[libmicrohttpd] shutdown of listen socket does not work on solaris 10

[Frank Meier]

hi

I tried to use libmicrohttpd on solaris 10, and my simple programm only 
starting and stopping the daemon (see below) did hang in.
after some investigation (see debug code) I found, that the shutdown 
call in daemon.c fails, since the daemon socket is not a connected 
fullduplex but a listening socket. this means the daemon thread keeps 
hanging in select() and main hangs in pthread_join() (see pstack 
output). problem is since the socket doesn't get closed, select does not 
interrupt. After adding CLOSE (fd) after the point of SHUTDOWN () the 
programm did work. It looks like solaris and linux behave differently 
when shutdown is called on a listening socket. But on the other hand I'm 
not sure if it is correct to call shutdown in the first place, since the 
man page states "The  shutdown() call causes all or part of a 
full-duplex connection on the socket associated with sockfd to be shut 
down" and the listening socket does not have a connection.

I think the socket should be closed with CLOSE before calling 
pthread_join() and use SHUTDOWN only on connection sockets.

regards, Frank


/*test programm*/
struct MHD_Daemon* mhdDaemon = 0;
mhdDaemon = MHD_start_daemon (MHD_USE_THREAD_PER_CONNECTION, mhdPort, 
NULL, NULL, &answer_to_connection, NULL, MHD_OPTION_END);
if (mhdDaemon)
{
    MHD_stop_daemon (mhdDaemon);  // <-here it hangs
    mhdDaemon = 0;
}

/*debug code in daemon.c*/
--- daemon/daemon.c     (revision 16873)
+++ daemon/daemon.c     (working copy)
@@ -2477,7 +2477,11 @@
       daemon->worker_pool[i].shutdown = MHD_YES;
       daemon->worker_pool[i].socket_fd = -1;
     }
-  SHUTDOWN (fd, SHUT_RDWR);
+       int res = SHUTDOWN (fd, SHUT_RDWR);
+       int tmpErrno = errno;
+       printf("shutdown res:%d  %s\n", res, strerror(tmpErrno));
+
+       CLOSE (fd);

->output with debug code:
shutdown res:-1  Transport endpoint is not connected

/*pstack output -> damon thread is in select, main hangs in pthread join*/
$ pstack 16802
16802:  ./test.bin
-----------------  lwp# 1 / thread# 1  --------------------
 feee9365 lwp_wait (2, 80478d8)
 feee2c1f _thrp_join (2, 0, 8047918, 1) + 5a
 feee2d9e pthread_join (2, 8047918, feeec7e0, fef9665d) + 2b
 fef96777 MHD_stop_daemon (8060d40, 0, 0, fee63301) + 12b
 0805080a main     (1, 8047988, 8047990) + 6f
 080506ac _start   (1, 8047a88, 0, 8047a93, 8047abe, 8047b78) + 60
-----------------  lwp# 2 / thread# 2  --------------------
 feee8da5 pollsys  (fed5ed50, 1, 0, 0)
 fee93afa pselect  (4, fed5ef30, fed5eeb0, fed5ee30, 0, 0) + 18e
 fee93df0 select   (4, fed5ef30, fed5eeb0, fed5ee30, 0, 0) + 82
 fef95ba4 MHD_select (fec50200, fec50200, fed5efec, feee59b9, 8060d40, 
0) + 130
 fef96248 MHD_select_thread (8060d40) + 18
 feee59b9 _thr_setup (fec50200) + 4e
 feee5ca0 _lwp_start (fec50200, 0, 0, fed5eff8, feee5ca0, fec50200)