1 use crate::codec::Codec;
2 use crate::frame::{self, Reason, StreamId};
3 
4 use bytes::Buf;
5 use std::io;
6 use std::task::{Context, Poll};
7 use tokio::io::AsyncWrite;
8 
9 /// Manages our sending of GOAWAY frames.
10 #[derive(Debug)]
11 pub(super) struct GoAway {
12     /// Whether the connection should close now, or wait until idle.
13     close_now: bool,
14     /// Records if we've sent any GOAWAY before.
15     going_away: Option<GoingAway>,
16     /// Whether the user started the GOAWAY by calling `abrupt_shutdown`.
17     is_user_initiated: bool,
18     /// A GOAWAY frame that must be buffered in the Codec immediately.
19     pending: Option<frame::GoAway>,
20 }
21 
22 /// Keeps a memory of any GOAWAY frames we've sent before.
23 ///
24 /// This looks very similar to a `frame::GoAway`, but is a separate type. Why?
25 /// Mostly for documentation purposes. This type is to record status. If it
26 /// were a `frame::GoAway`, it might appear like we eventually wanted to
27 /// serialize it. We **only** want to be able to look up these fields at a
28 /// later time.
29 ///
30 /// (Technically, `frame::GoAway` should gain an opaque_debug_data field as
31 /// well, and we wouldn't want to save that here to accidentally dump in logs,
32 /// or waste struct space.)
33 #[derive(Debug)]
34 pub(crate) struct GoingAway {
35     /// Stores the highest stream ID of a GOAWAY that has been sent.
36     ///
37     /// It's illegal to send a subsequent GOAWAY with a higher ID.
38     last_processed_id: StreamId,
39 
40     /// Records the error code of any GOAWAY frame sent.
41     reason: Reason,
42 }
43 
44 impl GoAway {
45     pub fn new() -> Self {
46         GoAway {
47             close_now: false,
48             going_away: None,
49             is_user_initiated: false,
50             pending: None,
51         }
52     }
53 
54     /// Enqueue a GOAWAY frame to be written.
55     ///
56     /// The connection is expected to continue to run until idle.
57     pub fn go_away(&mut self, f: frame::GoAway) {
58         if let Some(ref going_away) = self.going_away {
59             assert!(
60                 f.last_stream_id() <= going_away.last_processed_id,
61                 "GOAWAY stream IDs shouldn't be higher; \
62                  last_processed_id = {:?}, f.last_stream_id() = {:?}",
63                 going_away.last_processed_id,
64                 f.last_stream_id(),
65             );
66         }
67 
68         self.going_away = Some(GoingAway {
69             last_processed_id: f.last_stream_id(),
70             reason: f.reason(),
71         });
72         self.pending = Some(f);
73     }
74 
75     pub fn go_away_now(&mut self, f: frame::GoAway) {
76         self.close_now = true;
77         if let Some(ref going_away) = self.going_away {
78             // Prevent sending the same GOAWAY twice.
79             if going_away.last_processed_id == f.last_stream_id() && going_away.reason == f.reason()
80             {
81                 return;
82             }
83         }
84         self.go_away(f);
85     }
86 
87     pub fn go_away_from_user(&mut self, f: frame::GoAway) {
88         self.is_user_initiated = true;
89         self.go_away_now(f);
90     }
91 
92     /// Return if a GOAWAY has ever been scheduled.
93     pub fn is_going_away(&self) -> bool {
94         self.going_away.is_some()
95     }
96 
97     pub fn is_user_initiated(&self) -> bool {
98         self.is_user_initiated
99     }
100 
101     /// Returns the going away info, if any.
102     pub fn going_away(&self) -> Option<&GoingAway> {
103         self.going_away.as_ref()
new(codec: Codec<T, Prioritized<B>>, config: Config) -> Connection<T, P, B>104     }
105 
106     /// Returns if the connection should close now, or wait until idle.
107     pub fn should_close_now(&self) -> bool {
108         self.pending.is_none() && self.close_now
109     }
110 
111     /// Returns if the connection should be closed when idle.
112     pub fn should_close_on_idle(&self) -> bool {
113         !self.close_now
114             && self
115                 .going_away
116                 .as_ref()
117                 .map(|g| g.last_processed_id != StreamId::MAX)
118                 .unwrap_or(false)
119     }
120 
121     /// Try to write a pending GOAWAY frame to the buffer.
122     ///
123     /// If a frame is written, the `Reason` of the GOAWAY is returned.
124     pub fn send_pending_go_away<T, B>(
125         &mut self,
126         cx: &mut Context,
127         dst: &mut Codec<T, B>,
128     ) -> Poll<Option<io::Result<Reason>>>
129     where
130         T: AsyncWrite + Unpin,
131         B: Buf,
132     {
133         if let Some(frame) = self.pending.take() {
134             if !dst.poll_ready(cx)?.is_ready() {
135                 self.pending = Some(frame);
136                 return Poll::Pending;
137             }
138 
139             let reason = frame.reason();
140             dst.buffer(frame.into()).expect("invalid GOAWAY frame");
141 
142             return Poll::Ready(Some(Ok(reason)));
143         } else if self.should_close_now() {
144             return match self.going_away().map(|going_away| going_away.reason) {
set_target_window_size(&mut self, size: WindowSize)145                 Some(reason) => Poll::Ready(Some(Ok(reason))),
146                 None => Poll::Ready(None),
147             };
148         }
149 
set_initial_window_size(&mut self, size: WindowSize) -> Result<(), UserError>150         Poll::Ready(None)
151     }
152 }
153 
154 impl GoingAway {
155     pub(crate) fn reason(&self) -> Reason {
156         self.reason
157     }
158 }
159