refactor: move max_datagrams limit at poll_transmit from quinn-proto to quinn

Author: filipe-cantarelli

quinn-proto/src/connection/mod.rs

@@ -453,7 +453,7 @@ impl Connection {
         assert!(max_datagrams != 0);
         let max_datagrams = match self.config.enable_segmentation_offload {
             false => 1,
-            true => max_datagrams.min(MAX_TRANSMIT_SEGMENTS),
+            true => max_datagrams,
         };
 
         let mut num_datagrams = 0;
@@ -3950,13 +3950,6 @@ const MIN_PACKET_SPACE: usize = MAX_HANDSHAKE_OR_0RTT_HEADER_SIZE + 32;
 const MAX_HANDSHAKE_OR_0RTT_HEADER_SIZE: usize =
     1 + 4 + 1 + MAX_CID_SIZE + 1 + MAX_CID_SIZE + VarInt::from_u32(u16::MAX as u32).size() + 4;
 
-/// The maximum amount of datagrams that are sent in a single transmit
-///
-/// This can be lower than the maximum platform capabilities, to avoid excessive
-/// memory allocations when calling `poll_transmit()`. Benchmarks have shown
-/// that numbers around 10 are a good compromise.
-const MAX_TRANSMIT_SEGMENTS: usize = 10;
-
 /// Perform key updates this many packets before the AEAD confidentiality limit.
 ///
 /// Chosen arbitrarily, intended to be large enough to prevent spurious connection loss.

quinn/src/connection.rs

@@ -981,7 +981,10 @@ impl State {
         let now = self.runtime.now();
         let mut transmits = 0;
 
-        let max_datagrams = self.socket.max_transmit_segments();
+        let max_datagrams = self
+            .socket
+            .max_transmit_segments()
+            .min(MAX_TRANSMIT_SEGMENTS);
 
         loop {
             // Retry the last transmit, or get a new one.
@@ -1288,3 +1291,10 @@ pub enum SendDatagramError {
 /// This limits the amount of CPU resources consumed by datagram generation,
 /// and allows other tasks (like receiving ACKs) to run in between.
 const MAX_TRANSMIT_DATAGRAMS: usize = 20;
+
+/// The maximum amount of datagrams that are sent in a single transmit
+///
+/// This can be lower than the maximum platform capabilities, to avoid excessive
+/// memory allocations when calling `poll_transmit()`. Benchmarks have shown
+/// that numbers around 10 are a good compromise.
+const MAX_TRANSMIT_SEGMENTS: usize = 10;