Host/posix/ConnectionFileDescriptorPosix.cpp

//===-- ConnectionFileDescriptorPosix.cpp -----------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#if defined(__APPLE__)
// Enable this special support for Apple builds where we can have unlimited
// select bounds. We tried switching to poll() and kqueue and we were panicing
// the kernel, so we have to stick with select for now.
#define _DARWIN_UNLIMITED_SELECT
#endif

#include "lldb/Host/posix/ConnectionFileDescriptorPosix.h"
#include "lldb/Host/Config.h"
#include "lldb/Host/IOObject.h"
#include "lldb/Host/SocketAddress.h"
#include "lldb/Host/Socket.h"
#include "lldb/Host/StringConvert.h"

// C Includes
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>

#ifndef LLDB_DISABLE_POSIX
#include <termios.h>
#endif

// C++ Includes
// Other libraries and framework includes
#include "llvm/Support/ErrorHandling.h"
#if defined(__APPLE__)
#include "llvm/ADT/SmallVector.h"
#endif
// Project includes
#include "lldb/Core/Communication.h"
#include "lldb/Core/Log.h"
#include "lldb/Core/StreamString.h"
#include "lldb/Core/Timer.h"
#include "lldb/Host/Host.h"
#include "lldb/Host/Socket.h"
#include "lldb/Interpreter/Args.h"

using namespace lldb;
using namespace lldb_private;

ConnectionFileDescriptor::ConnectionFileDescriptor(bool child_processes_inherit)
    : Connection()
    , m_pipe()
    , m_mutex(Mutex::eMutexTypeRecursive)
    , m_shutting_down(false)
    , m_waiting_for_accept(false)
    , m_child_processes_inherit(child_processes_inherit)
{
    Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_CONNECTION | LIBLLDB_LOG_OBJECT));
    if (log)
        log->Printf("%p ConnectionFileDescriptor::ConnectionFileDescriptor ()", static_cast<void *>(this));
}

ConnectionFileDescriptor::ConnectionFileDescriptor(int fd, bool owns_fd)
    : Connection()
    , m_pipe()
    , m_mutex(Mutex::eMutexTypeRecursive)
    , m_shutting_down(false)
    , m_waiting_for_accept(false)
    , m_child_processes_inherit(false)
{
    m_write_sp.reset(new File(fd, owns_fd));
    m_read_sp.reset(new File(fd, false));

    Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_CONNECTION | LIBLLDB_LOG_OBJECT));
    if (log)
        log->Printf("%p ConnectionFileDescriptor::ConnectionFileDescriptor (fd = %i, owns_fd = %i)", static_cast<void *>(this), fd,
                    owns_fd);
    OpenCommandPipe();
}

ConnectionFileDescriptor::ConnectionFileDescriptor(Socket* socket)
    : Connection()
    , m_pipe()
    , m_mutex(Mutex::eMutexTypeRecursive)
    , m_shutting_down(false)
    , m_waiting_for_accept(false)
    , m_child_processes_inherit(false)
{
    InitializeSocket(socket);
}

ConnectionFileDescriptor::~ConnectionFileDescriptor()
{
    Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_CONNECTION | LIBLLDB_LOG_OBJECT));
    if (log)
        log->Printf("%p ConnectionFileDescriptor::~ConnectionFileDescriptor ()", static_cast<void *>(this));
    Disconnect(NULL);
    CloseCommandPipe();
}

void
ConnectionFileDescriptor::OpenCommandPipe()
{
    CloseCommandPipe();

    Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_CONNECTION));
    // Make the command file descriptor here:
    Error result = m_pipe.CreateNew(m_child_processes_inherit);
    if (!result.Success())
    {
        if (log)
            log->Printf("%p ConnectionFileDescriptor::OpenCommandPipe () - could not make pipe: %s", static_cast<void *>(this),
                        result.AsCString());
    }
    else
    {
        if (log)
            log->Printf("%p ConnectionFileDescriptor::OpenCommandPipe() - success readfd=%d writefd=%d", static_cast<void *>(this),
                        m_pipe.GetReadFileDescriptor(), m_pipe.GetWriteFileDescriptor());
    }
}

void
ConnectionFileDescriptor::CloseCommandPipe()
{
    Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_CONNECTION));
    if (log)
        log->Printf("%p ConnectionFileDescriptor::CloseCommandPipe()", static_cast<void *>(this));

    m_pipe.Close();
}

bool
ConnectionFileDescriptor::IsConnected() const
{
    return (m_read_sp && m_read_sp->IsValid()) || (m_write_sp && m_write_sp->IsValid());
}

ConnectionStatus
ConnectionFileDescriptor::Connect(const char *s, Error *error_ptr)
{
    Mutex::Locker locker(m_mutex);
    Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_CONNECTION));
    if (log)
        log->Printf("%p ConnectionFileDescriptor::Connect (url = '%s')", static_cast<void *>(this), s);

    OpenCommandPipe();

    if (s && s[0])
    {
        if (strstr(s, "listen://") == s)
        {
            // listen://HOST:PORT
            return SocketListenAndAccept(s + strlen("listen://"), error_ptr);
        }
        else if (strstr(s, "accept://") == s)
        {
            // unix://SOCKNAME
            return NamedSocketAccept(s + strlen("accept://"), error_ptr);
        }
        else if (strstr(s, "unix-accept://") == s)
        {
            // unix://SOCKNAME
            return NamedSocketAccept(s + strlen("unix-accept://"), error_ptr);
        }
        else if (strstr(s, "adb://") == s)
        {
            int port = -1;
            sscanf(s, "adb://%*[^:]:%d", &port);
            char host_and_port[sizeof("localhost:65535")];
            snprintf(host_and_port, sizeof(host_and_port), "localhost:%d", port);
            return ConnectTCP(host_and_port, error_ptr);
        }
        else if (strstr(s, "connect://") == s)
        {
            return ConnectTCP(s + strlen("connect://"), error_ptr);
        }
        else if (strstr(s, "tcp-connect://") == s)
        {
            return ConnectTCP(s + strlen("tcp-connect://"), error_ptr);
        }
        else if (strstr(s, "udp://") == s)
        {
            return ConnectUDP(s + strlen("udp://"), error_ptr);
        }
#ifndef LLDB_DISABLE_POSIX
        else if (strstr(s, "fd://") == s)
        {
            // Just passing a native file descriptor within this current process
            // that is already opened (possibly from a service or other source).
            s += strlen("fd://");
            bool success = false;
            int fd = StringConvert::ToSInt32(s, -1, 0, &success);

            if (success)
            {
                // We have what looks to be a valid file descriptor, but we
                // should make sure it is. We currently are doing this by trying to
                // get the flags from the file descriptor and making sure it
                // isn't a bad fd.
                errno = 0;
                int flags = ::fcntl(fd, F_GETFL, 0);
                if (flags == -1 || errno == EBADF)
                {
                    if (error_ptr)
                        error_ptr->SetErrorStringWithFormat("stale file descriptor: %s", s);
                    m_read_sp.reset();
                    m_write_sp.reset();
                    return eConnectionStatusError;
                }
                else
                {
                    // Don't take ownership of a file descriptor that gets passed
                    // to us since someone else opened the file descriptor and
                    // handed it to us.
                    // TODO: Since are using a URL to open connection we should
                    // eventually parse options using the web standard where we
                    // have "fd://123?opt1=value;opt2=value" and we can have an
                    // option be "owns=1" or "owns=0" or something like this to
                    // allow us to specify this. For now, we assume we must
                    // assume we don't own it.

                    std::unique_ptr<Socket> tcp_socket;
                    tcp_socket.reset(new Socket(fd, Socket::ProtocolTcp, false));
                    // Try and get a socket option from this file descriptor to
                    // see if this is a socket and set m_is_socket accordingly.
                    int resuse;
                    bool is_socket = !!tcp_socket->GetOption(SOL_SOCKET, SO_REUSEADDR, resuse);
                    if (is_socket)
                    {
                        m_read_sp = std::move(tcp_socket);
                        m_write_sp = m_read_sp;
                    }
                    else
                    {
                        m_read_sp.reset(new File(fd, false));
                        m_write_sp.reset(new File(fd, false));
                    }
                    m_uri.assign(s);
                    return eConnectionStatusSuccess;
                }
            }

            if (error_ptr)
                error_ptr->SetErrorStringWithFormat("invalid file descriptor: \"fd://%s\"", s);
            m_read_sp.reset();
            m_write_sp.reset();
            return eConnectionStatusError;
        }
        else if (strstr(s, "file://") == s)
        {
            // file:///PATH
            const char *path = s + strlen("file://");
            int fd = -1;
            do
            {
                fd = ::open(path, O_RDWR);
            } while (fd == -1 && errno == EINTR);

            if (fd == -1)
            {
                if (error_ptr)
                    error_ptr->SetErrorToErrno();
                return eConnectionStatusError;
            }

            if (::isatty(fd))
            {
                // Set up serial terminal emulation
                struct termios options;
                ::tcgetattr(fd, &options);

                // Set port speed to maximum
                ::cfsetospeed(&options, B115200);
                ::cfsetispeed(&options, B115200);

                // Raw input, disable echo and signals
                options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);

                // Make sure only one character is needed to return from a read
                options.c_cc[VMIN] = 1;
                options.c_cc[VTIME] = 0;

                ::tcsetattr(fd, TCSANOW, &options);
            }

            int flags = ::fcntl(fd, F_GETFL, 0);
            if (flags >= 0)
            {
                if ((flags & O_NONBLOCK) == 0)
                {
                    flags |= O_NONBLOCK;
                    ::fcntl(fd, F_SETFL, flags);
                }
            }
            m_read_sp.reset(new File(fd, true));
            m_write_sp.reset(new File(fd, false));
            return eConnectionStatusSuccess;
        }
#endif
        if (error_ptr)
            error_ptr->SetErrorStringWithFormat("unsupported connection URL: '%s'", s);
        return eConnectionStatusError;
    }
    if (error_ptr)
        error_ptr->SetErrorString("invalid connect arguments");
    return eConnectionStatusError;
}

bool
ConnectionFileDescriptor::InterruptRead()
{
    size_t bytes_written = 0;
    Error result = m_pipe.Write("i", 1, bytes_written);
    return result.Success();
}

ConnectionStatus
ConnectionFileDescriptor::Disconnect(Error *error_ptr)
{
    Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_CONNECTION));
    if (log)
        log->Printf("%p ConnectionFileDescriptor::Disconnect ()", static_cast<void *>(this));

    ConnectionStatus status = eConnectionStatusSuccess;

    if (!IsConnected())
    {
        if (log)
            log->Printf("%p ConnectionFileDescriptor::Disconnect(): Nothing to disconnect", static_cast<void *>(this));
        return eConnectionStatusSuccess;
    }

    if (m_read_sp && m_read_sp->IsValid() && m_read_sp->GetFdType() == IOObject::eFDTypeSocket)
        static_cast<Socket &>(*m_read_sp).PreDisconnect();

    // Try to get the ConnectionFileDescriptor's mutex.  If we fail, that is quite likely
    // because somebody is doing a blocking read on our file descriptor.  If that's the case,
    // then send the "q" char to the command file channel so the read will wake up and the connection
    // will then know to shut down.

    m_shutting_down = true;

    Mutex::Locker locker;
    bool got_lock = locker.TryLock(m_mutex);

    if (!got_lock)
    {
        if (m_pipe.CanWrite())
        {
            size_t bytes_written = 0;
            Error result = m_pipe.Write("q", 1, bytes_written);
            if (log)
                log->Printf("%p ConnectionFileDescriptor::Disconnect(): Couldn't get the lock, sent 'q' to %d, error = '%s'.",
                            static_cast<void *>(this), m_pipe.GetWriteFileDescriptor(), result.AsCString());
        }
        else if (log)
        {
            log->Printf("%p ConnectionFileDescriptor::Disconnect(): Couldn't get the lock, but no command pipe is available.",
                        static_cast<void *>(this));
        }
        locker.Lock(m_mutex);
    }

    Error error = m_read_sp->Close();
    Error error2 = m_write_sp->Close();
    if (error.Fail() || error2.Fail())
        status = eConnectionStatusError;
    if (error_ptr)
        *error_ptr = error.Fail() ? error : error2;

    // Close any pipes we were using for async interrupts
    m_pipe.Close();

    m_uri.clear();
    m_shutting_down = false;
    return status;
}

size_t
ConnectionFileDescriptor::Read(void *dst, size_t dst_len, uint32_t timeout_usec, ConnectionStatus &status, Error *error_ptr)
{
    Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_CONNECTION));

    Mutex::Locker locker;
    bool got_lock = locker.TryLock(m_mutex);
    if (!got_lock)
    {
        if (log)
            log->Printf("%p ConnectionFileDescriptor::Read () failed to get the connection lock.", static_cast<void *>(this));
        if (error_ptr)
            error_ptr->SetErrorString("failed to get the connection lock for read.");

        status = eConnectionStatusTimedOut;
        return 0;
    }

    if (m_shutting_down)
    {
        status = eConnectionStatusError;
        return 0;
    }

    status = BytesAvailable(timeout_usec, error_ptr);
    if (status != eConnectionStatusSuccess)
        return 0;

    Error error;
    size_t bytes_read = dst_len;
    error = m_read_sp->Read(dst, bytes_read);

    if (log)
    {
        log->Printf("%p ConnectionFileDescriptor::Read()  fd = %" PRIu64 ", dst = %p, dst_len = %" PRIu64 ") => %" PRIu64 ", error = %s",
                    static_cast<void *>(this), static_cast<uint64_t>(m_read_sp->GetWaitableHandle()), static_cast<void *>(dst),
                    static_cast<uint64_t>(dst_len), static_cast<uint64_t>(bytes_read), error.AsCString());
    }

    if (bytes_read == 0)
    {
        error.Clear(); // End-of-file.  Do not automatically close; pass along for the end-of-file handlers.
        status = eConnectionStatusEndOfFile;
    }

    if (error_ptr)
        *error_ptr = error;

    if (error.Fail())
    {
        uint32_t error_value = error.GetError();
        switch (error_value)
        {
            case EAGAIN: // The file was marked for non-blocking I/O, and no data were ready to be read.
                if (m_read_sp->GetFdType() == IOObject::eFDTypeSocket)
                    status = eConnectionStatusTimedOut;
                else
                    status = eConnectionStatusSuccess;
                return 0;

            case EFAULT:  // Buf points outside the allocated address space.
            case EINTR:   // A read from a slow device was interrupted before any data arrived by the delivery of a signal.
            case EINVAL:  // The pointer associated with fildes was negative.
            case EIO:     // An I/O error occurred while reading from the file system.
                          // The process group is orphaned.
                          // The file is a regular file, nbyte is greater than 0,
                          // the starting position is before the end-of-file, and
                          // the starting position is greater than or equal to the
                          // offset maximum established for the open file
                          // descriptor associated with fildes.
            case EISDIR:  // An attempt is made to read a directory.
            case ENOBUFS: // An attempt to allocate a memory buffer fails.
            case ENOMEM:  // Insufficient memory is available.
                status = eConnectionStatusError;
                break; // Break to close....

            case ENOENT:     // no such file or directory
            case EBADF:      // fildes is not a valid file or socket descriptor open for reading.
            case ENXIO:      // An action is requested of a device that does not exist..
                             // A requested action cannot be performed by the device.
            case ECONNRESET: // The connection is closed by the peer during a read attempt on a socket.
            case ENOTCONN:   // A read is attempted on an unconnected socket.
                status = eConnectionStatusLostConnection;
                break; // Break to close....

            case ETIMEDOUT: // A transmission timeout occurs during a read attempt on a socket.
                status = eConnectionStatusTimedOut;
                return 0;

            default:
                if (log)
                    log->Printf("%p ConnectionFileDescriptor::Read (), unexpected error: %s", static_cast<void *>(this),
                                strerror(error_value));
                status = eConnectionStatusError;
                break; // Break to close....
        }

        return 0;
    }
    return bytes_read;
}

size_t
ConnectionFileDescriptor::Write(const void *src, size_t src_len, ConnectionStatus &status, Error *error_ptr)
{
    Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_CONNECTION));
    if (log)
        log->Printf("%p ConnectionFileDescriptor::Write (src = %p, src_len = %" PRIu64 ")", static_cast<void *>(this),
                    static_cast<const void *>(src), static_cast<uint64_t>(src_len));

    if (!IsConnected())
    {
        if (error_ptr)
            error_ptr->SetErrorString("not connected");
        status = eConnectionStatusNoConnection;
        return 0;
    }

    Error error;

    size_t bytes_sent = src_len;
    error = m_write_sp->Write(src, bytes_sent);

    if (log)
    {
        log->Printf("%p ConnectionFileDescriptor::Write(fd = %" PRIu64 ", src = %p, src_len = %" PRIu64 ") => %" PRIu64 " (error = %s)",
                    static_cast<void *>(this), static_cast<uint64_t>(m_write_sp->GetWaitableHandle()), static_cast<const void *>(src),
                    static_cast<uint64_t>(src_len), static_cast<uint64_t>(bytes_sent), error.AsCString());
    }

    if (error_ptr)
        *error_ptr = error;

    if (error.Fail())
    {
        switch (error.GetError())
        {
            case EAGAIN:
            case EINTR:
                status = eConnectionStatusSuccess;
                return 0;

            case ECONNRESET: // The connection is closed by the peer during a read attempt on a socket.
            case ENOTCONN:   // A read is attempted on an unconnected socket.
                status = eConnectionStatusLostConnection;
                break; // Break to close....

            default:
                status = eConnectionStatusError;
                break; // Break to close....
        }

        return 0;
    }

    status = eConnectionStatusSuccess;
    return bytes_sent;
}

std::string
ConnectionFileDescriptor::GetURI()
{
    return m_uri;
}

// This ConnectionFileDescriptor::BytesAvailable() uses select().
//
// PROS:
//  - select is consistent across most unix platforms
//  - The Apple specific version allows for unlimited fds in the fd_sets by
//    setting the _DARWIN_UNLIMITED_SELECT define prior to including the
//    required header files.
// CONS:
//  - on non-Apple platforms, only supports file descriptors up to FD_SETSIZE.
//     This implementation  will assert if it runs into that hard limit to let
//     users know that another ConnectionFileDescriptor::BytesAvailable() should
//     be used or a new version of ConnectionFileDescriptor::BytesAvailable()
//     should be written for the system that is running into the limitations.

#if defined(__APPLE__)
#define FD_SET_DATA(fds) fds.data()
#else
#define FD_SET_DATA(fds) &fds
#endif

ConnectionStatus
ConnectionFileDescriptor::BytesAvailable(uint32_t timeout_usec, Error *error_ptr)
{
    // Don't need to take the mutex here separately since we are only called from Read.  If we
    // ever get used more generally we will need to lock here as well.

    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_CONNECTION));
    if (log)
        log->Printf("%p ConnectionFileDescriptor::BytesAvailable (timeout_usec = %u)", static_cast<void *>(this), timeout_usec);

    struct timeval *tv_ptr;
    struct timeval tv;
    if (timeout_usec == UINT32_MAX)
    {
        // Inifinite wait...
        tv_ptr = nullptr;
    }
    else
    {
        TimeValue time_value;
        time_value.OffsetWithMicroSeconds(timeout_usec);
        tv.tv_sec = time_value.seconds();
        tv.tv_usec = time_value.microseconds();
        tv_ptr = &tv;
    }

    // Make a copy of the file descriptors to make sure we don't
    // have another thread change these values out from under us
    // and cause problems in the loop below where like in FS_SET()
    const IOObject::WaitableHandle handle = m_read_sp->GetWaitableHandle();
    const int pipe_fd = m_pipe.GetReadFileDescriptor();

    if (handle != IOObject::kInvalidHandleValue)
    {
#if defined(_MSC_VER)
        // select() won't accept pipes on Windows.  The entire Windows codepath needs to be
        // converted over to using WaitForMultipleObjects and event HANDLEs, but for now at least
        // this will allow ::select() to not return an error.
        const bool have_pipe_fd = false;
#else
        const bool have_pipe_fd = pipe_fd >= 0;
#if !defined(__APPLE__)
        assert(handle < FD_SETSIZE);
        if (have_pipe_fd)
            assert(pipe_fd < FD_SETSIZE);
#endif
#endif
        while (handle == m_read_sp->GetWaitableHandle())
        {
            const int nfds = std::max<int>(handle, pipe_fd) + 1;
#if defined(__APPLE__)
            llvm::SmallVector<fd_set, 1> read_fds;
            read_fds.resize((nfds / FD_SETSIZE) + 1);
            for (size_t i = 0; i < read_fds.size(); ++i)
                FD_ZERO(&read_fds[i]);
// FD_SET doesn't bounds check, it just happily walks off the end
// but we have taken care of making the extra storage with our
// SmallVector of fd_set objects
#else
            fd_set read_fds;
            FD_ZERO(&read_fds);
#endif
            FD_SET(handle, FD_SET_DATA(read_fds));
            if (have_pipe_fd)
                FD_SET(pipe_fd, FD_SET_DATA(read_fds));

            Error error;

            if (log)
            {
                if (have_pipe_fd)
                    log->Printf(
                        "%p ConnectionFileDescriptor::BytesAvailable()  ::select (nfds=%i, fds={%i, %i}, NULL, NULL, timeout=%p)...",
                        static_cast<void *>(this), nfds, handle, pipe_fd, static_cast<void *>(tv_ptr));
                else
                    log->Printf("%p ConnectionFileDescriptor::BytesAvailable()  ::select (nfds=%i, fds={%i}, NULL, NULL, timeout=%p)...",
                                static_cast<void *>(this), nfds, handle, static_cast<void *>(tv_ptr));
            }

            const int num_set_fds = ::select(nfds, FD_SET_DATA(read_fds), NULL, NULL, tv_ptr);
            if (num_set_fds < 0)
                error.SetErrorToErrno();
            else
                error.Clear();

            if (log)
            {
                if (have_pipe_fd)
                    log->Printf("%p ConnectionFileDescriptor::BytesAvailable()  ::select (nfds=%i, fds={%i, %i}, NULL, NULL, timeout=%p) "
                                "=> %d, error = %s",
                                static_cast<void *>(this), nfds, handle, pipe_fd, static_cast<void *>(tv_ptr), num_set_fds,
                                error.AsCString());
                else
                    log->Printf("%p ConnectionFileDescriptor::BytesAvailable()  ::select (nfds=%i, fds={%i}, NULL, NULL, timeout=%p) => "
                                "%d, error = %s",
                                static_cast<void *>(this), nfds, handle, static_cast<void *>(tv_ptr), num_set_fds, error.AsCString());
            }

            if (error_ptr)
                *error_ptr = error;

            if (error.Fail())
            {
                switch (error.GetError())
                {
                    case EBADF: // One of the descriptor sets specified an invalid descriptor.
                        return eConnectionStatusLostConnection;

                    case EINVAL: // The specified time limit is invalid. One of its components is negative or too large.
                    default:     // Other unknown error
                        return eConnectionStatusError;

                    case EAGAIN: // The kernel was (perhaps temporarily) unable to
                                 // allocate the requested number of file descriptors,
                                 // or we have non-blocking IO
                    case EINTR:  // A signal was delivered before the time limit
                        // expired and before any of the selected events
                        // occurred.
                        break; // Lets keep reading to until we timeout
                }
            }
            else if (num_set_fds == 0)
            {
                return eConnectionStatusTimedOut;
            }
            else if (num_set_fds > 0)
            {
                if (FD_ISSET(handle, FD_SET_DATA(read_fds)))
                    return eConnectionStatusSuccess;
                if (have_pipe_fd && FD_ISSET(pipe_fd, FD_SET_DATA(read_fds)))
                {
                    // There is an interrupt or exit command in the command pipe
                    // Read the data from that pipe:
                    char buffer[1];

                    ssize_t bytes_read;

                    do
                    {
                        bytes_read = ::read(pipe_fd, buffer, sizeof(buffer));
                    } while (bytes_read < 0 && errno == EINTR);

                    switch (buffer[0])
                    {
                        case 'q':
                            if (log)
                                log->Printf("%p ConnectionFileDescriptor::BytesAvailable() "
                                            "got data: %c from the command channel.",
                                            static_cast<void *>(this), buffer[0]);
                            return eConnectionStatusEndOfFile;
                        case 'i':
                            // Interrupt the current read
                            return eConnectionStatusInterrupted;
                    }
                }
            }
        }
    }

    if (error_ptr)
        error_ptr->SetErrorString("not connected");
    return eConnectionStatusLostConnection;
}

ConnectionStatus
ConnectionFileDescriptor::NamedSocketAccept(const char *socket_name, Error *error_ptr)
{
    Socket *socket = nullptr;
    Error error = Socket::UnixDomainAccept(socket_name, m_child_processes_inherit, socket);
    if (error_ptr)
        *error_ptr = error;
    m_write_sp.reset(socket);
    m_read_sp = m_write_sp;
    if (error.Fail())
    {
        return eConnectionStatusError;
    }
    m_uri.assign(socket_name);
    return eConnectionStatusSuccess;
}

ConnectionStatus
ConnectionFileDescriptor::NamedSocketConnect(const char *socket_name, Error *error_ptr)
{
    Socket *socket = nullptr;
    Error error = Socket::UnixDomainConnect(socket_name, m_child_processes_inherit, socket);
    if (error_ptr)
        *error_ptr = error;
    m_write_sp.reset(socket);
    m_read_sp = m_write_sp;
    if (error.Fail())
    {
        return eConnectionStatusError;
    }
    m_uri.assign(socket_name);
    return eConnectionStatusSuccess;
}

ConnectionStatus
ConnectionFileDescriptor::SocketListenAndAccept(const char *s, Error *error_ptr)
{
    m_port_predicate.SetValue(0, eBroadcastNever);

    Socket *socket = nullptr;
    m_waiting_for_accept = true;
    Error error = Socket::TcpListen(s, m_child_processes_inherit, socket, &m_port_predicate);
    if (error_ptr)
        *error_ptr = error;
    if (error.Fail())
        return eConnectionStatusError;

    std::unique_ptr<Socket> listening_socket_up;

    listening_socket_up.reset(socket);
    socket = nullptr;
    error = listening_socket_up->BlockingAccept(s, m_child_processes_inherit, socket);
    listening_socket_up.reset();
    if (error_ptr)
        *error_ptr = error;
    if (error.Fail())
        return eConnectionStatusError;

    InitializeSocket(socket);
    return eConnectionStatusSuccess;
}

ConnectionStatus
ConnectionFileDescriptor::ConnectTCP(const char *s, Error *error_ptr)
{
    Socket *socket = nullptr;
    Error error = Socket::TcpConnect(s, m_child_processes_inherit, socket);
    if (error_ptr)
        *error_ptr = error;
    m_write_sp.reset(socket);
    m_read_sp = m_write_sp;
    if (error.Fail())
    {
        return eConnectionStatusError;
    }
    m_uri.assign(s);
    return eConnectionStatusSuccess;
}

ConnectionStatus
ConnectionFileDescriptor::ConnectUDP(const char *s, Error *error_ptr)
{
    Socket *send_socket = nullptr;
    Socket *recv_socket = nullptr;
    Error error = Socket::UdpConnect(s, m_child_processes_inherit, send_socket, recv_socket);
    if (error_ptr)
        *error_ptr = error;
    m_write_sp.reset(send_socket);
    m_read_sp.reset(recv_socket);
    if (error.Fail())
    {
        return eConnectionStatusError;
    }
    m_uri.assign(s);
    return eConnectionStatusSuccess;
}

uint16_t
ConnectionFileDescriptor::GetListeningPort(uint32_t timeout_sec)
{
    uint16_t bound_port = 0;
    if (timeout_sec == UINT32_MAX)
        m_port_predicate.WaitForValueNotEqualTo(0, bound_port);
    else
    {
        TimeValue timeout = TimeValue::Now();
        timeout.OffsetWithSeconds(timeout_sec);
        m_port_predicate.WaitForValueNotEqualTo(0, bound_port, &timeout);
    }
    return bound_port;
}

bool
ConnectionFileDescriptor::GetChildProcessesInherit() const
{
    return m_child_processes_inherit;
}

void
ConnectionFileDescriptor::SetChildProcessesInherit(bool child_processes_inherit)
{
    m_child_processes_inherit = child_processes_inherit;
}

void
ConnectionFileDescriptor::InitializeSocket(Socket* socket)
{
    m_write_sp.reset(socket);
    m_read_sp = m_write_sp;
    StreamString strm;
    strm.Printf("connect://%s:%u",socket->GetRemoteIPAddress().c_str(), socket->GetRemotePortNumber());
    m_uri.swap(strm.GetString());
}