feat(client): Add HTTP/2 builder options header_table_size() and `m…

…ax_concurrent_streams()` (#3731)

src/client/conn/http2.rs

@@ -337,13 +337,9 @@ where
 
     /// Sets the maximum frame size to use for HTTP2.
     ///
-    /// Passing `None` will do nothing.
-    ///
-    /// If not set, hyper will use a default.
+    /// Default is currently 16KB, but can change.
     pub fn max_frame_size(&mut self, sz: impl Into<Option<u32>>) -> &mut Self {
-        if let Some(sz) = sz.into() {
-            self.h2_builder.max_frame_size = sz;
-        }
+        self.h2_builder.max_frame_size = sz.into();
         self
     }
 
@@ -355,6 +351,46 @@ where
         self
     }
 
+    /// Sets the header table size.
+    ///
+    /// This setting informs the peer of the maximum size of the header compression
+    /// table used to encode header blocks, in octets. The encoder may select any value
+    /// equal to or less than the header table size specified by the sender.
+    ///
+    /// The default value of crate `h2` is 4,096.
+    pub fn header_table_size(&mut self, size: impl Into<Option<u32>>) -> &mut Self {
+        self.h2_builder.header_table_size = size.into();
+        self
+    }
+
+    /// Sets the maximum number of concurrent streams.
+    ///
+    /// The maximum concurrent streams setting only controls the maximum number
+    /// of streams that can be initiated by the remote peer. In other words,
+    /// when this setting is set to 100, this does not limit the number of
+    /// concurrent streams that can be created by the caller.
+    ///
+    /// It is recommended that this value be no smaller than 100, so as to not
+    /// unnecessarily limit parallelism. However, any value is legal, including
+    /// 0. If `max` is set to 0, then the remote will not be permitted to
+    /// initiate streams.
+    ///
+    /// Note that streams in the reserved state, i.e., push promises that have
+    /// been reserved but the stream has not started, do not count against this
+    /// setting.
+    ///
+    /// Also note that if the remote *does* exceed the value set here, it is not
+    /// a protocol level error. Instead, the `h2` library will immediately reset
+    /// the stream.
+    ///
+    /// See [Section 5.1.2] in the HTTP/2 spec for more details.
+    ///
+    /// [Section 5.1.2]: https://http2.github.io/http2-spec/#rfc.section.5.1.2
+    pub fn max_concurrent_streams(&mut self, max: impl Into<Option<u32>>) -> &mut Self {
+        self.h2_builder.max_concurrent_streams = max.into();
+        self
+    }
+
     /// Sets an interval for HTTP2 Ping frames should be sent to keep a
     /// connection alive.
     ///

src/proto/h2/client.rs

@@ -68,14 +68,16 @@ pub(crate) struct Config {
     pub(crate) initial_conn_window_size: u32,
     pub(crate) initial_stream_window_size: u32,
     pub(crate) initial_max_send_streams: usize,
-    pub(crate) max_frame_size: u32,
+    pub(crate) max_frame_size: Option<u32>,
     pub(crate) max_header_list_size: u32,
     pub(crate) keep_alive_interval: Option<Duration>,
     pub(crate) keep_alive_timeout: Duration,
     pub(crate) keep_alive_while_idle: bool,
     pub(crate) max_concurrent_reset_streams: Option<usize>,
     pub(crate) max_send_buffer_size: usize,
     pub(crate) max_pending_accept_reset_streams: Option<usize>,
+    pub(crate) header_table_size: Option<u32>,
+    pub(crate) max_concurrent_streams: Option<u32>,
 }
 
 impl Default for Config {
@@ -85,14 +87,16 @@ impl Default for Config {
             initial_conn_window_size: DEFAULT_CONN_WINDOW,
             initial_stream_window_size: DEFAULT_STREAM_WINDOW,
             initial_max_send_streams: DEFAULT_INITIAL_MAX_SEND_STREAMS,
-            max_frame_size: DEFAULT_MAX_FRAME_SIZE,
+            max_frame_size: Some(DEFAULT_MAX_FRAME_SIZE),
             max_header_list_size: DEFAULT_MAX_HEADER_LIST_SIZE,
             keep_alive_interval: None,
             keep_alive_timeout: Duration::from_secs(20),
             keep_alive_while_idle: false,
             max_concurrent_reset_streams: None,
             max_send_buffer_size: DEFAULT_MAX_SEND_BUF_SIZE,
             max_pending_accept_reset_streams: None,
+            header_table_size: None,
+            max_concurrent_streams: None,
         }
     }
 }
@@ -103,16 +107,24 @@ fn new_builder(config: &Config) -> Builder {
         .initial_max_send_streams(config.initial_max_send_streams)
         .initial_window_size(config.initial_stream_window_size)
         .initial_connection_window_size(config.initial_conn_window_size)
-        .max_frame_size(config.max_frame_size)
         .max_header_list_size(config.max_header_list_size)
         .max_send_buffer_size(config.max_send_buffer_size)
         .enable_push(false);
+    if let Some(max) = config.max_frame_size {
+        builder.max_frame_size(max);
+    }
     if let Some(max) = config.max_concurrent_reset_streams {
         builder.max_concurrent_reset_streams(max);
     }
     if let Some(max) = config.max_pending_accept_reset_streams {
         builder.max_pending_accept_reset_streams(max);
     }
+    if let Some(size) = config.header_table_size {
+        builder.header_table_size(size);
+    }
+    if let Some(max) = config.max_concurrent_streams {
+        builder.max_concurrent_streams(max);
+    }
     builder
 }