From 75b40281ac5aa04f5cfff35dfb6c8ce227660298 Mon Sep 17 00:00:00 2001
From: Vyacheslav Chigrin <vchigrin@yandex-team.ru>
Date: Wed, 7 May 2025 15:25:41 +0300
Subject: [PATCH] Fix sengind local replies after VM failure in decodeHeaders
 callback.

---
 src/context.cc | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/context.cc b/src/context.cc
index 5353a52a..2ff6e000 100644
--- a/src/context.cc
+++ b/src/context.cc
@@ -364,7 +364,11 @@ FilterMetadataStatus ContextBase::onRequestMetadata(uint32_t elements) {
 }
 
 FilterHeadersStatus ContextBase::onResponseHeaders(uint32_t headers, bool end_of_stream) {
-  CHECK_FAIL_HTTP(FilterHeadersStatus::Continue, FilterHeadersStatus::StopAllIterationAndWatermark);
+  // This callback may be called when WASM encountered fatal failure on earlier
+  // stages of request processing. In that case we are may be in process of
+  // sending local reply due to failStream() call.
+  // We must not block it to prevent request hang.
+  CHECK_FAIL_HTTP(FilterHeadersStatus::Continue, FilterHeadersStatus::Continue);
   if (!wasm_->on_response_headers_abi_01_ && !wasm_->on_response_headers_abi_02_) {
     return FilterHeadersStatus::Continue;
   }