feat(http2): allow configuring the HTTP/2 frame size

The default of 16K is taken from h2.

src/client/conn.rs

@@ -525,6 +525,18 @@ impl Builder {
         self
     }
 
+    /// Sets the maximum frame size to use for HTTP2.
+    ///
+    /// Passing `None` will do nothing.
+    ///
+    /// If not set, hyper will use a default.
+    pub fn http2_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
+    }
+
     /// Sets an interval for HTTP2 Ping frames should be sent to keep a
     /// connection alive.
     ///

src/proto/h2/client.rs

@@ -30,12 +30,14 @@ type ConnEof = oneshot::Receiver<Never>;
 // for performance.
 const DEFAULT_CONN_WINDOW: u32 = 1024 * 1024 * 5; // 5mb
 const DEFAULT_STREAM_WINDOW: u32 = 1024 * 1024 * 2; // 2mb
+const DEFAULT_MAX_FRAME_SIZE: u32 = 1024 * 16; // 16kb
 
 #[derive(Clone, Debug)]
 pub(crate) struct Config {
     pub(crate) adaptive_window: bool,
     pub(crate) initial_conn_window_size: u32,
     pub(crate) initial_stream_window_size: u32,
+    pub(crate) max_frame_size: u32,
     #[cfg(feature = "runtime")]
     pub(crate) keep_alive_interval: Option<Duration>,
     #[cfg(feature = "runtime")]
@@ -50,6 +52,7 @@ impl Default for Config {
             adaptive_window: false,
             initial_conn_window_size: DEFAULT_CONN_WINDOW,
             initial_stream_window_size: DEFAULT_STREAM_WINDOW,
+            max_frame_size: DEFAULT_MAX_FRAME_SIZE,
             #[cfg(feature = "runtime")]
             keep_alive_interval: None,
             #[cfg(feature = "runtime")]
@@ -74,6 +77,7 @@ where
     let (h2_tx, mut conn) = Builder::default()
         .initial_window_size(config.initial_stream_window_size)
         .initial_connection_window_size(config.initial_conn_window_size)
+        .max_frame_size(config.max_frame_size)
         .enable_push(false)
         .handshake::<_, SendBuf<B::Data>>(io)
         .await

src/proto/h2/server.rs

@@ -26,12 +26,14 @@ use crate::{Body, Response};
 // so is more likely to use more resources than a client would.
 const DEFAULT_CONN_WINDOW: u32 = 1024 * 1024; // 1mb
 const DEFAULT_STREAM_WINDOW: u32 = 1024 * 1024; // 1mb
+const DEFAULT_MAX_FRAME_SIZE: u32 = 1024 * 16; // 16kb
 
 #[derive(Clone, Debug)]
 pub(crate) struct Config {
     pub(crate) adaptive_window: bool,
     pub(crate) initial_conn_window_size: u32,
     pub(crate) initial_stream_window_size: u32,
+    pub(crate) max_frame_size: u32,
     pub(crate) max_concurrent_streams: Option<u32>,
     #[cfg(feature = "runtime")]
     pub(crate) keep_alive_interval: Option<Duration>,
@@ -45,6 +47,7 @@ impl Default for Config {
             adaptive_window: false,
             initial_conn_window_size: DEFAULT_CONN_WINDOW,
             initial_stream_window_size: DEFAULT_STREAM_WINDOW,
+            max_frame_size: DEFAULT_MAX_FRAME_SIZE,
             max_concurrent_streams: None,
             #[cfg(feature = "runtime")]
             keep_alive_interval: None,
@@ -98,7 +101,8 @@ where
         let mut builder = h2::server::Builder::default();
         builder
             .initial_window_size(config.initial_stream_window_size)
-            .initial_connection_window_size(config.initial_conn_window_size);
+            .initial_connection_window_size(config.initial_conn_window_size)
+            .max_frame_size(config.max_frame_size);
         if let Some(max) = config.max_concurrent_streams {
             builder.max_concurrent_streams(max);
         }

src/server/conn.rs

@@ -309,6 +309,18 @@ impl<E> Http<E> {
         self
     }
 
+    /// Sets the maximum frame size to use for HTTP2.
+    ///
+    /// Passing `None` will do nothing.
+    ///
+    /// If not set, hyper will use a default.
+    pub fn http2_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
+    }
+
     /// Sets the [`SETTINGS_MAX_CONCURRENT_STREAMS`][spec] option for HTTP2
     /// connections.
     ///