From 9890ea74b1f81330f181a62d3755deec333a6313 Mon Sep 17 00:00:00 2001
From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Tue, 9 Mar 2021 16:59:02 +0100
Subject: [PATCH] dnsdist: Better messages on TLS connection closed by the
 remote end

---
 pdns/tcpiohandler.cc | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/pdns/tcpiohandler.cc b/pdns/tcpiohandler.cc
index e4eef7bad0..7a2989c316 100644
--- a/pdns/tcpiohandler.cc
+++ b/pdns/tcpiohandler.cc
@@ -124,9 +124,12 @@ public:
     else if (error == SSL_ERROR_SYSCALL) {
       throw std::runtime_error("Syscall error while processing TLS connection: " + std::string(strerror(errno)));
     }
+    else if (error == SSL_ERROR_ZERO_RETURN) {
+      throw std::runtime_error("TLS connection closed by remote end");
+    }
     else {
       if (g_verbose) {
-        throw std::runtime_error("Error while processing TLS connection: " + libssl_get_error_string());
+        throw std::runtime_error("Error while processing TLS connection: (" + std::to_string(error) + ") " + libssl_get_error_string());
       } else {
         throw std::runtime_error("Error while processing TLS connection: " + std::to_string(error));
       }
@@ -875,7 +878,7 @@ public:
     do {
       ssize_t res = gnutls_record_recv(d_conn.get(), reinterpret_cast<char *>(&buffer.at(pos)), toRead - pos);
       if (res == 0) {
-        throw std::runtime_error("Error reading from TLS connection");
+        throw std::runtime_error("EOF while reading from TLS connection");
       }
       else if (res > 0) {
         pos += static_cast<size_t>(res);
@@ -906,7 +909,7 @@ public:
     do {
       ssize_t res = gnutls_record_recv(d_conn.get(), (reinterpret_cast<char *>(buffer) + got), bufferSize - got);
       if (res == 0) {
-        throw std::runtime_error("Error reading from TLS connection");
+        throw std::runtime_error("EOF while reading from TLS connection");
       }
       else if (res > 0) {
         got += static_cast<size_t>(res);
-- 
2.47.2