revert broken fix in #2624 (#2779)

* revert broken fix in #2624

* update changelog

actix-http/CHANGES.md

@@ -4,6 +4,11 @@
 ### Changed
 - Minimum supported Rust version (MSRV) is now 1.56 due to transitive `hashbrown` dependency.
 
+### Fixed
+- Revert broken fix in [#2624] that caused erroneous 500 error responses. Temporarily re-introduces [#2357] bug. [#2779]
+
+[#2779]: https://github.com/actix/actix-web/issues/2779
+
 
 ## 3.0.4 - 2022-03-09
 ### Fixed

actix-http/src/h1/dispatcher.rs

@@ -15,14 +15,14 @@ use bitflags::bitflags;
 use bytes::{Buf, BytesMut};
 use futures_core::ready;
 use pin_project_lite::pin_project;
-use tracing::{debug, error, trace};
+use tracing::{error, trace};
 
 use crate::{
     body::{BodySize, BoxBody, MessageBody},
     config::ServiceConfig,
     error::{DispatchError, ParseError, PayloadError},
     service::HttpFlow,
-    ConnectionType, Error, Extensions, OnConnectData, Request, Response, StatusCode,
+    Error, Extensions, OnConnectData, Request, Response, StatusCode,
 };
 
 use super::{
@@ -691,74 +691,12 @@ where
         let can_not_read = !self.can_read(cx);
 
         // limit amount of non-processed requests
-        if pipeline_queue_full {
+        if pipeline_queue_full || can_not_read {
             return Ok(false);
         }
 
         let mut this = self.as_mut().project();
 
-        if can_not_read {
-            debug!("cannot read request payload");
-
-            if let Some(sender) = &this.payload {
-                // ...maybe handler does not want to read any more payload...
-                if let PayloadStatus::Dropped = sender.need_read(cx) {
-                    debug!("handler dropped payload early; attempt to clean connection");
-                    // ...in which case poll request payload a few times
-                    loop {
-                        match this.codec.decode(this.read_buf)? {
-                            Some(msg) => {
-                                match msg {
-                                    // payload decoded did not yield EOF yet
-                                    Message::Chunk(Some(_)) => {
-                                        // if non-clean connection, next loop iter will detect empty
-                                        // read buffer and close connection
-                                    }
-
-                                    // connection is in clean state for next request
-                                    Message::Chunk(None) => {
-                                        debug!("connection successfully cleaned");
-
-                                        // reset dispatcher state
-                                        let _ = this.payload.take();
-                                        this.state.set(State::None);
-
-                                        // break out of payload decode loop
-                                        break;
-                                    }
-
-                                    // Either whole payload is read and loop is broken or more data
-                                    // was expected in which case connection is closed. In both
-                                    // situations dispatcher cannot get here.
-                                    Message::Item(_) => {
-                                        unreachable!("dispatcher is in payload receive state")
-                                    }
-                                }
-                            }
-
-                            // not enough info to decide if connection is going to be clean or not
-                            None => {
-                                error!(
-                                    "handler did not read whole payload and dispatcher could not \
-                                    drain read buf; return 500 and close connection"
-                                );
-
-                                this.flags.insert(Flags::SHUTDOWN);
-                                let mut res = Response::internal_server_error().drop_body();
-                                res.head_mut().set_connection_type(ConnectionType::Close);
-                                this.messages.push_back(DispatcherMessage::Error(res));
-                                *this.error = Some(DispatchError::HandlerDroppedPayload);
-                                return Ok(true);
-                            }
-                        }
-                    }
-                }
-            } else {
-                // can_not_read and no request payload
-                return Ok(false);
-            }
-        }
-
         let mut updated = false;
 
         // decode from read buf as many full requests as possible
@@ -904,10 +842,7 @@ where
             if timer.as_mut().poll(cx).is_ready() {
                 // timeout on first request (slow request) return 408
 
-                trace!(
-                    "timed out on slow request; \
-                        replying with 408 and closing connection"
-                );
+                trace!("timed out on slow request; replying with 408 and closing connection");
 
                 let _ = self.as_mut().send_error_response(
                     Response::with_body(StatusCode::REQUEST_TIMEOUT, ()),

actix-http/src/h1/dispatcher_tests.rs

@@ -783,6 +783,9 @@ async fn upgrade_handling() {
     .await;
 }
 
+// fix in #2624 reverted temporarily
+// complete fix tracked in #2745
+#[ignore]
 #[actix_rt::test]
 async fn handler_drop_payload() {
     let _ = env_logger::try_init();