src/main/java/io/github/hectorvent/floci/core/common/docker/CurrentContainerNetworkResolver.java

@@ -5,6 +5,7 @@ import com.github.dockerjava.api.command.InspectContainerResponse;
 import com.github.dockerjava.api.model.ContainerNetwork;
 import com.github.dockerjava.api.model.ExposedPort;
 import com.github.dockerjava.api.model.Ports;
+import io.github.hectorvent.floci.config.EmulatorConfig;
 import jakarta.enterprise.context.ApplicationScoped;
 import jakarta.inject.Inject;
 import org.jboss.logging.Logger;
@@ -32,14 +33,21 @@ public class CurrentContainerNetworkResolver {
 
     private final DockerClient dockerClient;
     private final ContainerDetector containerDetector;
+    private final EmulatorConfig config;
     private final Map<Integer, Integer> cachedPublishedPorts = new ConcurrentHashMap<>();
 
     private volatile Optional<CurrentContainerNetwork> cachedNetwork;
 
     @Inject
-    public CurrentContainerNetworkResolver(DockerClient dockerClient, ContainerDetector containerDetector) {
+    public CurrentContainerNetworkResolver(DockerClient dockerClient, ContainerDetector containerDetector,
+                                           EmulatorConfig config) {
         this.dockerClient = dockerClient;
         this.containerDetector = containerDetector;
+        this.config = config;
+    }
+
+    public CurrentContainerNetworkResolver(DockerClient dockerClient, ContainerDetector containerDetector) {
+        this(dockerClient, containerDetector, null);
     }
 
     public Optional<String> resolveNetworkName() {
@@ -148,11 +156,21 @@ public class CurrentContainerNetworkResolver {
         }
     }
 
+    /**
+     * Spawned containers join services.docker-network when it is set, so Floci's address on that
+     * network is the one they can reach. Floci can be attached to other networks too (for example
+     * the emulated VPC networks), whose addresses spawned containers cannot route to.
+     */
     private Optional<CurrentContainerNetwork> selectNetwork(Map<String, ContainerNetwork> networks) {
-        return networks.entrySet().stream()
-                .filter(entry -> isUsable(entry.getValue()))
-                .filter(entry -> isUserDefinedNetwork(entry.getKey()))
-                .findFirst()
+        Optional<String> configured = config == null ? Optional.empty()
+                : config.services().dockerNetwork().filter(name -> !name.isBlank());
+        return configured
+                .filter(name -> isUsable(networks.get(name)))
+                .map(name -> Map.entry(name, networks.get(name)))
+                .or(() -> networks.entrySet().stream()
+                        .filter(entry -> isUsable(entry.getValue()))
+                        .filter(entry -> isUserDefinedNetwork(entry.getKey()))
+                        .findFirst())
                 .or(() -> networks.entrySet().stream()
                         .filter(entry -> isUsable(entry.getValue()))
                         .findFirst())

src/test/java/io/github/hectorvent/floci/core/common/docker/CurrentContainerNetworkResolverTest.java

@@ -6,6 +6,7 @@ import com.github.dockerjava.api.command.InspectContainerResponse;
 import com.github.dockerjava.api.model.ContainerNetwork;
 import com.github.dockerjava.api.model.ExposedPort;
 import com.github.dockerjava.api.model.Ports;
+import io.github.hectorvent.floci.config.EmulatorConfig;
 import org.junit.jupiter.api.Test;
 
 import java.util.LinkedHashMap;
@@ -43,6 +44,55 @@ class CurrentContainerNetworkResolverTest {
         assertEquals(Optional.of("172.24.0.2"), resolver.resolveContainerIp());
     }
 
+    @Test
+    void resolveNetworkName_prefersConfiguredDockerNetworkOverOtherAttachedNetworks() {
+        DockerClient dockerClient = mock(DockerClient.class);
+        ContainerDetector containerDetector = mock(ContainerDetector.class);
+        when(containerDetector.isRunningInContainer()).thenReturn(true);
+
+        InspectContainerCmd inspectCmd = mock(InspectContainerCmd.class);
+        InspectContainerResponse inspect = mock(InspectContainerResponse.class, RETURNS_DEEP_STUBS);
+        Map<String, ContainerNetwork> networks = networks(
+                "floci-vpc-4566-us-east-1-vpc-default-us-east-1", "172.31.0.3",
+                "floci_default", "172.22.0.4");
+        when(dockerClient.inspectContainerCmd("floci-container")).thenReturn(inspectCmd);
+        when(inspectCmd.exec()).thenReturn(inspect);
+        when(inspect.getNetworkSettings().getNetworks()).thenReturn(networks);
+
+        EmulatorConfig config = mock(EmulatorConfig.class, RETURNS_DEEP_STUBS);
+        when(config.services().dockerNetwork()).thenReturn(Optional.of("floci_default"));
+
+        CurrentContainerNetworkResolver resolver =
+                new TestResolver(dockerClient, containerDetector, config, "floci-container");
+
+        assertEquals(Optional.of("floci_default"), resolver.resolveNetworkName());
+        assertEquals(Optional.of("172.22.0.4"), resolver.resolveContainerIp());
+    }
+
+    @Test
+    void resolveNetworkName_fallsBackWhenConfiguredNetworkIsNotAttached() {
+        DockerClient dockerClient = mock(DockerClient.class);
+        ContainerDetector containerDetector = mock(ContainerDetector.class);
+        when(containerDetector.isRunningInContainer()).thenReturn(true);
+
+        InspectContainerCmd inspectCmd = mock(InspectContainerCmd.class);
+        InspectContainerResponse inspect = mock(InspectContainerResponse.class, RETURNS_DEEP_STUBS);
+        Map<String, ContainerNetwork> networks = networks(
+                "bridge", "172.17.0.2",
+                "avoxx-network", "172.24.0.2");
+        when(dockerClient.inspectContainerCmd("floci-container")).thenReturn(inspectCmd);
+        when(inspectCmd.exec()).thenReturn(inspect);
+        when(inspect.getNetworkSettings().getNetworks()).thenReturn(networks);
+
+        EmulatorConfig config = mock(EmulatorConfig.class, RETURNS_DEEP_STUBS);
+        when(config.services().dockerNetwork()).thenReturn(Optional.of("floci_default"));
+
+        CurrentContainerNetworkResolver resolver =
+                new TestResolver(dockerClient, containerDetector, config, "floci-container");
+
+        assertEquals(Optional.of("avoxx-network"), resolver.resolveNetworkName());
+    }
+
     @Test
     void resolveNetworkName_returnsEmptyOutsideContainer() {
         DockerClient dockerClient = mock(DockerClient.class);
@@ -126,7 +176,12 @@ class CurrentContainerNetworkResolverTest {
         private final String containerId;
 
         TestResolver(DockerClient dockerClient, ContainerDetector containerDetector, String containerId) {
-            super(dockerClient, containerDetector);
+            this(dockerClient, containerDetector, null, containerId);
+        }
+
+        TestResolver(DockerClient dockerClient, ContainerDetector containerDetector, EmulatorConfig config,
+                     String containerId) {
+            super(dockerClient, containerDetector, config);
             this.containerId = containerId;
         }