From 2f1f96b08b71ac61bb327a104093196a3744da63 Mon Sep 17 00:00:00 2001
From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Mon, 25 Mar 2019 17:10:13 +0100
Subject: [PATCH] dnsdist: Properly handle an I/O error while sending a TCP
 response

---
 pdns/dnsdist-tcp.cc | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/pdns/dnsdist-tcp.cc b/pdns/dnsdist-tcp.cc
index ed9d896b5a..6a580a05ca 100644
--- a/pdns/dnsdist-tcp.cc
+++ b/pdns/dnsdist-tcp.cc
@@ -568,15 +568,21 @@ static void sendResponse(std::shared_ptr<IncomingTCPConnectionState>& state)
 
   state->d_currentPos = 0;
 
-  auto iostate = state->d_handler.tryWrite(state->d_responseBuffer, state->d_currentPos, state->d_responseBuffer.size());
-  if (iostate == IOState::Done) {
+  try {
+    auto iostate = state->d_handler.tryWrite(state->d_responseBuffer, state->d_currentPos, state->d_responseBuffer.size());
+    if (iostate == IOState::Done) {
 
-    handleResponseSent(state);
-    return;
+      handleResponseSent(state);
+      return;
+    }
+    else {
+      //cerr<<__func__<<": adding client write FD "<<state->d_ci.fd<<endl;
+      handleNewIOState(state, IOState::NeedWrite, state->d_ci.fd, handleIOCallback, state->getClientWriteTTD());
+    }
   }
-  else {
-    //cerr<<__func__<<": adding client write FD "<<state->d_ci.fd<<endl;
-    handleNewIOState(state, IOState::NeedWrite, state->d_ci.fd, handleIOCallback, state->getClientWriteTTD());
+  catch (const std::exception& e) {
+    vinfolog("Got an exception while writing TCP response to %s: %s", state->d_ci.remote.toStringWithPort(), e.what());
+    handleNewIOState(state, IOState::Done, state->d_ci.fd, handleIOCallback);
   }
 }
 
-- 
2.47.2