Fix loopback interface for MacOS (#3799)

* Add loopback interface helper for macos

* Define LOOPBACK_INTERFACE constant instead of helper function

* [pre-commit.ci lite] apply automatic fixes

---------

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>

Author: nycrat

src/shared/constants.h

@@ -22,6 +22,13 @@ static const std::unordered_map<int, std::string> ROBOT_MULTICAST_CHANNELS = {
     {12, "ff02::c3d0:42d2:bb12"}, {13, "ff02::c3d0:42d2:bb13"},
     {14, "ff02::c3d0:42d2:bb14"}, {15, "ff02::c3d0:42d2:bb15"}};
 
+// the name of the loopback network interface, which differs across platforms
+#ifdef __APPLE__
+static const std::string LOOPBACK_INTERFACE = "lo0";
+#else
+static const std::string LOOPBACK_INTERFACE = "lo";
+#endif
+
 // PlotJuggler's default host and port
 static const std::string PLOTJUGGLER_GUI_DEFAULT_HOST        = "ff02::c3d0:42d2:aaaa";
 static const short unsigned int PLOTJUGGLER_GUI_DEFAULT_PORT = 9870;

src/software/logger/plotjuggler_sink.h

@@ -4,6 +4,7 @@
 #include <string>
 
 #include "proto/visualization.pb.h"
+#include "shared/constants.h"
 #include "software/logger/custom_logging_levels.h"
 #include "software/networking/udp/threaded_udp_sender.h"
 
@@ -20,7 +21,7 @@ class PlotJugglerSink
      *
      * @param interface The interface to send Plotjuggler UDP packets on
      */
-    PlotJugglerSink(const std::string& interface = "lo");
+    PlotJugglerSink(const std::string& interface = LOOPBACK_INTERFACE);
 
     ~PlotJugglerSink() = default;
 

src/software/networking/udp/BUILD

@@ -17,6 +17,7 @@ cc_test(
     ],
     deps = [
         ":network_utils",
+        "//shared:constants",
         "//shared/test_util:tbots_gtest_main",
     ],
 )
@@ -68,6 +69,7 @@ cc_test(
     ],
     deps = [
         ":threaded_proto_udp_listener",
+        "//shared:constants",
         "//shared/test_util:tbots_gtest_main",
         "@protobuf//:empty_cc_proto",
     ],
@@ -90,6 +92,7 @@ cc_test(
     ],
     deps = [
         ":threaded_proto_udp_sender",
+        "//shared:constants",
         "//shared/test_util:tbots_gtest_main",
         "@protobuf//:empty_cc_proto",
     ],

src/software/networking/udp/network_utils_test.cpp

@@ -2,9 +2,11 @@
 
 #include <gtest/gtest.h>
 
+#include "shared/constants.h"
+
 TEST(NetworkUtilsTest, getLocalIpValidInterface)
 {
-    std::string interface               = "lo";
+    std::string interface               = LOOPBACK_INTERFACE;
     std::optional<std::string> local_ip = getLocalIp(interface, true);
     EXPECT_TRUE(local_ip);
     EXPECT_EQ(local_ip.value(), "127.0.0.1");

src/software/networking/udp/threaded_proto_udp_listener_test.cpp

@@ -3,6 +3,7 @@
 #include <gtest/gtest.h>
 
 #include "google/protobuf/empty.pb.h"
+#include "shared/constants.h"
 #include "software/networking/tbots_network_exception.h"
 
 TEST(ThreadedProtoUdpListenerTest, error_finding_local_ip_address)
@@ -17,12 +18,12 @@ TEST(ThreadedProtoUdpListenerTest, error_creating_socket)
 {
     // This will always fail because it requires root privileges to open this port
     EXPECT_THROW(ThreadedProtoUdpListener<google::protobuf::Empty>(
-                     "224.5.23.1", 1023, "lo", [](const auto&) {}, true),
+                     "224.5.23.1", 1023, LOOPBACK_INTERFACE, [](const auto&) {}, true),
                  TbotsNetworkException);
 }
 
 TEST(ThreadedProtoUdpListenerTest, no_error_creating_socket)
 {
     ThreadedProtoUdpListener<google::protobuf::Empty>(
-        "224.5.23.0", 40000, "lo", [](const auto&) {}, true);
+        "224.5.23.0", 40000, LOOPBACK_INTERFACE, [](const auto&) {}, true);
 }

src/software/networking/udp/threaded_proto_udp_sender_test.cpp

@@ -3,6 +3,7 @@
 #include <gtest/gtest.h>
 
 #include "google/protobuf/empty.pb.h"
+#include "shared/constants.h"
 #include "software/networking/tbots_network_exception.h"
 
 TEST(ThreadedProtoUdpSenderTest, error_finding_local_ip_address)
@@ -14,5 +15,6 @@ TEST(ThreadedProtoUdpSenderTest, error_finding_local_ip_address)
 
 TEST(ThreadedProtoUdpSenderTest, no_error_creating_socket)
 {
-    ThreadedProtoUdpSender<google::protobuf::Empty>("224.5.23.1", 40000, "lo", true);
+    ThreadedProtoUdpSender<google::protobuf::Empty>("224.5.23.1", 40000,
+                                                    LOOPBACK_INTERFACE, true);
 }