problem with popen - c++

Question

I have a strange problem. I have 2 binaries by the name cpp and another is called mnp_proxy_server.
cpp will start mnp_proxy_binary by calling a method executeScript. The code of this method is
int executeScript(string script, unsigned int scriptTmOut)
{
fd_set readfd;
const int BUFSIZE = 1024;
//stringstream strBuf;
char buf[ BUFSIZE];
time_t startTime = time(NULL);
struct timeval tv;
int ret, ret2 = 0;
FILE * pPipe = popen(script.c_str(), "r");
if (pPipe == NULL)
{
// cout << "popen() failed:"<< strerror(errno) << endl;
return -1;
}
while(1)
{
FD_ZERO(&readfd);
FD_SET(fileno(pPipe), &readfd);
/** Select Timeout Hardcode with 1 secs **/
tv.tv_sec = scriptTmOut;
tv.tv_usec = 0;
ret = select(fileno(pPipe)+1, &readfd, NULL, NULL, &tv);
if(ret < 0)
{
// cout << "select() failed " << strerror(errno) << endl;
}
else if (ret == 0)
{
// cout << "select() timeout" << endl;
break;
}
else
{
//cout << "Data is available now" <<endl;
if(FD_ISSET(fileno(pPipe), &readfd))
{
if(fgets(buf, sizeof(buf), pPipe) != NULL )
{
//cout << buf;
//strBuf << buf;
}
/** No Problem if there is no data ouput by script **/
#if 1
else
{
//ret2 = -1;
// cout << "fgets() failed " << strerror(errno) << endl;
break;
}
#endif
}
else
{
ret2 = -1;
// cout << "FD_ISSET() failed " << strerror(errno) << endl;
break;
}
}
/** Check the Script-timeout **/
if((startTime + scriptTmOut) < time(NULL))
{
// cout<<"Script Timeout"<<endl;
break ;
}
}
pclose(pPipe);
return ret2;
}
cpp is a server which listens on various ports 7001 and 7045. Once mnp_proxy_server is started it connects to 7001 port and starts sending messages.
Now coming to the problem. when i send ctr^c signal to cpp the signal is propagated to mnp_proxy_server and if i kill cpp process then all the ports on which cpp was listning now becomes the part of mnp_proxy_server process.
output of netstat after killing cpp process
[root#punith bin]# netstat -alpn | grep mnp_pr
tcp 0 0 0.0.0.0:7045 0.0.0.0:* LISTEN 26186/mnp_proxy_ser
tcp 0 0 0.0.0.0:7001 0.0.0.0:* LISTEN 26186/mnp_proxy_ser
I know it has something to do with the way I am executing the startup script of mnp_proxy_server through cpp.
There is a signal handler in both the binaries. And also to exit the socket select when ctr^c is pressed I have used pipes in select, so when ctr^c is pressed i close the write end of the pipe so that select is notified and select comes out and breaks the run loop.
Both of them are written in c++ and I am using rhel
Any clue will greatly help me in solving this. Thanking in advance.

Answer 1

You should set the flag CLOEXEC on the server sockets of cpp so that they are closed in the child process:
fcntl(fd, F_SETFD, FD_CLOEXEC);
While using socket like in your processes, I would suggest use fork and exec instead of popen to be able to close or manage all sockets between fork and exec, but the flag CLOEXEC might be enough to solve your problem.