From b9127ca07c37288f16b1fdc267d3f106721ed301 Mon Sep 17 00:00:00 2001
From: Julian Andres Klode <julian.klode@canonical.com>
Date: Thu, 22 Aug 2019 13:11:00 +0200
Subject: srvrec: Use re-entrant resolver functions

This should probably make those functions thread-safe, which
might be useful for some external users.
---
 CMakeLists.txt            | 2 +-
 apt-pkg/contrib/srvrec.cc | 9 +++++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0487429c6..160f7f913 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -186,7 +186,7 @@ if (NOT HAVE_SIGHANDLER_T)
 endif()
 
 # Handle resolving
-check_function_exists(res_init HAVE_LIBC_RESOLV)
+check_function_exists(res_ninit HAVE_LIBC_RESOLV)
 if(HAVE_LIBC_RESOLV)
     set(RESOLV_LIBRARIES)
 else()
diff --git a/apt-pkg/contrib/srvrec.cc b/apt-pkg/contrib/srvrec.cc
index a97d9c615..7d9bf116e 100644
--- a/apt-pkg/contrib/srvrec.cc
+++ b/apt-pkg/contrib/srvrec.cc
@@ -17,6 +17,7 @@
 #include <time.h>
 
 #include <algorithm>
+#include <memory>
 #include <tuple>
 
 #include <apt-pkg/configuration.h>
@@ -61,11 +62,15 @@ bool GetSrvRecords(std::string name, std::vector<SrvRec> &Result)
    unsigned char answer[PACKETSZ];
    int answer_len, compressed_name_len;
    int answer_count;
+   struct __res_state res;
 
-   if (res_init() != 0)
+   if (res_ninit(&res) != 0)
       return _error->Errno("res_init", "Failed to init resolver");
 
-   answer_len = res_query(name.c_str(), C_IN, T_SRV, answer, sizeof(answer));
+   // Close on return
+   std::shared_ptr<void> guard(&res, res_nclose);
+
+   answer_len = res_nquery(&res, name.c_str(), C_IN, T_SRV, answer, sizeof(answer));
    if (answer_len == -1)
       return false;
    if (answer_len < (int)sizeof(HEADER))
-- 
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