Implement pion commit 2184 - mux: drop packets when buffer is full (#516)

* implement logic changes

* add tests, switch to 2184

* remove superfluous loop

* fix fmt

---------

Co-authored-by: Rusty Rain <2069201+rainliu@users.noreply.github.com>

Author: stuqdog

webrtc/src/mux/mod.rs

@@ -14,6 +14,7 @@ use util::{Buffer, Conn};
 use crate::error::Result;
 use crate::mux::endpoint::Endpoint;
 use crate::mux::mux_func::MatchFunc;
+use crate::util::Error;
 
 /// mux multiplexes packets on a single socket (RFC7983)
 
@@ -64,8 +65,6 @@ impl Mux {
 
         let id = self.id.fetch_add(1, Ordering::SeqCst);
         // Set a maximum size of the buffer in bytes.
-        // NOTE: We actually won't get anywhere close to this limit.
-        // SRTP will constantly read from the endpoint and drop packets if it's full.
         let e = Arc::new(Endpoint {
             id,
             buffer: Buffer::new(0, MAX_BUFFER_SIZE),
@@ -135,7 +134,14 @@ impl Mux {
         }
 
         if let Some(ep) = endpoint {
-            ep.buffer.write(buf).await?;
+            match ep.buffer.write(buf).await {
+                // Expected when bytes are received faster than the endpoint can process them
+                Err(Error::ErrBufferFull) => {
+                    log::info!("mux: endpoint buffer is full, dropping packet")
+                }
+                Ok(_) => (),
+                Err(e) => return Err(crate::Error::Util(e)),
+            }
         } else if !buf.is_empty() {
             log::warn!(
                 "Warning: mux: no endpoint for packet starting with {}",

webrtc/src/mux/mux_test.rs

@@ -6,26 +6,10 @@ use async_trait::async_trait;
 use util::conn::conn_pipe::pipe;
 
 use super::*;
-use crate::mux::mux_func::match_all;
+use crate::mux::mux_func::{match_all, match_srtp};
 
 const TEST_PIPE_BUFFER_SIZE: usize = 8192;
 
-async fn pipe_memory() -> (Arc<Endpoint>, impl Conn) {
-    // In memory pipe
-    let (ca, cb) = pipe();
-
-    let mut m = Mux::new(Config {
-        conn: Arc::new(ca),
-        buffer_size: TEST_PIPE_BUFFER_SIZE,
-    });
-
-    let e = m.new_endpoint(Box::new(match_all)).await;
-    m.remove_endpoint(&e).await;
-    let e = m.new_endpoint(Box::new(match_all)).await;
-
-    (e, cb)
-}
-
 #[tokio::test]
 async fn test_no_endpoints() -> crate::error::Result<()> {
     // In memory pipe
@@ -129,3 +113,25 @@ async fn test_non_fatal_read() -> Result<()> {
 
     Ok(())
 }
+
+#[tokio::test]
+async fn test_non_fatal_dispatch() -> Result<()> {
+    let (ca, cb) = pipe();
+
+    let mut m = Mux::new(Config {
+        conn: Arc::new(ca),
+        buffer_size: TEST_PIPE_BUFFER_SIZE,
+    });
+
+    let e = m.new_endpoint(Box::new(match_srtp)).await;
+    e.buffer.set_limit_size(1).await;
+
+    for _ in 0..25 {
+        let srtp_packet = [128, 1, 2, 3, 4].to_vec();
+        cb.send(&srtp_packet).await?;
+    }
+
+    m.close().await;
+
+    Ok(())
+}