refactor: enhance hostname resolution for Zenoh router configuration

Author: takasehideki

README.md

@@ -449,7 +449,7 @@ Arguments:
 - `--zenoh-router`: Router target used only when `--rmw zenoh`.
   - (default): first host listed in the JSON topology file (e.g., `host1`)
   - `<host-name>` / `<ipv4>`: explicit host name or IPv4 address (e.g., `host2` / `192.168.1.10`)
-  - `Manager`: the manager machine running `performance_test.py` (IP address auto-detected)
+  - `Manager`: the manager machine running `performance_test.py`
 
 Example:
 
@@ -487,6 +487,8 @@ For `docker` and `native` modes, `--zenoh-router` selects the target:
 - `<host-name>` / `<ipv4>`: explicit hostname or IPv4 address
 - `Manager`: the machine running `performance_test.py`
 
+The specified target (hostname or `Manager`) is automatically resolved to an IP address, which is then used as the `connect/endpoints` value in `ZENOH_CONFIG_OVERRIDE`.
+
 `performance_test.py` also sets `ZENOH_CONFIG_OVERRIDE` so that every bench node connects to the router as a client:
 
 - `mode="client"`

performance_test/performance_test.py

@@ -44,8 +44,25 @@ def _resolve_zenoh_router_target(target, hosts):
     )
 
 
+def _hostname_to_ip(hostname):
+    """Resolve a hostname to an IPv4 address.
+
+    Docker containers do not inherit the host's /etc/hosts even with
+    network_mode: host, so ZENOH_CONFIG_OVERRIDE must use a routable IP
+    address rather than a hostname that may only appear in /etc/hosts.
+    Falls back to the original value if resolution fails.
+    """
+    if _looks_like_ipv4(hostname):
+        return hostname
+    try:
+        return socket.gethostbyname(hostname)
+    except socket.gaierror:
+        return hostname
+
+
 def _build_zenoh_config_override(connect_host):
-    return f'mode="client";connect/endpoints=["tcp/{connect_host}:7447"]'
+    ip = _hostname_to_ip(connect_host)
+    return f'mode="client";connect/endpoints=["tcp/{ip}:7447"]'
 
 
 _ROUTER_PORT = 7447