APMLP-350 fix crash in crashtracker when agent url is an ipv6 address

ext/libdatadog_api/crashtracker.c

@@ -54,6 +54,9 @@ static VALUE _native_start_or_update_on_fork(int argc, VALUE *argv, DDTRACE_UNUS
   // Tags and endpoint are heap-allocated, so after here we can't raise exceptions otherwise we'll leak this memory
   // Start of exception-free zone to prevent leaks {{
   ddog_Endpoint *endpoint = ddog_endpoint_from_url(char_slice_from_ruby_string(agent_base_url));
+  if (endpoint == NULL) {
+    rb_raise(rb_eRuntimeError, "Failed to create endpoint from agent_base_url: %"PRIsVALUE, agent_base_url);
+  }
   ddog_Vec_Tag tags = convert_tags(tags_as_array);
 
   ddog_crasht_Config config = {

lib/datadog/core/crashtracking/agent_base_url.rb

@@ -7,10 +7,17 @@ module Core
     module Crashtracking
       # This module provides a method to resolve the base URL of the agent
       module AgentBaseUrl
+        # IPv6 regular expression from
+        # https://stackoverflow.com/questions/53497/regular-expression-that-matches-valid-ipv6-addresses
+        # Does not match IPv4 addresses.
+        IPV6_REGEXP = /\A(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\z)/.freeze # rubocop:disable Layout/LineLength
+
         def self.resolve(agent_settings)
           case agent_settings.adapter
           when Datadog::Core::Configuration::Ext::Agent::HTTP::ADAPTER
-            "#{agent_settings.ssl ? 'https' : 'http'}://#{agent_settings.hostname}:#{agent_settings.port}/"
+            hostname = agent_settings.hostname
+            hostname = "[#{hostname}]" if hostname =~ IPV6_REGEXP
+            "#{agent_settings.ssl ? 'https' : 'http'}://#{hostname}:#{agent_settings.port}/"
           when Datadog::Core::Configuration::Ext::Agent::UnixSocket::ADAPTER
             "unix://#{agent_settings.uds_path}"
           end

sig/datadog/core/crashtracking/agent_base_url.rbs

@@ -2,6 +2,7 @@ module Datadog
   module Core
     module Crashtracking
       module AgentBaseUrl
+        IPV6_REGEXP: Regexp
         def self.resolve: (Datadog::Core::Configuration::AgentSettingsResolver::AgentSettings) -> ::String?
       end
     end

spec/datadog/core/crashtracking/agent_base_url_spec.rb

@@ -37,6 +37,38 @@
           expect(described_class.resolve(agent_settings)).to eq('http://example.com:8080/')
         end
       end
+
+      context 'when hostname is an IPv4 address' do
+        let(:agent_settings) do
+          instance_double(
+            Datadog::Core::Configuration::AgentSettingsResolver::AgentSettings,
+            adapter: Datadog::Core::Configuration::Ext::Agent::HTTP::ADAPTER,
+            ssl: false,
+            hostname: '1.2.3.4',
+            port: 8080
+          )
+        end
+
+        it 'returns the correct base URL' do
+          expect(described_class.resolve(agent_settings)).to eq('http://1.2.3.4:8080/')
+        end
+      end
+
+      context 'when hostname is an IPv6 address' do
+        let(:agent_settings) do
+          instance_double(
+            Datadog::Core::Configuration::AgentSettingsResolver::AgentSettings,
+            adapter: Datadog::Core::Configuration::Ext::Agent::HTTP::ADAPTER,
+            ssl: false,
+            hostname: '1234:1234::1',
+            port: 8080
+          )
+        end
+
+        it 'returns the correct base URL' do
+          expect(described_class.resolve(agent_settings)).to eq('http://[1234:1234::1]:8080/')
+        end
+      end
     end
 
     context 'when using UnixSocket adapter' do

spec/datadog/core/crashtracking/component_spec.rb

@@ -95,6 +95,27 @@
         expect(described_class.build(settings, agent_settings, logger: logger)).to be_nil
       end
     end
+
+    context 'when agent_base_url is invalid (e.g. hostname is an IPv6 address)' do
+      let(:agent_base_url) { 'http://1234:1234::1/' }
+
+      it 'returns an instance of Component that failed to start' do
+        expect(Datadog::Core::Crashtracking::TagBuilder).to receive(:call).with(settings)
+          .and_return(tags)
+        expect(Datadog::Core::Crashtracking::AgentBaseUrl).to receive(:resolve).with(agent_settings)
+          .and_return(agent_base_url)
+        expect(::Libdatadog).to receive(:ld_library_path)
+          .and_return(ld_library_path)
+        expect(::Libdatadog).to receive(:path_to_crashtracking_receiver_binary)
+          .and_return(path_to_crashtracking_receiver_binary)
+
+        # Diagnostics is only provided via the error report to logger,
+        # there is no indication in the object state that it failed to start.
+        expect(logger).to receive(:error).with(/Failed to start crash tracking/)
+
+        expect(described_class.build(settings, agent_settings, logger: logger)).to be_a(described_class)
+      end
+    end
   end
 
   context 'instance methods' do