Fix infinite loop in single-stream connection (#2751)

Fix #2750

bin/wasm-node/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Fixed
+
+- Fix potential infinite loop in networking connection task. ([#2751](https://github.com/paritytech/smoldot/pull/2751))
+
 ### Changed
 
 - No longer try to connect to a peer for 20 seconds after failing to connect to it. This prevents loops where we keep trying to connect to the same address(es) over and over again ([#2747](https://github.com/paritytech/smoldot/pull/2747)).

src/libp2p/connection/established/single_stream.rs

@@ -258,11 +258,14 @@ where
 
                 if let Some(event) = event {
                     return Ok((self, Some(event)));
+                } else if num_read == 0 {
+                    // Substream doesn't accept anymore data because it is blocked on writing out.
+                    return Ok((self, None));
+                } else {
+                    // Jump back to the beginning of the loop. We don't want to read more data
+                    // until this specific substream's data has been processed.
+                    continue;
                 }
-
-                // Jump back to the beginning of the loop. We don't want to read more data until
-                // this specific substream's data has been processed.
-                continue;
             }
 
             // Transfer data from `incoming_data` to the internal buffer in `self.encryption`.