udt / Discussion / 中文版论坛: epoll 监听不到close事件

reg2011 - 2012-06-03

epoll 监听不到close事件，不知为何，谢谢！

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chenbin0522 - 2012-06-05

我也发现了，如果客户端不掉用UDT::close(fhandle) 那么服务器端可以读到错误。如果客户端调用UDT::close(fhandle)就收不到，比较奇怪。我是客户端和服务器端在一台电脑上，不知到有没有关系。

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Yunhong Gu - 2012-06-05

是个bug，正在修改，估计一两天之内会把新的代码放到cvs上去。

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Yunhong Gu - 2012-06-06

已经更新了CVS。谢谢。

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yavey - 2013-01-29

请问这个更新是版本5？

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bluex - 2014-02-25

确实有这个BUG。。。在底层检测到broken的socket时,然后调用close候会添加一个ERROR事件，但是并没添加成功，代码如下：
void CUDT::close()
｛
.............
s_UDTUnited.m_EPoll.update_events(m_SocketID, m_sPollID, UDT_EPOLL_ERR, true);
.............
｝
但是跟踪代码发现update_events(m_SocketID, m_sPollID, UDT_EPOLL_ERR, true)会调用：
update_epoll_sets(uid, p->second.m_sUDTSocksEx, p->second.m_sUDTExcepts, enable);
进而调用
void update_epoll_sets(const UDTSOCKET& uid, const set<udtsocket>& watch, set<udtsocket>& result, bool enable)
{
if (enable && (watch.find(uid) != watch.end()))
{
result.insert(uid);
}
else if (!enable)
{
result.erase(uid);
}
}</udtsocket></udtsocket>

此时的set<udtsocket>& watch即为p->second.m_sUDTExcepts，但是p->second.m_sUDTExcepts为empty()，
所以事件添加不成功，导致上层不能接受到事件。
为什么m_sUDTExcepts为空，查看代码就能发现跟epoll之前调用的add_usock有关，当我们需要关注ERROR时，并没有往这里面添加socket描述符：
int CEPoll::add_usock(const int eid, const UDTSOCKET& u, const int* events)
{
CGuard pg(m_EPollLock);</udtsocket>

map<int, cepolldesc="">::iterator p = m_mPolls.find(eid);
if (p == m_mPolls.end())
throw CUDTException(5, 13);</int,>

if (!events || (events & UDT_EPOLL_IN))
p->second.m_sUDTSocksIn.insert(u);
if (!events || (events & UDT_EPOLL_OUT))
p->second.m_sUDTSocksOut.insert(u);

return 0;
}

查看函数int CEPoll::wait(const int eid, set<udtsocket> readfds, set<udtsocket></udtsocket> writefds, int64_t msTimeOut, set<syssocket> lrfds, set<syssocket></syssocket> lwfds)可以发现：即使有一个error事件触发，在事件收集的时候也是合并为EPOLL_IN事件来处理的。</syssocket></udtsocket>

// Sockets with exceptions are returned to both read and write sets. if ((NULL != readfds) && (!p->second.m_sUDTReads.empty() || !p->second.m_sUDTExcepts.empty())) { *readfds = p->second.m_sUDTReads; for (set<UDTSOCKET>::const_iterator i = p->second.m_sUDTExcepts.begin(); i != p->second.m_sUDTExcepts.end(); ++ i) readfds->insert(*i); total += p->second.m_sUDTReads.size() + p->second.m_sUDTExcepts.size(); }

所以可以这样修改：
1）在close函数里面修改 s_UDTUnited.m_EPoll.update_events(m_SocketID, m_sPollID, UDT_EPOLL_ERR, true);
为 s_UDTUnited.m_EPoll.update_events(m_SocketID, m_sPollID, UDT_EPOLL_IN, true);
这样就能导致上层收到一个读事件。
2）然后上层调用recv或者recvmsg，此时因为socket已经在udt层面不存在了，会引发一个异常，这时候要在异常里面做处理
就是剔除跟这个socket有关的事件，职位为false，否则会导致这个事件一直存在，不停的循环告诉上层有读的事件发生。
所以需要修改recv和recvmsg函数的异常处理分支
int CUDT::recv(UDTSOCKET u, char buf, int len, int)
{
try
{
CUDT udt = s_UDTUnited.lookup(u);
return udt->recv(buf, len);
}
catch (CUDTException e)
{
s_UDTUnited.m_EPoll.remove_events(u); //////////因为bug新增行remove_events在源代码里面是没有的。
s_UDTUnited.setError(new CUDTException(e));
return ERROR;
}
catch (...)
{
s_UDTUnited.setError(new CUDTException(-1, 0, 0));
return ERROR;
}
}
recvmsg函数的修改同上。。。。。。
新增函数：
void CEPoll::remove_events(const UDTSOCKET& uid)
{
CGuard pg(m_EPollLock);

map<int, CEPollDesc>::iterator p; for (p = m_mPolls.begin(); p != m_mPolls.end(); ++p) { p->second.m_sUDTReads.erase(uid); p->second.m_sUDTWrites.erase(uid); p->second.m_sUDTExcepts.erase(uid); }

}
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bluex - 2014-02-26

我用的是utd的最新版本udt4.11，udt5好像还没出来。。。

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- wang hui - 2014-02-26
  
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  - wang hui - 2014-02-26
    
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    我最喜欢淘东西了，最近运气好，前几天看到这个活动，拍了两双，没想到发过来去专柜检验确实是正品~赚了~还有情侣款!http://dfhtdh.gxsl.net
    
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    - wang hui - 2014-02-26
      
      <meta http-equiv="Content-Type" content="text/html; charset=gb2312">
      我最喜欢淘东西了，最近运气好，前几天看到这个活动，拍了两双，没想到发过来去专柜检验确实是正品~赚了~还有情侣款!http://dfhtdh.gxsl.net
      
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bluex - 2014-02-27

上次回复修改这个bug并不完善，还有自动检测的地方，并没有关闭事件通知到上层，接着上面的帖子，还要修稿到文件为api.cpp，在函数
void CUDTUnited::checkBrokenSockets()里面加上事件通知
//EPOLL SIGNAL
m_EPoll.update_events(i->first, i->second->m_pUDT->m_sPollID, UDT_EPOLL_IN, true);

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- wang hui - 2014-02-27
  
  <meta http-equiv="Content-Type" content="text/html; charset=gb2312">
  我最喜欢淘东西了，最近运气好，前几天看到这个活动，拍了两双，没想到发过来去专柜检验确实是正品~赚了~还有情侣款!http://dfhtdh.gxsl.net
  
  This is an automatic reply, confirming that your e-mail was received.Thank you
  
  邮箱使用小提示
  
  想让对方更及时看到你的邮件，可以试试发到"对方手机号@163.com"。
  
  无需事先开通，还有短信提醒。了解网易手机邮箱详情
  
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  - wang hui - 2014-02-27
    
    <meta http-equiv="Content-Type" content="text/html; charset=gb2312">
    我最喜欢淘东西了，最近运气好，前几天看到这个活动，拍了两双，没想到发过来去专柜检验确实是正品~赚了~还有情侣款!http://dfhtdh.gxsl.net
    
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    想让对方更及时看到你的邮件，可以试试发到"对方手机号@163.com"。
    
    无需事先开通，还有短信提醒。了解网易手机邮箱详情
    
    If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
    - wang hui - 2014-02-27
      
      <meta http-equiv="Content-Type" content="text/html; charset=gb2312">
      我最喜欢淘东西了，最近运气好，前几天看到这个活动，拍了两双，没想到发过来去专柜检验确实是正品~赚了~还有情侣款!http://dfhtdh.gxsl.net
      
      This is an automatic reply, confirming that your e-mail was received.Thank you
      
      邮箱使用小提示
      
      想让对方更及时看到你的邮件，可以试试发到"对方手机号@163.com"。
      
      无需事先开通，还有短信提醒。了解网易手机邮箱详情
      
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epoll 监听不到close事件

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