limit custom settings

src/client.rs

@@ -143,6 +143,7 @@ use crate::{FlowControl, PingPong, RecvStream, SendStream};
 
 use bytes::{Buf, Bytes};
 use http::{uri, HeaderMap, Method, Request, Response, Version};
+use std::collections::BTreeSet;
 use std::fmt;
 use std::future::Future;
 use std::pin::Pin;
@@ -343,6 +344,9 @@ pub struct Builder {
     ///
     /// When this gets exceeded, we issue GOAWAYs.
     local_max_error_reset_streams: Option<usize>,
+
+    /// Custom settings IDs to be tracked from the remote
+    allowed_custom_settings: BTreeSet<u16>,
 }
 
 #[derive(Debug)]
@@ -673,6 +677,7 @@ impl Builder {
             settings: Default::default(),
             stream_id: 1.into(),
             local_max_error_reset_streams: Some(proto::DEFAULT_LOCAL_RESET_COUNT_MAX),
+            allowed_custom_settings: BTreeSet::new(),
         }
     }
 
@@ -879,6 +884,16 @@ impl Builder {
         self
     }
 
+    /// By default, unknown settings recieved from the remote will be ignored.
+    ///
+    /// See [Section 6.5] in the HTTP/2 spec for more details.
+    ///
+    /// [Section 6.5]: https://httpwg.org/specs/rfc7540.html#rfc.section.6.5
+    pub fn allow_custom_setting(&mut self, id: u16) -> &mut Self {
+        self.allowed_custom_settings.insert(id);
+        self
+    }
+
     /// Sets the initial maximum of locally initiated (send) streams.
     ///
     /// The initial settings will be overwritten by the remote peer when
@@ -1355,6 +1370,7 @@ where
                 remote_reset_stream_max: builder.pending_accept_reset_stream_max,
                 local_error_reset_streams_max: builder.local_max_error_reset_streams,
                 settings: builder.settings.clone(),
+                allowed_custom_settings: builder.allowed_custom_settings,
             },
         );
         let send_request = SendRequest {

src/frame/settings.rs

@@ -136,8 +136,8 @@ impl Settings {
         }
     }
 
-    pub fn custom_settings(&self) -> &BTreeMap<u16, u32> {
-        &self.custom
+    pub fn custom_setting(&self, id: u16) -> Option<u32> {
+        self.custom.get(&id).copied()
     }
 
     pub fn load(head: Head, payload: &[u8]) -> Result<Settings, Error> {

src/proto/connection.rs

@@ -7,6 +7,7 @@ use crate::proto::*;
 
 use bytes::Bytes;
 use futures_core::Stream;
+use std::collections::BTreeSet;
 use std::io;
 use std::marker::PhantomData;
 use std::pin::Pin;
@@ -83,6 +84,7 @@ pub(crate) struct Config {
     pub remote_reset_stream_max: usize,
     pub local_error_reset_streams_max: Option<usize>,
     pub settings: frame::Settings,
+    pub allowed_custom_settings: BTreeSet<u16>,
 }
 
 #[derive(Debug)]
@@ -123,6 +125,7 @@ where
                     .max_concurrent_streams()
                     .map(|max| max as usize),
                 local_max_error_reset_streams: config.local_error_reset_streams_max,
+                allowed_custom_settings: config.allowed_custom_settings.clone(),
             }
         }
         let streams = Streams::new(streams_config(&config));

src/proto/streams/mod.rs

@@ -29,6 +29,7 @@ use crate::frame::{StreamId, StreamIdOverflow};
 use crate::proto::*;
 
 use bytes::Bytes;
+use std::collections::BTreeSet;
 use std::time::Duration;
 
 #[derive(Debug)]
@@ -72,4 +73,7 @@ pub struct Config {
     ///
     /// When this gets exceeded, we issue GOAWAYs.
     pub local_max_error_reset_streams: Option<usize>,
+
+    /// Custom settings IDs to be tracked from the remote
+    pub allowed_custom_settings: BTreeSet<u16>,
 }

src/proto/streams/send.rs

@@ -10,7 +10,7 @@ use bytes::Buf;
 use tokio::io::AsyncWrite;
 
 use std::cmp::Ordering;
-use std::collections::BTreeMap;
+use std::collections::{BTreeMap, BTreeSet};
 use std::io;
 use std::task::{Context, Poll, Waker};
 
@@ -42,6 +42,7 @@ pub(super) struct Send {
 
     /// Custom settings
     custom_settings: BTreeMap<u16, u32>,
+    allowed_custom_settings: BTreeSet<u16>,
 }
 
 /// A value to detect which public API has called `poll_reset`.
@@ -62,6 +63,7 @@ impl Send {
             is_push_enabled: true,
             is_extended_connect_protocol_enabled: false,
             custom_settings: BTreeMap::new(),
+            allowed_custom_settings: config.allowed_custom_settings.clone(),
         }
     }
 
@@ -439,7 +441,11 @@ impl Send {
         if let Some(val) = settings.is_extended_connect_protocol_enabled() {
             self.is_extended_connect_protocol_enabled = val;
         }
-        self.custom_settings.extend(settings.custom_settings());
+        for id in &self.allowed_custom_settings {
+            if let Some(val) = settings.custom_setting(*id) {
+                self.custom_settings.insert(*id, val);
+            }
+        }
 
         // Applies an update to the remote endpoint's initial window size.
         //
@@ -590,6 +596,6 @@ impl Send {
     }
 
     pub(crate) fn custom_setting(&self, id: u16) -> Option<u32> {
-        self.custom_settings.get(&id).map(|v| *v)
+        self.custom_settings.get(&id).copied()
     }
 }

src/server.rs

@@ -122,6 +122,7 @@ use crate::{FlowControl, PingPong, RecvStream, SendStream};
 
 use bytes::{Buf, Bytes};
 use http::{HeaderMap, Method, Request, Response};
+use std::collections::BTreeSet;
 use std::future::Future;
 use std::pin::Pin;
 use std::task::{Context, Poll};
@@ -258,6 +259,9 @@ pub struct Builder {
     ///
     /// When this gets exceeded, we issue GOAWAYs.
     local_max_error_reset_streams: Option<usize>,
+
+    /// Custom settings IDs to be tracked from the remote
+    allowed_custom_settings: BTreeSet<u16>,
 }
 
 /// Send a response back to the client
@@ -675,8 +679,8 @@ impl Builder {
             settings: Settings::default(),
             initial_target_connection_window_size: None,
             max_send_buffer_size: proto::DEFAULT_MAX_SEND_BUFFER_SIZE,
-
             local_max_error_reset_streams: Some(proto::DEFAULT_LOCAL_RESET_COUNT_MAX),
+            allowed_custom_settings: BTreeSet::new(),
         }
     }
 
@@ -1058,6 +1062,16 @@ impl Builder {
         self
     }
 
+    /// By default, unknown settings recieved from the remote will be ignored.
+    ///
+    /// See [Section 6.5] in the HTTP/2 spec for more details.
+    ///
+    /// [Section 6.5]: https://httpwg.org/specs/rfc7540.html#rfc.section.6.5
+    pub fn allow_custom_setting(&mut self, id: u16) -> &mut Self {
+        self.allowed_custom_settings.insert(id);
+        self
+    }
+
     /// Creates a new configured HTTP/2 server backed by `io`.
     ///
     /// It is expected that `io` already be in an appropriate state to commence
@@ -1420,6 +1434,7 @@ where
                                 .builder
                                 .local_max_error_reset_streams,
                             settings: self.builder.settings.clone(),
+                            allowed_custom_settings: self.builder.allowed_custom_settings.clone(),
                         },
                     );