From a5c7aa1b19eaf30b4b2f25ac6bd2002e23b25454 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Wed, 29 Jul 2015 09:55:47 +1000
Subject: [PATCH] HAL_Linux: allow startup before network bringup

this makes it possible to bootup ardupilot before the desired network
interface is available. This is very useful for when using 3G dongles
in aircraft
---
 libraries/AP_HAL_Linux/TCPServerDevice.cpp | 28 ++++++++++++++--------
 libraries/AP_HAL_Linux/TCPServerDevice.h   |  1 +
 libraries/AP_HAL_Linux/UARTDriver.cpp      | 19 +++++++++++----
 libraries/AP_HAL_Linux/UDPDevice.cpp       |  4 ++--
 4 files changed, 35 insertions(+), 17 deletions(-)

diff --git a/libraries/AP_HAL_Linux/TCPServerDevice.cpp b/libraries/AP_HAL_Linux/TCPServerDevice.cpp
index 5ae18a1fff..f7ead18037 100644
--- a/libraries/AP_HAL_Linux/TCPServerDevice.cpp
+++ b/libraries/AP_HAL_Linux/TCPServerDevice.cpp
@@ -9,6 +9,8 @@
 
 #include "TCPServerDevice.h"
 
+extern const AP_HAL::HAL& hal;
+
 TCPServerDevice::TCPServerDevice(const char *ip, uint16_t port, bool wait):
     _ip(ip),
     _port(port),
@@ -62,19 +64,25 @@ bool TCPServerDevice::open()
     listener.reuseaddress();
 
     if (!listener.bind(_ip, _port)) {
-        ::printf("bind failed on %s port %u - %s\n",
-                 _ip,
-                 _port,
-                 strerror(errno));
-        ::exit(1);
+        if (hal.scheduler->millis() - _last_bind_warning > 5000) {
+            ::printf("bind failed on %s port %u - %s\n",
+                     _ip,
+                     _port,
+                     strerror(errno));
+            _last_bind_warning = hal.scheduler->millis();
+        }
+        return false;
     }
 
     if (!listener.listen(1)) {
-        ::printf("listen failed on %s port %u - %s\n",
-                 _ip,
-                 _port,
-                 strerror(errno));
-        ::exit(1);
+        if (hal.scheduler->millis() - _last_bind_warning > 5000) {
+            ::printf("listen failed on %s port %u - %s\n",
+                     _ip,
+                     _port,
+                     strerror(errno));
+            _last_bind_warning = hal.scheduler->millis();
+        }
+        return false;
     }
 
     listener.set_blocking(false);
diff --git a/libraries/AP_HAL_Linux/TCPServerDevice.h b/libraries/AP_HAL_Linux/TCPServerDevice.h
index 75c280c842..26bf555403 100644
--- a/libraries/AP_HAL_Linux/TCPServerDevice.h
+++ b/libraries/AP_HAL_Linux/TCPServerDevice.h
@@ -23,6 +23,7 @@ private:
     uint16_t _port;
     bool _wait;
     bool _blocking = false;
+    uint32_t _last_bind_warning = 0;
 };
 
 #endif
diff --git a/libraries/AP_HAL_Linux/UARTDriver.cpp b/libraries/AP_HAL_Linux/UARTDriver.cpp
index 099afe32f9..ba05dbf41c 100644
--- a/libraries/AP_HAL_Linux/UARTDriver.cpp
+++ b/libraries/AP_HAL_Linux/UARTDriver.cpp
@@ -251,7 +251,7 @@ errout:
 bool LinuxUARTDriver::_serial_start_connection()
 {
     _device = new UARTDevice(device_path);
-    _device->open();
+    _connected = _device->open();
     _device->set_blocking(false);
     _flow_control = FLOW_CONTROL_DISABLE;
 
@@ -264,7 +264,7 @@ bool LinuxUARTDriver::_serial_start_connection()
 void LinuxUARTDriver::_udp_start_connection(void)
 {
     _device = new UDPDevice(_ip, _base_port);
-    _device->open();
+    _connected = _device->open();
     _device->set_blocking(false);
 
     /* try to write on MAVLink packet boundaries if possible */
@@ -276,9 +276,7 @@ void LinuxUARTDriver::_tcp_start_connection(void)
     bool wait = (_flag && strcmp(_flag, "wait") == 0);
     _device = new TCPServerDevice(_ip, _base_port, wait);
 
-    if (_device->open()) {
-        _connected = true;
-    }
+    _connected = _device->open();
 }
 
 /*
@@ -445,6 +443,17 @@ size_t LinuxUARTDriver::write(const uint8_t *buffer, size_t size)
 int LinuxUARTDriver::_write_fd(const uint8_t *buf, uint16_t n)
 {
     int ret = 0;
+
+    /*
+      allow for delayed connection. This allows ArduPilot to start
+      before a network interface is available.
+     */
+    if (!_connected) {
+        _connected = _device->open();
+    }
+    if (!_connected) {
+        return 0;
+    }
     
     ret = _device->write(buf, n);
 
diff --git a/libraries/AP_HAL_Linux/UDPDevice.cpp b/libraries/AP_HAL_Linux/UDPDevice.cpp
index 56e09a7bbe..0b5718ecbc 100644
--- a/libraries/AP_HAL_Linux/UDPDevice.cpp
+++ b/libraries/AP_HAL_Linux/UDPDevice.cpp
@@ -19,7 +19,7 @@ UDPDevice::~UDPDevice()
 
 ssize_t UDPDevice::write(const uint8_t *buf, uint16_t n)
 {
-    return socket.sendto(buf, n, _ip, _port);
+    return socket.send(buf, n);
 }
 
 ssize_t UDPDevice::read(uint8_t *buf, uint16_t n)
@@ -29,7 +29,7 @@ ssize_t UDPDevice::read(uint8_t *buf, uint16_t n)
 
 bool UDPDevice::open()
 {
-    return true;
+    return socket.connect(_ip, _port);
 }
 
 bool UDPDevice::close()