XmlRpcServer.cpp

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// this file modified by Morgan Quigley on 22 Apr 2008.
// added features: server can be opened on port 0 and you can read back
// what port the OS gave you

#include "xmlrpcpp/XmlRpcServer.h"
#include "xmlrpcpp/XmlRpcServerConnection.h"
#include "xmlrpcpp/XmlRpcServerMethod.h"
#include "xmlrpcpp/XmlRpcSocket.h"
#include "xmlrpcpp/XmlRpcUtil.h"
#include "xmlrpcpp/XmlRpcException.h"

#include <errno.h>
#include <string.h>
#include <sys/resource.h>

using namespace XmlRpc;

const int XmlRpcServer::FREE_FD_BUFFER = 32;
const double XmlRpcServer::ACCEPT_RETRY_INTERVAL_SEC = 1.0;

XmlRpcServer::XmlRpcServer()
  : _introspectionEnabled(false),
    _listMethods(0),
    _methodHelp(0),
    _port(0),
    _accept_error(false),
    _accept_retry_time_sec(0.0)
{
  struct rlimit limit = { .rlim_cur = 0, .rlim_max = 0 };
  unsigned int max_files = 1024;

  if(getrlimit(RLIMIT_NOFILE, &limit) == 0) {
    max_files = limit.rlim_max;
    if( limit.rlim_max == RLIM_INFINITY ) {
      max_files = 0;
    }
  } else {
    XmlRpcUtil::error("Could not get open file limit: %s", strerror(errno));
  }
  pollfds.resize(max_files);
  for(unsigned int i=0; i<max_files; i++) {
    // Set up file descriptor query for all events.
    pollfds[i].fd = i;
    pollfds[i].events = POLLIN | POLLPRI | POLLOUT;
  }

  // Ask dispatch not to close this socket if it becomes unreadable.
  setKeepOpen(true);
}


XmlRpcServer::~XmlRpcServer()
{
  this->shutdown();
  _methods.clear();
  delete _listMethods;
  delete _methodHelp;
}


// Add a command to the RPC server
void 
XmlRpcServer::addMethod(XmlRpcServerMethod* method)
{
  _methods[method->name()] = method;
}

// Remove a command from the RPC server
void 
XmlRpcServer::removeMethod(XmlRpcServerMethod* method)
{
  MethodMap::iterator i = _methods.find(method->name());
  if (i != _methods.end())
    _methods.erase(i);
}

// Remove a command from the RPC server by name
void 
XmlRpcServer::removeMethod(const std::string& methodName)
{
  MethodMap::iterator i = _methods.find(methodName);
  if (i != _methods.end())
    _methods.erase(i);
}


// Look up a method by name
XmlRpcServerMethod* 
XmlRpcServer::findMethod(const std::string& name) const
{
  MethodMap::const_iterator i = _methods.find(name);
  if (i == _methods.end())
    return 0;
  return i->second;
}


// Create a socket, bind to the specified port, and
// set it in listen mode to make it available for clients.
bool 
XmlRpcServer::bindAndListen(int port, int backlog /*= 5*/)
{
  int fd = XmlRpcSocket::socket();
  if (fd < 0)
  {
    XmlRpcUtil::error("XmlRpcServer::bindAndListen: Could not create socket (%s).", XmlRpcSocket::getErrorMsg().c_str());
    return false;
  }

  this->setfd(fd);

  // Don't block on reads/writes
  if ( ! XmlRpcSocket::setNonBlocking(fd))
  {
    this->close();
    XmlRpcUtil::error("XmlRpcServer::bindAndListen: Could not set socket to non-blocking input mode (%s).", XmlRpcSocket::getErrorMsg().c_str());
    return false;
  }

  // Allow this port to be re-bound immediately so server re-starts are not delayed
  if ( ! XmlRpcSocket::setReuseAddr(fd))
  {
    this->close();
    XmlRpcUtil::error("XmlRpcServer::bindAndListen: Could not set SO_REUSEADDR socket option (%s).", XmlRpcSocket::getErrorMsg().c_str());
    return false;
  }

  // Bind to the specified port on the default interface
  if ( ! XmlRpcSocket::bind(fd, port))
  {
    this->close();
    XmlRpcUtil::error("XmlRpcServer::bindAndListen: Could not bind to specified port (%s).", XmlRpcSocket::getErrorMsg().c_str());
    return false;
  }

  // Set in listening mode
  if ( ! XmlRpcSocket::listen(fd, backlog))
  {
    this->close();
    XmlRpcUtil::error("XmlRpcServer::bindAndListen: Could not set socket in listening mode (%s).", XmlRpcSocket::getErrorMsg().c_str());
    return false;
  }

  _port = XmlRpcSocket::get_port(fd);

  XmlRpcUtil::log(2, "XmlRpcServer::bindAndListen: server listening on port %d fd %d", _port, fd);

  // Notify the dispatcher to listen on this source when we are in work()
  _disp.addSource(this, XmlRpcDispatch::ReadableEvent);

  return true;
}


// Process client requests for the specified time
void 
XmlRpcServer::work(double msTime)
{
  XmlRpcUtil::log(2, "XmlRpcServer::work: waiting for a connection");
  if(_accept_error && _disp.getTime() > _accept_retry_time_sec) {
    _disp.addSource(this, XmlRpcDispatch::ReadableEvent);
  }
  _disp.work(msTime);
}



// Handle input on the server socket by accepting the connection
// and reading the rpc request.
unsigned
XmlRpcServer::handleEvent(unsigned)
{
  return acceptConnection();
}


// Accept a client connection request and create a connection to
// handle method calls from the client.
unsigned
XmlRpcServer::acceptConnection()
{
  int s = XmlRpcSocket::accept(this->getfd());
  XmlRpcUtil::log(2, "XmlRpcServer::acceptConnection: socket %d", s);
  if (s < 0)
  {
    //this->close();
    XmlRpcUtil::error("XmlRpcServer::acceptConnection: Could not accept connection (%s).", XmlRpcSocket::getErrorMsg().c_str());

    // Note that there was an accept error; retry in 1 second
    _accept_error = true;
    _accept_retry_time_sec = _disp.getTime() + ACCEPT_RETRY_INTERVAL_SEC;
    return 0; // Stop monitoring this FD
  }
  else if( countFreeFDs() < FREE_FD_BUFFER )
  {
    XmlRpcSocket::close(s);
    XmlRpcUtil::error("XmlRpcServer::acceptConnection: Rejecting client, not enough free file descriptors");
  }
  else if ( ! XmlRpcSocket::setNonBlocking(s))
  {
    XmlRpcSocket::close(s);
    XmlRpcUtil::error("XmlRpcServer::acceptConnection: Could not set socket to non-blocking input mode (%s).", XmlRpcSocket::getErrorMsg().c_str());
  }
  else  // Notify the dispatcher to listen for input on this source when we are in work()
  {
    XmlRpcUtil::log(2, "XmlRpcServer::acceptConnection: creating a connection");
    _disp.addSource(this->createConnection(s), XmlRpcDispatch::ReadableEvent);
  }
  return XmlRpcDispatch::ReadableEvent; // Continue to monitor this fd
}

int XmlRpcServer::countFreeFDs() {
  // NOTE(austin): this function is not free, but in a few small tests it only
  // takes about 1.2mS when querying 50k file descriptors.
  //
  // If the underlying system calls here fail, this will print an error and
  // return 0
  int free_fds = 0;

  struct rlimit limit = { .rlim_cur = 0, .rlim_max = 0 };

  // Get the current soft limit on the number of file descriptors.
  if(getrlimit(RLIMIT_NOFILE, &limit) == 0) {
    // If we have infinite file descriptors, always return FREE_FD_BUFFER so
    // that we never hit the low-water mark.
    if( limit.rlim_max == RLIM_INFINITY ) {
      return FREE_FD_BUFFER;
    }

    // Poll the available file descriptors.
    // The POSIX specification guarantees that rlim_cur will always be less or
    // equal to the process's initial rlim_max, so we don't need an additonal
    // bounds check here.
    if(poll(&pollfds[0], limit.rlim_cur, 1) >= 0) {
      for(rlim_t i=0; i<limit.rlim_cur; i++) {
        if(pollfds[i].revents & POLLNVAL) {
          free_fds++;
        }
      }
    } else {
      // poll() may fail if interrupted, if the pollfds array is a bad pointer,
      // if nfds exceeds RLIMIT_NOFILE, or if the system is out of memory.
      XmlRpcUtil::error("XmlRpcServer::countFreeFDs: poll() failed: %s",
                        strerror(errno));
    }
  } else {
    // The man page for getrlimit says that it can fail if the requested
    // resource is invalid or the second argument is invalid. I'm not sure
    // either of these can actually fail in this code, but it's better to
    // check.
    XmlRpcUtil::error("XmlRpcServer::countFreeFDs: Could not get open file "
                      "limit, getrlimit() failed: %s", strerror(errno));
  }

  return free_fds;
}


// Create a new connection object for processing requests from a specific client.
XmlRpcServerConnection*
XmlRpcServer::createConnection(int s)
{
  // Specify that the connection object be deleted when it is closed
  return new XmlRpcServerConnection(s, this, true);
}


void 
XmlRpcServer::removeConnection(XmlRpcServerConnection* sc)
{
  _disp.removeSource(sc);
}


// Stop processing client requests
void 
XmlRpcServer::exit()
{
  _disp.exit();
}


// Close the server socket file descriptor and stop monitoring connections
void 
XmlRpcServer::shutdown()
{
  // This closes and destroys all connections as well as closing this socket
  _disp.clear();
}


// Introspection support
static const std::string LIST_METHODS("system.listMethods");
static const std::string METHOD_HELP("system.methodHelp");
static const std::string MULTICALL("system.multicall");


// List all methods available on a server
class ListMethods : public XmlRpcServerMethod
{
public:
  ListMethods(XmlRpcServer* s) : XmlRpcServerMethod(LIST_METHODS, s) {}

  void execute(XmlRpcValue&, XmlRpcValue& result)
  {
    _server->listMethods(result);
  }

  std::string help() { return std::string("List all methods available on a server as an array of strings"); }
};


// Retrieve the help string for a named method
class MethodHelp : public XmlRpcServerMethod
{
public:
  MethodHelp(XmlRpcServer* s) : XmlRpcServerMethod(METHOD_HELP, s) {}

  void execute(XmlRpcValue& params, XmlRpcValue& result)
  {
    if (params[0].getType() != XmlRpcValue::TypeString)
      throw XmlRpcException(METHOD_HELP + ": Invalid argument type");

    XmlRpcServerMethod* m = _server->findMethod(params[0]);
    if ( ! m)
      throw XmlRpcException(METHOD_HELP + ": Unknown method name");

    result = m->help();
  }

  std::string help() { return std::string("Retrieve the help string for a named method"); }
};

    
// Specify whether introspection is enabled or not. Default is enabled.
void 
XmlRpcServer::enableIntrospection(bool enabled)
{
  if (_introspectionEnabled == enabled)
    return;

  _introspectionEnabled = enabled;

  if (enabled)
  {
    if ( ! _listMethods)
    {
      _listMethods = new ListMethods(this);
      _methodHelp = new MethodHelp(this);
    } else {
      addMethod(_listMethods);
      addMethod(_methodHelp);
    }
  }
  else
  {
    removeMethod(LIST_METHODS);
    removeMethod(METHOD_HELP);
  }
}


void
XmlRpcServer::listMethods(XmlRpcValue& result)
{
  int i = 0;
  result.setSize(_methods.size()+1);
  for (MethodMap::iterator it=_methods.begin(); it != _methods.end(); ++it)
    result[i++] = it->first;

  // Multicall support is built into XmlRpcServerConnection
  result[i] = MULTICALL;
}