Bug#48929 Error in Accept() if using many file descriptors

In POSIX systems, the file descriptor set used in the select(2)
system call is represented by a bit vector of size FD_SETSIZE.
When select(2) is used on file/socket descriptors with a value
that is beyond this size, unpredictable errors may occur.

In this case, the error happens when there are a large number
of tables that need repair.  These tables are opened before
the sockets for incoming connections are acquired, resulting
in these sockets getting descriptor id which is higher than
FD_SETSIZE.

Replacing the call to select(2) with poll(2) fixes the problem,
as poll takes an array of the wanted descriptors, instead of
a bit vector.  

MS Windows has a different implementation of 'select', and is not
affected by this bug.  


configure.in:
  Added a test for the <poll.h> file
sql/mysqld.cc:
  Restructured some of the code to reduce the number of
  #ifdef's.  Removed some HP/UX 10-specific code.

configure.in

@@ -839,7 +839,7 @@ AC_HEADER_DIRENT
 AC_HEADER_STDC
 AC_HEADER_SYS_WAIT
 AC_CHECK_HEADERS(fcntl.h fenv.h float.h floatingpoint.h ieeefp.h limits.h \
- memory.h pwd.h select.h \
+ memory.h pwd.h select.h poll.h \
  stdlib.h stddef.h \
  strings.h string.h synch.h sys/mman.h sys/socket.h netinet/in.h arpa/inet.h \
  sys/timeb.h sys/types.h sys/un.h sys/vadvise.h sys/wait.h term.h \

sql/mysqld.cc

@@ -52,6 +52,10 @@
 #include "sp_rcontext.h"
 #include "sp_cache.h"
 
+#ifdef HAVE_POLL_H
+#include <poll.h>
+#endif
+
 #define mysqld_charset &my_charset_latin1
 
 /* stack traces are only supported on linux intel */
@@ -5343,26 +5347,47 @@ void handle_connections_sockets()
 {
   my_socket sock,new_sock;
   uint error_count=0;
-  uint max_used_connection= (uint) (max(ip_sock,unix_sock)+1);
-  fd_set readFDs,clientFDs;
   THD *thd;
   struct sockaddr_storage cAddr;
-  int ip_flags=0,socket_flags=0,flags;
+  int ip_flags=0,socket_flags=0,flags,retval;
   st_vio *vio_tmp;
+#ifdef HAVE_POLL
+  int socket_count= 0;
+  struct pollfd fds[2]; // for ip_sock and unix_sock
+#else
+  fd_set readFDs,clientFDs;
+  uint max_used_connection= (uint) (max(ip_sock,unix_sock)+1);
+#endif
+
   DBUG_ENTER("handle_connections_sockets");
 
   LINT_INIT(new_sock);
 
+#ifndef HAVE_POLL
   FD_ZERO(&clientFDs);
+#endif
+
   if (ip_sock != INVALID_SOCKET)
   {
+#ifdef HAVE_POLL
+    fds[socket_count].fd= ip_sock;
+    fds[socket_count].events= POLLIN;
+    socket_count++;
+#else
     FD_SET(ip_sock,&clientFDs);
+#endif    
 #ifdef HAVE_FCNTL
     ip_flags = fcntl(ip_sock, F_GETFL, 0);
 #endif
   }
 #ifdef HAVE_SYS_UN_H
+#ifdef HAVE_POLL
+  fds[socket_count].fd= unix_sock;
+  fds[socket_count].events= POLLIN;
+  socket_count++;
+#else
   FD_SET(unix_sock,&clientFDs);
+#endif
 #ifdef HAVE_FCNTL
   socket_flags=fcntl(unix_sock, F_GETFL, 0);
 #endif
@@ -5372,12 +5397,15 @@ void handle_connections_sockets()
   MAYBE_BROKEN_SYSCALL;
   while (!abort_loop)
   {
-    readFDs=clientFDs;
-#ifdef HPUX10
-    if (select(max_used_connection,(int*) &readFDs,0,0,0) < 0)
-      continue;
+#ifdef HAVE_POLL
+    retval= poll(fds, socket_count, -1);
 #else
-    if (select((int) max_used_connection,&readFDs,0,0,0) < 0)
+    readFDs=clientFDs;
+
+    retval= select((int) max_used_connection,&readFDs,0,0,0);
+#endif
+
+    if (retval < 0)
     {
       if (socket_errno != SOCKET_EINTR)
       {
@@ -5387,7 +5415,7 @@ void handle_connections_sockets()
       MAYBE_BROKEN_SYSCALL
       continue;
     }
-#endif	/* HPUX10 */
+
     if (abort_loop)
     {
       MAYBE_BROKEN_SYSCALL;
@@ -5395,6 +5423,21 @@ void handle_connections_sockets()
     }
 
     /* Is this a new connection request ? */
+#ifdef HAVE_POLL
+    for (int i= 0; i < socket_count; ++i) 
+    {
+      if (fds[i].revents & POLLIN)
+      {
+        sock= fds[i].fd;
+#ifdef HAVE_FCNTL
+        flags= fcntl(sock, F_GETFL, 0);
+#else
+        flags= 0;
+#endif // HAVE_FCNTL
+        break;
+      }
+    }
+#else  // HAVE_POLL
 #ifdef HAVE_SYS_UN_H
     if (FD_ISSET(unix_sock,&readFDs))
     {
@@ -5402,11 +5445,12 @@ void handle_connections_sockets()
       flags= socket_flags;
     }
     else
-#endif
+#endif // HAVE_SYS_UN_H
     {
       sock = ip_sock;
       flags= ip_flags;
     }
+#endif // HAVE_POLL
 
 #if !defined(NO_FCNTL_NONBLOCK)
     if (!(test_flags & TEST_BLOCKING))