From 5f5a75158ef2444b5d3a6fe448966835dae07c4d Mon Sep 17 00:00:00 2001
From: Roni Kreinin <59886299+roni-kreinin@users.noreply.github.com>
Date: Fri, 31 Jan 2025 11:31:08 -0500
Subject: [PATCH] Wait for interface to be up before launching node (#7)

* Wait for interface to be UP before starting node
---
 launch/receiver.launch.py | 22 +++++++++++++++++++---
 launch/sender.launch.py   | 22 +++++++++++++++++++---
 package.xml               |  2 ++
 3 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/launch/receiver.launch.py b/launch/receiver.launch.py
index 805c581..5c5c57a 100644
--- a/launch/receiver.launch.py
+++ b/launch/receiver.launch.py
@@ -29,11 +29,12 @@
 from launch.actions import (
     DeclareLaunchArgument,
     EmitEvent,
+    ExecuteProcess,
     RegisterEventHandler)
 from launch.conditions import IfCondition
-from launch.event_handlers import OnProcessStart
+from launch.event_handlers import OnProcessExit, OnProcessStart
 from launch.events import matches_action
-from launch.substitutions import LaunchConfiguration
+from launch.substitutions import FindExecutable, LaunchConfiguration
 from launch_ros.actions import LifecycleNode
 from launch_ros.event_handlers import OnStateTransition
 from launch_ros.events.lifecycle import ChangeState
@@ -102,6 +103,20 @@ def generate_launch_description():
         remappings=[('from_can_bus', from_can_bus_topic)],
         output='screen')
 
+    # Wait for interface to be up
+    wait_for_can_interface_proc = ExecuteProcess(
+        cmd=[['until ', FindExecutable(name='ip'), ' link show ', interface, ' | ',
+              FindExecutable(name='grep'), ' \"state UP\"', '; do sleep 1; done']],
+        shell=True
+    )
+
+    launch_node = RegisterEventHandler(
+        event_handler=OnProcessExit(
+            target_action=wait_for_can_interface_proc,
+            on_exit=node
+        )
+    )
+
     configure_event = RegisterEventHandler(
         event_handler=OnProcessStart(
             target_action=node,
@@ -144,7 +159,8 @@ def generate_launch_description():
     ld.add_action(arg_auto_configure)
     ld.add_action(arg_auto_activate)
     ld.add_action(arg_from_can_bus_topic)
-    ld.add_action(node)
+    ld.add_action(wait_for_can_interface_proc)
+    ld.add_action(launch_node)
     ld.add_action(configure_event)
     ld.add_action(activate_event)
     return ld
diff --git a/launch/sender.launch.py b/launch/sender.launch.py
index d2b0181..7fa795a 100644
--- a/launch/sender.launch.py
+++ b/launch/sender.launch.py
@@ -29,11 +29,12 @@
 from launch.actions import (
     DeclareLaunchArgument,
     EmitEvent,
+    ExecuteProcess,
     RegisterEventHandler)
 from launch.conditions import IfCondition
-from launch.event_handlers import OnProcessStart
+from launch.event_handlers import OnProcessExit, OnProcessStart
 from launch.events import matches_action
-from launch.substitutions import LaunchConfiguration
+from launch.substitutions import FindExecutable, LaunchConfiguration
 from launch_ros.actions import LifecycleNode
 from launch_ros.event_handlers import OnStateTransition
 from launch_ros.events.lifecycle import ChangeState
@@ -90,6 +91,20 @@ def generate_launch_description():
         remappings=[('to_can_bus', to_can_bus_topic)],
         output='screen')
 
+    # Wait for interface to be up
+    wait_for_can_interface_proc = ExecuteProcess(
+        cmd=[['until ', FindExecutable(name='ip'), ' link show ', interface, ' | ',
+              FindExecutable(name='grep'), ' \"state UP\"', '; do sleep 1; done']],
+        shell=True
+    )
+
+    launch_node = RegisterEventHandler(
+        event_handler=OnProcessExit(
+            target_action=wait_for_can_interface_proc,
+            on_exit=node
+        )
+    )
+
     configure_event = RegisterEventHandler(
         event_handler=OnProcessStart(
             target_action=node,
@@ -130,7 +145,8 @@ def generate_launch_description():
     ld.add_action(arg_auto_configure)
     ld.add_action(arg_auto_activate)
     ld.add_action(arg_to_can_bus_topic)
-    ld.add_action(node)
+    ld.add_action(wait_for_can_interface_proc)
+    ld.add_action(launch_node)
     ld.add_action(configure_event)
     ld.add_action(activate_event)
     return ld
diff --git a/package.xml b/package.xml
index 18ff13d..e87f9a0 100644
--- a/package.xml
+++ b/package.xml
@@ -18,6 +18,8 @@
   <depend>rclcpp</depend>
   <depend>can_msgs</depend>
 
+  <exec_depend>iproute2</exec_depend>
+
   <test_depend>ament_lint_auto</test_depend>
   <test_depend>ament_lint_common</test_depend>