internal/catalogue/declaration.go

@@ -693,6 +693,14 @@ func here(r Resolution, requirement string) *Needed {
 //
 // Copied rather than edited in place: these maps come from a module's manifest, and mutating one
 // would change what the catalogue holds for every other machine running that module.
+//
+// A host-network container gets the names too. It was once skipped, on the belief that it "shares
+// the machine's hosts file already" — but it does not: `docker run --network host` still gives the
+// container its own /etc/hosts (localhost and its own id only), so every `<node>.internal` name the
+// mesh wrote for the machine is invisible inside it, and a client that dials one gets EAI_AGAIN. The
+// remedy is the same `--add-host` every other container gets — the runtime accepts it with
+// `--network host` (verified), and without it a host-network consumer cannot reach a provider by the
+// `.internal` address the mesh hands it as `${bound:...:at}`.
 func withMeshNames(resources []map[string]any, names map[string]string) []map[string]any {
 	out := make([]map[string]any, 0, len(resources))
 	for _, r := range resources {
@@ -700,13 +708,6 @@ func withMeshNames(resources []map[string]any, names map[string]string) []map[st
 			out = append(out, r)
 			continue
 		}
-		// A container on the machine's own network shares its hosts file already, and a runtime
-		// refuses to write one for it. Adding names there would be an argument the runtime
-		// rejects, which fails the whole container for something it did not need.
-		if network, on := r["network"].(string); on && network == "host" {
-			out = append(out, r)
-			continue
-		}
 
 		copied := map[string]any{}
 		for k, v := range r {

internal/catalogue/names_test.go

@@ -73,18 +73,22 @@ func TestAContainersOwnNamesAreKept(t *testing.T) {
 	}
 }
 
-// A container on the machine's own network already shares its hosts file, and a runtime refuses
-// to write one for it — so adding names there fails the whole container for something it did not
-// need.
-func TestAContainerOnTheMachinesNetworkIsLeftAlone(t *testing.T) {
+// A container on the machine's own network gets the names too — it does NOT share the machine's
+// hosts file. `docker run --network host` still gives the container its own /etc/hosts (localhost
+// and its own id only), so every `<node>.internal` name the mesh wrote is invisible inside it, and a
+// client that dials one gets EAI_AGAIN. It gets the same `--add-host` entries every other container
+// gets (the runtime accepts them with `--network host`), so a host-network consumer can reach a
+// provider by the `.internal` address the mesh hands it.
+func TestAContainerOnTheMachinesNetworkIsGivenTheNamesToo(t *testing.T) {
 	got := containersOf(t, Resolution{Node: "anchor", Modules: []Manifest{{
 		Module: "control",
 		Resources: []map[string]any{{"id": "c", "type": "container", "name": "c",
 			"image": "registry.example/c@sha256:" + strings.Repeat("a", 64), "network": "host"}},
 	}}}, Rendering{Names: map[string]string{"anchor.internal": "10.42.0.1"}})
 
-	if len(namesOf(got[0])) != 0 {
-		t.Fatalf("a host-networked container was given names a runtime will refuse: %v", got[0])
+	given := namesOf(got[0])
+	if len(given) != 1 || given[0] != "anchor.internal:10.42.0.1" {
+		t.Fatalf("a host-networked container was not given the mesh's names: %v", got[0])
 	}
 }