feat(driver-docker): use host networking for sandboxes

architecture/README.md

@@ -299,6 +299,7 @@ This opens an interactive SSH session into the sandbox, with all provider creden
 | [Docs Site Architecture](docs-site.md) | Documentation source layout, navigation structure, local validation and preview workflow, and publish pipeline. |
 | [Policy Language](security-policy.md) | The YAML/Rego policy system that governs sandbox behavior. |
 | [Inference Routing](inference-routing.md) | Transparent interception and sandbox-local routing of AI inference API calls to configured backends. |
+| [Docker Driver](docker-driver.md) | Docker compute driver implementation, host networking, loopback gateway connectivity. |
 | [System Architecture](system-architecture.md) | Top-level system architecture diagram with all deployable components and communication flows. |
 | [Gateway Settings Channel](gateway-settings.md) | Runtime settings channel: two-tier key-value configuration, global policy override, settings registry, CLI/TUI commands. |
 | [TUI](tui.md) | Terminal user interface for sandbox interaction. |

architecture/docker-driver.md

@@ -0,0 +1,129 @@
+# Docker Driver
+
+The Docker compute driver manages sandbox containers through the local Docker
+daemon using the `bollard` client. It targets local developer environments
+where running a full Kubernetes cluster is unnecessary but Docker is already
+available.
+
+The gateway remains a host process. Each sandbox container bind-mounts a Linux
+`openshell-sandbox` supervisor binary and uses Docker host networking so the
+supervisor can connect to a gateway that is listening on host loopback without
+requiring an additional bridge-reachable listener on Linux.
+
+## Source Map
+
+| Path | Purpose |
+|---|---|
+| `crates/openshell-driver-docker/src/lib.rs` | Docker compute driver implementation |
+| `crates/openshell-driver-docker/src/tests.rs` | Unit tests for container spec, env, TLS paths, GPU, resource limits, and cache helpers |
+| `crates/openshell-server/src/cli.rs` | Gateway CLI flags for Docker driver configuration |
+| `crates/openshell-server/src/lib.rs` | In-process Docker compute runtime wiring |
+
+## Runtime Model
+
+```mermaid
+flowchart LR
+    CLI["OpenShell CLI<br/>host"] -->|gRPC/HTTP<br/>127.0.0.1:8080| GW["Gateway<br/>host process"]
+    GW -->|Docker API| DA["Docker daemon"]
+    DA --> C["Sandbox container<br/>network_mode=host"]
+    C --> SV["openshell-sandbox<br/>supervisor"]
+    SV -->|ConnectSupervisor<br/>OPENSHELL_ENDPOINT| GW
+    SV --> NS["Nested sandbox netns<br/>workload + policy proxy"]
+```
+
+The Docker container itself uses `network_mode = "host"`. This is intentional
+for now: it makes a gateway bound to `127.0.0.1` reachable from the supervisor
+as `127.0.0.1`, matching the host process' endpoint without a bridge listener,
+NAT rule, or userland proxy.
+
+The container also gets a Docker-managed `/etc/hosts` entry for
+`host.openshell.internal` that resolves to `127.0.0.1`. This gives callers a
+stable OpenShell-owned hostname for host services without requiring changes to
+the host machine's hosts file.
+
+The supervisor still creates a nested network namespace for the actual workload
+and routes workload traffic through its policy proxy. Agent network requests are
+enforced by the supervisor in that nested namespace.
+
+## Container Spec
+
+`build_container_create_body()` constructs the Docker container:
+
+| Field | Value | Reason |
+|---|---|---|
+| `image` | Sandbox template image | User-selected runtime image |
+| `user` | `"0"` | Supervisor needs root inside the container for namespace and mount setup |
+| `entrypoint` | `/opt/openshell/bin/openshell-sandbox` | Bind-mounted supervisor binary |
+| `cmd` | Empty vector | Prevents image CMD args from being appended to the supervisor entrypoint |
+| `network_mode` | `"host"` | Lets supervisor connect to host loopback gateway endpoints |
+| `extra_hosts` | `host.openshell.internal:127.0.0.1` | Stable container-local alias for host loopback services |
+| `cap_add` | `SYS_ADMIN`, `NET_ADMIN`, `SYS_PTRACE`, `SYSLOG` | Required for supervisor isolation setup and process inspection |
+| `security_opt` | `apparmor=unconfined` | Docker's default AppArmor profile blocks mount operations required by network namespace setup |
+| `restart_policy` | `unless-stopped` | Resume managed sandboxes after Docker or gateway restarts |
+| `device_requests` | CDI all-GPU request when `spec.gpu` is true | Enables Docker CDI GPU sandboxes when daemon support is detected |
+
+## Gateway Callback
+
+The Docker driver injects `OPENSHELL_ENDPOINT` into each sandbox container from
+`Config::grpc_endpoint` without rewriting it. This is the key difference from a
+bridge-network design.
+
+Examples:
+
+```shell
+OPENSHELL_GRPC_ENDPOINT=http://127.0.0.1:8080
+```
+
+and:
+
+```shell
+OPENSHELL_GRPC_ENDPOINT=https://127.0.0.1:8080
+```
+
+are passed into the supervisor as-is. Because the container shares the host
+network namespace, `127.0.0.1` resolves to the host loopback interface and the
+gateway is reachable when it binds loopback.
+
+The endpoint can also use the stable alias:
+
+```shell
+OPENSHELL_GRPC_ENDPOINT=http://host.openshell.internal:8080
+```
+
+In host network mode this name resolves to `127.0.0.1` inside the container.
+
+For TLS endpoints, the gateway certificate must include the exact endpoint host
+as a subject alternative name. For `https://127.0.0.1:8080`, the certificate
+needs an IP SAN for `127.0.0.1`. For `https://localhost:8080`, it needs a DNS
+SAN for `localhost`. For `https://host.openshell.internal:8080`, it needs a DNS
+SAN for `host.openshell.internal`. Docker sandboxes also require client TLS
+material:
+
+| Env / flag | Purpose |
+|---|---|
+| `OPENSHELL_DOCKER_TLS_CA` / `--docker-tls-ca` | CA certificate mounted at `/etc/openshell/tls/client/ca.crt` |
+| `OPENSHELL_DOCKER_TLS_CERT` / `--docker-tls-cert` | Client certificate mounted at `/etc/openshell/tls/client/tls.crt` |
+| `OPENSHELL_DOCKER_TLS_KEY` / `--docker-tls-key` | Client private key mounted at `/etc/openshell/tls/client/tls.key` |
+
+When `OPENSHELL_GRPC_ENDPOINT` uses `http://`, these TLS mounts are not
+required and providing them is rejected. When it uses `https://`, all three are
+required.
+
+## Environment
+
+`build_environment()` merges template environment, spec environment, and
+driver-controlled keys. Driver-controlled keys win:
+
+| Variable | Value |
+|---|---|
+| `OPENSHELL_ENDPOINT` | Exact configured gateway endpoint |
+| `OPENSHELL_SANDBOX_ID` | Sandbox id |
+| `OPENSHELL_SANDBOX` | Sandbox name |
+| `OPENSHELL_SSH_SOCKET_PATH` | Unix socket path used by the supervisor's embedded SSH daemon |
+| `OPENSHELL_SANDBOX_COMMAND` | `sleep infinity` |
+| `OPENSHELL_TLS_CA` | Mounted CA path when HTTPS is enabled |
+| `OPENSHELL_TLS_CERT` | Mounted client cert path when HTTPS is enabled |
+| `OPENSHELL_TLS_KEY` | Mounted client key path when HTTPS is enabled |
+
+The Docker driver does not inject `OPENSHELL_SSH_HANDSHAKE_SECRET`; the
+supervisor-to-gateway path relies on mTLS for the Docker callback.

crates/openshell-core/src/config.rs

@@ -105,6 +105,15 @@ pub struct Config {
     #[serde(default)]
     pub metrics_bind_address: Option<SocketAddr>,
 
+    /// Additional bind addresses that serve the same multiplexed gRPC/HTTP
+    /// surface as `bind_address`.
+    ///
+    /// Compute drivers may register extra listeners during startup so that
+    /// sandbox workloads can call back into the gateway over an interface
+    /// that the operator-supplied `bind_address` does not expose.
+    #[serde(default)]
+    pub extra_bind_addresses: Vec<SocketAddr>,
+
     /// Log level (trace, debug, info, warn, error).
     #[serde(default = "default_log_level")]
     pub log_level: String,
@@ -292,6 +301,7 @@ impl Config {
             bind_address: default_bind_address(),
             health_bind_address: None,
             metrics_bind_address: None,
+            extra_bind_addresses: Vec::new(),
             log_level: default_log_level(),
             tls,
             oidc: None,
@@ -333,6 +343,19 @@ impl Config {
         self
     }
 
+    /// Append an extra listener address to the multiplex service.
+    ///
+    /// Duplicate entries (matching `bind_address` or any existing entry) are
+    /// silently dropped so callers can naively push driver-derived addresses
+    /// without checking for collisions.
+    #[must_use]
+    pub fn with_extra_bind_address(mut self, addr: SocketAddr) -> Self {
+        if addr != self.bind_address && !self.extra_bind_addresses.contains(&addr) {
+            self.extra_bind_addresses.push(addr);
+        }
+        self
+    }
+
     /// Create a new configuration with the given log level.
     #[must_use]
     pub fn with_log_level(mut self, level: impl Into<String>) -> Self {

crates/openshell-driver-docker/Cargo.toml

@@ -19,7 +19,6 @@ futures = { workspace = true }
 tokio-stream = { workspace = true }
 tracing = { workspace = true }
 bytes = { workspace = true }
-url = { workspace = true }
 bollard = { version = "0.20" }
 tar = "0.4"
 tempfile = "3"

crates/openshell-driver-docker/src/lib.rs

@@ -38,7 +38,6 @@ use tokio::sync::{broadcast, mpsc};
 use tokio_stream::wrappers::ReceiverStream;
 use tonic::{Request, Response, Status};
 use tracing::{info, warn};
-use url::{Host, Url};
 
 const WATCH_BUFFER: usize = 128;
 const WATCH_POLL_INTERVAL: Duration = Duration::from_secs(2);
@@ -55,8 +54,7 @@ const TLS_CA_MOUNT_PATH: &str = "/etc/openshell/tls/client/ca.crt";
 const TLS_CERT_MOUNT_PATH: &str = "/etc/openshell/tls/client/tls.crt";
 const TLS_KEY_MOUNT_PATH: &str = "/etc/openshell/tls/client/tls.key";
 const SANDBOX_COMMAND: &str = "sleep infinity";
-const HOST_OPENSHELL_INTERNAL: &str = "host.openshell.internal";
-const HOST_DOCKER_INTERNAL: &str = "host.docker.internal";
+const HOST_OPENSHELL_INTERNAL_HOSTS_ENTRY: &str = "host.openshell.internal:127.0.0.1";
 
 /// Default image holding the Linux `openshell-sandbox` binary. The gateway
 /// pulls this image and extracts the binary to a host-side cache when no
@@ -852,7 +850,7 @@ fn build_environment(sandbox: &DriverSandbox, config: &DockerDriverRuntimeConfig
 
     environment.insert(
         "OPENSHELL_ENDPOINT".to_string(),
-        container_visible_openshell_endpoint(&config.grpc_endpoint),
+        config.grpc_endpoint.clone(),
     );
     environment.insert("OPENSHELL_SANDBOX_ID".to_string(), sandbox.id.clone());
     environment.insert("OPENSHELL_SANDBOX".to_string(), sandbox.name.clone());
@@ -950,17 +948,27 @@ fn build_container_create_body(
                 "SYS_PTRACE".to_string(),
                 "SYSLOG".to_string(),
             ]),
-            // AppArmor's default Docker profile blocks mount(2) with MS_SHARED
-            // even when SYS_ADMIN is granted, which prevents ip-netns from
-            // creating network namespaces for proxy-mode isolation. The sandbox
-            // enforces its own isolation via seccomp, Landlock, and network
-            // namespaces, so the host AppArmor profile adds no meaningful
-            // defence here.
+            // The sandbox supervisor needs to bind-mount `/run/netns`,
+            // mark it shared, and create per-process network namespaces.
+            // Docker's default AppArmor profile (`docker-default`) denies
+            // these mount operations even with CAP_SYS_ADMIN, so we opt
+            // out of AppArmor confinement for sandbox containers. The
+            // sandbox enforces its own security boundary via Landlock,
+            // seccomp, OPA policy evaluation, and the dedicated network
+            // namespace it sets up for the agent — AppArmor at the
+            // container layer is redundant relative to those controls
+            // and conflicts with them in this case.
             security_opt: Some(vec!["apparmor=unconfined".to_string()]),
-            extra_hosts: Some(vec![
-                format!("{HOST_DOCKER_INTERNAL}:host-gateway"),
-                format!("{HOST_OPENSHELL_INTERNAL}:host-gateway"),
-            ]),
+            // Run in the host network namespace so a gateway bound to
+            // 127.0.0.1 is reachable from the supervisor as 127.0.0.1.
+            // The supervisor still creates a nested network namespace for
+            // the sandboxed workload and forces workload traffic through
+            // its policy proxy.
+            network_mode: Some("host".to_string()),
+            // Keep a stable host alias available inside the container without
+            // requiring users to edit the host's /etc/hosts. In host network
+            // mode this resolves back to the host loopback gateway.
+            extra_hosts: Some(vec![HOST_OPENSHELL_INTERNAL_HOSTS_ENTRY.to_string()]),
             ..Default::default()
         }),
         ..Default::default()
@@ -991,25 +999,6 @@ fn sandbox_log_level(sandbox: &DriverSandbox, default_level: &str) -> String {
         .to_string()
 }
 
-fn container_visible_openshell_endpoint(endpoint: &str) -> String {
-    let Ok(mut url) = Url::parse(endpoint) else {
-        return endpoint.to_string();
-    };
-
-    let should_rewrite = match url.host() {
-        Some(Host::Ipv4(ip)) => ip.is_loopback() || ip.is_unspecified(),
-        Some(Host::Ipv6(ip)) => ip.is_loopback() || ip.is_unspecified(),
-        Some(Host::Domain(host)) => host.eq_ignore_ascii_case("localhost"),
-        None => false,
-    };
-
-    if should_rewrite && url.set_host(Some(HOST_OPENSHELL_INTERNAL)).is_ok() {
-        return url.to_string();
-    }
-
-    endpoint.to_string()
-}
-
 fn docker_resource_limits(
     template: &DriverSandboxTemplate,
 ) -> Result<DockerResourceLimits, Status> {

crates/openshell-driver-docker/src/tests.rs

@@ -57,19 +57,16 @@ fn runtime_config() -> DockerDriverRuntimeConfig {
 }
 
 #[test]
-fn container_visible_endpoint_rewrites_loopback_hosts() {
-    assert_eq!(
-        container_visible_openshell_endpoint("https://localhost:8443"),
-        "https://host.openshell.internal:8443/"
-    );
-    assert_eq!(
-        container_visible_openshell_endpoint("http://127.0.0.1:8080"),
-        "http://host.openshell.internal:8080/"
-    );
-    assert_eq!(
-        container_visible_openshell_endpoint("https://gateway.internal:8443"),
-        "https://gateway.internal:8443"
-    );
+fn build_environment_preserves_loopback_endpoint_for_host_network() {
+    let mut config = runtime_config();
+    config.grpc_endpoint = "http://127.0.0.1:8080".to_string();
+
+    let env = build_environment(&test_sandbox(), &config);
+    assert!(env.contains(&"OPENSHELL_ENDPOINT=http://127.0.0.1:8080".to_string()));
+
+    config.grpc_endpoint = "https://localhost:8443".to_string();
+    let env = build_environment(&test_sandbox(), &config);
+    assert!(env.contains(&"OPENSHELL_ENDPOINT=https://localhost:8443".to_string()));
 }
 
 #[test]
@@ -231,6 +228,23 @@ fn require_sandbox_identifier_rejects_when_id_and_name_are_empty() {
     require_sandbox_identifier("sbx-1", "demo").expect("id and name is accepted");
 }
 
+#[test]
+fn build_container_create_body_uses_host_network() {
+    let create_body = build_container_create_body(&test_sandbox(), &runtime_config()).unwrap();
+    let host_config = create_body.host_config.expect("host_config is populated");
+
+    assert_eq!(
+        host_config.network_mode,
+        Some("host".to_string()),
+        "sandbox must use host networking so 127.0.0.1 reaches the host gateway"
+    );
+    assert_eq!(
+        host_config.extra_hosts,
+        Some(vec!["host.openshell.internal:127.0.0.1".to_string()]),
+        "sandbox should expose a stable host alias without host /etc/hosts edits"
+    );
+}
+
 #[test]
 fn build_container_create_body_uses_runtime_namespace_label() {
     // Regression test: the namespace label must come from the driver's