Disconnected secondary interface socket leads to SIGPIPE

[RobertWilbrandt]

The following sequence leads to the ros 2 driver crashing due to a SIGPIPE:

1. ros2 run ur_robot_driver start_ursim.sh
2. Shortly after that, while the robot is still booting: ros2 launch ur_robot_driver ur_control.launch.py ur_type:=ur5e robot_ip:=192.168.56.101 headless_mode:=true launch_rviz:=false
3. Wait until robot is started and driver is connected
4. ros2 service call /dashboard_client/power_on std_srvs/srv/Trigger "{}"
5. ros2 service call /dashboard_client/brake_release std_srvs/srv/Trigger "{}"
6. ros2 control load_controller io_and_status_controller --set-state start
7. ros2 service call /io_and_status_controller/resend_robot_program std_srvs/srv/Trigger "{}"

The backtrace:

Thread 20 "ur_ros2_control" received signal SIGPIPE, Broken pipe.
[Switching to Thread 0x7fffceffd640 (LWP 153506)]
__libc_send (flags=<optimized out>, len=4420, buf=0x7fff94001cc0, fd=28) at ../sysdeps/unix/sysv/linux/send.c:28
28      ../sysdeps/unix/sysv/linux/send.c: No such file or directory.
(gdb) bt
#0  __libc_send (flags=<optimized out>, len=4420, buf=0x7fff94001cc0, fd=28) at ../sysdeps/unix/sysv/linux/send.c:28
#1  __libc_send (fd=28, buf=0x7fff94001cc0, len=4420, flags=0) at ../sysdeps/unix/sysv/linux/send.c:23
#2  0x00007fffecdfa820 in urcl::comm::TCPSocket::write (this=this@entry=0x5555558d6400, 
    buf=buf@entry=0x7fff94001cc0 "def externalControl():\n\t\n\t\n\t# HEADER_BEGIN\n\t\n\tsteptime = get_steptime()\n\t\n\ttextmsg(\"ExternalControl: steptime=\", steptime)\n\tMULT_jointstate = 1000000\n\t\n\t#Constants\n\tSERVO_UNINITIALIZED = -1\n\tSERVO_IDL"..., 
    buf_len=buf_len@entry=4420, written=@0x7fffceffbcd8: 0)
    at /home/wilbrandt/robot_folders/checkout/ur_rolling/colcon_ws/src/Universal_Robots_Client_Library/src/comm/tcp_socket.cpp:187
#3  0x00007fffece1072b in urcl::comm::URStream<urcl::primary_interface::PrimaryPackage>::write (written=@0x7fffceffbcd8: 0, buf_len=4420, 
    buf=0x7fff94001cc0 "def externalControl():\n\t\n\t\n\t# HEADER_BEGIN\n\t\n\tsteptime = get_steptime()\n\t\n\ttextmsg(\"ExternalControl: steptime=\", steptime)\n\tMULT_jointstate = 1000000\n\t\n\t#Constants\n\tSERVO_UNINITIALIZED = -1\n\tSERVO_IDL"..., this=0x5555558d6400)
    at /home/wilbrandt/robot_folders/checkout/ur_rolling/colcon_ws/src/Universal_Robots_Client_Library/include/ur_client_library/comm/stream.h:133
#4  urcl::UrDriver::sendScript (this=0x5555558702f0, program=...)
    at /home/wilbrandt/robot_folders/checkout/ur_rolling/colcon_ws/src/Universal_Robots_Client_Library/src/ur/ur_driver.cpp:299
#5  0x00007fffecef4930 in ur_robot_driver::URPositionHardwareInterface::checkAsyncIO (this=0x5555558c4390)
    at /home/wilbrandt/robot_folders/checkout/ur_rolling/colcon_ws/src/Universal_Robots_ROS2_Driver/ur_robot_driver/src/hardware_interface.cpp:633
#6  0x00007fffecef50b8 in ur_robot_driver::URPositionHardwareInterface::asyncThread (this=0x5555558c4390)
    at /home/wilbrandt/robot_folders/checkout/ur_rolling/colcon_ws/src/Universal_Robots_ROS2_Driver/ur_robot_driver/src/hardware_interface.cpp:464
#7  0x00007ffff7b602c3 in ?? () from /lib/x86_64-linux-gnu/libstdc++.so.6
#8  0x00007ffff78d0b43 in start_thread (arg=<optimized out>) at ./nptl/pthread_create.c:442
#9  0x00007ffff7962a00 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81

The send function in TCPSocket is called on a secondary interface connection that is disconnected. This not only returns an EPIPE error, but additionally sends the SIGPIPE signal which is not handled and therefore kills the process.