Greengrass china endpoint (#276)

* Temporary fix for connection with greengrass china endpoint

* replace '-' with '.'

* allow gg server name to be passed as optional parameter

* move gg server to config

* update comments for discovery client config

* fix formating as suggested in clang-format lint

* fix format

* fix formatting again

Author: jmklix

discovery/include/aws/discovery/DiscoveryClient.h

@@ -45,7 +45,7 @@ namespace Aws
 
             /**
              * The value of the Aws region to connect to.
-             * Required.
+             * Optional. (mutually exclusive with ggServerName)
              */
             Crt::String Region;
 
@@ -59,6 +59,12 @@ namespace Aws
              * Optional.
              */
             Crt::Optional<Crt::Http::HttpClientConnectionProxyOptions> ProxyOptions;
+
+            /** The full string of the greengrass server endpoint that you want to connect to.
+             * Defaults to this over using Region to connect to server
+             * Optional. (mutually exclusive with ggServerName)
+             */
+            Crt::Optional<Crt::String> ggServerName;
         };
 
         class AWS_DISCOVERY_API DiscoveryClient final

discovery/source/DiscoveryClient.cpp

@@ -15,7 +15,8 @@ namespace Aws
     namespace Discovery
     {
         DiscoveryClientConfig::DiscoveryClientConfig() noexcept
-            : Bootstrap(nullptr), TlsContext(), SocketOptions(), Region(), MaxConnections(2), ProxyOptions()
+            : Bootstrap(nullptr), TlsContext(), SocketOptions(), Region(), MaxConnections(2), ProxyOptions(),
+              ggServerName()
         {
         }
 
@@ -29,7 +30,16 @@ namespace Aws
             m_allocator = allocator;
 
             Crt::StringStream ss;
-            ss << "greengrass-ats.iot." << clientConfig.Region << ".amazonaws.com";
+
+            // Fix for connection with china endpoint
+            if (clientConfig.ggServerName)
+            {
+                ss << *clientConfig.ggServerName;
+            }
+            else
+            {
+                ss << "greengrass-ats.iot." << clientConfig.Region << ".amazonaws.com";
+            }
 
             Crt::Io::TlsConnectionOptions tlsConnectionOptions = clientConfig.TlsContext->NewConnectionOptions();
             uint16_t port = 443;