NFD » ndn-cxx

Why did the priority for this issue get lowered? It remains important to the application team for trying to make field deployments of NDN more resilient to connectivity changes. Needs to target v0.5 of dependent Feature #3521.

what would be the criteria to test this and the other patch? Just run integration test and observe that information is being properly updated?
NetworkMonitor itself is intrinsically not unit-testable. On the other hand, NetworkAddress and NetworkInterface could be unit tested.

This can be structured as a "manual test". A document should be placed at tests/integrated/network-monitor.txt, which looks like:

1. start build/tests/integrated/network-monitor program
2. execute ip link add link eth0 name eth0-1, NM should output "[eth0-1] onInterfaceAdded"
3. execute ip addr 192.168.7.2/24 dev eth0-1, NM should output "[eth0-1] onAddressAdded 192.168.7.2/24"
4. unplug the Ethernet cord on eth1 interface, NM should output "[eth1] onStateChanged no-carrier"

The steps may require the use of USB Ethernet adapters, WiFi interfaces, etc. Any step may be skipped if equipment is unavailable.
This allows anyone to test the program manually, given they have the right equipment. Compared to not providing this document, this removes the uncertainty on what would be the correct behavior given a certain action.

On Ubuntu 16.04 32-bit, http://gerrit.named-data.net/2708 patchset29 crashes if NetworkMonitor is destructed before onEnumerationCompleted is invoked.

// g++ -std=c++11 -o x x.cpp $(pkg-config --cflags --libs libndn-cxx)

#include <boost/asio.hpp>
#include <ndn-cxx/util/network-interface.hpp>

int
main()
{
  boost::asio::io_service io;
  std::unique_ptr<ndn::util::NetworkMonitor> nm(new ndn::util::NetworkMonitor(io));
  nm->onInterfaceAdded.connect([&] (std::shared_ptr<ndn::util::NetworkInterface>) {
    io.post([&] {
      nm.reset();
    });
  });
  io.run();
}

terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<ndn::util::NetworkMonitor::Error> >'
  what():  Netlink socket read failed (Bad file descriptor)

Thread 1 "x" received signal SIGABRT, Aborted.
0xb7fdac31 in __kernel_vsyscall ()
(gdb) bt full
#0  0xb7fdac31 in __kernel_vsyscall ()
No symbol table info available.
#1  0xb7b8cea9 in __GI_raise (sig=6) at ../sysdeps/unix/sysv/linux/raise.c:54
        resultvar = <optimized out>
        resultvar = <optimized out>
        pid = 27239
        selftid = 27239
#2  0xb7b8e407 in __GI_abort () at abort.c:89
        save_stage = 2
        act = {__sigaction_handler = {sa_handler = 0xb7d3dfec, 
            sa_sigaction = 0xb7d3dfec}, sa_mask = {__val = {5, 3086997664, 
              3086895472, 3084112684, 5, 3086997664, 3085598748, 3086915490, 
              3086998104, 3081672512, 1, 5, 0, 3083939840, 3087003648, 
              3084198700, 3083943104, 3082577437, 3087003648, 3084198700, 48, 
              3084536027, 3086915307, 3082187192, 3083943416, 135031812, 
              3086915307, 3085598720, 3083943416, 135031812, 3221222088, 
              3086941968}}, sa_flags = 135031888, 
          sa_restorer = 0xb7b8e2b0 <__GI_abort>}
        sigs = {__val = {32, 0 <repeats 31 times>}}
#3  0xb7da7d35 in __gnu_cxx::__verbose_terminate_handler() ()
   from /usr/lib/i386-linux-gnu/libstdc++.so.6
No symbol table info available.
#4  0xb7da5833 in ?? () from /usr/lib/i386-linux-gnu/libstdc++.so.6
---Type <return> to continue, or q <return> to quit---
No symbol table info available.
#5  0xb7da58ad in std::terminate() ()
   from /usr/lib/i386-linux-gnu/libstdc++.so.6
No symbol table info available.
#6  0xb7da5b70 in __cxa_throw () from /usr/lib/i386-linux-gnu/libstdc++.so.6
No symbol table info available.
#7  0x08070331 in boost::throw_exception<boost::exception_detail::error_info_injector<ndn::util::NetworkMonitor::Error> > (e=...)
    at /usr/include/boost/throw_exception.hpp:69
No locals.
#8  0x08070412 in boost::exception_detail::throw_exception_<ndn::util::NetworkMonitor::Error> (x=..., 
    current_function=0x809e880 <ndn::util::NetworkMonitor::Impl::onReceiveRtnl(boost::system::error_code const&, unsigned int)::__PRETTY_FUNCTION__> "void ndn::util::NetworkMonitor::Impl::onReceiveRtnl(const boost::system::error_code&, size_t)", file=0x809e310 "../src/util/detail/network-monitor-impl-rtnl.cpp", 
    line=173) at /usr/include/boost/throw_exception.hpp:86
No locals.
#9  0x0806cb6f in ndn::util::NetworkMonitor::Impl::onReceiveRtnl (
    this=0x80c1e78, error=..., nBytesReceived=0)
    at ../src/util/detail/network-monitor-impl-rtnl.cpp:173
        __func__ = "onReceiveRtnl"
        __PRETTY_FUNCTION__ = "void ndn::util::NetworkMonitor::Impl::onReceiveRt---Type <return> to continue, or q <return> to quit---
nl(const boost::system::error_code&, size_t)"
        nlh = <optimized out>
#10 0x08072577 in std::_Mem_fn_base<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int), true>::operator()<boost::system::error_code const&, unsigned int const&, void> (__object=<optimized out>, 
    this=0xbffff4e4) at /usr/include/c++/5/functional:600
No locals.
#11 std::_Bind<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)> (ndn::util::NetworkMonitor::Impl*, std::_Placeholder<1>, std::_Placeholder<2>)>::__call<void, boost::system::error_code const&, unsigned int const&, 0u, 1u, 2u>(std::tuple<boost::system::error_code const&, unsigned int const&>&&, std::_Index_tuple<0u, 1u, 2u>) (
    __args=<unknown type in /home/ubuntu/x, CU 0x2c49d, DIE 0x89fd0>, 
    this=0xbffff4e4) at /usr/include/c++/5/functional:1074
No locals.
#12 std::_Bind<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)> (ndn::util::NetworkMonitor::Impl*, std::_Placeholder<1>, std::_Placeholder<2>)>::operator()<boost::system::error_code const&, unsigned int const&, void>(boost::system::error_code const&, unsigned int const&) (this=0xbffff4e4) at /usr/include/c++/5/functional:1133
No locals.
#13 boost::asio::detail::binder2<std::_Bind<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)> (ndn::util::---Type <return> to continue, or q <return> to quit---
NetworkMonitor::Impl*, std::_Placeholder<1>, std::_Placeholder<2>)>, boost::system::error_code, unsigned int>::operator()() (this=0xbffff4e4)
    at /usr/include/boost/asio/detail/bind_handler.hpp:127
No locals.
#14 boost::asio::asio_handler_invoke<boost::asio::detail::binder2<std::_Bind<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)> (ndn::util::NetworkMonitor::Impl*, std::_Placeholder<1>, std::_Placeholder<2>)>, boost::system::error_code, unsigned int> >(boost::asio::detail::binder2<std::_Bind<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)> (ndn::util::NetworkMonitor::Impl*, std::_Placeholder<1>, std::_Placeholder<2>)>, boost::system::error_code, unsigned int>&, ...) (function=...)
    at /usr/include/boost/asio/handler_invoke_hook.hpp:69
No locals.
#15 boost_asio_handler_invoke_helpers::invoke<boost::asio::detail::binder2<std::_Bind<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)> (ndn::util::NetworkMonitor::Impl*, std::_Placeholder<1>, std::_Placeholder<2>)>, boost::system::error_code, unsigned int>, std::_Bind<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)> (ndn::util::NetworkMonitor::Impl*, std::_Placeholder<1>, std::_Placeholder<2>)> >(boost::asio::detail::binder2<std::_Bind<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)> (ndn::util::NetworkMonitor::Impl*, std::_Placeholder<1>, std::_Pla---Type <return> to continue, or q <return> to quit---
ceholder<2>)>, boost::system::error_code, unsigned int>&, std::_Bind<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)> (ndn::util::NetworkMonitor::Impl*, std::_Placeholder<1>, std::_Placeholder<2>)>&) (context=..., function=...)
    at /usr/include/boost/asio/detail/handler_invoke_helpers.hpp:37
No locals.
#16 boost::asio::detail::descriptor_read_op<boost::asio::mutable_buffers_1, std::_Bind<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)> (ndn::util::NetworkMonitor::Impl*, std::_Placeholder<1>, std::_Placeholder<2>)> >::do_complete(boost::asio::detail::task_io_service*, boost::asio::detail::task_io_service_operation*, boost::system::error_code const&, unsigned int) (owner=0x80c1d70, base=0x80c6af8)
    at /usr/include/boost/asio/detail/descriptor_read_op.hpp:104
        o = <optimized out>
        p = {h = 0xbffff4e4, v = 0x0, p = 0x0}
        handler = {
          handler_ = {<std::_Weak_result_type<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)> >> = {<std::_Weak_result_type_impl<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)> >> = {<std::_Maybe_get_result_type<std::_Mem_fn<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int)>, void>> = {<No data fields>}, <No data fields>}, <No data fields>}, 
---Type <return> to continue, or q <return> to quit---
            _M_f = {<std::_Mem_fn_base<void (ndn::util::NetworkMonitor::Impl::*)(boost::system::error_code const&, unsigned int), true>> = {<std::_Maybe_unary_or_binary_function<void, ndn::util::NetworkMonitor::Impl*, boost::system::error_code const&, unsigned int>> = {<No data fields>}, 
                _M_pmf = (void (ndn::util::NetworkMonitor::Impl::*)(ndn::util::NetworkMonitor::Impl * const, const boost::system::error_code &, 
    unsigned int)) 0x806c36e <ndn::util::NetworkMonitor::Impl::onReceiveRtnl(boost::system::error_code const&, unsigned int)>}, <No data fields>}, 
            _M_bound_args = std::tuple containing = {[1] = 0x80c1e78, 
              [2] = {<std::_Placeholder<1>> = {<No data fields>}, <No data fields>}, [3] = {<std::_Placeholder<2>> = {<No data fields>}, <No data fields>}}}, 
          arg1_ = {m_val = 9, m_cat = 0xb7fcb064}, arg2_ = 0}
#17 0x08061018 in boost::asio::detail::task_io_service_operation::complete(boost::asio::detail::task_io_service&, boost::system::error_code const&, unsigned int) ()
No symbol table info available.
#18 0x08061eef in boost::asio::detail::task_io_service::do_run_one(boost::asio::detail::scoped_lock<boost::asio::detail::posix_mutex>&, boost::asio::detail::task_io_service_thread_info&, boost::system::error_code const&) ()
No symbol table info available.
#19 0x08061b1e in boost::asio::detail::task_io_service::run(boost::system::error_code&) ()
No symbol table info available.
---Type <return> to continue, or q <return> to quit---
#20 0x0806214d in boost::asio::io_service::run() ()
No symbol table info available.
#21 0x0805f2db in main ()
No symbol table info available.

Junxiao Shi wrote:

On Ubuntu 16.04 32-bit, http://gerrit.named-data.net/2708 patchset29 crashes if NetworkMonitor is destructed before onEnumerationCompleted is invoked.

The crash is somewhat expected since an exception is being thrown from a destructor, which causes std::terminate to be invoked. The real question is: why are you getting "bad file descriptor" at that point in the code?

We already encountered this problem in NFD (#1856).

When an Asio socket is destructed (or .close() is called), pending handlers are invoked with no error (instead of boost::asio::error::operation_aborted as documented). Therefore the handlers proceeds as if nothing bad happened and schedules another async read from the socket. However at that point the socket is closed, so the read results in a "bad file descriptor" error as above.

Patch set 30 solves this.