From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Mon, 28 Apr 2025 10:47:39 +0000 (+0200)
Subject: dnsdist: Gracefully handle timeout/response for a closed HTTP stream
X-Git-Tag: dnsdist-2.0.0-alpha2~46^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=refs%2Fpull%2F15481%2Fhead;p=thirdparty%2Fpdns.git

dnsdist: Gracefully handle timeout/response for a closed HTTP stream

The remote end might very well have already closed the HTTP stream
corresponding to the timeout or response we are processing. While
this means we need to discard the event we were processing, it is
not an unexpected event and we should thus not raise an exception
since the caller cannot do anything about it.
---

diff --git a/pdns/dnsdistdist/dnsdist-nghttp2-in.cc b/pdns/dnsdistdist/dnsdist-nghttp2-in.cc
index 5ecc687f50..26f6d881bc 100644
--- a/pdns/dnsdistdist/dnsdist-nghttp2-in.cc
+++ b/pdns/dnsdistdist/dnsdist-nghttp2-in.cc
@@ -558,7 +558,12 @@ IOState IncomingHTTP2Connection::sendResponse(const struct timeval& now, TCPResp
   if (response.d_idstate.d_streamID == -1) {
     throw std::runtime_error("Invalid DoH stream ID while sending response");
   }
-  auto& context = d_currentStreams.at(response.d_idstate.d_streamID);
+  auto streamIt = d_currentStreams.find(response.d_idstate.d_streamID);
+  if (streamIt == d_currentStreams.end()) {
+    /* it might have been closed by the remote end in the meantime */
+    return hasPendingWrite() ? IOState::NeedWrite : IOState::Done;
+  }
+  auto& context = streamIt->second;
 
   uint32_t statusCode = 200U;
   std::string contentType;
@@ -593,7 +598,12 @@ void IncomingHTTP2Connection::notifyIOError(const struct timeval& now, TCPRespon
     throw std::runtime_error("Invalid DoH stream ID while handling I/O error notification");
   }
 
-  auto& context = d_currentStreams.at(response.d_idstate.d_streamID);
+  auto streamIt = d_currentStreams.find(response.d_idstate.d_streamID);
+  if (streamIt == d_currentStreams.end()) {
+    /* it might have been closed by the remote end in the meantime */
+    return;
+  }
+  auto& context = streamIt->second;
   context.d_buffer = std::move(response.d_buffer);
   sendResponse(response.d_idstate.d_streamID, context, 502, d_ci.cs->dohFrontend->d_customResponseHeaders);
 }