote peer)
105    fn mark_remote_initial_settings_as_received(&mut self) -> bool {
106        let has_received = self.has_received_remote_initial_settings;
107        self.has_received_remote_initial_settings = true;
108        !has_received
109    }
110
111    pub(crate) fn poll_send<T, B, C, P>(
112        &mut self,
113        cx: &mut Context,
114        dst: &mut Codec<T, B>,
115        streams: &mut Streams<C, P>,
116    ) -> Poll<Result<(), Error>>
117    where
118        T: AsyncWrite + Unpin,
119        B: Buf,
120        C: Buf,
121        P: Peer,
122    {
123        if let Some(settings) = self.remote.clone() {
124            if !dst.poll_ready(cx)?.is_ready() {
125                return Poll::Pending;
126            }
127
128            // Create an ACK settings frame
129            let frame = frame::Settings::ack();
130
131            // Buffer the settings frame
132            dst.buffer(frame.into()).expect("invalid settings frame");
133
134            tracing::trace!("ACK sent; applying settings");
135
136            let is_initial = self.mark_remote_initial_settings_as_received();
137            streams.apply_remote_settings(&settings, is_initial)?;
138
139            if let Some(val) = settings.header_table_size() {
140                dst.set_send_header_table_size(val as usize);
141            }
142
143            if let Some(val) = settings.max_frame_size() {
144                dst.set_max_send_frame_size(val as usize);
145            }
146        }
147
148        self.remote = None;
149
150        match &self.local {
151            Local::ToSend(settings) => {
152                if !dst.poll_ready(cx)?.is_ready() {
153                    return Poll::Pending;
154                }
155
156                // Buffer the settings frame
157                dst.buffer(settings.clone().into())
158                    .expect("invalid settings frame");
159                tracing::trace!("local settings sent; waiting for ack: {:?}", settings);
160
161                self.local = Local::WaitingAck(settings.clone());
162            }
163            Local::WaitingAck(..) | Local::Synced => {}
164        }
165
166        Poll::Ready(Ok(()))
167    }
168}
h2/proto/settings.rs

h2/proto/
settings.rs
