sasl-xoauth2: force ipv4

xoauth2-force-ipv4.patch

diff --git a/src/config.cc b/src/config.cc
index 6bd780c..1f4d3bf 100644
--- a/src/config.cc
+++ b/src/config.cc
@@ -148,6 +148,9 @@ int Config::Init(const Json::Value &root) {
                 &log_full_trace_on_failure_);
     if (err != SASL_OK) return err;

+    err = Fetch(root, "force_ipv4", true, &force_ipv4_);
+    if (err != SASL_OK) return err;
+
     return 0;

   } catch (const std::exception &e) {
diff --git a/src/config.h b/src/config.h
index 2268b6b..9e8c2f2 100644
--- a/src/config.h
+++ b/src/config.h
@@ -33,6 +33,7 @@ class Config {
   std::string client_secret() const { return client_secret_; }
   bool log_to_syslog_on_failure() const { return log_to_syslog_on_failure_; }
   bool log_full_trace_on_failure() const { return log_full_trace_on_failure_; }
+  bool force_ipv4() const { return force_ipv4_; }

  private:
   Config() = default;
@@ -43,6 +44,7 @@ class Config {
   std::string client_secret_;
   bool log_to_syslog_on_failure_ = true;
   bool log_full_trace_on_failure_ = false;
+  bool force_ipv4_ = false;
 };

 }  // namespace sasl_xoauth2
diff --git a/src/http.cc b/src/http.cc
index 25bc36f..6bbbed0 100644
--- a/src/http.cc
+++ b/src/http.cc
@@ -20,6 +20,8 @@

 #include <vector>

+#include "config.h"
+
 namespace sasl_xoauth2 {

 namespace {
@@ -113,6 +115,11 @@ int HttpPost(const std::string &url, const std::string &data,
   // Errors.
   curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, transport_error);

+  // IPv4/IPv6
+  if (Config::Get()->force_ipv4()) {
+    curl_easy_setopt(curl, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);
+  }
+
   // Network.
   curl_easy_setopt(curl, CURLOPT_URL, url.c_str());