add support to specify the default vrf name

Summary: Adding the option to specify the default VRF Open/R should return to after starting a thrift instance on a non-default VRF.

Reviewed By: xiangxu1121

Differential Revision: D47784714

fbshipit-source-id: 0911f462daa1d416f94c1eb98dc77b41893425b1

openr/config/Config.h

@@ -300,6 +300,11 @@ class Config {
     return *getThriftServerConfig().vrf_names();
   }
 
+  const std::string
+  getDefaultVrfName() const {
+    return getThriftServerConfig().default_vrf_name().value_or("");
+  }
+
   const std::string
   getSSLCertPath() const {
     auto certPath = getThriftServerConfig().x509_cert_path();

openr/config/tests/ConfigTest.cpp

@@ -615,4 +615,30 @@ TEST(ConfigTest, NonDefaultVrfConfigGetter) {
   EXPECT_EQ(1, vrfs.size());
   EXPECT_EQ(mgmtVrf, vrfs.front());
 }
+
+TEST(ConfigTest, DefaultVrfConfigGetter) {
+  std::string defaultVrf{"defaultVrf"};
+  thrift::ThriftServerConfig thrift_server_config;
+  thrift_server_config.default_vrf_name() = defaultVrf;
+
+  auto tConfig = getBasicOpenrConfig();
+  tConfig.thrift_server() = thrift_server_config;
+
+  // no soft-drained flag
+  auto config = Config(tConfig);
+  const auto vrf = config.getDefaultVrfName();
+  EXPECT_EQ(defaultVrf, vrf);
+}
+
+TEST(ConfigTest, DefaultVrfConfigGetterUnsetValue) {
+  thrift::ThriftServerConfig thrift_server_config;
+
+  auto tConfig = getBasicOpenrConfig();
+  tConfig.thrift_server() = thrift_server_config;
+
+  // no soft-drained flag
+  auto config = Config(tConfig);
+  const auto vrf = config.getDefaultVrfName();
+  EXPECT_EQ("", vrf);
+}
 } // namespace openr

openr/if/OpenrConfig.thrift

@@ -342,6 +342,12 @@ struct ThriftServerConfig {
    *  `enable_non_default_vrf_thrift_server = true`
    */
   13: list<string> vrf_names = [];
+
+  /**
+   * User specified default vrf name to pivot the thrift server to.
+   * This VRF is only used when pivoting back from a non-default VRF
+   */
+  14: optional string default_vrf_name;
 }
 
 struct ThriftClientConfig {