From cf752ffcdc3e9996e74e9e03215f038a2a58aac5 Mon Sep 17 00:00:00 2001
From: Ryan Friedman <ryanfriedman5410+github@gmail.com>
Date: Mon, 13 May 2024 22:10:30 -0600
Subject: [PATCH] AP_Networking: add AutoIP support

* This allows link local addressing for zero-config setup

Signed-off-by: Ryan Friedman <ryanfriedman5410+github@gmail.com>
---
 libraries/AP_Networking/AP_Networking.cpp         |  2 +-
 libraries/AP_Networking/AP_Networking.h           | 15 +++++++++++++++
 libraries/AP_Networking/AP_Networking_ChibiOS.cpp | 10 ++++++++++
 libraries/AP_Networking/AP_Networking_Config.h    |  3 +++
 4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/libraries/AP_Networking/AP_Networking.cpp b/libraries/AP_Networking/AP_Networking.cpp
index 19016f3f7044e..762e31204fb48 100644
--- a/libraries/AP_Networking/AP_Networking.cpp
+++ b/libraries/AP_Networking/AP_Networking.cpp
@@ -89,7 +89,7 @@ const AP_Param::GroupInfo AP_Networking::var_info[] = {
     // @Param: OPTIONS
     // @DisplayName: Networking options
     // @Description: Networking options
-    // @Bitmask: 0:EnablePPP Ethernet gateway
+    // @Bitmask: 0:EnablePPP Ethernet gateway,1:Enable AUTOIP (Link Local IPv4 Addressing)
     // @RebootRequired: True
     // @User: Advanced
     AP_GROUPINFO("OPTIONS", 9,  AP_Networking,    param.options, 0),
diff --git a/libraries/AP_Networking/AP_Networking.h b/libraries/AP_Networking/AP_Networking.h
index 128e6c2c29398..a80c43d9c5de8 100644
--- a/libraries/AP_Networking/AP_Networking.h
+++ b/libraries/AP_Networking/AP_Networking.h
@@ -70,6 +70,20 @@ class AP_Networking
 #endif
     }
 
+
+    // returns true if AUTOIP is enabled
+    bool get_autoip_enabled() const
+    {
+#if AP_NETWORKING_AUTOIP_AVAILABLE
+        return option_is_set(OPTION::AUTOIP);
+#else
+        // AUTOIP is not available from our scope but could be enabled/controlled
+        // by the OS which is the case on Linux builds, including SITL
+        // TODO: ask the OS if link local IPv4 addressing is enabled
+        return false;
+#endif
+    }
+
     // Sets DHCP to be enabled or disabled
     void set_dhcp_enable(const bool enable)
     {
@@ -155,6 +169,7 @@ class AP_Networking
 
     enum class OPTION {
         PPP_ETHERNET_GATEWAY=(1U<<0),
+        AUTOIP=(1u<<1)
     };
     bool option_is_set(OPTION option) const {
         return (param.options.get() & int32_t(option)) != 0;
diff --git a/libraries/AP_Networking/AP_Networking_ChibiOS.cpp b/libraries/AP_Networking/AP_Networking_ChibiOS.cpp
index 889a8526be752..57ca043b41640 100644
--- a/libraries/AP_Networking/AP_Networking_ChibiOS.cpp
+++ b/libraries/AP_Networking/AP_Networking_ChibiOS.cpp
@@ -148,6 +148,11 @@ void AP_Networking_ChibiOS::link_up_cb(void *p)
     if (driver->frontend.get_dhcp_enabled()) {
         dhcp_start(driver->thisif);
     }
+# if LWIP_AUTOIP
+    if(driver->frontend.get_autoip_enabled()) {
+        autoip_start(driver->thisif);
+    }
+#endif // LWIP_AUTOIP
 #endif
 }
 
@@ -158,6 +163,11 @@ void AP_Networking_ChibiOS::link_down_cb(void *p)
     if (driver->frontend.get_dhcp_enabled()) {
         dhcp_stop(driver->thisif);
     }
+# if LWIP_AUTOIP
+    if(driver->frontend.get_autoip_enabled()) {
+        autoip_stop(driver->thisif);
+    }
+#endif // LWIP_AUTOIP
 #endif
 }
 
diff --git a/libraries/AP_Networking/AP_Networking_Config.h b/libraries/AP_Networking/AP_Networking_Config.h
index 5b66134957849..897edb7f22d2d 100644
--- a/libraries/AP_Networking/AP_Networking_Config.h
+++ b/libraries/AP_Networking/AP_Networking_Config.h
@@ -65,6 +65,9 @@
 #define AP_NETWORKING_DHCP_AVAILABLE (AP_NETWORKING_CONTROLS_HOST_IP_SETTINGS_ENABLED || AP_NETWORKING_BACKEND_CHIBIOS)
 #endif
 
+#ifndef AP_NETWORKING_AUTOIP_AVAILABLE
+#define AP_NETWORKING_AUTOIP_AVAILABLE AP_NETWORKING_DHCP_AVAILABLE
+#endif
 
 // ---------------------------
 // Below are default params