Add support for IPv6 addresses for the agent in the tracer configuration

CLAUDE.md

@@ -0,0 +1 @@
+Follow [AGENTS.md](AGENTS.md).

CONTRIBUTING.md

@@ -6,7 +6,7 @@ Before submitting new features or changes to current functionality, please [open
 issue](https://github.com/DataDog/dd-trace-cpp/issues/new) and discuss your ideas or propose the
 changes you wish to make. After a resolution is reached, a PR can be submitted for review.
 
-Sefer to the [documentation](docs) to learn about the architecture of the Datadog C++ Tracer Library
+Refer to the [documentation](docs) to learn about the architecture of the Datadog C++ Tracer Library
 and its development processes. In particular, review:
 
 - [Conventions](docs/conventions.md);

include/datadog/datadog_agent_config.h

@@ -11,20 +11,15 @@
 // Typical usage of `DatadogAgentConfig` is implicit as part of `TracerConfig`.
 // See `tracer_config.h`.
 
-#include <chrono>
 #include <memory>
-#include <string>
-#include <unordered_map>
-#include <vector>
 
 #include "clock.h"
 #include "config.h"
 #include "expected.h"
 #include "http_client.h"
 #include "remote_config/listener.h"
 
-namespace datadog {
-namespace tracing {
+namespace datadog::tracing {
 
 class EventScheduler;
 class Logger;
@@ -100,5 +95,4 @@ Expected<FinalizedDatadogAgentConfig> finalize_config(
     const DatadogAgentConfig& config, const std::shared_ptr<Logger>& logger,
     const Clock& clock);
 
-}  // namespace tracing
-}  // namespace datadog
+}  // namespace datadog::tracing

src/datadog/datadog_agent_config.cpp

@@ -1,17 +1,42 @@
 #include <datadog/datadog_agent_config.h>
 #include <datadog/environment.h>
 
-#include <algorithm>
-#include <chrono>
-#include <cstddef>
-
 #include "default_http_client.h"
 #include "parse_util.h"
-#include "platform_util.h"
 #include "threaded_event_scheduler.h"
 
-namespace datadog {
-namespace tracing {
+namespace datadog::tracing {
+
+namespace {
+
+Optional<std::string> build_agent_url_from_environment_variables() {
+  if (Optional<StringView> url_env = lookup(environment::DD_TRACE_AGENT_URL)) {
+    return std::string{*url_env};
+  }
+
+  Optional<StringView> env_host = lookup(environment::DD_AGENT_HOST);
+  Optional<StringView> env_port = lookup(environment::DD_TRACE_AGENT_PORT);
+  if (env_host || env_port) {
+    std::string agent_url = "http://";
+    const StringView host = env_host.value_or("localhost");
+    const bool is_ipv6_without_brackets =
+        (host.find(':') != StringView::npos) && (host.front() != '[');
+    if (is_ipv6_without_brackets) {
+      agent_url += '[';
+    }
+    append(agent_url, host);
+    if (is_ipv6_without_brackets) {
+      agent_url += ']';
+    }
+    agent_url += ':';
+    append(agent_url, env_port.value_or("8126"));
+    return agent_url;
+  }
+
+  return nullopt;
+}
+
+}  // namespace
 
 Expected<DatadogAgentConfig> load_datadog_agent_env_config() {
   DatadogAgentConfig env_config;
@@ -31,18 +56,9 @@ Expected<DatadogAgentConfig> load_datadog_agent_env_config() {
     env_config.remote_configuration_poll_interval_seconds = *res;
   }
 
-  auto env_host = lookup(environment::DD_AGENT_HOST);
-  auto env_port = lookup(environment::DD_TRACE_AGENT_PORT);
-
-  if (auto url_env = lookup(environment::DD_TRACE_AGENT_URL)) {
-    env_config.url = std::string{*url_env};
-  } else if (env_host || env_port) {
-    std::string configured_url = "http://";
-    append(configured_url, env_host.value_or("localhost"));
-    configured_url += ':';
-    append(configured_url, env_port.value_or("8126"));
-
-    env_config.url = std::move(configured_url);
+  if (Optional<std::string> agent_url =
+          build_agent_url_from_environment_variables()) {
+    env_config.url = *std::move(agent_url);
   }
 
   return env_config;
@@ -158,5 +174,4 @@ Expected<FinalizedDatadogAgentConfig> finalize_config(
   return result;
 }
 
-}  // namespace tracing
-}  // namespace datadog
+}  // namespace datadog::tracing

test/test_otel_process_ctx.cpp

@@ -13,6 +13,7 @@ using namespace datadog::tracing;
 
 namespace {
 
+#ifdef __linux__
 std::map<std::string, std::string> to_map(const char** key_value_array) {
   std::map<std::string, std::string> out;
   if (key_value_array == nullptr) return out;
@@ -23,7 +24,6 @@ std::map<std::string, std::string> to_map(const char** key_value_array) {
   return out;
 }
 
-#ifdef __linux__
 std::unique_ptr<Tracer> make_tracer(
     const RuntimeID& runtime_id, const std::string& service = "otel-ctx-svc",
     std::shared_ptr<Logger> logger = std::make_shared<MockLogger>()) {

test/test_tracer_config.cpp

@@ -1,11 +1,7 @@
-#include <datadog/id_generator.h>
-#include <datadog/optional.h>
-#include <datadog/propagation_style.h>
 #include <datadog/threaded_event_scheduler.h>
 #include <datadog/tracer.h>
-#include <datadog/tracer_config.h>
 
-#if defined(__linux__)
+#ifdef __linux__
 // Used to test writing to the `datadog-tracer-info` file; this is a Linux-only
 // feature.
 #include <dirent.h>
@@ -15,19 +11,8 @@
 #include <msgpack.hpp>
 #endif
 
-#include <chrono>
-#include <cmath>
-#include <cstddef>
-#include <cstdlib>
-#include <filesystem>
 #include <fstream>
 #include <iostream>
-#include <limits>
-#include <ostream>
-#include <stdexcept>
-#include <string>
-#include <system_error>
-#include <unordered_map>
 
 #include "common/environment.h"
 #include "mocks/collectors.h"
@@ -36,23 +21,21 @@
 #include "null_logger.h"
 #include "test.h"
 
-#if defined(__linux__)
+#ifdef __linux__
 // Used to test writing to the `datadog-tracer-info` file; this is a Linux-only
 // feature.
 #include "common/ctx_sharing_helpers.h"
 #include "platform_util.h"
 #include "string_util.h"
 #endif
 
-namespace datadog {
-namespace tracing {
+namespace datadog::tracing {
 
 std::ostream& operator<<(std::ostream& stream, PropagationStyle style) {
   return stream << to_string_view(style);
 }
 
-}  // namespace tracing
-}  // namespace datadog
+}  // namespace datadog::tracing
 
 using namespace datadog::test;
 using namespace datadog::tracing;
@@ -480,6 +463,7 @@ TRACER_CONFIG_TEST("TracerConfig::agent") {
           {"http://dd-agent:8126", nullopt, "http", "dd-agent:8126", ""},
           {"http://dd-agent:8126/", nullopt, "http", "dd-agent:8126", "/"},
           {"https://dd-agent:8126/", nullopt, "https", "dd-agent:8126", "/"},
+          {"http://[::1]:8126/", nullopt, "http", "[::1]:8126", "/"},
           {"unix:///var/run/datadog/trace-agent.sock", nullopt, "unix",
            "/var/run/datadog/trace-agent.sock"},
           {"unix://var/run/datadog/trace-agent.sock",
@@ -526,6 +510,9 @@ TRACER_CONFIG_TEST("TracerConfig::agent") {
            "dd-agent:8080"},
           {"override port with default host", nullopt, "8080", nullopt, "http",
            "localhost:8080"},
+          {"IPv6 host", "::1", nullopt, nullopt, "http", "[::1]:8126"},
+          {"IPv6 host with brackets", "[::1]", nullopt, nullopt, "http",
+           "[::1]:8126"},
           // A bogus port number will cause an error in the TCPClient, not
           // during configuration. For the purposes of configuration, any
           // value is accepted.