From: Frank Kardel <kardel@ntp.org>
Date: Sat, 24 Jun 2006 16:50:45 +0000 (+0000)
Subject: ntp_io.c:
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=da76966cb23fd39ed6280da9d8130d5cda461093;p=thirdparty%2Fntp.git

ntp_io.c:
  implement fix for bug 614
  socket fds will be moved out of the
  stdio reserved area if at all possible

bk: 449d6d65LfduRi_VAkUQvF0_2T2EHA
---

diff --git a/ntpd/ntp_io.c b/ntpd/ntp_io.c
index b91e71fab3..468522f396 100644
--- a/ntpd/ntp_io.c
+++ b/ntpd/ntp_io.c
@@ -151,12 +151,7 @@ static  void update_interfaces P((u_short, interface_receiver_t, void *));
 static  void remove_interface P((struct interface *));
 static  struct interface *create_interface P((u_short, struct interface *));
 
-#if !defined(SYS_WINNT) && defined(F_DUPFD)
 static int	move_fd		P((int));
-#ifndef FOPEN_MAX
-#define FOPEN_MAX	20
-#endif
-#endif
 
 /*
  * Multicast functions
@@ -287,29 +282,114 @@ connection_reset_fix(SOCKET fd) {
 }
 #endif
 
-#if !defined(SYS_WINNT) && defined(F_DUPFD)
-static int move_fd(int fd)
+/*
+ * on Unix systems the stdio library typically
+ * makes use of file descriptor in the lower
+ * integer range. stdio usually will make use
+ * of the file descriptor in the range of
+ * [0..FOPEN_MAX)
+ * in order to keep this range clean for socket
+ * file descriptions to attempt to move them above
+ * FOPEM_MAX. This is not as easy as it sounds as
+ * FOPEN_MAX changes from implementation to implementation
+ * and may exceed to current file decriptor limits.
+ * We are using following strategy:
+ * - keep a current socket fd boundary initialized with
+ *   max(0, min(getdtablesize() - FD_CHUNK, FOPEN_MAX))
+ * - attempt to move the descriptor to the boundary or
+ *   above.
+ *   - if that fails and boundary > 0 set boundary
+ *     to min(0, socket_fd_boundary - FD_CHUNK)
+ *     -> retry
+ *     if failure and boundary == 0 return old fd
+ *   - on success close old fd return new fd
+ *
+ * effects:
+ *   - fds will be moved above the socket fd boundary
+ *     if at all possible.
+ *   - the socket boundary will be reduced until
+ *     allocation is possible or 0 is reached - at this
+ *     point the algrithm will be disabled
+ */
+static int move_fd(SOCKET fd)
 {
-	int newfd;
-        /*
-         * Leave a space for stdio to work in.
-         */
-        if (fd >= 0 && fd < FOPEN_MAX) {
-                newfd = fcntl(fd, F_DUPFD, FOPEN_MAX);
+#if !defined(SYS_WINNT) && defined(F_DUPFD)
+#ifndef FD_CHUNK
+#define FD_CHUNK	10
+#endif
+/*
+ * number of fds we would like to have for
+ * stdio FILE* available.
+ * we can pick a "low" number as our use of
+ * FILE* is limited to log files and temporarily
+ * to data and config files. Except for log files
+ * we don't keep the other FILE* open beyond the
+ * scope of the function that opened it.
+ */
+#ifndef FD_PREFERRED_SOCKBOUNDARY
+#define FD_PREFERRED_SOCKBOUNDARY 48
+#endif
 
-                if (newfd == -1)
-		{
-			msyslog(LOG_ERR, "Error duplicating file descriptor: %m");
-                        return (fd);
-		}
-                (void)close(fd);
-                return (newfd);
-        }
-	else
-		return (fd);
-}
+#ifndef HAVE_GETDTABLESIZE
+/*
+ * if we have no idea about the max fd value set up things
+ * so we will start at FOPEN_MAX
+ */
+#define getdtablesize() (FOPEN_MAX+FD_CHUNK)
 #endif
 
+#ifndef FOPEN_MAX
+#define FOPEN_MAX	20	/* assume that for the lack of anything better */
+#endif
+	static SOCKET socket_boundary = -1;
+	SOCKET newfd;
+
+	/*
+	 * check whether boundary has be set up
+	 * already
+	 */
+	if (socket_boundary == -1) {
+		socket_boundary = max(0, min(getdtablesize() - FD_CHUNK, 
+					     min(FOPEN_MAX, FD_PREFERRED_SOCKBOUNDARY)));
+#ifdef DEBUG
+		msyslog(LOG_DEBUG, "ntp_io: estimated max descriptors: %d, initial socket boundary: %d",
+			getdtablesize(), socket_boundary);
+#endif
+	}
+
+	/*
+	 * with socket_boundary == 0 we stop attempting to move fds
+	 */
+	if (socket_boundary > 0) {
+		/*
+		 * Leave a space for stdio to work in. potentially moving the
+		 * socket_boundary lower until allocation succeeds.
+		 */
+		do {
+			if (fd >= 0 && fd < socket_boundary) {
+				/* inside reserved range: attempt to move fd */
+				newfd = fcntl(fd, F_DUPFD, socket_boundary);
+				
+				if (newfd != -1) {
+					/* success: drop the old one - return the new one */
+					(void)close(fd);
+					return (newfd);
+				}
+			} else {
+				/* outside reserved range: no work - return the original one */
+				return (fd);
+			}
+			socket_boundary = max(0, socket_boundary - FD_CHUNK);
+#ifdef DEBUG
+			msyslog(LOG_DEBUG, "ntp_io: selecting new socket boundary: %d",
+				socket_boundary);
+#endif
+		} while (socket_boundary > 0);
+	}
+#endif /* !defined(SYS_WINNT) && defined(F_DUPFD) */
+	return (fd);
+}
+
 #ifdef DEBUG_TIMING
 /*
  * collect timing information for various processing
@@ -2079,13 +2159,11 @@ open_socket(
 	}
 #endif /* SYS_WINNT */
 
-#if !defined(SYS_WINNT) && defined(F_DUPFD)
 	/*
 	 * Fixup the file descriptor for some systems
 	 * See bug #530 for details of the issue.
 	 */
 	fd = move_fd(fd);
-#endif
 
 	/*
 	 * set SO_REUSEADDR since we will be binding the same port
@@ -3573,6 +3651,7 @@ init_async_notifications()
 	int fd = socket(PF_ROUTE, SOCK_RAW, 0);
 	
 	if (fd >= 0) {
+		fd = move_fd(fd);
 		init_nonblocking_io(fd);
 #if defined(HAVE_SIGNALED_IO)
 		init_socket_sig(fd);